Estas jornadas de Física Médica, organizadas por la Real Sociedad Española de Física y el IFIC (laboratorio de física médica IFIMED), tienen el objetivo de favorecer el contacto entre profesionales de diversas ramas que trabajan en este campo (imagen médica, radioterapia, física de la visión, etc), tanto de la universidad y centros de investigación como hospitales, empresas, etc.
En esta ocasión se enmarcan en el proyecto Severo Ochoa del IFIC, que tiene como uno de sus objetivos fomentar la transferencia de resultados y tecnologías de física de partículas y nuclear a la sociedad, y en particular a la física médica.
Tras la edición presencial de 2023 en el CNA de Sevilla y la edición virtual de 2020, las jornadas vuelven a Valencia y se celebrarán en el Jardín Botánico los días 27-29 de Octubre de 2025.
Las jornadas tendrán lugar en formato presencial. La asistencia virtual estará limitada a ponentes de fuera de España y a casos excepcionales.
En caso de seleccionar una opción de registro con fee (opción SOLO DISPONIBLE HASTA EL 23/10/2025):
Payment must be performed via bank transfer to / Pago se debe realizar por transferencia bancaria a:
Recipient/Beneficiario: RSEF - GEFM
IBAN: ES40 0182 4572 4802 0160 1552
Concept(o): Fee GEFM - Nombre y Apellidos / Name and Surname
In case of further questions, please contact / En caso de más dudas, por favor contactar Chabely.Prats@ific.uv.es
Ceremonia de apertura a cargo de:
Miguel Ángel Sanchis, vicepresidente de la RSEF
Verónica Sanz, IP del proyecto Severo Ochoa del IFIC (CSIC-UV)
Gabriela Llosá, IFIC (CSIC-UV)
Nuria Rius, directora del IFIC (CSIC-UV)
Boron Neutron Capture Therapy (BNCT) is a neutron-based treatment designed to eliminate tumors, mainly head and neck tumors or Glioblastoma Multiforme (GBM), using 1 or 2 sessions, which is an advantage over conventional therapies that could use more than 20 individual sessions. It is a two-step strategy: first, the administration of a boron-containing compound to selectively enrich tumor cells with boron-10 nuclei; and second, irradiation with thermal neutrons. The aim is to induce reactions between thermal neutrons and boron-10 nuclei, releasing high-LET alpha particles with an average range shorter than the cell size. This feature gives BNCT a highly selective and destructive character, maximizing the dose contrast between tumor and healthy tissue.
The uptake of boron-rich nanoparticles and the response to BNCT can be studied in-vitro with cell cultures. This requires access to a source of thermal neutrons at very high flux. In this work, a nanoparticle-based boron compound was tested through a series of experiments carried out at the TRIGA nuclear reactor in Mainz. The objectives focused on the one hand, on characterizing the background dose generated by the reactor. For this purpose, pre-calibrated radiochromic films (RCF) were used under different reactor power and irradiation time configurations. In some experiments, parts of the RCF were covered with cadmium or lead to attenuate this background dose. These results allow for estimating the dose absorbed by a cell population exposed to the reactor in the absence of alpha particle production. It is worth noting that this dose originates both from the photon background and from fast, unmoderated neutrons emitted from the reactor core.
On the other hand, aqueous solutions of the boron-containing compound were prepared at different concentrations and irradiated under variable power and time conditions in wells of Petri plates. The well openings were covered with PADC (CR-39) detectors to register alpha-particle tracks generated by the interaction between boron-10 nuclei and thermal neutrons. After etching, holes associated with alpha particles were observed, superimposed on a rough background attributed to secondary protons produced by fast neutrons. These observations qualitatively confirm alpha production.
As a future perspective, we plan to use cell lines incubated with these boron-based nanoparticles to evaluate both the absorbed dose and the cell survival fraction under nuclear reactor irradiation.
Approximately half of newly diagnosed cancer patients undergo radiotherapy, most
commonly with X-rays. Proton therapy has emerged as an advanced alternative,
offering highly localized energy deposition at the Bragg peak, which reduces
irradiation of healthy tissues and associated toxicity. Technological advances have
enhanced its availability in clinical routine, which has redirected research efforts
toward maximizing the therapeutic potential of proton therapy and improving
patients’ long-term quality of life.
Within this framework, a promising strategy is the combination of proton therapy
with radiosensitizers. Among them, gold nanoparticles (AuNPs) stand out because of
their high atomic number, biocompatibility, low toxicity, and natural tendency to
accumulate in tumors, which makes them especially attractive for improving
therapeutic outcomes. Their use has demonstrated radiation enhancement effects in
both in vitro and in vivo studies. However, the underlying mechanisms responsible
for the observed increase in effectiveness under proton irradiation remain poorly
understood, underscoring the need for further research to enable an efficient.
This work is being conducted by a multidisciplinary collaboration involving physicists
from the Universidad de Sevilla (US) and the Instituto de Física Corpuscular (IFIC),
biochemists from the Universitat de València (UV), and biologists from the Centro
Andaluz de Biología Molecular y Regenerativa (CABIMER). Irradiations of cell samples
were carried out at the Centro Nacional de Aceleradores (Seville, Spain) using a
Cyclone 18/9 cyclotron (Ion Beam Applications, IBA, Belgium), which can accelerate
protons and deuterons to 18 and 9 MeV, respectively. Significant efforts have been
devoted to improving experimental conditions through the development and
implementation of new technologies, such as a robotic arm for remote sample
handling, which facilitate data acquisition and enable a greater number of
irradiations per experimental campaign. The study investigates the radiosensitizing
effects of 50 nm diameter gold nanoparticles (AuNPs) in HeLa cells irradiated with
protons. A comprehensive set of assays, including clonogenic survival assays and
immunofluorescence analyses with Hela cells, was performed to assess cell survival
and DNA damage response in the presence and absence of AuNPs. Preliminary
findings support the potential of AuNPs as effective radiosensitizers in proton
therapy.
Cardiac Positron Emission Tomography (PET) is a powerful molecular imaging technique, but its use is severely limited by poor spatial resolution. This limitation is particularly critical in preclinical studies with rodents, where small anatomical structures, high respiratory and heart rates exacerbate image blurring, partial volume effects, and quantitative errors [1]. These degradations arise from fundamental physical factors—positron range (PR), finite detector size, acollinearity, photon scatter—and are further amplified by physiological cardiac and respiratory motion [2]. To address this, we developed a novel deep learning-based super-resolution framework that integrates high-resolution ultrafast ultrasound (UUS) images as a priori anatomical and motion information to guide cardiac PET resolution recovery. Unlike previous approaches relying only on low-resolution PET data, this method leverages UUS images acquired simultaneously and co-registered with PET on the hybrid system PETRUS (PET/CT combined with UUS) [3], capturing fine structural boundaries and cardiac motion patterns.
Realistic PET data were generated using 50 digital mouse phantoms with the MOBY numerical phantom [4] to model diverse anatomies, cardiac and respiratory cycles. Physical and instrumental degradation factors -such as PR effects (simulated with PENEASY [5]), point spread function (PSF) blurring, and statistical noise - were applied to FDG activity maps, using experimentally measured parameters from the PETRUS scanner [6]. In parallel, corresponding UUS images were simulated for the same anatomical models using MUST simulations [7]. Two U-Net [8] convolutional neural networks were trained: one using only PET images, and another combining PET with co-registered UUS guidance.
The UUS-guided model clearly outperformed the PET-only model, achieving superior recovery of fine myocardial structures, higher SUV accuracy, and enhanced contrast in high-uptake regions (Fig.1). When applied to experimental datasets acquired with PETRUS, it produced sharper images with reduced noise and partial volume effects. These results show that incorporating anatomical and motion priors from UUS can overcome intrinsic resolution limits of cardiac PET, enabling more reliable quantification in cardiovascular diseases.
[1] J.J. Vaquero, P. Kinahan, Positron Emission Tomography: Current Challenges and Opportunities for Technological Advances in Clinical and Preclinical Imaging Systems, Annu. Rev. Biomed. Eng. 17, 385 (2015).
[2] M. Perez-Liva et al., Ultrafast Ultrasound Imaging for Super-Resolution Preclinical Cardiac PET, Mol. Imaging Biol. 22, 1342 (2020).
[3] J. Provost et al., Simultaneous positron emission tomography and ultrafast ultrasound for hybrid molecular, anatomical and functional imaging, Nat. Biomed. Eng. 2, 85–94 (2018).
[4] W.P. Segars et al., Development of a 4-D digital mouse phantom for molecular imaging research. Mol. Imaging Biol. 6, 149–159 (2004).
[5] J. Sempau et al., A PENELOPE‐based system for the automated Monte Carlo simulation of clinacs and voxelized geometries—application to far‐from‐axis fields. Med. Phys., 38(11), 5887-5895 (2011).
[6 ] M. Perez-Liva et al., Performance evaluation of the PET component of a hybrid PET/CT-ultrafast ultrasound imaging instrument, Phys. Med. Biol. 63, 19NT01 (2018).
[7] D. Garcia, Make the Most of MUST: An Open-Source Matlab Ultrasound Toolbox, IEEE IUS (2021).
[8] G. Du et al., Medical Image Segmentation Based on U-Net: A Review, J. Imaging Sci. Technol. 64(2) (2020).
Positron Emission Tomography (PET) relies on CT-based attenuation maps for accurate image reconstruction. The quality of these attenuation maps depends on CT acquisition parameters, particularly tube voltage and current. Higher tube currents improve image quality by reducing noise, but at the cost of higher radiation exposure. Conversely, reducing the current lowers the radiation dose but introduces more noise, which may affect PET quantification. Optimizing this balance is especially relevant in new long axial field-of-view PET systems, where higher sensitivity enables lower CT doses. This study evaluates how different CT dose levels affect PET image reliability, using the IMAS Total-Body PET system installed at La Fe Hospital in Valencia.
The experimental setup included the IMAS PET system, a GE Brightspeed CT scanner, and the NEMA IEC Body Phantom. The IMAS system employs semi-monolithic crystals, provides a 71.4 cm axial field of view, includes time-of-flight capabilities, and delivers spatial resolution below 4 mm uniformly across the field of view. CT scans were acquired at 80, 100, and 120 kV, with tube currents ranging from 10 to 120 mA in steps 10, producing 48 CT datasets. PET images were reconstructed with the OSEM algorithm using 20 iterations. Quantitative analysis of the CT images was performed with two regions of interest (ROIs): one covering the phantom background, excluding the lung insert, and one inside the lung insert. The mean and standard deviation of voxel values were extracted for each ROI. Additionally, representative CT dose levels were selected, and the corresponding PET images were evaluated according to the NEMA NU 2-2018 image quality protocol.
ROI analysis of the CT confirmed stable mean attenuation across tube currents and voltages, even at low doses. Noise increased in the background at low currents, especially at 80 kV, while the lung insert remained more stable, indicating that noise propagation affects uniform regions.
The analysis based of the PET images using the NEMA protocol, compared low, mid, and high CT dose levels. Contrast recovery improved with increasing sphere diameter, and was higher for mid and high dose acquisitions, while low-dose conditions consistently showed lower recovery values. Background variability decreased with sphere size but was always higher in the low-dose group than in the mid and high doses. Importantly, differences between mid and high dose conditions were minimal, suggesting that intermediate CT dose levels are sufficient to ensure robust PET image quality while avoiding unnecessary exposure.
In conclusion, the reliability of PET images in the IMAS system remains consistent across most CT dose levels, with mean attenuation preserved even at low doses. Still, very low currents, particularly at 80 kV, increase noise and reduce contrast recovery. NEMA analysis shows that mid-level doses perform similarly to high doses, offering the best balance between safety and diagnostic quality. The study confirms the feasibility of optimized low-dose PET/CT protocols.
Total-Body Positron Emission Tomography (TB-PET) systems have become very popular in the recent times, due to their increased sensitivity with respect to Whole-Body (WB) PET systems. This is mainly attributed to their extended axial Field of View (FOV) and, in a few cases, the capability of Time of Flight (TOF) information. This combination enables the simultaneous visualization of the biomarker distribution across multiple organs.
The DMIL group from i3M has recently developed and built, with the collaboration of other research groups and companies, a new TB-PET scanner, named IMAS, already installed at Hospital La Fe in Valencia,
The IMAS scanner features five rings with an inner diameter of 82 cm and an axial length of around 10 cm each, separated by 5 cm gaps between rings. This gives a total axial coverage of 70 cm. The IMAS scanner is based on semi-monolithic scintillator crystal with a total of 15,260 LYSO slabs, grouped into mini-modules (MM). Each MM contains an array of 1x8 LYSO slabs of 25×3×20 mm3, wrapped with Enhanced Specular Reflector (ESR) and coupled to an array of 8×8 Silicon Photomultipliers (SiPM) from Hamamatsu Photonics, model S13361-3075AE-08. Our design also uses novel multiplexed read-out electronics that reduce the number of signals from N2 to N. The x-(pixelated) coordinates are directly inferred from the triggered pixel, while y-(monolithic) and DOI (z) coordinates were estimated using two different Multilayer Perceptron’s (MLPs). Images were reconstructed using iterative methods. For the entire NEMA protocol, we used the Maximum-Likelihood Expectation-Maximization (MLEM) algorithm. We also carried out the first studies with patients. These images were reconstructed using the Ordered Subset Expectation Maximization (OSEM) algorithm.
A preliminary experimental evaluation of the IMAS system was performed . A system spatial resolution of 3.37 mm was obtained at the center of the scanner. This value remains almost constant along the radial direction due to the DOI capabilities of the system. The system has a peak sensitivity of 7.6% at the center of the scanner.
A significant step forward has been accomplished by acquiring the first patient images with the system. Clinically, image quality of our IMAS system seems to be superior to the conventional WB-PET/CT.
PET has consolidated as one of the most used and important molecular imaging techniques. However, there is still room for improvement. Specifically, boosting the system’s sensitivity will allow dose and/or time acquisition reduction without impacting the reconstructed image’s quality. BGO detectors have higher density when compared with the most used lutetium-based detectors, which translates into an increased sensitivity,. Moreover, the BGO crystals produce Cherenkov photons, generated much faster than the scintillation ones, that can be used and positively impact the timing performance of the PET detector. Furthermore, DOI capability is key in PET, for correcting parallax errors, allowing a uniform spatial resolution across the entire FOV.
We propose two BGO PET detectors designs, both with DOI and timing capabilities. The first is a semi-monolithic block of 1×8 slab of 3×25×15 mm3 each. All faces of each slab are polished and covered with ESR, except for the face coupled to the photosensor. The second detector proposed is a BGO crystal with the so-called pseudo-slabs geometry. This crystal is composed of 1×8 pseudo-slabs of 3×25×15 mm3 each, covered in BaSO4. Each pseudo-slab consists of 8 pixels of 3×3×15 mm3 with the four lateral faces unpolished and glued together. The entrance face of the block has an ESR film. The external dimensions of both crystal blocks is 25.8×25.8×15 mm3 and for all the studies these were coupled to a Silicon SiPM matrix. The TOFPET2 ASIC from PETsys Electronics was used as the readout electronics. Experimental data was acquired to study the spatial capabilities of the proposed detectors.
A uniform measurement was performed and the floodmap for each detector was generated. The x-monolithic and the y-pixelated direction were estimated using the RTP2 and CoG algorithms, respectively.
The monolithic spatial resolution of the semi-monolithic block and the DOI resolution of both crystals were studied. In each case a NN based on a MLP was used. For the training and testing along the monolithic direction, a slit collimator was moved in 1 mm steps between the detector under study and a single BGO pixel. For the DOI evaluation, the slit was displaced in 2 mm steps along the 25.8×15 mm2 face. In all cases the data was split into training, evaluation and testing datasets. The testing dataset was used for predicting the monolithic/DOI positions and the FWHM and MAE of the error profiles are reported. The mean monolithic spatial resolution of the semi-monolithic block was 3.4±1.1 mm. For the pseudo-slabs crystal, all pixels are well resolved. The mean DOI spatial resolution values was 3.8± 0.9 mm and 4.3±0.5 mm for the semi-monolithic and pseudo-slabs crystal, respectively.
The results obtained indicate that both crystals are suitable for a clinical PET system. We are currently working on the timing capabilities for these BGO blocks using ASICs.
Hybrid imaging systems integrating Positron Emission Tomography (PET), Magnetic Resonance Imaging (MRI), and Focused Ultrasound (FUS) are increasingly demanded in preclinical and translational research, yet no trimodal commercial solution currently exists. We have designed, assembled, and validated a dedicated PET insert based on monolithic LYSO crystals (33×25.4×8 mm³) with 67 mm of axial FOV, capable of simultaneous operation with high-field MRI and commercial FUS devices. We evaluated the system inspired on NEMA NU-4 2008 protocol. The PET insert achieved a homogeneous submillimeter resolution (0.9 mm with Depth of Interaction), a sensitivity of 3.8%, and a Noise Equivalent Count Rate peak of 80 kcps. Image quality metrics yielded recovery coefficients up to 0.89 and spill-over ratios of 11% (air) and 22% (water), matching state-of-the-art preclinical PET scanners.
Beyond performance characterization, the PET insert was employed in various trimodal studies. In a proof-of-concept phantom experiment, the PET was combined with a custom low-field MRI and a custom FUS device. Localized sonication was used to heat up the phantom and melt a gelatin compartment, allowing the initially confined ¹⁸F-FDG solution to diffuse into the gel matrix. This redistribution process was successfully monitored in real time by PET-MRI.
Subsequently, in vivo feasibility was demonstrated in murine brain studies using our PET insert combined with a 9.4T MRI and a commercial RK-300 FUS system. FUS-induced BBB opening was achieved with microbubbles, while Gd-DOTA (MRI) and ⁶⁴Cu-DOTA (PET) were co-administered. PET-MRI images confirmed co-localization of contrast enhancement with sonicated regions, validating the ability of the trimodal system to perform concurrent imaging and therapy monitoring in vivo.
In parallel, we investigated the impact of high magnetic fields on PET resolution through a positron range confinement study. A microDerenzo phantom was sequentially filled with ¹⁸F, ⁸⁹Zr, and ⁶⁸Ga and imaged with the PET insert inside and outside a 9.4T MRI. Results confirmed that the magnetic field confines positron trajectories perpendicular to B₀, with the most pronounced benefits for high-energy emitters: rods as small as 0.9 mm with ⁸⁹Zr and 1.0 mm with ⁶⁸Ga were resolved inside the MRI, while only the 1.2 mm and 1.5 mm rods were distinguished when the PET insert was outside the MRI, respectively.
These results establish the developed PET insert as the first preclinical trimodal PET-MRI-FUS platform, offering both state-of-the-art PET performance and unique multimodal capabilities. By enabling simultaneous imaging and therapy guidance, as well as demonstrating positron range confinement at 9.4T, this system opens new avenues for molecular imaging, BBB-targeted drug delivery, and advanced preclinical FUS research.
Introduction
Compton cameras are a promising tool in radiopharmaceutical therapy (RPT) treatment assessment and dosimetry, where gamma cameras perform sub-optimally due to the high energies of the emitted photons and low activities. The IRIS group is developing MACACO, a LaBr3-based Compton camera, for this application. The prototype MACACO III has been successfully used to visualize I-131 and Ac-225 [1,2] in phantoms. The latest prototype, MACACO III+, was tested at CIC biomaGUNE using a mouse phantom with several organs filled with I-131 and live mice injected with [I-131]NaI. The images were compared with those obtained using a commercial pre-clinical SPECT system. Simulations of a mouse with a realistic biodistribution of [Ac-225]Ac-DOTA were performed to test the viability of using MACACO III+ for imaging Ac-225 in small animals.
Methods
MACACO III+ features two detector planes, the first one composed of a single detector with 25.8 mm x 25.5 mm x 5 mm crystal size, and the second plane comprising four such detectors. The system was tested at CIC biomaGUNE with a mouse phantom, filling different combinations of the brain, heart, kidney and bladder in 45 minute acquisitions. Two living mice injected with 1.20 MBq and 2.16 MBq of [I-131]NaI were imaged during 30 minutes. The mouse phantom and the living mice were also imaged in a γ-CUBE SPECT system from Molecubes for 3 hours in a tomographic acquisition.
Simulations were performed using GATE and a digital 3D mouse phantom containing 25 kBq of Ac-225, with activity per organ based on data from biodistributions in mice injected with [Ac-225]Ac-DOTA [3], including a tumor of realistic size and uptake located in the brain.
Results/Discussion
Measurements of the mouse phantom filled with I-131 resulted in images comparable to those obtained using the γ-CUBE. When four organs were filled, the brain, heart, bladder and individual kidneys were clearly distinguishable. Images of the two live mice acquired using MACACO III+ are also similar to those obtained with the γ-CUBE, as can be seen in the attached figure. Here, I-131 uptake can be clearly identified in the thyroid gland as well as in the bladder and stomach. Form the simulation studies, Ac-225 accumulation can be clearly visualized in the tumor and the individual kidneys.
Conclusion
The MACACO Compton camera developed by the IRIS group successfully imaged I-131 distributions in a mouse phantom and living mice for the first time and shows great promise for imaging Ac-225, as shown by realistic simulations. Images of I-131 distributions were obtained with lower acquisition times and of similar quality compared to those obtained using a commercial pre-clinical SPECT. Future studies will be aimed at imaging other isotopes in live animals, in particular Ac-225.
References
[1] J Roser et al. 2024 Phys Medica 132:104928
[2] K. Brzezinski et al, Talk at 2024 IEEE NSS MIC, Tampa, USA, 26 Oct - 2 Nov 2024.
[3] M. Rodak et al. 2022 Mol Cancer Ther. 21(12) 1835–1845
Objective:
To evaluate the effect of a dermoprotective bra on the progression of acute radiodermatitis induced by radiotherapy, using as an objective biomarker a quantitative skin perfusion index obtained by Laser Doppler imaging.
Materials and methods:
Forty-seven patients with breast cancer treated with ultra-hypofractionated radiotherapy (total dose 26 Gy delivered in five fractions of 5.2 Gy) were included. According to the bra worn during RT, patients were assigned to two groups: dermoprotective bra, seamless and made of viscose/chitin fiber with ionic silver (n = 21), and conventional bra (n = 26). Skin toxicity was assessed clinically with the CTCAE scale and objectively by skin perfusion measured with Laser Doppler Imaging.
The upper-outer region of the irradiated breast and the contralateral breast (internal control) were scanned to obtain mean perfusion. A Microcirculation Index (MCI) was defined as the relative difference in mean perfusion between the treated and contralateral breast. Measurements were performed at four time points: pre-RT, mid-treatment, at RT completion and at one month. Receipt of chemotherapy was also recorded.
Statistical analysis was performed using a general linear model for repeated measures, including main effects of time, bra type and chemotherapy, and their interactions. Post-hoc comparisons were adjusted by the Bonferroni method.
Results:
By CTCAE scale, at RT completion 90.5% of the dermoprotective-bra group remained Grade 0 and 9.5% had mild erythema (Grade 1). In the conventional-bra group, 65.4% were Grade 0 and 34.6% Grade 1.
Objective analysis using the MCI showed significant differences: at the end of RT the conventional-bra group exhibited a significantly higher MCI than the dermoprotective-bra group (p = 0.037). At 30 days, the dermoprotective-bra group showed a trend toward lower MCI, close to statistical significance (p = 0.065), suggesting faster microvascular recovery. Analysis of chemotherapy effect indicated that, among patients who did not receive chemotherapy, those who did not use the dermoprotective bra had a significantly greater increase in MCI at RT completion (p = 0.017).
Conclusion:
Use of the dermoprotective bra during breast radiotherapy reduces the incidence and severity of acute radiodermatitis and moderates the acute increase in skin perfusion at treatment completion (p = 0.037), with a tendency to accelerate microvascular recovery at one month (p = 0.065). Furthermore, it attenuates the adverse vascular effect observed in patients receiving RT alone (p = 0.017). These findings support the relevance of the dermoprotective bra’s design and composition and warrant consideration of its clinical implementation.
Compton cameras (CCs) are promising imaging devices for nuclear medicine applications, as they can produce 3D images over a broad range of gamma-ray energies. Their flexible geometry suits compact and unconventional imaging setups. High energy resolution also improves background rejection and supports multi-isotope imaging, crucial in clinical contexts. Silicon detectors, due to their superior energy resolution are well-suited as scatterers in Compton camera systems.
The IRIS group at IFIC (Valencia), after developing several scintillator-based CCs under the MACACO project, is now working on a new prototype using silicon detectors, with the aim of improving the performance for radionuclides emitting photons with energies below 300 keV such as ¹⁷⁷Lu. The system combines a silicon pad detector as the scatterer and a scintillator crystal coupled to a SiPM array as the absorber. This design aims to enhance spatial resolution over previous setups, while preserving compactness and high detection efficiency. To evaluate its performance, experimental tests at the laboratory have been conducted using a ¹³³Ba source, focusing on the 356 keV gamma-ray line.
The dimensions of the silicon detector are 46.4 x 11.6 x 0.5 mm³ and 1 mm x 1 mm pads manufactured by SINTEF for the MADEIRA project. The second detector of the CC consists of a Lanthanum (III) Bromide scintillator crystal from Saint Gobain of size 25.8 x 25.8 x 5 mm³ coupled to a SiPM array S13360-3025CS with a pixel size of 3 mm². Data acquisition is handled by two time-synchronized AliVATA readout boards, each tailored to operate the ASIC for its respective detector: the VATA64HDR16 collects charge from the SiPM signals, while the VATAGP7.2 interfaces with the silicon detector, both developed by IDEAS.
Functional verification was performed by acquiring data in singles and coincidence mode using a point-like source of ¹³³Ba with an activity of 683 kBq. Energy spectra from both detectors were analyzed, and correlations between energy deposits are being evaluated to identify valid Compton events. System optimization is ongoing.
To complement the experimental work, Monte Carlo simulations using GATE v8.2 were performed, replicating the physical system. Two radionuclides (¹³³Ba and ¹³¹I) were studied using a point-like source and a simplified Derenzo-like phantom to assess the spatial resolution. Simulations indicate that the silicon–scintillator configuration achieves superior performance at low energies relative to earlier MACACO prototypes.
Current efforts focus on comprehensive characterization of the silicon detector, expanded simulations for radionuclides emitting photons near 200 keV, and ongoing imaging experiments.
La terapia con protones es una forma de radioterapia más precisa, eficaz y segura que la radioterapia convencional en muchos casos de cáncer. Se trata de una técnica innovadora que está experimentando un notable crecimiento e interés. Actualmente, en España existen dos centros de protonterapia en funcionamiento, y está prevista la instalación de diez nuevos centros en distintas regiones del país en los próximos años.
Esta terapia permite una deposición muy precisa y concentrada de la dosis en la zona que se trata. No obstante, la administración de radiación más precisa y concentrada sobre el tumor puede convertirse en una desventaja si, por mala posición del paciente o por el movimiento de los órganos internos, el haz de protones no se dirige a la masa tumoral afectando las zonas sanas colindantes.
La verificación de la dosis en la terapia con protones administrada al paciente inmediatamente después de cada sesión juega un papel decisivo en la validación del tratamiento, seguridad del procedimiento y el objetivo clínico. Actualmente no se aplica ningún método de forma rutinaria en la clínica para la verificación de dosis. Por ello, existe la necesidad de desarrollar técnicas de verificación precisas y aplicables en la práctica clínica.
Para abordar esta necesidad, proponemos el desarrollo de un prototipo PET, llamado INSPIRE, dedicado a verificar la dosis administrada tras una terapia con protones en el cerebro del paciente. La propuesta se centra en la detección de $^{18}$F, uno de los radioisótopos emisores de positrones que se producen cuando el haz de protones interacciona con el tejido. Esto supone un desafío debido a la baja concentración de $^{18}$F que se genera (~0.1 Bq/ml con 3 Gy). Nuestra propuesta se basa en el uso de detectores PET basado en cristales semi-monolíticos de BGO. El uso de este material para nuestro diseño se debe a tres razones principales: reducción del coste de fabricación (3 veces menor al del LYSO), alta densidad (más fotones de aniquilación capturados a mismo volumen) y ausencia de radioactividad natural de Lu-176.
Presentaremos resultados de medidas de $^{18}$F-FDG a muy baja actividad, realizadas con un prototipo PET basado en LYSO (DeepBreast) y con un escáner PET comercial basado en BGO (GE Omni Legend). Además, mostraremos los resultados de las primeras simulaciones del equipo completo INSPIRE y de una evaluación experimental de los detectores del equipo.
Boron Neutron Capture Therapy (BNCT) is an experimental form of radiotherapy that uses boron, injected to the patient within a target molecule that accumulates selectively in cancerous cells. This therapy exploits the large boron neutron capture cross-section to deliver a targeted dose from neutron irradiation. BNCT has shown great promise with the advent of accelerator-based technologies, which facilitate high-quality neutron beams in clinical environments [1].
One of the primary challenges in current BNCT is the accurate determination of the dose delivered to the patient. The state-of-the-art method uses simple extrapolations from previous PET scans and online monitoring of boron concentration in blood. Since neutron captures in boron produce 478 keV gamma rays, this radiation could be potentially used for real-time dose monitoring. To date, the main challenges remain dealing with very intense radiation fields that generate large count rates above detector reach; and in achieving enough boron sensitivity to image the boron in the tumor (65 ppm) above the overall boron in nearby tissues (18 ppm), on top of the strong background induced by harsh neutron and gamma ray fields generated during the treatments; while attaining the spatial resolution required and moving towards true online capabilities during treatment.
The i-TED Compton Camera array, originally designed for nuclear physics measurements of astrophysics interest, has expanded into medical physics through ion-range monitoring in HT [2], and further aiming now at BNCT [3]. Its large efficiency design and low neutron sensitivity make i-TED especially well suited for this task.
This contribution will present the adaptations of the original i-TED imager, to optimize its performance for BNCT dosimetry. In this context, we require the use of pixelated detectors in order to cope with the very large count rates present in these treatments. We will discuss the characterization and implementation of a first pixelated crystal and its integration in the i-TED module and data process pipeline. Additionally, since BNCT requires imaging of large body regions, we have integrated LM-MLEM algorithms to enable 3D image reconstruction. For that purpose, we have developed in our lab a tomographic Compton-PET-capable rotatory system using i-TED modules.
References
[1] K. Hirose et al., “Boron neutron capture therapy using cyclotron-based epithermal neutron source and borofalan (10B) for recurrent or locally advanced head and neck cancer (JHN002): An open-label phase II trial”, Rad. & Onc. Vol 155, pp. 182-187, (2021)
[2] J. Balibrea-Correa et al., “Hybrid compton-PET imaging for ion-range verification: a preclinical study for proton, helium, and carbon therapy at HIT”, The Eur. Phys. Jour. Plus, Volume 140, 870 (2025)
[3] P. Torres-Sánchez et al., “The potential of the i-TED Compton camera array for real-time boron imaging and determination during treatments in Boron Neutron Capture Therapy”, App. Radiat. Isot. 217, 111649 (2025)
Hadron therapy provides notable advantages compared to traditional radiotherapy, largely because it allows for precise dose delivery at the Bragg peak. The effectiveness of this approach could be further improved with the implementation of a near real-time ion-range verification system. Such monitoring would make it possible to minimize safety margins and better exploit the full potential of the treatment by mitigating sources of systematic uncertainty.
Two of the most promising methodologies for in-room, real-time monitoring are positron emission tomography (PET) and prompt-gamma imaging (PGI). The PGI technique is particularly well-suited for real-time monitoring because of the prompt nature of the emitted radiation. In contrast, PET imaging offers tomographic and functional information, making it valuable for studying physiological processes and tumor response. A PGI-PET hybrid imaging system could help to address some of the limitations inherent to each technique. This expectation arises from the complementary strengths of the two techniques: prompt-gamma emission is more suitable for real-time monitoring, while PET imaging provides tomographic and functional information valuable for studying physiological processes and tumor response.
In this contribution I will summarize the status of hybrid PGI-PET technique explored at three different types of ion-therapy machines: the large synchrotron at HIT, the Proteus Plus iso-cyclotron and the Proteus One synchro-cyclotron from IBA. The main experimental results will be presented, together with a discussion on the present experimental limitations and future steps to further develop this promising technique towards the clinical environment.
The PRIDE project (Proton Range and Imaging Device) aims to integrate a proton computed tomography (pCT) scanner and a proton range verification (pRV) detector into a single device for proton therapy. Our collaboration has carried out extensive work on pCT with experiments taking place in June and December 2022 at the Krakow CCB facility.
Proton range verification (pRV) consists of determining the proton range in a patient during treatment by inferring the Bragg peak position from the detection of scattered secondary radiation. In February 2025, we performed measurements at the Krakow CCB facility to evaluate the components of our setup, using water and PMMA phantoms, and varying the beam energies between 70 and 160 MeV. Two independent measurements were carried out: one with a non-commercial, pure LaCl3 crystal providing excellent neutron-gamma discrimination in a coaxial configuration for independent detection of forward-emitted gamma rays and neutrons, and another with a position-sensitive plastic scintillator combined with two double-sided silicon strip detectors for the detection of laterally scattered neutrons and protons.
In this work, we present a preliminary analysis of the experimental results and discuss their relevance for the development of the integrated PRIDE device, and compare them with Monte Carlo simulations for validation.
Metastatic bone cancer contributes to approximately 2 to 3 million cancer-related deaths worldwide annually. Between 5% and 10% of new cancer patients will develop bone metastases. A major challenge in treating this disease is the inability to perform imaging during particle radiation therapy (PRT), due to high radiation doses from frequent scans, patient pain, and mobility constraints. Consequently, tumour imaging is typically limited to pre and post treatment assessments—often several months apart, which hinder timely treatment adjustments and personalized care.
The BoneOscopy project, funded by the European Innovation Council under Horizon Europe, seeks to transform metastatic bone cancer treatment by enabling daily, real time monitoring of tumour regression and calcium content without additional radiation exposure, using a novel prompt-gamma spectroscopy (PGS) approach. The system utilizes specific detectors, custom nanosecond electronics, and a robotic arm to perform precise spectroscopic measurements focused on calcium concentration in the bone tissue, which is the indicator of tumour regression and bone health status.
BoneOscopy’s research integrates a broad spectrum of technical and scientific expertise, as it brings together skills in bioengineering (DKFZ, Germany), the institute leader of the project, molecular imaging and robotics (CSIC, specifically i3M in Valencia, Spain), high-speed electronics (LIP, Portugal), clinical PRT experience and Monte Carlo simulation modeling (THM, Germany), medical device software, and hardware integration and mechanical design (Cosylab, Slovenia).
In its first six months, the BoneOscopy project has established the clinical contexts in which the detection system must operate. Monte Carlo simulations (via Geant4) using proton beams, modeled from the ones delivered in centres like HIT and MIT in Germany, have allowed the project team to estimate prompt gamma–ray generation under realistic clinical conditions. In parallel, simulation work has been carried out to optimize the detector’s crystal design supporting decisions on sensor types, geometric layout, and mechanical integration. With this groundwork completed, the project is ready to transition into the implementation phase.
The presentation will offer an overview of the BoneOscopy initiative, detailing the clinical environment requirements—including beam parameters, patient positioning mechanics, and expected variations in calcium concentration. It will then present comprehensive results from the simulation studies achieved with Geant4 focused on prompt-gamma generation and detection. Finally, it will include an in-depth analysis of critical detector components, particularly the crystal materials and configurations used in the primary detection system.
Objective: The quantitative relationship between dose delivered outside the treated volume and stochastic effects is not well understood, although epidemiological evidence supports the hypothesis that low to moderate doses of ionizing radiation are associated with measurable excess risk of several types of cancer. Current studies of second primary cancer after radiotherapy demand the possibility of computing whole-body dose distributions on patients treated with modern photon and proton external beam radiotherapy (EBRT) techniques.
Methods: In the framework of the Horizon Euratom HARMONIC project a database of pediatric modern radiotherapy patients, treated with photon or proton EBRT, was created. This database stores for each patient DICOM-RT computed tomography images and treatment plans. The whole-body dose computation requires a patient geometry in which to compute the corresponding dose distribution. A software developed within HARMONIC was employed for that purpose using anthropomorphic phantoms. For the computation of the whole-body absorbed dose distribution in photon treatments, the Monte Carlo system PRIMO was used, while proton treatments were computed with the Monte Carlo code TOPAS/Geant4 . The imaging whole-body dose associated with diagnostic and positioning procedures during therapy was also computed with the Monte Carlo code PENELOPE. The developed codes and geometries were experimentally validated by means of an anthropomorphic pediatric material phantom (ATOM) irradiated with the considered therapeutic and imaging procedures.
Results: Out-of-field organ equivalent dose of proton therapy is up to two orders of magnitude lower when compared to modern photon therapy. As an example, for a brain glioma treatment, with a total target dose of 50.4Gy(RBE), it was found that the organ doses from the proton treatment ranged between 0.6 mSv (testes) and 120 mSv (thyroid), while for photon therapy (IMRT) 43 mSv (testes) and 575 mSv (thyroid). Dose delivered by planning CT ranged between 0.01 mSv (testes) and 72 mSv (scapula), while for the 28 fractions, the imaging procedure for positioning (CBCT) yielded doses ranging between 56 uSv (testes) and 36 mSv (thyroid).
Conclusions: The developed and validated code systems for dose computation have shown to be suitable for the computation of whole-body dose distributions of patients stored in the HARMONIC database. The lower out-of-field dose of proton treatments respect to equivalent photon irradiations results in the fact that the imaging dose from diagnostic and positioning procedures becomes significant in proton therapy. This research is the result of the work conducted at the West German Proton Therapy Centre Essen, the Belgian Nuclear Research Centre, the French Alternative Energies and Atomic Energy Commission, the University Hospital Essen, the University Hospital of Zürich and the Institut Gustave Roussy.
X-ray fluorescence imaging (XFI) is an emerging molecular imaging technique that combines high sensitivity with high spatial resolution, offering significant penetration depth in tissues while minimizing ionizing radiation exposure compared to current methods. This makes XFI a promising tool for early cancer detection and personalized treatment. The “Integrated Molecular Imaging for Personalized Biomarker-based Breast Cancer Characterization and Treatment (IMMPRINT)” project aims to develop a proof-of-principle (POP) demonstrator that leverages X-ray fluorescence computed tomography (XFCT) as a novel hybrid modality for tumor profiling, with a focus on breast cancer (BC). Within IMMPRINT, specifically engineered and targeted nanoparticles, such as gold nanoparticles (GNPs), will be employed to identify distinct signatures of intra and inter – tumor heterogeneity in BC. The sensors chosen for the POP are the pnCCD sensors produced by MPI HLL in Munich. To support system development, Monte Carlo simulations are being performed on a tumor – bearing mouse model loaded with GNPs, using the GEANT4 simulation toolkit. Fluorescence photons are generated when GNPs are excited by incident X-rays and detected with a silicon detector. Simulation results that outline critical parameters for detector development and system design will be presented.
When it comes to treating cancer in critical regions such as the brain, precision is vital, as reducing margins of error can significantly decrease negative side effects of treatment. Due to their finite range and deposition profile, protons are an ideal candidate for this sort of treatment. However, this finite range of protons is both their biggest advantage and their biggest challenge, as a minor miscalculation of penetration depth can have severe consequences for the patient. As such, continuous monitoring of the proton energy deposition throughout treatment is of the upmost importance. A class of continuous monitoring techniques that has shown great promise in recent years is prompt-gamma ray detection. Prompt-gamma ray detection functions on the principle that, as protons penetrate the patient, gamma rays are emitted along their path. Currently, this method depends largely on Monte Carlo simulations, which is restricting as these simulations are very computationally expensive.
In practice, a treatment of ~1000 spots typically lasts a few minutes, whereas the simulation of this treatment typically takes several hours. In cases where the continuous monitoring results during treatment do not match the simulation, it becomes completely impractical to re-simulate scenarios in search of the discrepancy between simulated and true treatment parameters. Therefore, if the computation time of a single spot could be reduced to approximately one-tenth of a second, real-time re-simulation of results would be possible. To achieve such simulation speeds, standard Monte Carlo simulations have been shown to be insufficient, and as such simulation with a high degree of parallelisation is the theoretical solution.
The goal of this project is to provide an open source solution to this problem. The code is currently being written in SYCL (SYstem-wide Compute Language), a hardware-agnostic language which creates parallelised software that can be ran on either GPU or CPU with minimal overhead. The present simulation model has shown great promise in terms of computation times and accuracy when tested on a water phantom. The code has shown an increase in computation speed by several orders of magnitude for energy deposition and depth of penetration calculations when compared with TOPAS, whilst maintaining a maximal deviation of 0.5 mm in 90% drop-off position (R90) and 3 MeV for total energy deposition across the full treatment range. These results are thought to be improvable with a more complex model and the appropriate optimisations. The future aim of this project is to gradually increase simulation complexity by incorporating more processes such as gamma-ray transport and detection in an external scintillation detector, whilst maintaining code clarity and structure for possible public contributions, and continuously simplifying user experience.
gVirtualXray is an open-source library designed to simulate X-ray images in real time using the power of the GPU. Its core relies on the Beer–Lambert law to model the absorption of photons by three-dimensional objects, such as polygon meshes. This project has received numerous awards and recognitions related to its use in education and digital twins, including the recent Dirk Bartz Prize for Visual Computing in Medicine and Life Sciences, granted among others to the authors of this presentation (Vidal, 2025).
gVirtualXray is based on the following technical principles:
Beyond its reputed use as a software product, gVirtualXray has been academically discussed in several publications such as Vidal et al. (2017) and Corbi et al. (2024). Moreover:
The applications of gVirtualXray are diverse and multidisciplinary:
As mentioned earlier, gVirtualXray has been presented and awarded at multiple events and conferences:
gVirtualXray is a powerful X-ray image simulation library that combines scientific accuracy with speed, thanks to its GPU implementation. It is accessible to developers and researchers due to its cross-platform compatibility and wrappers in multiple languages. Rigorously validated and adopted in education, medicine, materials science, ML, and interactive simulation, the project remains active and recognized for its technical, scientific, and educational contributions. In the context of the V RSEF/IFIMED Conference, a brief and outreach-oriented presentation of the tool will be delivered, showcasing its potential and wide range of applications, with an emphasis on its educational use.
El uso de dispositivos digitales ha incrementado la exposición a fuentes de luz artificial con espectros distintos a los medios impresos. Muchas pantallas emiten un pico en la región azul del espectro visible(440-460 nm), inexistente en el papel bajo iluminación normal(1). La luz azul, por su mayor energía, puede afectar a la fatiga ocular, la supresión de melatonina y otros procesos biológicos(2). Para reducirla se emplean filtros de absorbancia selectiva(3). Este trabajo compara la emisión espectral de una pantalla digital con y sin filtro frente a la reflectancia del papel.
Para la caracterización espectral del papel, se dividió un folio en 9 áreas y se registraron mediciones espectrofotométricas en cada una, bajo una iluminación de 16.8cd/m² medida con luxómetro. Los valores obtenidos se promediaron y se analizaron las longitudes de onda de 440 y 470nm principalmente.
De la misma forma, la pantalla de un iPhone 13 se dividió en 9 áreas, realizándose mediciones en cada una con y sin filtro selectivo, y con el brillo ajustado a tres niveles(mínimo, medio y máximo). Los datos resultantes se promediaron para las mismas longitudes de onda de interés.
Los resultados mostraron que la reflectancia del papel se mantuvo baja y estable en ambas longitudes de onda, con una intensidad ≈700 cuentas, en contraste con la pantalla digital, cuya intensidad de emisión se incrementó notablemente, especialmente en 470nm, alcanzando valores superiores a 10.000 cuentas con brillo máximo. La aplicación del filtro de absorbancia selectiva redujo la intensidad emitida en esta banda, con descensos de alrededor del 10–20% según el nivel de brillo, mientras que en 440nm las diferencias fueron menores.
Los resultados evidencian diferencia entre la emisión espectral de las pantallas digitales y la reflectancia del papel en la región de 460-470nm, lo que refuerza la importancia de implementar medidas que limiten la exposición a esta franja del espectro durante el uso prolongado de pantallas, en particular cuando se utilizan con niveles altos de brillo.
Purpose:
This study aimed to compare static pupillometry under mesopic conditions between European
and African populations, given the limited data directly contrasting pupillary dimensions across
ethnic groups. Characterizing pupil diameter is relevant in detecting ocular alterations,
particularly in a multicultural context. While age-related pupillary changes are well documented
in Caucasian and Asian populations, evidence in Africans is scarce. This work establishes initial
reference values for the Senegalese population as a starting point for further studies.
Settings:
Data were collected at three locations: Caucasian participants at the Optometry Clinic of the
Complutense University of Madrid; Afro-Europeans (AFE, African origin but lifelong residents in
Europe) in the Lavapiés district of Madrid; and Africans (AFR) at Abass Ndao Hospital, Dakar.
The study complied with the Declaration of Helsinki.
Methods:
Analytical cross-sectional observational study with 88 CAU, 129 AFR, and 78 AFE, aged 18–75
years. All provided written informed consent. Static pupillometry was measured with the Nidek
HandyRef-K portable autorefractor-keratometer; five measurements per participant by the same
examiner.
Results:
• Ethnic comparison: mean pupil diameters: CAU 4.67 ± 0.7 mm; AFR 5.11 ± 1.0 mm;
AFE 4.44 ± 1.0 mm (p < 0.001).
• Age comparison: In CAU, no significant differences among young, adult, and >45
years groups (p > 0.05). Both AFR and AFE showed significant differences (p < 0.05),
with younger participants having the largest diameters, followed by adults, and the
smallest values in those >45 years.
Conclusions:
Africans showed larger pupil diameters compared to Caucasians and Afro-Europeans, between
whom no significant differences were observed. Age had no effect in Caucasians, while both
Africans and Afro-Europeans showed decreasing diameters with age. These findings provide
reference data for Senegalese populations and support further cross-ethnic research.
Key words: Axial length, Race, Sex, Ocular Biometry, Africans, Caucasians
References:
1. Birren JE, Casperson RC, Botwinick J. Age changes in pupil size. Journal of
Gerontology. 1950;5(3):216-21.
2. Winn B, Whitaker D, Elliott DB, Phillips NJ. Factors affecting light-adapted pupil size
in normal human subjects. Investigative ophthalmology & visual science.
1994;35(3):1132-7
3. Tekin K, Sekeroglu MA, Kiziltoprak H, Doguizi S, Inanc M, Yilmazbas P. Static and
dynamic pupillometry data of healthy individuals. Clin Exp Optom. 2018
Sep;101(5):659-665. doi: 10.1111/cxo.12659. Epub 2018 Jan 21. PMID: 2935607
In the last years there is an increasing demand for advanced medical treatments, a field where particle accelerators play a crucial role. However, their availability is significantly limited due to high maintenance and operational costs, on the one hand, and the need for advanced technology and highly skilled personnel for their design and construction, on the other. The main goal of the project LINAC7 is to face these limitations with the design, fabrication and testing of a low energy proton accelerator. For this, all the components of the accelerator are being developed by the personnel involved in the project and, once constructed, the accelerator will serve for training students as well as for research studies.
In the current design, two experimental stations are to be constructed, one for protons with 3 MeV and other for protons with 7 MeV. In the first case, a 7Li target is aimed to be used for neutron production for different research purposes. In the second case, irradiation of different materials, such as cell cultures, and studies related with radioisotope generation are expected. Apart from that, a beam stop for beam characterization will be placed at the end of a third line.
The accelerator will be installed in the university of the Basque Country and its shielding design must guarantee adequate dose rate values in the surrounding areas in beam-on and beam-off conditions. The present work considers the above-mentioned applications to calculate the radiation that will be generated and the shielding needs. Moreover, a portable neutron source that will also be located in the room has been taken into account.
The tools used for the calculations are the MCNP6.2 for radiation transport and the ACAB-2008 software to determine the radioisotope inventory resultant from the activation of the materials. The starting shielding configuration has been defined based on the literature, and its optimization consists of an iterative process in which the geometry and type of the attenuating materials is modified basing on the dose rate values calculated in detectors positioned out from the accelerator room, for beam-on conditions, and in detectors located inside, for beam-off conditions. The plans of the building have been considered to obtain realistic results.
The final solution consists of three different shieldings, one of them moveable to be used for the portable neutron source and for the target station aimed for neutron generation. Highly efficient attenuating materials, such as lead for gammas and polyethylene for neutrons, allowed for a more compact design. Moreover, reduction of the iron quantity in the external layer reduces dose values in beam-off conditions.
In conclusion, different shielding designs that guarantee dose rates below the limit have been calculated and the next step is to discuss aspects related to fabrication and present the proposal to the CSN to advance with the construction of the setup.
Operating medical linear accelerators (LINACs) above 6 MV generates unwanted neutrons through (γ,n) interactions with high-Z materials in the accelerator head. These secondary neutrons contribute additional dose to healthy tissues and may lead to late-onset adverse effects [1]. Moreover, the neutron yield shows high variability, depending on several factors, e.g., LINAC model, beam energy, and delivery modality. Consequently, real-time, patient-specific neutron characterization is essential for accurate assessment of secondary exposure and for optimized radiation safety measures.
To address this challenge, IMB-CNM has developed an ultra-thin (20 μm) neutron sensor based on silicon with an innovative 3D architecture coupled to a (45 ± 5) μm thick ¹⁰B-enriched conversion layer to quantify thermal neutron fields. The ultra-thin active volume provides a high gamma-rejection factor (>10⁻⁸), crucial for isolating neutron signals in high-gamma-ray environments. Custom readout electronics enabled online acquisition.
Real-time thermal neutron contributions were measured in two treatment rooms comparing two widely used LINACs—Varian TrueBeam and Elekta Synergy—operated with flattened (FF) 15 MV X-ray beams and 10×10 cm² field size. Measurements were compared against PHITS Monte Carlo simulations using an extended 15 MV TrueBeam head model that, for the first time, includes detailed head shielding and was validated with PDD data (TPR20,10 difference <1.3%, see Figure 1) [2]. A neutron distribution map throughout the treatment room was also simulated (Figure 2).
The sensors reliably characterized the thermal neutron field, achieving a detection efficiency of (1.53 ± 0.02)% at a 660 keV energy threshold and operating without interference from the intense photon background and without saturation effects up to the maximum dose rate 600 MU min-1 (Figure 3). The secondary neutron field produced by the Varian TrueBeam was approximately four times higher than that of the Elekta Synergy throughout the room and under similar conditions in agreement with the literature [3].
Ongoing work focuses on optimizing the conversion layers to enhance efficiency and on developing a new portable neutron spectroscopy system for more accurate total neutron dose estimation.
References
[1] Banaee, et al. (2021). Journal of Radiation Research, 62(6), 947-954.
[2] Zamorano, et al. (2025). Phys. Med. Biol, 70(16), 5001.
[3] Belousov, et al. (2020). Radiation Protection Dosimetry, 188(2), 145-152.
The electron LINAC ElectronFlash installed at the Institut Curie (France) is dedicated to the investigation of the FLASH effect on pre-clinical trials and radiobiology studies [1]. The accurate beam characterization is essential for a proper dose calibration. Although a few dosimeters operate under FLASH conditions, e.g., diamond [2], ultra-thin ionization chambers (UTIC) [3], and SiC-based detectors [4], Monte Carlo (MC) simulations are a complementary tool for estimating doses in scenarios where those dosimeters can have a limited use.
This study aims to present the experimental and simulated characterization of the ElectronFlash Linac for both FLASH and conventional modalities using a set of dosimeters and MC simulations.
Irradiations were performed at 7 MeV, with 0.5 – 5 μs pulse widths, and up to 250 Hz with different poly methyl methacrylate (PMMA) applicators. The experimental setup consisted in a PTW Water Phantom and a PEEK plastic collimator designed for irradiating mouse lungs (Fig. 1, left). The absolute dosimetry was made with Radiochromic EBT3 films, a PTW FlashDiamond, and UTIC to characterize the percentage depth dose (PDD) in that water tank (Fig. 2, left). The scatter factors were evaluated with new SiC detectors designed and fabricated at IMB-CNM. The beam FWHMs were also quantified with the radiochromic films. We used the open-source GATE MC (vs 10.0.2) to model the beamline starting from the experimental data gathered using the dosimeters mentioned above. Simulations were run in the computational cluster TIRANT v4.
Considering the experimental work, the PDDs obtained showed loss of electron equilibrium at the beginning of the curve and non-negligible differences between FLASH and conventional modalities (Fig 1, right). Additionally, there was a significant difference (43%) in the FWHMs between these two modalities, which suggests notable differences in the beam configuration for each one. The scatter factors evaluated with SiC diodes were in good agreement with those from flashDiamond. Interestingly, these PDDs yielded an increase of electron energy compared to the previous PDD reported [3], which reinforce the need to model the LINAC. Regarding the MC study, the simulated PDD showed an excellent agreement with the experimental measured (Fig 2, right) validating the accuracy of the MC modelling. This enables calculate the dose distributions in cases where the dosimeters cannot easily be used, e.g., for small field sizes or large dose gradients.
This work shows the first comparison of experimental dose distributions with those obtained with accuracy MC model of the electronFLASH LINAC at Inst. Curie.
The spatial distribution of energy deposition events produced by the different types of ionizing radiation is a key factor to determine their radiobiological effects at the cellular scale. The theoretical framework provided by microdosimetry has been widely employed to describe these stochastic interactions, particularly in studies addressing the characterization of Linear Energy Transfer (LET) and Relative Biological Effectiveness (RBE) of ion beams in the context of hadron therapy. Such quantities are typically calculated through Monte Carlo simulations.
To fulfill the purpose of calculating these energy distributions, a new track-structure Monte Carlo application has been developed to incorporate it as a new Geant4-DNA example of the Geant4 toolkit. The code, named Microtrack, is designed to study the energy deposition in spherical sensitive volumes, known as sites, whose diameter sizes may vary from nanometer to micrometer scale. These sensitive volumes are sampled within a cubic water volume. This geometry is defined by two input parameters: the site radius and the maximum electron range.
A flexible primary generator controls particle type (protons by default), energy, and beam source position, enabling reproducible irradiation setups relevant to microdosimetry, LET and RBE studies.
Scoring is implemented through a dedicated sensitive detector that records per-step energy deposition and aggregates event-level observables. Simulation outputs are handled by the Geant4 analysis manager and written to a ROOT file, containing useful histograms for the aforementioned studies, including distributions of single-event energy imparted up to the second moment to calculate weighted quantities such as dose-mean lineal energy.
Microtrack emphasizes transparency and flexibility: default options, such as the volume material, particle, beam energy, or physics list, can be modified through Messenger classes and macro files, while multithreading enables faster simulations by distributing runs across multiple threads and merging results.
In summary, the future Geant4-DNA example Microtrack constitutes a versatile Monte Carlo tool for the calculation of microscopic energy deposition patterns and assists research on microdosimetry for hadron therapy.
The distribution of produced isotopes during proton therapy can be imaged with Positron Emission Tomography (PET) to verify dose delivery. However, biological washout, driven by tissue-dependent processes such as perfusion and cellular metabolism, reduces PET signal-to-noise ratio (SNR) and limits quantitative analysis. In this work, we propose an uncertainty-aware deep learning framework to improve the estimation of washout parameters in post-proton therapy PET, not only enabling accurate correction for washout effects, but also mapping intratumoral heterogeneity as a surrogate marker of tumor status and treatment response. We trained the models on Monte Carlo-simulated data from eight head-and-neck cancer patients, and tested them on four additional head-and-neck and one liver patient. Each patient was represented by 75 digital twins with distinct tumoral washout dynamics and imaged 15 minutes after treatment, when slow washout components dominate. We also introduced "washed-out" maps, quantifying the contribution of medium and fast washout components to the loss in activity between the end of treatment and the start of PET imaging. Trained models significantly improved resolution and accuracy, reducing average absolute errors by 60% and 28% for washout rate and washed-out maps, respectively. For intratumoral regions as small as 5 mL, errors predominantly fell below thresholds for differentiating vascular status, and the models generalized across anatomical areas and acquisition delays. This study shows the potential of deep learning in post-proton therapy PET to non-invasively map washout kinetics and reveal intratumoral heterogeneity, supporting dose verification, tumor characterization, and treatment personalization. The framework is currently being validated using phantom experiments at Clínica Universidad de Navarra, Spain, and clinical data at Massachusetts General Hospital, USA. The implementation code is available at https://github.com/pcabrales/ppw.
The central challenge in radiotherapy (RT) is to deliver a sufficiently high dose to achieve tumour control while sparing healthy tissues. FLASH RT, which delivers radiation at ultra-high dose rates (≥40 Gy/s) compared with conventional RT (≈0.05 Gy/s), has emerged as a promising approach. Preclinical studies have shown that FLASH reduces toxicity in normal tissues while preserving or even improving tumour control. It also shortens treatment times, reducing the impact of patient and organ motion. However, the clinical translation of FLASH RT requires new dosimetry solutions, since conventional detectors saturate, lose linearity, or degrade rapidly under ultra-high dose rate conditions.
Silicon carbide (SiC) is a promising semiconductor material to address these needs. Compared to silicon, SiC has a wide bandgap that reduces leakage current and noise, a higher displacement energy threshold that increases radiation hardness, and lower signal yield per unit dose, which prevents saturation at very high instantaneous dose rates. Nowadays, SiC technology is mature, with reproducible wafer-scale fabrication.
At IMB-CNM (CSIC), 4H-SiC PiN diodes have been designed and fabricated specifically for FLASH RT applications. Their performance has been validated in different facilities and radiation conditions. At PTB (Germany), the devices showed linearity up to 11 Gy per pulse (≈4 MGy/s) with 20 MeV electron beams and a performance comparable to PTW’s flashDiamond. At CMAM (Spain), the diodes showed reproducible, linear response to 7 MeV protons up to 26 Gy per pulse. In addition, radiation hardness experiments at CNA (Spain) demonstrated that, after an initial sensitivity loss of ~1.3%/kGy, stability was reached near 1 MGy of 2 MeV protons, with linear response preserved up to cumulative doses of at least 4 MGy. All measurements were performed without external bias, like conventional silicon diodes are used in clinical settings, meaning no adaptation of existing workflows would be required.
In parallel, pixelated SiC arrays have been produced for spatially resolved dosimetry. A 12-pixel array was fabricated and tested with 7 MeV electrons at the Institut Curie (France). The array produced accurate 2D dose maps at 10 Gy per pulse, demonstrating the feasibility of SiC arrays for real-time QA under FLASH conditions. Efforts are currently underway to scale up the pixellated system to a larger array of 400 channels with a custom readout electronics for broader clinical and preclinical applications.
Recientemente, se han reportado algunas toxicidades en la terapia con protones [1–2]. Esto podría deberse a que los protones generan una mayor transferencia lineal de energía (LET) al final de su rango, lo que puede generar daños colaterales, como efectos agudos y tardíos. Por esto, evaluar las distribuciones de LET podría ayudar a mejorar los resultados de la terapia.
En este contexto, el Centro Nacional de Microelectrónica (IMB-CNM) ha diseñado y fabricado nuevos detectores de silicio 3D [3], basados en una novedosa arquitectura de electrodos cilíndricos con tamaños microscópicos comparables a los de las células (15-25 μm). Esto permite cuantificar el LET a escala micrométrica, es decir, la energía lineal. El sistema desarrollado es el primer conjunto de estos microdetectores 3D, con una matriz de 3 × 3 celdas unitarias y un espaciamiento de 200 μm entre ellas, cubriendo un área total sensible a la radiación de 0.4 mm × 12 cm, con una resolución espacial de 600 μm [4].
Se realizaron pruebas de microdosimetría con esta matriz de sensores en el Danish Center for Particle Therapy (DCPT). Los experimentos se llevaron a cabo en diferentes configuraciones: desde una condición relativamente monoenergética –la meseta de entrada–, pasando por la parte media del SOBP, hasta el borde distal del SOBP –al 75% y 95% de la dosis–. Para obtener estas posiciones en los espectros, se utilizaron fantomas de agua sólida. Asimismo, se empleó un fantoma antropomórfico con un campo clínico específico (Figura 1). Además, se realizaron simulaciones Montecarlo (MC) basadas en TOPAS [5] para su comparación con los resultados experimentales.
Se registraron espectros de energía de microdosimetría en cada caso (Figura 2), y los valores experimentales promedio de energía lineal por dosis (¯yD) en los detectores de silicio se compararon con los valores de LETd simulados para el paciente mediante el software RayStation, así como con los valores de las simulaciones (Figura 3).
Estos resultados demuestran, por primera vez, la viabilidad de cuantificar mapas de energía lineal de microdosimetría en condiciones clínicas. Esta matriz de sensores puede ser una herramienta poderosa para verificar los valores de LETd simulados por RaySearch.
Introduction: Pencil beam scanning (PBS) is one of the main delivery techniques in proton therapy (PT). A narrow proton beam irradiates the tumor layer by layer, delivering dose to specific locations (spots) within each layer. However, PBS is highly sensitive to uncertainties, making the treatment of moving targets in PT especially challenging due to respiratory motion. The interplay effect, caused by the relative motion between the tumor and the scanning beam, can degrade the delivered dose and reduce treatment effectiveness. The main objective of this study is to accurately determine the dose received by moving tumors by quantifying the dosimetric impact of the interplay effect.
Material and Methods: A planning computed tomography (pCT), in which the treatment dose is planned, and a 4D-CT, consisting of eight CT images corresponding to different respiratory phases, were used to evaluate tumor motion. A stochastic model based on the compact HITACHI synchrotron was employed to predict the proton beam temporal structure. After determining the delivery time of each spot in the treatment plan, we can assign spots to each of the eight respiratory phases depending on the phase in which irradiation begins, and the patient’s respiratory frequency. The frequency was varied between 5, 12 and 20 breaths per minute (bpm), and the initial respiratory phase was randomized for each treatment session/fraction across 100 simulations per frequency. The treatment plan dose was computed for each phase according to the spot distribution and summed on the pCT.
Results: Variability in delivery times and frequency influences layer deposition within the tumor (Figure 1), resulting in regions receiving higher doses (layers overlap, in red) or lower doses (layers are separated, in blue). Multiple (30) treatment sessions help mitigate the dosimetric impact of different starting respiratory phases (Figure 2). Higher frequencies reduce the interplay effect, especially when fewer (3) sessions are used, with standard deviations (SD) over 100 simulations in the tumor of ±0.43 Gy (5 bpm), ±0.20 Gy (12 bpm), and ±0.13 Gy (20 bpm).
Conclusion: Interplay between motion and dynamic beam delivery in PBS-PT degrades the dose distribution and can compromise the absorption of the prescribed dose in the tumor. Understanding the beam’s temporal structure, which depends on the proton accelerator, and considering tumor motion, frequency, and number of treatment fractions, are critical for accurately determining the dose delivered to each tumor.
Introducción. La hipoxia es una condición tumoral que dificulta la eficacia de la radioterapia y exige modelos in vitro controlables y reproducibles. Presentamos una plataforma experimental compuesta por dos cámaras hipóxicas diseñadas y construidas in-house (una portátil y una de gran volumen con guantes) y un modelo 1D de difusión de oxígeno para planificar y validar exposiciones hipóxicas en ensayos biológicos.
Métodos. La cámara portátil permite transporte y sellado rápido y, además, posibilita irradiar las muestras en su interior, asegurando un entorno hipóxico; la cámara de guantes posibilita manipulación interna de las muestras sin reoxigenación. El O₂ se monitoriza con un sensor óptico PicoO₂ y con un LuminOx integrado a Arduino/BT para registro continuo. Se ha implementado un modelo explícito de difusión (Fick 1D) con condición superficial dependiente del tiempo, que distingue una fase de purga y una de reposo. Este código de difusión se utiliza para determinar cuánto deben permanecer las muestras dentro de la cámara (en función de la altura del medio) hasta alcanzar el nivel de O₂ objetivo. Se ha llevado a cabo un análisis de sensibilidad de los parámetros del modelo (constante de difusión, altura del medio y discretización espacio-temporal). Para validación biológica se emplearon células de cáncer de mama humano MDA-MB-231, que fueron irradiadas con fotones (¹³⁷Cs) con dosis entre 2.5–12.5 Gy en condiciones de normoxia (21%O₂) e hipoxia (4%O₂) y analizadas en un ensayo clonogénico.
Resultados. La cámara portátil permite alcanzar un nivel de hipoxia del 4% O₂ en aproximadamente 60 s y mantiene la estabilidad por más de 3h; la cámara de guantes permite alcanzar 4%O₂ en 1 h 41 min y asegura una estabilidad hasta 8h sin volver a gasearla. El modelo de difusión 1D reprodujo los tiempos de establecimiento de hipoxia con desviaciones menores al 5% frente a mediciones directas en el medio (PicoO₂). En el clonogénico, las células hipoxicas mostraron mayor supervivencia y morfología más alargada en comparación con las en normoxia. Se estimó un Oxygen Enhancement Ratio (OER) ≈1.7 y no se observaron diferencias significativas entre las curvas de supervivencia realizadas en la cámara portátil y en la cámara con guantes
Conclusiones. El sistema de cámara dual, junto con el modelo 1D, permite generar y sostener hipoxia fisiológica. El modelo cuantifica los tiempos de exposición en función de la altura del medio, con concordancia <5% frente a medidas directas, lo que facilita una planificación reproducible de ensayos. El sistema es robusto y escalable para estudios de radioresistencia y evaluación de radiosensibilizadores.
Objetivo
La imagen médica en radioterapia mejora la optimización de los tratamientos mediante adaptación off y on-line. La radioterapia guiada por resonancia magnética (MRgRT) supone una revolución, permitiendo seguir el tumor en tiempo real. Aun así, los sistemas actuales no permiten cuantificar la dosis recibida en el tumor debido a sus movimientos.
El objetivo es usar imágenes de un equipo de MRgRT para el seguimiento del tumor y, mediante un proceso de re-cálculo de la dosis en nuevas geometrías deformadas y su acumulación posterior, estimar la dosis recibida. Esta dosis se compara con una dosimetría en un equipo convencional.
Material/Métodos
El equipo empleado (Elekta Unity) combina LINAC y Resonancia Magnética (RM). Mediante el algoritmo Comprehensive Motion Management (CMM) toma imágenes RM 2D en tiempo real (6fps) y rastrea la posición tumoral. El CMM pausa el haz si el tumor sobresale de unos márgenes establecidos (3mm en cada dirección en el caso analizado). Las posiciones se almacenan en un fichero analizable. Estos datos los separamos en dos secuencias: completa (movimiento completo del tumor) y restringida (dentro de márgenes).
Con el planificador RayStation se generaron RM sintéticas simulando el movimiento del tumor, deformándolo en la RM diaria con Registro Deformable (ANACONDA) a las posiciones obtenidas. Se calculó la matriz de dosis en cada RM con el planificador MONACO. Finalmente, se acumuló la dosis recibida en cada fracción en RayStation ponderando cada RM según el tiempo que el tumor estuvo en esa posición. Así, calculamos la dosis recibida en el caso restringido (MRgRT). Esta dosis se compara con la recibida en un LINAC convencional, sin adaptación ni guiado (movimiento completo).
Con este método se analizó un sarcoma cardiaco de 68cc en el pre-tratamiento. Se realizó una secuencia T2 para la delimitación, planificando una dosimetría de 35Gy en 5 fracciones que se adaptó diariamente a los cambios anatómicos.
Resultados
La figura 1(a) muestra las posiciones del centroide en la serie completa en una matriz de vóxeles de 1.5mm de lado del primer día de tratamiento, y la 1(b) la serie restringida (margen de 3mm). El haz estuvo activo un 69% del tiempo de irradiación.
Las dosis obtenidas en el caso MRgRT, figura 2(a), y el convencional, figura 2(b), difieren en la zona posterior del tumor y próxima al esófago.
Si comparamos histogramas (figura 3) del caso MRgRT (línea continua) y del convencional (línea discontinua), se observa que en el segundo la dosis en GTV sería un 16% inferior.
Conclusión
Proponemos un método para estimar la dosis recibida en una fracción con los movimientos registrados en un equipo de MRgRT. Lo hemos aplicado a un sarcoma cardíaco, analizando la diferencia entre dosis planificada y depositada.
Esta herramienta evidencia que en patologías sólo visibles en RM y afectadas por movimiento interno de órganos se experimenta una degradación dosimétrica si no se aplican estrategias de adaptación y guiado por imagen.
Introducción: La dosimetría sanguínea en radioterapia de protones o fotones representa un desafío significativo debido al comportamiento dinámico de la sangre como órgano a riesgo. Cuantificar con precisión la dosis recibida por la sangre circulante de un paciente específico es esencial para poder minimizar efectos adversos en los pacientes. Por ello, presentamos FLIP-HEDOS, un modelo innovador que integra el método FLIP (FLow and Irradiation Personalized) con la herramienta computacional HEDOS (HEmatological DOSe).
Material y métodos: La metodología FLIP cuantifica la dosis que recibe la sangre circulante de un paciente específico haciendo uso de la segmentación obtenida de sus grandes vasos y el correspondiente campo de velocidad de la sangre medido a partir de la RM de contraste de fase. Por el contrario, HEDOS es un modelo compartimental estándar y estocástico que simula la distribución espacio-temporal de las partículas de sangre, blood particles (BPs), en los órganos de todo el cuerpo. Así, FLIP se integra como un módulo arterial y venoso específico del paciente que considera la localización del tumor, el caudal de los vasos y el volumen vascular para mantener el sistema en equilibrio. Asumiendo un volumen total sanguíneo de 5.3 L, se discretiza en BPs de 1 mm³. Las BPs simuladas viajan por los módulos de FLIP con un enfoque Lagrangiano a lo largo de trayectorias de flujo definidas por el campo de velocidad, pero se mueven estocásticamente a través de los compartimentos de HEDOS basándose en distribuciones temporales de tránsito predeterminadas. La simulación de la distribución espaciotemporal de las BPs nos permitió acumular la dosis en sangre, haciendo uso del conjunto de distribuciones 3D de dosis y de los tiempos de irradiación de los haces. La cohorte de pacientes presenta tumores en regiones de tórax-abdomen y cabeza-cuello.
Resultados: FLIP-HEDOS cuantifica la dosis recibida por cada BP (Figura 1) y verifica el número de veces que una BP ha (re)visitado la vasculatura específica del paciente (Tabla 1).
Discusión: Los resultados indican que, con independencia de la modalidad de radioterapia, si el tumor está cerca de grandes vasos (tumor de páncreas e hígado, Figura 1), un mayor volumen de sangre recibirá dosis superiores a un umbral de 0.1 Gy, lo que puede causar daños en los linfocitos. Además, se observó que el número de veces que una BP visita el módulo FLIP aumenta con el tiempo total de tratamiento.
Conclusiones: FLIP-HEDOS puede ser crucial en escenarios clínicos en los que los tumores están cerca de la vasculatura, el volumen de los vasos circundantes es comparable al volumen del tumor y el tiempo total de irradiación es extenso. Este modelo podría permitir dosimetrías más precisas y personalizadas.
Targeted radionuclide therapy (TRT) with alpha-emitters is rapidly gaining importance in oncology due to the high linear energy transfer and short range of alpha particles, enabling effective tumour control while sparing healthy tissue. However, accurate dosimetry remains a major challenge, as conventional nuclear medicine imaging is not optimized to determine radionuclide distributions from high-energy photons commonly associated with alpha decay. In theranostics, $^{212}$Pb has seen increasing therapeutic use due to its favourable chemistry, half-life, and decay properties, but dosimetry relies on $^{203}$Pb as an imaging surrogate, providing an indirect and limited estimate of the true $^{212}$Pb biodistribution. This work investigates the feasibility of Compton camera imaging for TRT verification with improved accuracy.
The IRIS group has developed imaging and dosimetry methods for radiotherapy applications using the MACACO III+ Compton camera, which is well-suited for high-energy photons. A model of the camera has been implemented in GATE 10, enabling efficient simulations with recent GATE features. To support correlation of detected photons and absorbed dose, dose point kernels for the $^{212}$Pb decay chain were calculated with 1E6 primaries in a 13.38$\,$mm water sphere, equal to 1.2$\times$ the CSDA range of the maximum-energy $\beta^-$ emission. The therapeutic range $X_{90}$ was defined as the radius containing 90% of energy deposited, and emission profiles were benchmarked with NuDat 3.0.
Following $^{212}$Pb disintegration, decays of $^{212}$Bi and $^{212}$Po contributed ~95% of the total energy deposited. The full decay chain deposited 8.9$\,$MeV/decay on average with a therapeutic range of $X_{90}\,$=$\,$0.091$\,$mm. Individual contributions from $^{212}$Pb, $^{212}$Bi, $^{212}$Po, and $^{208}$Tl yielded $X_{90}$ values of 0.41$\,$mm, 1.8$\,$mm, 0.086$\,$mm, and 5.8$\,$mm, respectively, highlighting that dose is dominated by $^{212}$Po decay and accurate reconstruction of radionuclide distributions requires high-resolution imaging. Furthermore, discriminating the 727$\,$keV photons (6.7% intensity) in the $^{212}$Bi to $^{212}$Po branch from abundant $^{208}$Tl photons can help distinguish $\alpha$ and $\beta^-$ decay pathways, supporting precision dosimetry. Photon intensity histograms (photons/decay) showed excellent agreement with NuDat 3.0 and single-source GATE simulations. However, initializing multiple sources to establish transient equilibrium uncovered a GATE timing issue that condensed emissions into the acquisition window, inflating apparent count rates and potentially biasing activity and dose estimates.
Future work will address the GATE timing issue and establish correlations between Compton camera images and absorbed dose. Once validated, the recent Photon from Ion Decay (PHID) source will be used to efficiently simulate photon emission without tracking charged particles. This approach is expected to accelerate Compton camera studies and support robust dosimetry in TRT with alpha-emitters, ultimately contributing to more precise and clinically viable treatment verification.
The development of novel medical imaging techniques such as PET (Positron Emission Tomography) and SPECT (Single-Photon Emission Computed Tomography) has increased the demand for nuclear radioisotopes in medical diagnostics. Currently, the production of radioisotopes for medical imaging and treatment is primarily carried out using conventional accelerators (cyclotrons) and dedicated nuclear reactors. In the case of positron emitters used in PET imaging, the current approach involves producing positron radiotracers at large facilities that are responsible for supplying radioisotopes on a regional or national scale. Due to the cost of production centres, accelerators, radio-pharmacies and, in particular, radiation shielding, the economic viability of these centres depends on mass-producing single doses for distribution to as many hospitals and research centres as possible. As a result of this regional scope, commercial production of PET radioisotopes is mainly limited to 18F, which has a half-life of around 110 minutes and can therefore endure the time required for production, post-processing and distribution. Consequently, the production of a limited number of doses of shorter-lived radioisotopes, such as 11C (with a half-life of ~20 min), 13N (with a half-life of ~10 min) and 15O (with a half-life of ~2 min), is generally beyond the capabilities of these facilities.
Over the last few decades, the use of ultra-short, ultra-intense lasers for radioisotope production has been proposed as a cost-efficient alternative for the on-demand production of single doses of short-lived radioisotopes. Through the target normal sheath acceleration (TNSA) mechanism, ultra-intense laser pulses (I > 10¹⁸ W/cm²) impinging on a micrometre-thick target can result in the acceleration of ion beams to energies of several tens of MeV. The nature and properties of this laser-induced acceleration process overcome the main constraint of conventional production facilities. As the laser-target interaction occurs over a micrometre-scale distance, the shielding requirements are much lower than for nuclear reactors or accelerators. Thus, laser systems of this class become significantly more affordable for hospitals, clinics and research centres. These facilities could then produce radioisotopes on demand and explore shorter-lived emitters that are not currently produced.
In this talk, we will present our key accomplishments in this area. In particular, we will demonstrate our ability to produce 11C using the 11B(p,n)11C reaction with activation levels exceeding 4 MBq in a recent experiment conducted at CLPU in Salamanca.