Ponente
Descripción
Magnetic Resonance Imaging (MRI) of hard tissues is challenging due to the short lifetime and low strength of their resonance signals, due to strong spin-spin couplings and proton escarcity. Thus, the impact of MRI on some dental applications continues to be minor compared to X-rays techniques [1]. However, the latter employ ionizing radiation and only detect hard tissues.
MRI pulse sequences, such as Zero Echo Time, have demonstrated their potential for dental imaging [2], but they typically rely on extremely expensive hardware. A clinically viable MR-based solution must be competitive also in terms of cost, which imposes the use of weak magnetic fields (B0<0.3T). However, the signal-to-noise ratio of the signal scales as SNR α B07/4, so the quality of low-field reconstructions can be compromised unless every step of the process is exquisitely optimized.
Our group has been pearheading this challengue, reporting the first 3D MRI images of ex vivo tooth samples featuring soft and hard tissues simultaneously at sub-Tesla magnets [3]. This achievement was reached in a home-made, pre-medical MRI scanner (Fig. 1) with Zero Echo Time sequences. We have also reported on caries diagnosis, enamel demineralization or fast tooth thresholding (Fig. 2). Moreover, to accelerate image acquisitions, we have developed, patented and succesfully tested a slice-seletion method with Zero Echo Time [4].
The next step is to translate this proof of concept to a system compatible with clinical life, which poses major physical and engineering challengues. The compromise between system weight and achieving a size large enough for human anatomy means magnetic fields can be strongly inhomogeneous in the región of interest, mandating advanced reconstruction strategies that incorporate spatial knowledge of the magnetic field. Presently, our team has finished building of the first dental, low cost MRI scanner reported until now (Fig. 3). In this work, we present the system and the first images of phantoms and ex vivo dental pieces (Fig. 4), a milestone in the road towards clinical application.
[1] Weiger et al. Short-T2 MRI: Principles and recent advances. Prog Nucl Magn Reson Spectrosc. 2019.
[2] Weiger et al. MRI with Zero Echo Time. In eMagRes. 2012.
[3] Algarín et al. Simultaneous imaging of hard and soft biological tissues in a low-field dental MRI scanner. Sci Rep. 2020.
[4] Borreguero et al. Low field slice-selective ZTE imaging of ultra-short T2 tissues based on spin-locking. Sci Rep. 2023
