I Jornadas RSEF / IFIMED de Física Médica

Evaluation with experimental phantoms of the effect of motion on the variability of PET texture features.

No programado

Parque Científico. Salon de Actos Edificio de Cabecera (IFIC-Valencia)

Descripción

Recent publications have investigated the value of texture features (TF) with positron emission tomography (PET) for prognosis and monitoring of therapy response in different cancer sites. A major source of error in PET image quantification of lung cancer tumors is respiratory motion. Although recent studies have investigated the variability of PET-TF, the impact of respiratory motion has not been yet properly studied. The primary aim of this work was to evaluate the current use of PET-TF for heterogeneity characterization in lesions affected by respiratory motion. Twenty-eight heterogeneous lesions were simulated by a mixture of alginate with a solution of 18F-uoro-2-deoxy-D-glucose (FDG). Sixteen respiratory patterns were applied. For TF computation, targets were segmented by a threshold of 40% of the voxel maximum intensity. We studied the variability for TF derived from PET image with (gated, G-) and without (ungated, U-) motion compensation when respiratory patterns were applied to the phantoms. For the analysis of variability, we investigated the linear correlations, the coefficient of variance (CV= mean/SD) and the relative deviation (δ12(%)=100*(TF1-TF2)/TF1). Results obtained in the comparison of TF derived from U-image and from G-image showed that the average of the δGU(%) for 8/8 TF were lower than for the volume, δGU(%)Vol=-20±9 and for 4/8 TF were lower than for the maximum activity concentration (Cmax), δGU(%)Cmax=9±18. Independence of the lesion movement (lineal correlation in 100% of the combined pairs of movements, p<0.05) was obtained for 1/8 TF with U-image (width of the volume-activity histogram, WH) and 4/8 TF with G-image (WH and energy ENG, local-homogeneity LH and entropy ENT, derived from the co-ocurrence matrix). On G-image these 4 TF resulted in CV (WH)=0.21, CV (ENG)=0.10, CV (LH)=0.06 and CV (ENT)=0.05. In conclusion, effect of respiratory motion should be taken into account when heterogeneity of lung cancer lesions is quantified on PET/CT images. ENG, LH, WH and ENT derived from 40% contours on G-image may minimize this effect.