ESTRO 36 Abstract Book

S924 ESTRO 36 _______________________________________________________________________________________________

Material and Methods 118 patients with LACC were retrospectively included. All patients underwent a 18 F-FDG PET-CT scan before treatment. They were classified in 2 groups depending on the PET device used for acquisition (G1: Siemens Biograph installed in 2003, N=79; G2: GE Discovery installed 2011, N=39). Treatment consisted in a concomitant chemoradiation delivering 45 Gy in 25 fractions of 1.8 Gy to the pelvis +/- the para-aortic area followed by a pulse- dose rate image-guided uterovaginal brachytherapy of 15 Gy. The primary tumor was delineated on the PET images using a fixed threshold (40% of SUV max ) within a manually drawn volume of interest (VOI), called VOI-T. A 73 mL sphere was drawn in the healthy liver considered as homogeneous (VOI-L). For each VOI, 5 conventional indices (SUV mean , SUV max , SUV peak in a 1 mL sphere, metabolic volume, tumor lesion glycolysis) and 6 3D textural indices were calculated after resampling the VOI SUV between 0 and 40 using 128 gray levels: Homogeneity and Entropy from the Gray-Level Co-occurrence Matrix, Short-Run Emphasis (SRE), Long- Run Emphasis (LRE), Low Gray-level Zone Emphasis (LGZE) and High Gray-level Zone Emphasis (HGZE). Wilcoxon’s tests were performed between G1 and G2 in VOI-L to determine to what extent technological differences and image properties influence radiomic feature values. A stepwise model selection using the Akaike Information Criterion was applied to determine the best 4-feature signature for local recurrence prediction in both groups, used successively for training and validation. Delong’s tests between AUC were performed to evaluate if the signature was more powerful than SUV max only.

correlate the extra-vascular volume fraction (v e ) and apparent diffusion coefficient (ADC) from DCE-MRI/CT and DWI MRI done at the same time points in patients with brain metastases. Material and Methods A total of 26 tumours in 19 patients were treated under ethics-approved trials with stereotactic radiosurgery (SRS) alone (n=14) or SRS on day 7 of sunitinib (n=12) and underwent multi-parametric imaging at baseline, post drug (if applicable), then 7 and 21 days post- radiosurgery. Each patient received a comparative DCE- MRI scan on the same day as the CT imaging on a Verio 3T System (IMRIS) with Variable Flip Angle (VFA) T1 quantification and 3D-FLASH and Gadolinium injection (Magnevist 20cc); T2-weighted imaging; DWI (echo-planar imaging with TR/TE 7700/110; 3D-diffusion gradient encoding). Volumetric DCE-CT was acquired following a 60cc Visipaque320® injection in an intermittent time sequence up to 3 mins (Toshiba, Aquilion ONE). A temporal dynamic analysis (TDA) method for voxel-based CT perfusion [1] was remodeled to enable using GPU-based optimization on a high throughput cluster to include various complimentary transport processes into a common framework. As DCE-CT is considered a gold standard for tracer-kinetic validation given its signal linearity, we compared extravascular extracellular volume maps from DCE-CT to those from DCE-MRI and ADC values by Pearson correlation on a voxel-by-voxel basis as well as other kinetic parameters using the Modified Tofts model (AUC, K trans , K ep ). Results Voxel-wise Pearson’s analysis showed statistically significant correlations in K trans (P<0.001) between DCE-CT and DCE-MRI over all imaging time points as well as excellent agreement with very little bias (see Figure 1). The correlation between ADC and v e values were strong in the Sunitinib cohort (R=0.6, p<0.01, all days) and peaked at day 3 post SRS (R=0.75, p<0.008). No such statistically significant correlation was seen between ADC and v e in the SRS alone group. Correlation of ADC histogram parameters between imaging days was highly correlated however, again peaking at Day 7 (R=0.85, p<0.001). Conclusion Using a common analysis platform has improved the correlations in pharmaco-kinetic parameters, Ktrans and ve, obtained from CT and MR than previously reported. Consistent with our hypothesis that ADC and ve values would describe a similar physiological effect, the observed correlation between extravascular volume fraction and ADC values was high for the cohort treated with Sunitinib and SRS, but this correlation was not seen for the SRS alone group. [1] Coolens C et al . IJROBP. 2015;91(1):48-57. EP-1692 Multi-device textural analysis on 18F-FDG PET images for predicting cervical cancer recurrence S. Reuzé 1,2,3 , F. Orlhac 3,4 , C. Chargari 1 , C. Nioche 4 , F. Riet 1 , A. Escande 1 , C. Haie-Meder 1 , L. Dercle 5 , I. Buvat 4 , E. Deutsch 1,2,3 , C. Robert 1,2,3 1 Gustave Roussy, Radiotherapy, Villejuif, France 2 Univ. Paris-Sud, Université Paris-Saclay, Le Kremlin- Bicêtre, France 3 INSERM, U1030, Villejuif, France 4 IMIV, CEA- Inserm- CNRS- Univ. Paris-Sud- Université Paris-Saclay- CEA-SHFJ, Orsay, France 5 Gustave Roussy, Nuclear Medicine and Endocrine Oncology, Villejuif, France Purpose or Objective The aim of this study was to evaluate the possibility of gathering images from 2 different PET devices in a radiomic study, and to propose a signature of local recurrence for locally advanced cervical cancer (LACC).