ESTRO 36 Abstract Book

S911 ESTRO 36 2017 _______________________________________________________________________________________________

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). 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-

Conclusion This study indicates that not all PET features are robust in a multicenter setting. Care has to be taken in feature selection and binning method, especially if harmonization of methods across centers is not accomplished. Dissimilarity, homogeneity 1, and inertia seem robust and promising PET features for use in a multicenter setting. Use of fixed bin size should be avoided. EP-1691 Multi-modal voxel-based correlation between DCE-CT/MRI and DWI in metastatic brain cancer C. Coolens 1,2,3 , W. Foltz 1,4 , N. Sinno 1 , C. Wang 1 , B. Driscoll 1 , C. Chung 2,5 1 Princess Margaret Cancer Centre and University Health Network, Radiation Medicine Program, Toronto, Canada 2 University Health Network, TECHNA Institute, Toronto, Canada 3 University of Toronto, Radiation Oncology and IBBME, Toronto, Canada 4 University of Toronto, Radiation Oncology, Toronto, Canada 5 MD Anderson Cancer Center, Radiation Oncology, Houston, USA Purpose or Objective Quantitative model-based measures of dynamic contrast enhanced (DCE) and Diffusion Weighted (DW) MRI parameters have shown variable findings to-date that may reflect variability in the MR acquisition and analysis. This work investigates the use of a voxel-based, multi-modality GPU architecture to include various complimentary solute transport processes into a common framework and 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)