ESTRO 36 Abstract Book

S917 ESTRO 36 _______________________________________________________________________________________________

Z eff presented a 84.0% sensitivity and 81.8% specificity for a threshold of 8.96 in ROC curves.

(50%) patients have distant metastasis, including 7 (23%) non-regional lymph nodes metastasis, 11 (36%) bone metastasis, 1 (3%) visceral organ metastasis. The individual clinical risk factors (PSA >20 ng/ml, or Gleason score of 8–10, or clinical stage T3a) are not significantly associated with distant metastasis (P-value is 0.493, 0.087, 0.109, respectively). In the multivariate forward analysis, imaging characteristics of main tumor side wall invasion by anatomical T2 MRI is the only significant risk factor predicting distant metastasis (odds ratio 42.25, confidence interval 5.1-346.5, P-value <0.001). The PET regional tumor texture features can further divide patients into with or without distant metastasis by using high intensity long run emphasis value > -0.40 and low intensity run emphasis value <0.26 (Figure 1). The Sensitivity and specificity of the multivariate tree model was 80% and 80%, respectively.

Conclusion DECT imaging gives information on tumour necrosis. Quantitative parameters (ρ I and Z eff ) showed better sensibility and specificity compared to standard HU imaging. Mean Z eff showed better correlation with necrosis status, due to necrotic core absorbs less iodine contrast. Our approach has some advantages. Whole tumour semi- automatic contouring had excellent reproducibility. No cases were excluded due to geometry or mediastinal contact. This method could be a solid approach to assess necrosis condition. However, we have not studied relationship with the actual location of necrosis, so it would not be useful for dose-painting protocols at necrotic core. EP-1681 [C11]Choline PET/MRI for Prostate Cancer: Identify Imaging Characteristics Predicting Metastasis J.R. Tseng 1 , L.Y. Yang 2 , H.Y. Chang 2 , T.C. Yen 1 1 Chang Gung Memorial Hospital at Linkou, Nuclear Medicine and Molecular Imaging Center, Kwei-Shan- Taoyuan City, Taiwan 2 Chang Gung Memorial Hospital at Linkou, Biostatistics Unit- Clinical Trial Center of Chang Gung Memorial Hospital, Kwei-Shan- Taoyuan City, Taiwan Purpose or Objective Intergraded PET/MRI is a powerful imaging modality for prostate cancer (Pca) in several aspects, from cancer detection, primary staging, to staging of recurrent Pca. The goal of primary staging is to detect metastatic spread from the main tumor. In high risk Pca patients (PSA >20 ng/ml, or Gleason score of 8–10, or clinical stage T3a), intergraded PET/MRI imaging may have great potential to change clinical management. In the current study, we aimed to identify imaging characteristics of main tumor which can significantly predict distant metastasis. Material and Methods This prospective clinical study was approved by the Ethics Committee (approval 102-3271A and 103-4561C). Since January 2015 to June 2016, total 30 Pca patients committed high risk criteria were enrolled to conduct whole body integrated [C11]Choline PET/MRI (biograph mMR, Simens). The PET and MRI imaging was interpreted independently by one clinically-experienced nuclear medicine physician and radiologist. In the PET imaging analysis, main tumors were segmented using PMOD 3.3 software package. The borders of volumes of interest were set by manual adjustment to avoid physiological [C11]Choline uptake in the urine or intestine. The tumor boundaries were automatically contoured based on the thresholds of SUV 2.65. The gray-level run length encoding matrix (GLRLM) was used for assessing the regional texture features. In the MRI imaging analysis, anatomic (T2- weighted MRI) and functional (diffusion-weighted MRI) imaging features were documented. Multivariate classification and regression tree analysis was used to determine the best combination of variables and the related cutoffs to predict risk for distant metastasis. Results The mean age is 70.1±6.2 years, and the mean PSA level is 91.6 ± 139.4 ng/ml. In these 30 patients, 26 (87%) are categorized as clinical stage IV, 4 (13%) as stage III. Fifteen

Conclusion By providing excellent anatomical, functional, and metabolic information, integrated PET/MR enhances the staging of metastatic disease in high risk Pca. Imaging characteristics including pelvic side wall invasion and tumor metabolic heterogeneity may have crucial role in patient management. EP-1682 Comparison of SUV based on different ROIs and VOIs definitions: a multi-center 4D phantom study M. Lambrecht 1 , K. Ortega Marin 1 , M. La Fontaine 2 , J.J. Sonke 2 , R. Boellaard 3 , M. Verheij 2 , C.W. Hurkmans 1 1 Catharina Ziekenhuis, Physics/Radiotherapy, Eindhoven, The Netherlands 2 Netherlands cancer institute, Radiotherapy, Amsterdam, The Netherlands 3 University medical center- university of Groningen, Nuclear medicine, Groningen, The Netherlands Purpose or Objective In the context of the EORTC LungTech trial, a QA procedure including a PET/CT credentialing has been developed. This procedure will ultimately allow us to pool data from 23 institutions with the overall goal of investigating the impact of tumour motion on quantification. As no standardised procedure exists under respiratory conditions, we investigated the variability of 14 SUV metrics to assess their robustness over respiratory noise. Material and Methods The customized CIRS-008A phantom was scanned at 13 institutions. This phantom consists of a 18 cm long body, a rod attached to a motion actuator, and a sphere of either 1.5 or 2.5cm diameters. Body, rods and spheres were filled with homogeneous 18FDG solutions representative of activity concentrations in mediastinum, lung and tumour for a 70kg patient. Three respiratory patterns with peak-to-peak amplitudes and periods of 15mm/3sec, 15mm/6sec and 25mm/4sec were tested. Prior to scanning in respiratory condition, a 3D static PET/CT was acquired as reference. During motion, images