S 24 I NSTRUMENTATION/ IMAGE GENERATION/ DATA ANALYSIS Conclusions: Respiratory information can be obtained directly from PET data with a reasonable accuracy, and at only the "cost" of processing time. The processing time itself has been shown to be small. If such an algorithm could be integrated with a PET acquisition system, it could enable one can ac- quire a respiratory characterization of a patient, to be used for reconstructing respiratory gated images, in real time. Such an easy implementation of res- piratory gating in PET may provide a wider availability of gated PET images in research and the clinic. 59 poster EFFECT OF RESPIRATION MOTION ON SUV ASSESSEMENT V. Longari 1 , L. Calabrese 2 , F. Zito 2 , R. Lambertini 2 , R. Leo 2 , M. Rognoni 2 , G. Marotta 2 , P. Gerundini 3 1 FONDAZIONE IRCCS OSPEDALE MAGGIORE POLICLINICO,MANGIAGALLI E REGINA ELENA, Department of Nuclear Medicine PET, Milano, Italy 2 FONDAZIONE IRCCS OSPEDALE MAGGIORE POLICLINICO,MANGIAGALLI E REGINA ELENA, Milano, Italy 3 FONDAZIONE IRCCS OSPEDALE MAGGIORE POLICLINICO,MANGIAGALLI E REGINA ELENA, Department of Nuclear Medicine, Milano, Italy Purpose: Respiratory motion during PET/CT acquisition can cause lesion misregistration and inaccuracies in calculation of standardized uptake values (SUV). Several studies have demonstrated large SUV underestimations of lung lesions on whole body PET/CT (WBPETCT) images with respect to res- piratory gated thoracic PET/CT (RGPETCT) ones. However few studies have considered the interference of elapsed time between WBPETCT and RG- PETCT on SUV assessment. The aim of the present study was to compare the SUVmax measured on lung lesions with and without respiratory gating by considering also the effect of temporal changes due to different up-take time of 18F-FDG. Materials: Fourteen patients with lung lesions were enrolled (9 m, 5 f, mean age 68,6 ± 6,6 y). One hour after i.v. of 18F-FDG administration a WBPETCT scan was acquired for 10-15 min followed by a RGPETCT chest acquisition of 10-15 min. All acquisitions were performed on a Siemens Biograph True V PET_CT system. Always CT preceded PET scan and was acquired under free shallow breathing. Respiratory gated data were acquired in list mode and then reframed by dividing the respiratory cycle into 6 phases (frames) by using the AZ7333V System (Anzai Medical) for synchronism. From the list mode acquisition a single frame (SF) by summing all frames was also derived. In order to investigate the influence of time on SUVmax the data obtained from WBPETCT and RGPETCT (free vs gated breathing images in different time), RGPETCT and SF (free vs gated breathing images in same time), WBPETCT and SF (free breathing images in different time) were compared. The SUVmax on RGPETCT study was assessed by selecting the one out of the 6 frames in which nodule up-take better matched the correspondent CT lesion position. Results: In fourteen patients 28 lung nodules were detected. The mean SUVmax derived from WBPETCT, RGPETCT and SF are reported in the table.The Δ % SUVmax resulted for: -WBPETCT vs RGPETCT = 44,3% (p< 0.001), -RGPETCT vs SF = 31% ( p<0.001)and -SF vs WBPETCT = 11,6% (p<0.005). Conclusions: These findings suggest that the elapsed time between PET scans has to be considered in the determination of SUVmax (about 11% increase can be due to15 min elapsed time). Nevertheless due to the better coupling of TC and PET images the SUVmax of PET/CT with respiratory gating is significantly higher (on average 31% increase) than the one without. 60 poster IMPACT OF THE IMAGE SPATIAL SAMPLING ON TUMOUR DETEC- TION IN 18F-FDG PET R. Maroy 1 , L. Saint Christophe 2 , C. Lartizien 3 , P. Merlet 1 , C. Comtat 1 , R. Trebossen 1 1 COMMISSARIAT À L ’ENERGIE ATOMIQUE, Service Hospitalier Frédéric Joliot, Orsay, France 2 DOSI SOFT S.A, Oncology, Cachan, France 3 CREATIS-LRMN CNRS UMR5220 - INSERM U630, UNIVERSITÉ DE LYON, Lyon, France Purpose: Tumour or metastasis early detection may change the therapy strategy and thus the patient’s outcome. To our knowledge, the impact of images spatial sampling on small tumour detection has not been assessed. The objective of the work is to compare tumour detection performance for im- ages reconstructed either with a 128128 (most often used in oncology) or a 256256 grid in the transaxial plane. Materials: 50 18F-FDG PET acquisitions of torso anthropomorphic phan- toms were simulated using an analytical simulator including realistic noise [Comtat, 1999]. Each phantom contained 8 tumors of 0.5mm radius at ran- dom locations inside three structures. Two datasets of 50 images each were generated and reconstructed using the AWOSEM method with a spatial sam- pling of either 128128 grid of 4.1mm (dataset S128) or 256256 grid of 2.05mm (dataset S256). Detection performance between S128 and S256 was com- pared using an AFROC with 2 sets of 4 observers each. The S128 and S256 areas Az under the ROC curves were compared using a Student’s t-test. Results: The figure shows the ROC curves for the lesion detection on the S128 and S256 datasets. Results obtained using S256 are significantly bet- ter than using S128 for the liver (Az128=0.54<Az256=0.73,p<0.05) and the soft tissue (Az128=0.56<Az256=0.73,p<0.05) and seem better for the lung (Az128=0.76<Az256=0.81,p=0.15). Conclusions: The use of a fine spatial sampling (e.g. a transaxial plane 256256 grid with 2.05mm) significantly improves the lesion detection task performance for small nodules showing a low contrast with the surrounding background. This work suggests a fine spatial sampling should systematically be used in place of most often used 128x128 grid in the transaxial plane in oncology PET. 61 poster INTEGRATION OF 3D MAGNETIC RESONANCE SPECTROSCOPY MAPS INTO TREATMENT PLANNING OF GLIOBLASTOMA S. Ken 1 , X. Franceries 2 , J. A. Lotterie 2 , V. Lubrano 4 , I. Catalaa 5 , H. Metwaly 1 , L. Vieillevigne 1 , I. Berry 2 , P. Celsis 2 , E. Moyal-Cohen-Jonathan 1 , A. Laprie 1 1 I NSTITUT CLAUDIUS REGAUD, Department of Radiotherapy Oncology, Toulouse, France 2 INSERM UMRS 825, Department of Clinical and Functional Neuroimag- ing, Toulouse, France 3 CENTRE HOSPITALIER UNIVERSITAIRE, Department of Nuclear Medicine, Toulouse, France 4 CENTRE HOSPITALIER UNIVERSITAIRE, Department of Stereotactic Neurosurgery, Toulouse, France 5 UNIVERSITE TOULOUSE III PAUL SABATIER, Laboratory of Biophysics and Medical Imaging, Toulouse, France Purpose: To integrate 3D magnetic resonance spectroscopy imaging (MRSI) maps into radiotherapy (RT) treatment planning system (TPS) for integrated boost of glioblastoma intensity modulated radiotherapy (IMRT).