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CT scanner
Abstracts/Physica Medica 32 (2016) e97–e115
Conclusion: For some isotopes the knowledge of the calibrator behavior with different geometry is essential to evaluate accurately the activity value. With 123I the measure is significantly affected by composition and thickness of container; with 90Y the volume correction is essential. http://dx.doi.org/10.1016/j.ejmp.2016.01.341
C.336 PERFORMANCE CHARACTERISTICS OF BIOGRAPH MCT TOF-PET/CT SCANNER I. Bonetti *,a, G. Sceni b, E. Cefalì b, S. Morano c, V. Scaffidi c, M. Guerrisi d. a Section of Medical Physics, School of Medical Physics – University of Rome Tor Vergata – Faculty of Medicine, Roma, Italy; b Department of Medica Physics, A.O. Bianche Melacrino Morelli, Reggio Calabria, Italy; c Department of Nuclear Medicine, A.O. Bianche Melacrino Morelli, Reggio Calabria, Italy; d Section of Medical Physics, Department of Biomedicine and Prevention, University of Rome Tor Vergata-Faculty of Medicine, Roma, Italy Introduction: The aim of this work is to characterize the physical properties of the Biograph mCT – TOF PET/CT scanner recently installed at Nuclear Medicine Department in Ospedali Riuniti Reggio Calabria. Materials and Methods: The Biograph mCT scanner combines a 64-slice CT scanner (Siemens Somatom Definition AS) with an LSO PET scanner which incorporates Time of Flight (TOF) reconstruction and has TrueV Option. The PET component is configured with 32,448 LSO crystals arranged in 4 rings of 48 detector blocks in a matrix 13 × 13 of 4 mm × 4 mm × 20 mm. This configuration covers an axial field-of-view (FOV) of 21.8 cm corresponding to 109 image planes with a slice thickness of 2 mm. Performance characteristics of PET component have been evaluated according to NEMA NU-2 2007 standards by means of Siemens NEMA kit (NEMA PET SelfTest-mCT) provided with the scanner. Results: Preliminary data analysis confirms that the values of measured major machine parameters (sensitivity, spatial resolution stability, count rate performance, scatter fraction, image quality) are in agreement with manufacturer specification. Conclusions: In this work we have assessed the performance characteristics of Biograph mCT PET/CT scanner according to NEMA NU-2 2007 standard test. Preliminary results confirm the good performance of the system in agreement with recent publications on similar devices. http://dx.doi.org/10.1016/j.ejmp.2016.01.342
C.337 AUTOMATIC GTV CONTOURING APPLYING ANOMALY DETECTION ALGORITHM ON DYNAMIC FDG PET IMAGES C. Bracco *,a, F. Verdoja b, M. Grangetto b, A. Di Dia a, M. Racca c, T. Varetto c, M. Stasi a. a Medical Physics Department, Candiolo Cancer Institute – FPO- IRCCS, Candiolo, Italy; b Computer Science Department, University of Turin, Turin, Italy; c Nuclear Medicine Department, Candiolo Cancer Institute – FPO- IRCCS, Candiolo, Italy Introduction: The aim of this work is to show the results of GTV automatic segmentation based on dynamic PET acquisition. With respect to single voxel segmentation the temporal information is used to improve quality of GTV delineation. The segmentation algorithm proposed exploits the theoretic assumption that FDG uptake over time in cancer cells is very different from the one in normal tissues and therefore in this study anomaly detection is used to look for tumor peculiar-anomalous TACs. Material and Methods: For each patient two list mode datasets of images were acquired. The first one scan (basal) was acquired one hour after FDG injection and reconstructed as static frame. The last one (delayed) was acquired half one hour after the first scan and reconstructed as dynamic scan. Two delayed scans were registered to the basal scan. A modified version of the RX Detector was used. RX Detector usually works in RGB, but in this study its use on TACs has been explored passing the three grayscale images in place of the three channels of RGB. The resulting single image, which actually is a matrix of Mahalanobis distances, presents values that are very
e99
high for voxels whose TAC has anomalous temporal behavior. Finally, threshold segmentation is performed on the distance matrix. On a dataset of 10 patients segmentation techniques present in the literature working on single PET scan have been implemented as well as segmentation techniques based on RX Detector output. Results: Spatial overlap index (SOI) was used as metric to evaluate the segmentation accuracy. All of the segmentation algorithms implemented on RXD output show better SOI (0.507 ± 0.158) than algorithm based on SUV, i.e. Brambilla, SOI 0.278 ± 0.236. A manual contour drawn by experienced Nuclear Physician was the reference. Conclusion: Although a small dataset, the segmentation of dynamic PET images based on RXD output seems to be promising. http://dx.doi.org/10.1016/j.ejmp.2016.01.343
C.338 BREATHING MOTION CORRECTION IN DOSIMETRY OF LIVER LESION BASED ON 90Y-PET/CT IMAGING G. Iaccarino, A. Cacciatore *, S. Ungania, M. Cazzato, M. D’Andrea, L. Strigari. Istituto Nazionale Tumori Regina Elena, Roma, Italy Introduction: A degrading factor in quantitative PET imaging is internal organ motion due to respiration which is a primary cause of image blurring. The aim of this work was to investigate a method to correct PET images for breathing artifacts in order to improve the dosimetry of liver radioembolization with 90Y microspheres. Materials and Method: PET/CT images were acquired in list mode modality (LM) with an acquisition time of 30 minutes due to the low branching ratio of 90Y. The breath curve was constantly monitored by an external monitor system. The respiratory signal was generated from a small load cell placed in an elastic belt which was fastened just below the diaphragm on the patient’s abdomen. The trigger signal sent by the device to the PET was used to perform the synchronization of the LM and the respiratory curve. Using a Matlab script, the LM file was split into sub-files, each corresponding to a different breath amplitude. Images corresponding to each breath amplitude were reconstructed correcting for scatter, attenuation and system resolution. All images were finally co-registered to the end-exhale position at which the CT scan was acquired. Dose distribution was then calculated by convolving the activity distribution with a Monte Carlo 90Y-kernel. Different volumes of interest were contoured by gradient and threshold methods and dose volume histograms were calculated with and without breathing correction. Results: Depending on lesion size and breathing amplitude, the correction incremented both mean and maximum doses. In the most dramatic case a patient with an amplitude of about 3.2 cm and a lesion size of 2.7 cm showed a difference of about 50% in mean dose estimation. Conclusion: Our study shows that taking into account organ motion is mandatory for an accurate dose evaluation. In particular absence of breathing correction always causes dose underestimation. The magnitude of correction strongly depends on lesion size and respiratory amplitude. http://dx.doi.org/10.1016/j.ejmp.2016.01.344
C.339 THE IMPACT OF EANM (2013) FORMALISM FOR RADIOIODINE DOSIMETRY IN HYPERTHYROIDISM DISEASE: A COMPARATIVE EVALUATION OF THERAPEUTIC ACTIVITY M. Cacciatori *,a, G. Frigerio a, M. Duchini a, A. Bresolin b, A. Ostinelli a. a Department of Medical Physics, Sant’Anna Hospital, Como, Italy; b Physics Department, University of Milan, Milano, Italy Introduction: The treatment of choice in most of hyperthyroidism cases is the radioiodine therapy. An accurate assessment of the pathological volume and an individual dosimetry procedure implementation prior to therapy are mandatory by Council Directive 97/43/Euratom. The aim of this study is to assess the differences arising in the 131I therapeutic activity depending on whether the SIE-AIMN-AIFM (2005) or EANM (2013) formalism is used.
Conclusion: For some isotopes the knowledge of the calibrator behavior with different geometry is essential to evaluate accurately the activity value. With 123I the measure is significantly affected by composition and thickness of container; with 90Y the volume correction is essential. http://dx.doi.org/10.1016/j.ejmp.2016.01.341
C.336 PERFORMANCE CHARACTERISTICS OF BIOGRAPH MCT TOF-PET/CT SCANNER I. Bonetti *,a, G. Sceni b, E. Cefalì b, S. Morano c, V. Scaffidi c, M. Guerrisi d. a Section of Medical Physics, School of Medical Physics – University of Rome Tor Vergata – Faculty of Medicine, Roma, Italy; b Department of Medica Physics, A.O. Bianche Melacrino Morelli, Reggio Calabria, Italy; c Department of Nuclear Medicine, A.O. Bianche Melacrino Morelli, Reggio Calabria, Italy; d Section of Medical Physics, Department of Biomedicine and Prevention, University of Rome Tor Vergata-Faculty of Medicine, Roma, Italy Introduction: The aim of this work is to characterize the physical properties of the Biograph mCT – TOF PET/CT scanner recently installed at Nuclear Medicine Department in Ospedali Riuniti Reggio Calabria. Materials and Methods: The Biograph mCT scanner combines a 64-slice CT scanner (Siemens Somatom Definition AS) with an LSO PET scanner which incorporates Time of Flight (TOF) reconstruction and has TrueV Option. The PET component is configured with 32,448 LSO crystals arranged in 4 rings of 48 detector blocks in a matrix 13 × 13 of 4 mm × 4 mm × 20 mm. This configuration covers an axial field-of-view (FOV) of 21.8 cm corresponding to 109 image planes with a slice thickness of 2 mm. Performance characteristics of PET component have been evaluated according to NEMA NU-2 2007 standards by means of Siemens NEMA kit (NEMA PET SelfTest-mCT) provided with the scanner. Results: Preliminary data analysis confirms that the values of measured major machine parameters (sensitivity, spatial resolution stability, count rate performance, scatter fraction, image quality) are in agreement with manufacturer specification. Conclusions: In this work we have assessed the performance characteristics of Biograph mCT PET/CT scanner according to NEMA NU-2 2007 standard test. Preliminary results confirm the good performance of the system in agreement with recent publications on similar devices. http://dx.doi.org/10.1016/j.ejmp.2016.01.342
C.337 AUTOMATIC GTV CONTOURING APPLYING ANOMALY DETECTION ALGORITHM ON DYNAMIC FDG PET IMAGES C. Bracco *,a, F. Verdoja b, M. Grangetto b, A. Di Dia a, M. Racca c, T. Varetto c, M. Stasi a. a Medical Physics Department, Candiolo Cancer Institute – FPO- IRCCS, Candiolo, Italy; b Computer Science Department, University of Turin, Turin, Italy; c Nuclear Medicine Department, Candiolo Cancer Institute – FPO- IRCCS, Candiolo, Italy Introduction: The aim of this work is to show the results of GTV automatic segmentation based on dynamic PET acquisition. With respect to single voxel segmentation the temporal information is used to improve quality of GTV delineation. The segmentation algorithm proposed exploits the theoretic assumption that FDG uptake over time in cancer cells is very different from the one in normal tissues and therefore in this study anomaly detection is used to look for tumor peculiar-anomalous TACs. Material and Methods: For each patient two list mode datasets of images were acquired. The first one scan (basal) was acquired one hour after FDG injection and reconstructed as static frame. The last one (delayed) was acquired half one hour after the first scan and reconstructed as dynamic scan. Two delayed scans were registered to the basal scan. A modified version of the RX Detector was used. RX Detector usually works in RGB, but in this study its use on TACs has been explored passing the three grayscale images in place of the three channels of RGB. The resulting single image, which actually is a matrix of Mahalanobis distances, presents values that are very
e99
high for voxels whose TAC has anomalous temporal behavior. Finally, threshold segmentation is performed on the distance matrix. On a dataset of 10 patients segmentation techniques present in the literature working on single PET scan have been implemented as well as segmentation techniques based on RX Detector output. Results: Spatial overlap index (SOI) was used as metric to evaluate the segmentation accuracy. All of the segmentation algorithms implemented on RXD output show better SOI (0.507 ± 0.158) than algorithm based on SUV, i.e. Brambilla, SOI 0.278 ± 0.236. A manual contour drawn by experienced Nuclear Physician was the reference. Conclusion: Although a small dataset, the segmentation of dynamic PET images based on RXD output seems to be promising. http://dx.doi.org/10.1016/j.ejmp.2016.01.343
C.338 BREATHING MOTION CORRECTION IN DOSIMETRY OF LIVER LESION BASED ON 90Y-PET/CT IMAGING G. Iaccarino, A. Cacciatore *, S. Ungania, M. Cazzato, M. D’Andrea, L. Strigari. Istituto Nazionale Tumori Regina Elena, Roma, Italy Introduction: A degrading factor in quantitative PET imaging is internal organ motion due to respiration which is a primary cause of image blurring. The aim of this work was to investigate a method to correct PET images for breathing artifacts in order to improve the dosimetry of liver radioembolization with 90Y microspheres. Materials and Method: PET/CT images were acquired in list mode modality (LM) with an acquisition time of 30 minutes due to the low branching ratio of 90Y. The breath curve was constantly monitored by an external monitor system. The respiratory signal was generated from a small load cell placed in an elastic belt which was fastened just below the diaphragm on the patient’s abdomen. The trigger signal sent by the device to the PET was used to perform the synchronization of the LM and the respiratory curve. Using a Matlab script, the LM file was split into sub-files, each corresponding to a different breath amplitude. Images corresponding to each breath amplitude were reconstructed correcting for scatter, attenuation and system resolution. All images were finally co-registered to the end-exhale position at which the CT scan was acquired. Dose distribution was then calculated by convolving the activity distribution with a Monte Carlo 90Y-kernel. Different volumes of interest were contoured by gradient and threshold methods and dose volume histograms were calculated with and without breathing correction. Results: Depending on lesion size and breathing amplitude, the correction incremented both mean and maximum doses. In the most dramatic case a patient with an amplitude of about 3.2 cm and a lesion size of 2.7 cm showed a difference of about 50% in mean dose estimation. Conclusion: Our study shows that taking into account organ motion is mandatory for an accurate dose evaluation. In particular absence of breathing correction always causes dose underestimation. The magnitude of correction strongly depends on lesion size and respiratory amplitude. http://dx.doi.org/10.1016/j.ejmp.2016.01.344
C.339 THE IMPACT OF EANM (2013) FORMALISM FOR RADIOIODINE DOSIMETRY IN HYPERTHYROIDISM DISEASE: A COMPARATIVE EVALUATION OF THERAPEUTIC ACTIVITY M. Cacciatori *,a, G. Frigerio a, M. Duchini a, A. Bresolin b, A. Ostinelli a. a Department of Medical Physics, Sant’Anna Hospital, Como, Italy; b Physics Department, University of Milan, Milano, Italy Introduction: The treatment of choice in most of hyperthyroidism cases is the radioiodine therapy. An accurate assessment of the pathological volume and an individual dosimetry procedure implementation prior to therapy are mandatory by Council Directive 97/43/Euratom. The aim of this study is to assess the differences arising in the 131I therapeutic activity depending on whether the SIE-AIMN-AIFM (2005) or EANM (2013) formalism is used.