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Impact of attenuation and scatter correction in previsional dosimetry based on SPECT-CT images for radioembolization of liver lesions with 90Y microspheres
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Abstracts/Physica Medica 32 (2016) e97–e115
(3.3 ± 1.3 mSv for CT and 4.5 ± 0.3 mSv for PET contribution) and 7.3 ± 1.5 mSv for women (3.2 ± 1.4 mSv for CT and 4.1 ± 0.2 mSv for PET contribution). The mean Effective Dose was 7.5 ± 1.5 mSv for all patients (3.2 ± 1.3 mSv for CT and 4.3 ± 0.3 mSv for PET contribution). These values were then compared with the published literature (Tonkopi, AJR 2013). Conclusions: Our results were in good agreement with the published literature and were presented to physicians and technicians of the Nuclear Medicine Dept. We have recently installed a new PET-CT (GE DiscoveryIQ) and we will evaluate the effective dose obtained with the new scanner. http://dx.doi.org/10.1016/j.ejmp.2016.01.392
C.387 EVALUATION OF COMMERCIAL SOFTWARE PERFORMANCE IN RETRIEVING INFORMATION FROM MERGED SPECT AND CT IMAGES: A PHANTOM STUDY C. Giliberti a, S. Strolin b, S. Ungania b, A. Cacciatore b, A. Soriani b, G. Iaccarino b, M. D’Andrea b, L. Strigari *,b. a INAIL Dipartimento Innovazioni Tecnologiche e Sicurezza degli Impianti, Prodotti e Insediamenti Antropici, Rome, Italy; b Laboratory of Medical Physics and Expert Systems, Regina Elena National Cancer Institute, Rome, Italy Introduction: Tumor displacement in patients with liver metastasis may be registered by multimodal imaging. The aim of this study was to investigate the performance of commercial image fusion software in measuring the activity and the volumes of inserts simulating liver lesions at different positions in a phantom. Materials and Methods: A novel experimental setup has been designed using Jaszczak phantom and fillable plastic balloons. A solution with a contrast agent at 1% and a concentration of 0.42 MBq/mL were prepared. Two balloons were filled with the solution and fixed to the phantom in order to simulate liver lesions of equal size at different phantom position. All acquisitions were performed using a three-head 3/8’’ (9.5 mm) NaI crystal Philips IRIX gamma-camera. Two iterative algorithms were used to reconstruct SPECT images: the maximum likelihood expectation maximization (MLEM) and the ordered subsets expectation maximization (OSEM). The number of iterations was 10, 20, 50 and 4, 10, 20 for MLEM and OSEM respectively. Using the MIMvistaTM software, several regions of interest (ROIs) were generated on both SPECT and CT images with a threshold method at different percentages of maximum activity values. Image based recovered data have been compared with the expected activity to find the most appropriate threshold to recover the activity values under controlled experimental conditions. Results: MLEM algorithm with 20 iterations was the most accurate reconstruction method with a 1% of difference between expected and recovered activity. A 30% threshold gave the smallest volume difference between the two ROIs and a measured value closest to the true volume measured on the CT. Conclusion: This experimental setup can be used to identify appropriate thresholds for hepatic lesions when considering internal lesion movements using multimodal imaging. http://dx.doi.org/10.1016/j.ejmp.2016.01.393
C.388 ABSOLUTE GAMMA CAMERA CALIBRATION FOR QUANTITATIVE SPECT IMAGING WITH 177LU M. D’Arienzo a,b, M.L. Cozzella a, A. Fazio a, S. Ungania *,c,d, M. Cazzato c, G. Iaccarino c, M. D’Andrea c, L. Strigari c, A. Fenwick e, M. Cox e, L. Johansson e, P. De Felice a. a ENEA, National Institute of Ionizing Radiation Metrology, Rome, Italy; b Department of Anatomical, Histological, Forensic Medicine and Orthopedic Sciences, La Sapienza University, Rome, Italy; c Laboratory of Medical Physics and Expert Systems, Regina Elena National Cancer Institute, Rome, Italy; d Medical Physics Specialization School, Faculty of Medicine, Tor Vergata University, Rome, Italy; e National Physical Laboratory (NPL), Teddington, UK Introduction: Gamma camera calibration in molecular radiotherapy is currently performed either in-air or in-water using a source with a known amount of activity. However, at present there are no standard protocols or
any established methods for calibration and verification of system performance. The aim of this work was to develop an approach to gamma camera calibration for absolute quantification of 177Lu. Materials and Methods: Calibration studies were performed on a Philips IRIX and AXIS gamma camera using four reference geometries: a point source in air, a 16 mL Jaszczak sphere surrounded by non-radioactive water, a 16 mL Jaszczak sphere in air and a 20 cm diameter cylinder filled with 177LuCl. Acquisitions were corrected both for scatter and attenuation. We validated our method using an anthropomorphic phantom provided with liver cavity filled with 177LuCl. Results: Acquisitions performed with the IRIX gamma camera provided better results, with agreements within 5% for all geometries for acquisitions at 208 keV. The Jaszczak sphere in water provided sensitivity values capable of recovering the activity in anthropomorphic geometry within 1% for the 208 keV peak, for both gamma cameras. The point source provided the poorest results, most likely because scatter and attenuation correction are not incorporated in the calibration factor. For both systems the activity in anthropomorphic geometry was recovered with an agreement in the range −11.6%/+7.3% at 208 keV. Conclusions: Scatter and attenuation play a major role at 113 keV and are likely to hinder an accurate quantification. Acquisitions at 208 keV are therefore recommended in the clinical practice. Preliminary results suggest that the gamma camera calibration factor can be determined with a standard uncertainty below 3% if activity measurements are performed with equipment traceable to primary standards, accurate volume measurements are made, and a favourable chemistry is used during the experimental activity. http://dx.doi.org/10.1016/j.ejmp.2016.01.394
C.389 IMPACT OF ATTENUATION AND SCATTER CORRECTION IN PREVISIONAL DOSIMETRY BASED ON SPECT-CT IMAGES FOR RADIOEMBOLIZATION OF LIVER LESIONS WITH 90Y MICROSPHERES S. Valzano *,a, C. Cutaia a, E. Richetta a, M. Pasquino a, R.E. Pellerito b, M. Stasi a. a Medical Physics Unit, AO Ordine Mauriziano, Turin, Italy; b Nuclear Medicine Unit, AO Ordine Mauriziano, Turin, Italy Introduction: Previsional dosimetry of hepatic radioembolization with 90Y microsphere is performed with 99mTc-MAA acquisitions in order to avoid shunts and to estimate dose to lesions and normal liver. The accuracy of the dose calculation depends both on the dosimetric method and on the image reconstruction algorithms. The aim of this study was to compare doses calculated with MIRD and voxel methods based on SPECT-CT images with or without attenuation and scatter corrections. Materials and Methods: 10 HCC patients were treated with 90Y-resin spheres (1.4 ± 0.4 GBq). For previsional dosimetry 99mTc-MAA SPECT-CT (SIEMENS Symbia Intevo, LEHR, 128 × 128, 60 views, 18 s/view) acquisitions were performed. Images were reconstructed with iterative (IT) algorithm (Flash3D, 8i8s) with attenuation and scatter corrections and with FBP algorithm without any correction. Lesion (T) and normal liver (NL) doses were estimated from SPECT-CT images with MIRD compartmental method (VOI counts, isocontour) and with a homemade voxel dosimetry MatLab code. T and NL volumes were obtained on IT and FBP reconstructions and employed for the two dosimetric approaches. MIRD and voxel mean doses to T and NL were calculated on IT and FBP reconstructed images: absolute and percentage comparisons were performed. Results: MIRD compartmental T mean doses were 205 Gy for IT and 224 Gy for FBP; NL mean doses were 57 Gy (IT) and 67 Gy (FBP). Mean T doses, obtained with voxel method, were 167 Gy (IT) and 170 Gy (FBP); NL mean doses were 48 Gy (IT) and 54 Gy (FBP). Using MIRD compartmental method, the mean percent dose differences (±sd), estimated on IT and FBP images, were 11% (±35%) for T and 13% (±34%) for NL. For voxel dosimetry method, the mean percent dose differences (±sd), estimated on reconstructed images, were 2% (±22%) and 7% (±27%) for T and NL respectively. Conclusions: SPECT-CT reconstruction algorithms and attenuation and scatter corrections could significantly affect dose calculation and must be considered in different dosimetric approaches. http://dx.doi.org/10.1016/j.ejmp.2016.01.395
Abstracts/Physica Medica 32 (2016) e97–e115
(3.3 ± 1.3 mSv for CT and 4.5 ± 0.3 mSv for PET contribution) and 7.3 ± 1.5 mSv for women (3.2 ± 1.4 mSv for CT and 4.1 ± 0.2 mSv for PET contribution). The mean Effective Dose was 7.5 ± 1.5 mSv for all patients (3.2 ± 1.3 mSv for CT and 4.3 ± 0.3 mSv for PET contribution). These values were then compared with the published literature (Tonkopi, AJR 2013). Conclusions: Our results were in good agreement with the published literature and were presented to physicians and technicians of the Nuclear Medicine Dept. We have recently installed a new PET-CT (GE DiscoveryIQ) and we will evaluate the effective dose obtained with the new scanner. http://dx.doi.org/10.1016/j.ejmp.2016.01.392
C.387 EVALUATION OF COMMERCIAL SOFTWARE PERFORMANCE IN RETRIEVING INFORMATION FROM MERGED SPECT AND CT IMAGES: A PHANTOM STUDY C. Giliberti a, S. Strolin b, S. Ungania b, A. Cacciatore b, A. Soriani b, G. Iaccarino b, M. D’Andrea b, L. Strigari *,b. a INAIL Dipartimento Innovazioni Tecnologiche e Sicurezza degli Impianti, Prodotti e Insediamenti Antropici, Rome, Italy; b Laboratory of Medical Physics and Expert Systems, Regina Elena National Cancer Institute, Rome, Italy Introduction: Tumor displacement in patients with liver metastasis may be registered by multimodal imaging. The aim of this study was to investigate the performance of commercial image fusion software in measuring the activity and the volumes of inserts simulating liver lesions at different positions in a phantom. Materials and Methods: A novel experimental setup has been designed using Jaszczak phantom and fillable plastic balloons. A solution with a contrast agent at 1% and a concentration of 0.42 MBq/mL were prepared. Two balloons were filled with the solution and fixed to the phantom in order to simulate liver lesions of equal size at different phantom position. All acquisitions were performed using a three-head 3/8’’ (9.5 mm) NaI crystal Philips IRIX gamma-camera. Two iterative algorithms were used to reconstruct SPECT images: the maximum likelihood expectation maximization (MLEM) and the ordered subsets expectation maximization (OSEM). The number of iterations was 10, 20, 50 and 4, 10, 20 for MLEM and OSEM respectively. Using the MIMvistaTM software, several regions of interest (ROIs) were generated on both SPECT and CT images with a threshold method at different percentages of maximum activity values. Image based recovered data have been compared with the expected activity to find the most appropriate threshold to recover the activity values under controlled experimental conditions. Results: MLEM algorithm with 20 iterations was the most accurate reconstruction method with a 1% of difference between expected and recovered activity. A 30% threshold gave the smallest volume difference between the two ROIs and a measured value closest to the true volume measured on the CT. Conclusion: This experimental setup can be used to identify appropriate thresholds for hepatic lesions when considering internal lesion movements using multimodal imaging. http://dx.doi.org/10.1016/j.ejmp.2016.01.393
C.388 ABSOLUTE GAMMA CAMERA CALIBRATION FOR QUANTITATIVE SPECT IMAGING WITH 177LU M. D’Arienzo a,b, M.L. Cozzella a, A. Fazio a, S. Ungania *,c,d, M. Cazzato c, G. Iaccarino c, M. D’Andrea c, L. Strigari c, A. Fenwick e, M. Cox e, L. Johansson e, P. De Felice a. a ENEA, National Institute of Ionizing Radiation Metrology, Rome, Italy; b Department of Anatomical, Histological, Forensic Medicine and Orthopedic Sciences, La Sapienza University, Rome, Italy; c Laboratory of Medical Physics and Expert Systems, Regina Elena National Cancer Institute, Rome, Italy; d Medical Physics Specialization School, Faculty of Medicine, Tor Vergata University, Rome, Italy; e National Physical Laboratory (NPL), Teddington, UK Introduction: Gamma camera calibration in molecular radiotherapy is currently performed either in-air or in-water using a source with a known amount of activity. However, at present there are no standard protocols or
any established methods for calibration and verification of system performance. The aim of this work was to develop an approach to gamma camera calibration for absolute quantification of 177Lu. Materials and Methods: Calibration studies were performed on a Philips IRIX and AXIS gamma camera using four reference geometries: a point source in air, a 16 mL Jaszczak sphere surrounded by non-radioactive water, a 16 mL Jaszczak sphere in air and a 20 cm diameter cylinder filled with 177LuCl. Acquisitions were corrected both for scatter and attenuation. We validated our method using an anthropomorphic phantom provided with liver cavity filled with 177LuCl. Results: Acquisitions performed with the IRIX gamma camera provided better results, with agreements within 5% for all geometries for acquisitions at 208 keV. The Jaszczak sphere in water provided sensitivity values capable of recovering the activity in anthropomorphic geometry within 1% for the 208 keV peak, for both gamma cameras. The point source provided the poorest results, most likely because scatter and attenuation correction are not incorporated in the calibration factor. For both systems the activity in anthropomorphic geometry was recovered with an agreement in the range −11.6%/+7.3% at 208 keV. Conclusions: Scatter and attenuation play a major role at 113 keV and are likely to hinder an accurate quantification. Acquisitions at 208 keV are therefore recommended in the clinical practice. Preliminary results suggest that the gamma camera calibration factor can be determined with a standard uncertainty below 3% if activity measurements are performed with equipment traceable to primary standards, accurate volume measurements are made, and a favourable chemistry is used during the experimental activity. http://dx.doi.org/10.1016/j.ejmp.2016.01.394
C.389 IMPACT OF ATTENUATION AND SCATTER CORRECTION IN PREVISIONAL DOSIMETRY BASED ON SPECT-CT IMAGES FOR RADIOEMBOLIZATION OF LIVER LESIONS WITH 90Y MICROSPHERES S. Valzano *,a, C. Cutaia a, E. Richetta a, M. Pasquino a, R.E. Pellerito b, M. Stasi a. a Medical Physics Unit, AO Ordine Mauriziano, Turin, Italy; b Nuclear Medicine Unit, AO Ordine Mauriziano, Turin, Italy Introduction: Previsional dosimetry of hepatic radioembolization with 90Y microsphere is performed with 99mTc-MAA acquisitions in order to avoid shunts and to estimate dose to lesions and normal liver. The accuracy of the dose calculation depends both on the dosimetric method and on the image reconstruction algorithms. The aim of this study was to compare doses calculated with MIRD and voxel methods based on SPECT-CT images with or without attenuation and scatter corrections. Materials and Methods: 10 HCC patients were treated with 90Y-resin spheres (1.4 ± 0.4 GBq). For previsional dosimetry 99mTc-MAA SPECT-CT (SIEMENS Symbia Intevo, LEHR, 128 × 128, 60 views, 18 s/view) acquisitions were performed. Images were reconstructed with iterative (IT) algorithm (Flash3D, 8i8s) with attenuation and scatter corrections and with FBP algorithm without any correction. Lesion (T) and normal liver (NL) doses were estimated from SPECT-CT images with MIRD compartmental method (VOI counts, isocontour) and with a homemade voxel dosimetry MatLab code. T and NL volumes were obtained on IT and FBP reconstructions and employed for the two dosimetric approaches. MIRD and voxel mean doses to T and NL were calculated on IT and FBP reconstructed images: absolute and percentage comparisons were performed. Results: MIRD compartmental T mean doses were 205 Gy for IT and 224 Gy for FBP; NL mean doses were 57 Gy (IT) and 67 Gy (FBP). Mean T doses, obtained with voxel method, were 167 Gy (IT) and 170 Gy (FBP); NL mean doses were 48 Gy (IT) and 54 Gy (FBP). Using MIRD compartmental method, the mean percent dose differences (±sd), estimated on IT and FBP images, were 11% (±35%) for T and 13% (±34%) for NL. For voxel dosimetry method, the mean percent dose differences (±sd), estimated on reconstructed images, were 2% (±22%) and 7% (±27%) for T and NL respectively. Conclusions: SPECT-CT reconstruction algorithms and attenuation and scatter corrections could significantly affect dose calculation and must be considered in different dosimetric approaches. http://dx.doi.org/10.1016/j.ejmp.2016.01.395