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CT images for radiation oncology
Abstratcs / Physica Medica 32 (2016) 141–160
classified radon as a human lung carcinogen. For this reason, there has been a lot of concern about the effect of radon exposure to people all over the world and Nigeria is no exception. The aim of this study is to investigate the radon concentration in selected houses in three local government areas of Ibadan. Materials and methods. In this study, indoor radon was measured in both mud and brick houses. Fifty houses were considered from the three local government areas. A calibrated portable continuous radon monitor type (RAD7) manufactured by Durridge company was used for the measurement. A distance of 100–200 m was maintained between houses in all the locations. The living room was kept closed during the measurements. Results. The mean radon concentration (in Bqm 3) measured in Egbeda is 10.54 1.30; Lagelu is 16.90 6.31 and Ona-Ara is 17.95 1.72. The mean value of the annual absorbed dose and annual effective dose for the locations in the three local government areas was 0.19 mSvy 1 and 0.48 mSvy 1 respectively. Conclusion. The radon concentration for location 10 in Ono-Ara local government exceeded the recommended limit. However, the overall average indoor radon concentration of the three local government areas was found to be lower than the world average value of 40 Bqm 3. Hence, there is need for proper awareness about the danger of radon accumulation in dwelling places. http://dx.doi.org/10.1016/j.ejmp.2016.07.033
O26. A review on target volume delineation using FDG-PET/CT images for radiation oncology M. du Toit a,b, A. Potgieter b, M. Heunis a, R. Boellaard b, J. Pruim b,a a Department of Medical Imaging and Clinical Oncology, University of Stellenbosch and Tygerberg Hospital, Cape Town, South Africa b Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
Introduction. In recent years, Positron Emission Tomography (PET) became available as a complementary imaging modality to CT and MRI for radiotherapy planning. PET provides information on radiotracer uptake heterogeneity within a tumour which in turn can indicate the distribution of the molecular process. Thus the primary tumour can be characterized more accurately to deliver an effective treatment plan and reduce the side effects associated with radiation treatment. It has been shown that PET/CT reduces the intra- and inter-observer variation of the tumour delineation and it increases the turnover and accuracy of the delineation process from using only CT images. However to detect the tumour boundary visually from PET images alone is challenging, therefore numerous automatic delineation algorithms have been developed. The purpose was to assess the efficacy and accuracy of existing delineation methods for FDG-PET/CT images for the oncologist to improve tumour volume delineation for radiotherapy planning. Materials and methods. A systematic literature review was conducted to find tumour delineation techniques applied to FDG-PET scans which are likely to be considered by the oncologist as a possible solution to the delineation problem. Visual variation of PET images is shown in comparison to CT images with NEMA phantom images. Results. Apart from the thresholding techniques, current automated methods prove to be tumour site specific and need additional calibrations and/or measurements on the PET/CT units. A good departmental protocol such as Research for Life (EARL) should be followed to ensure a uniform platform for reporting and contouring of images especially if visual contouring is applied. Current research
149
is investigating combinations of algorithms and prediction methods based on statistical information and atlas data. Machine learning methodologies are also under discussion since it can handle big data sets and assist with decision making. Conclusion. We believe that until these methods have been clinically tested and verified, the oncologist would be hesitant to apply the suggested changes to the GTV as indicated by the PET. http://dx.doi.org/10.1016/j.ejmp.2016.07.034
O27. Gamma camera SPECT calibration for improved quantitative dosimetry T.C.G. Moalosi a, M. Mix b, A. Ellmann a, L. Nolan c, T. Mkhize c a
Stellenbosch University, South Africa University of Freiburg, Germany c Tygerberg Hospital, Cape Town, South Africa b
Introduction. The recent emergence of theranostic pharmaceuticals has made it possible to treat while doing in-vivo dosimetry with a gamma camera. PRRT requires individualized internal dosimetry for every patient because uptake differs across patients. In our department we used to do planar image dosimetry; however this method was prone to errors, because it could not account for overlapping organs and dose underestimation. Quantitative SPECT/CT can mitigate problems encountered in planar image dosimetry by providing a three dimensional image of organs, thereby avoiding overlapping and resulting in more accurate dose estimation. Materials and methods. A 10-‘ acrylic phantom (NEMA2007/ IEC2008) with six fillable spheres was filled with a 177Lu concentration. The spheres were filled with a higher activity concentration than the background. A SPECT/CT was done on a phantom using a GE Infinia-Hawkeye with clinical acquisition protocol. A 120 projections were acquired using a medium energy general purpose collimator (MEGP) with upper energy peak of 208 keV 10%. A low dose CT was used for attenuation correction and the acquired images were reconstructed using an OSEM algorithm using 3 iterations and 15 subsets. A Monte-Carlo-based scatter correction was applied on a workstation from Hermes medical solutions. A cylindrical volume of interest was drawn on the background region, the mean count rate was calculated and the system’s volume sensitivity was determined. Results. The volume sensitivity of our gamma camera was determined as 0.535 counts/sec/kBq with STDev: 0.0228, which was then used to determine and compare with known activity concentration in the hot spheres. Under consideration of the known partial volume effect, all spheres showed an accuracy of within 5%. Conclusion. The gamma camera was successfully calibrated and validated for quantitative dosimetry of 177Lu studies. http://dx.doi.org/10.1016/j.ejmp.2016.07.035
O28. Optimization of Lu-177 SPECT/CT acquisition protocol at Tygerberg Hospital Nuclear Medicine Department T. Mkhize a, T. Moalosi b, M. Mix c, A. Ellmann b, L. Nolan a a
Medical Physics Department, Tygerberg Hospital, South Africa Stellenbosch University, Stellenbosch, South Africa c University of Freiburg, Freiburg, Germany b
Introduction. 177Lu is a radionuclide which is used for the treatment of the neuroendocrine tumours, bone pain from metastatic disease, and prostate cancer. 177Lu has two prominent gamma energies of 113 and 208 keV (6.8% and 10.4% yield) used for imaging, and a
classified radon as a human lung carcinogen. For this reason, there has been a lot of concern about the effect of radon exposure to people all over the world and Nigeria is no exception. The aim of this study is to investigate the radon concentration in selected houses in three local government areas of Ibadan. Materials and methods. In this study, indoor radon was measured in both mud and brick houses. Fifty houses were considered from the three local government areas. A calibrated portable continuous radon monitor type (RAD7) manufactured by Durridge company was used for the measurement. A distance of 100–200 m was maintained between houses in all the locations. The living room was kept closed during the measurements. Results. The mean radon concentration (in Bqm 3) measured in Egbeda is 10.54 1.30; Lagelu is 16.90 6.31 and Ona-Ara is 17.95 1.72. The mean value of the annual absorbed dose and annual effective dose for the locations in the three local government areas was 0.19 mSvy 1 and 0.48 mSvy 1 respectively. Conclusion. The radon concentration for location 10 in Ono-Ara local government exceeded the recommended limit. However, the overall average indoor radon concentration of the three local government areas was found to be lower than the world average value of 40 Bqm 3. Hence, there is need for proper awareness about the danger of radon accumulation in dwelling places. http://dx.doi.org/10.1016/j.ejmp.2016.07.033
O26. A review on target volume delineation using FDG-PET/CT images for radiation oncology M. du Toit a,b, A. Potgieter b, M. Heunis a, R. Boellaard b, J. Pruim b,a a Department of Medical Imaging and Clinical Oncology, University of Stellenbosch and Tygerberg Hospital, Cape Town, South Africa b Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
Introduction. In recent years, Positron Emission Tomography (PET) became available as a complementary imaging modality to CT and MRI for radiotherapy planning. PET provides information on radiotracer uptake heterogeneity within a tumour which in turn can indicate the distribution of the molecular process. Thus the primary tumour can be characterized more accurately to deliver an effective treatment plan and reduce the side effects associated with radiation treatment. It has been shown that PET/CT reduces the intra- and inter-observer variation of the tumour delineation and it increases the turnover and accuracy of the delineation process from using only CT images. However to detect the tumour boundary visually from PET images alone is challenging, therefore numerous automatic delineation algorithms have been developed. The purpose was to assess the efficacy and accuracy of existing delineation methods for FDG-PET/CT images for the oncologist to improve tumour volume delineation for radiotherapy planning. Materials and methods. A systematic literature review was conducted to find tumour delineation techniques applied to FDG-PET scans which are likely to be considered by the oncologist as a possible solution to the delineation problem. Visual variation of PET images is shown in comparison to CT images with NEMA phantom images. Results. Apart from the thresholding techniques, current automated methods prove to be tumour site specific and need additional calibrations and/or measurements on the PET/CT units. A good departmental protocol such as Research for Life (EARL) should be followed to ensure a uniform platform for reporting and contouring of images especially if visual contouring is applied. Current research
149
is investigating combinations of algorithms and prediction methods based on statistical information and atlas data. Machine learning methodologies are also under discussion since it can handle big data sets and assist with decision making. Conclusion. We believe that until these methods have been clinically tested and verified, the oncologist would be hesitant to apply the suggested changes to the GTV as indicated by the PET. http://dx.doi.org/10.1016/j.ejmp.2016.07.034
O27. Gamma camera SPECT calibration for improved quantitative dosimetry T.C.G. Moalosi a, M. Mix b, A. Ellmann a, L. Nolan c, T. Mkhize c a
Stellenbosch University, South Africa University of Freiburg, Germany c Tygerberg Hospital, Cape Town, South Africa b
Introduction. The recent emergence of theranostic pharmaceuticals has made it possible to treat while doing in-vivo dosimetry with a gamma camera. PRRT requires individualized internal dosimetry for every patient because uptake differs across patients. In our department we used to do planar image dosimetry; however this method was prone to errors, because it could not account for overlapping organs and dose underestimation. Quantitative SPECT/CT can mitigate problems encountered in planar image dosimetry by providing a three dimensional image of organs, thereby avoiding overlapping and resulting in more accurate dose estimation. Materials and methods. A 10-‘ acrylic phantom (NEMA2007/ IEC2008) with six fillable spheres was filled with a 177Lu concentration. The spheres were filled with a higher activity concentration than the background. A SPECT/CT was done on a phantom using a GE Infinia-Hawkeye with clinical acquisition protocol. A 120 projections were acquired using a medium energy general purpose collimator (MEGP) with upper energy peak of 208 keV 10%. A low dose CT was used for attenuation correction and the acquired images were reconstructed using an OSEM algorithm using 3 iterations and 15 subsets. A Monte-Carlo-based scatter correction was applied on a workstation from Hermes medical solutions. A cylindrical volume of interest was drawn on the background region, the mean count rate was calculated and the system’s volume sensitivity was determined. Results. The volume sensitivity of our gamma camera was determined as 0.535 counts/sec/kBq with STDev: 0.0228, which was then used to determine and compare with known activity concentration in the hot spheres. Under consideration of the known partial volume effect, all spheres showed an accuracy of within 5%. Conclusion. The gamma camera was successfully calibrated and validated for quantitative dosimetry of 177Lu studies. http://dx.doi.org/10.1016/j.ejmp.2016.07.035
O28. Optimization of Lu-177 SPECT/CT acquisition protocol at Tygerberg Hospital Nuclear Medicine Department T. Mkhize a, T. Moalosi b, M. Mix c, A. Ellmann b, L. Nolan a a
Medical Physics Department, Tygerberg Hospital, South Africa Stellenbosch University, Stellenbosch, South Africa c University of Freiburg, Freiburg, Germany b
Introduction. 177Lu is a radionuclide which is used for the treatment of the neuroendocrine tumours, bone pain from metastatic disease, and prostate cancer. 177Lu has two prominent gamma energies of 113 and 208 keV (6.8% and 10.4% yield) used for imaging, and a