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Survey of CT practice in sudan: Updates on radiation exposure and setting national diagnostic reference levels
278
Abstracts / Physica Medica 32 (2016) 274–283
SURVEY OF CT PRACTICE IN SUDAN: UPDATES ON RADIATION EXPOSURE AND SETTING NATIONAL DIAGNOSTIC REFERENCE LEVELS I.I. Suliman *, M. Mohamed, S. Ahmed, I. Osman, N. Ahmed Sudan Atomic Energy Commission, P.O. Box 3001, Khartoum, Sudan Corresponding author.
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Introduction. The increase in the use of mutislice CT in Sudan has resulted in an increased examinations frequency and population radiation burden. Dose surveys are important for medical exposure control. Purpose. The aims of this survey were to updates on radiation exposure, and use the results in setting national diagnostic reference levels. Materials and methods. Scan parameters were collected from 840 CT examinations in patients carried out in eight CT scanners comprising one (128 Slice), five (64 Slice) and two (16 Slice) mulitislice CT scanners in Khartoum State, Sudan. CTDIvol and DLP and effective dose were calculated by using CT-Expo 2.5 CT dosimetry software were compared with published data. Results. Doses are presented Brian, PNS, and Chest, pulmonary, Abdomen-Pelvis, Pelvis, KUB and CTU CT examinations. Mean CTDIvol ranged: from 63.8 to 16.4 mGy in Brain and KUB; respectively; Mean DLP ranged from 1744 to 670 mGy.cm in CTU and Pelvic CT; respectively; While mean effective dose ranged from 21.71 to 1.96 mSv in CTU and BNS; respectively. The results presented wide variations in technique and radiation dose for similar examinations indicating significant room for dose optimisation. Conclusion. 75 percentile of hospital mean doses obtained in this study were used to propose a national DRLs. Study highlighted the radiation protection challenge and dose consequences of Mutislice CT in a developing country. Disclosure. Authors do not have any relationship that may bias their presentation. http://dx.doi.org/10.1016/j.ejmp.2016.07.614
RADIATION DOSE COMPARISON BETWEEN V/P-SPECT AND CT-ANGIOGRAPHY IN THE DIAGNOSIS OF PULMONARY EMBOLISM J. Isidoro a,*, P. Gil a, G. Costa a, J. Pedroso Lima a,d, F. Caseiro Alves b, N.C. Ferreira c,d a Serviço de Medicina Nuclear, Centro Hospitalar e Universitário de Coimbra, Portugal b Serviço de Imagiologia, Centro Hospitalar e Universitário de Coimbra, Portugal c Instituto de Biofísica e Biomatemática, Faculdade de Medicina da Universidade de Coimbra, Portugal d ICNAS – Instituto de Ciências Nucleares Aplicadas à Saúde, Universidade de Coimbra, Portugal ⇑ Corresponding author.
Introduction. CT pulmonary angiography (CTPA) has become the preferred diagnostic tool in patients suspected of having pulmonary embolism (PE). Ventilation/perfusion single photon emission computed tomography (V/P-SPECT), despite yields similar diagnostic output, it is left to cases were CTPA is inappropriate. Radiation burden should play an important role in modality selection especially in follow-up studies, young woman and pregnant patients. Purpose. The aim of this study is to compare CTPA versus V/PSPECT, routine protocols of our institution, regarding radiation dose to the more exposed organs (lung and breast) or the embryo/fetus.
Materials and methods. In our institution the CTPA protocol includes contrast media administration and scan parameters: 100 kVp, 700 mA, 0,5s/rot, pitch 0,984. In V/P-SPECT protocol: ventilation was performed after inhalation of 99mTc-Technegas, reaching 30 MBq in the lungs; perfusion was performed after i.v. administration of 60–120 MBq 99mTc-MAA. Radiation dose to lungs and breast form CTPA was estimated using the ‘‘ImPACT CT Patient Dosimetry Calculator”, the embryo/ fetus dose was estimated for different gestational stages (0–7, 8– 12, 13–25 and 26–40 weeks) using the web based calculation tool ‘‘COnceptus Dose Estimation” (CODE). V/P-SPECT organs and embryo/fetus doses were estimated based on published dose data normalized to administered activity (mGy/MBq). Results. Embryo/fetus absorbed doses are similar for CTPA and V/ P-SPECT. Doses to lungs is 1.7–2.6 and to breast is 25–41 times higher from CTPA compared with V/P-SPECT. Conclusion. For the diagnosis of PE in woman, if both imaging modalities are available, it is recommended to proceed with V/PSPECT rather than CTPA due to the considerable lower radiation dose to the breast. Disclosure. Authors disclose any relationship that may bias their presentation. http://dx.doi.org/10.1016/j.ejmp.2016.07.616
CLINICAL APPLICATION OF A CT DOSE REDUCTION SIMULATOR A. Serna a,*, M.A. Chans b, A. Ramos b, D. Ramos a a
Medical Physics Department, Hospital Universitario Santa Lucia, Cartagena, Spain b Diagnostic Imaging Department, Hospital Universitario Santa Lucia, Cartagena, Spain ⇑ Corresponding author. Purpose. To validate an exposure reduction algorithm for head CT examinations in clinical practice. Material and methods. CT images from Head Adult protocol in a Siemens CT Somatom Definition AS+ was used for this study. Dose reduction was simulated through the addition of noise to each pixel value of the original image. A homogeneous phantom was used to measure the autocorrelation function, which is convolved with a white noise matrix to get the spatially correlated statistical noise to be added. A Matlab code was written to perform this task. Firstly, the algorithm was validated using two phantoms, i.e. a homogeneous and an anthropomorphic heterogeneous phantom, CT-scanned with different exposure reductions, up to 75%, from the original reference mAs. Noise values comparison between CTsimulated and CT-real images was done. Secondly, from our PACS 10 patients previously CT-scanned, with subtle pathologies and normal brain, were selected. CT-simulated images, up to an exposure reduction of 50%, were reviewed by two experienced radiologists, not aware of the applied exposure reduction. Results. The algorithm reproduces well the image noise variation with the reduction of the mAs. Differences were less than 2% in both phantoms in the exposure range analysed. CT-simulated images with exposure reductions equal or larger than 30% were clearly identified by both radiologists. Mostly, a 20% reduction was deemed appropriate for clinical diagnosis. Conclusion. Dose reduction simulation software might be a powerful tool for patient dose optimization. http://dx.doi.org/10.1016/j.ejmp.2016.07.617
Abstracts / Physica Medica 32 (2016) 274–283
SURVEY OF CT PRACTICE IN SUDAN: UPDATES ON RADIATION EXPOSURE AND SETTING NATIONAL DIAGNOSTIC REFERENCE LEVELS I.I. Suliman *, M. Mohamed, S. Ahmed, I. Osman, N. Ahmed Sudan Atomic Energy Commission, P.O. Box 3001, Khartoum, Sudan Corresponding author.
⇑
Introduction. The increase in the use of mutislice CT in Sudan has resulted in an increased examinations frequency and population radiation burden. Dose surveys are important for medical exposure control. Purpose. The aims of this survey were to updates on radiation exposure, and use the results in setting national diagnostic reference levels. Materials and methods. Scan parameters were collected from 840 CT examinations in patients carried out in eight CT scanners comprising one (128 Slice), five (64 Slice) and two (16 Slice) mulitislice CT scanners in Khartoum State, Sudan. CTDIvol and DLP and effective dose were calculated by using CT-Expo 2.5 CT dosimetry software were compared with published data. Results. Doses are presented Brian, PNS, and Chest, pulmonary, Abdomen-Pelvis, Pelvis, KUB and CTU CT examinations. Mean CTDIvol ranged: from 63.8 to 16.4 mGy in Brain and KUB; respectively; Mean DLP ranged from 1744 to 670 mGy.cm in CTU and Pelvic CT; respectively; While mean effective dose ranged from 21.71 to 1.96 mSv in CTU and BNS; respectively. The results presented wide variations in technique and radiation dose for similar examinations indicating significant room for dose optimisation. Conclusion. 75 percentile of hospital mean doses obtained in this study were used to propose a national DRLs. Study highlighted the radiation protection challenge and dose consequences of Mutislice CT in a developing country. Disclosure. Authors do not have any relationship that may bias their presentation. http://dx.doi.org/10.1016/j.ejmp.2016.07.614
RADIATION DOSE COMPARISON BETWEEN V/P-SPECT AND CT-ANGIOGRAPHY IN THE DIAGNOSIS OF PULMONARY EMBOLISM J. Isidoro a,*, P. Gil a, G. Costa a, J. Pedroso Lima a,d, F. Caseiro Alves b, N.C. Ferreira c,d a Serviço de Medicina Nuclear, Centro Hospitalar e Universitário de Coimbra, Portugal b Serviço de Imagiologia, Centro Hospitalar e Universitário de Coimbra, Portugal c Instituto de Biofísica e Biomatemática, Faculdade de Medicina da Universidade de Coimbra, Portugal d ICNAS – Instituto de Ciências Nucleares Aplicadas à Saúde, Universidade de Coimbra, Portugal ⇑ Corresponding author.
Introduction. CT pulmonary angiography (CTPA) has become the preferred diagnostic tool in patients suspected of having pulmonary embolism (PE). Ventilation/perfusion single photon emission computed tomography (V/P-SPECT), despite yields similar diagnostic output, it is left to cases were CTPA is inappropriate. Radiation burden should play an important role in modality selection especially in follow-up studies, young woman and pregnant patients. Purpose. The aim of this study is to compare CTPA versus V/PSPECT, routine protocols of our institution, regarding radiation dose to the more exposed organs (lung and breast) or the embryo/fetus.
Materials and methods. In our institution the CTPA protocol includes contrast media administration and scan parameters: 100 kVp, 700 mA, 0,5s/rot, pitch 0,984. In V/P-SPECT protocol: ventilation was performed after inhalation of 99mTc-Technegas, reaching 30 MBq in the lungs; perfusion was performed after i.v. administration of 60–120 MBq 99mTc-MAA. Radiation dose to lungs and breast form CTPA was estimated using the ‘‘ImPACT CT Patient Dosimetry Calculator”, the embryo/ fetus dose was estimated for different gestational stages (0–7, 8– 12, 13–25 and 26–40 weeks) using the web based calculation tool ‘‘COnceptus Dose Estimation” (CODE). V/P-SPECT organs and embryo/fetus doses were estimated based on published dose data normalized to administered activity (mGy/MBq). Results. Embryo/fetus absorbed doses are similar for CTPA and V/ P-SPECT. Doses to lungs is 1.7–2.6 and to breast is 25–41 times higher from CTPA compared with V/P-SPECT. Conclusion. For the diagnosis of PE in woman, if both imaging modalities are available, it is recommended to proceed with V/PSPECT rather than CTPA due to the considerable lower radiation dose to the breast. Disclosure. Authors disclose any relationship that may bias their presentation. http://dx.doi.org/10.1016/j.ejmp.2016.07.616
CLINICAL APPLICATION OF A CT DOSE REDUCTION SIMULATOR A. Serna a,*, M.A. Chans b, A. Ramos b, D. Ramos a a
Medical Physics Department, Hospital Universitario Santa Lucia, Cartagena, Spain b Diagnostic Imaging Department, Hospital Universitario Santa Lucia, Cartagena, Spain ⇑ Corresponding author. Purpose. To validate an exposure reduction algorithm for head CT examinations in clinical practice. Material and methods. CT images from Head Adult protocol in a Siemens CT Somatom Definition AS+ was used for this study. Dose reduction was simulated through the addition of noise to each pixel value of the original image. A homogeneous phantom was used to measure the autocorrelation function, which is convolved with a white noise matrix to get the spatially correlated statistical noise to be added. A Matlab code was written to perform this task. Firstly, the algorithm was validated using two phantoms, i.e. a homogeneous and an anthropomorphic heterogeneous phantom, CT-scanned with different exposure reductions, up to 75%, from the original reference mAs. Noise values comparison between CTsimulated and CT-real images was done. Secondly, from our PACS 10 patients previously CT-scanned, with subtle pathologies and normal brain, were selected. CT-simulated images, up to an exposure reduction of 50%, were reviewed by two experienced radiologists, not aware of the applied exposure reduction. Results. The algorithm reproduces well the image noise variation with the reduction of the mAs. Differences were less than 2% in both phantoms in the exposure range analysed. CT-simulated images with exposure reductions equal or larger than 30% were clearly identified by both radiologists. Mostly, a 20% reduction was deemed appropriate for clinical diagnosis. Conclusion. Dose reduction simulation software might be a powerful tool for patient dose optimization. http://dx.doi.org/10.1016/j.ejmp.2016.07.617