- Email: [email protected]
Size specific dose estimates in pediatric chest, abdomen and pelvis CT examinations
182
Abstracts / Physica Medica 32 (2016) 179–183
UNBORN CHILDREN: RADIATION PROTECTION IN PREGNANCY John Damilakis. University of Crete, Greece A diagnostic or interventional X-ray examination of a pregnant patient is sometimes considered to be necessary. In these cases, conceptus dose estimation is needed to assess radiogenic risks to the unborn child. During extra-abdominal examinations, the unborn child is exposed to scattered radiation and in most cases its dose is lower than 1 mGy. A detailed embryo/fetus dose evaluation is not needed for these examinations. Abdominal and/or pelvis X-ray examinations may deliver higher radiation doses to the conceptus. An abdominal CT examination performed on the mother is associated with an embryo/ fetus dose of about 10–25 mGy. However, this is only a typical range of dose values. The actual dose depends on factors such as exposure parameters, x-ray tube filtration and use of dose reduction tools such as automatic exposure control. Doses to the unborn child below 100 mGy should not lead to therapeutic abortion. The risk to the embryo/fetus for stochastic effects is assessed on the basis of radiation dose using appropriate conversion coefficients provided by international organizations. Several methods have been developed to estimate doses to unborn children from X-ray examinations. CODE (COnceptus Dose Estimation) is a free web-based software tool (uploaded on embryodose.med.uoc.gr) developed for the estimation of conceptus radiation dose and risks in case of: a) pregnant patients subjected to radiological examinations and b) pregnant employees exposed during fluroscopically guided interventional procedures. http://dx.doi.org/10.1016/j.ejmp.2016.07.305
OPTIMIZATION OF PAEDIATRIC CT Mannudeep K. Kalra. Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA Children have a special place in the hearts of their parents and the same should be true for CT practices too! They have longer life expectancy, more dividing cells which have greater risk potential from radiation exposure. Plus, they can range from less than a kilogram to more than 100 kg with childhood obesity. Younger children also provide additional challenges when they cannot or do not cooperate during CT scanning, which can result in motion artifacts and suboptimal interpretations. These issues demand special attention to details during paediatric CT. The best way to optimize dose for children is to rationalize clinical indications for CT in children. Whenever possible and appropriate, non-ionizing radiation based imaging techniques should be used in children. When CT is appropriately indicated, careful attention must be given to patient positioning and counselling. Several scan techniques can help optimize radiation doses, and these must be liberally employed. Each paediatric CT should be tailored to personalize scan technique, image reconstruction and radiation doses to specific clinical indication, body region, and patient size. In this presentation, we will review strategies to optimize paediatric CT. http://dx.doi.org/10.1016/j.ejmp.2016.07.306
SIZE SPECIFIC DOSE ESTIMATES IN PEDIATRIC CHEST, ABDOMEN AND PELVIS CT EXAMINATIONS Aysegul Yurt a, Ismail Ozsoykal a, Kadir Akgungor K. b. aDokuz Eylul University, Department of Medical Physics, Turkey b
Dokuz Eylul University, Department of Physics, Turkey
Introduction. Volume computed tomography dose index (CTDIvol) does not contain any dose information regarding the patient size. Size specific dose estimates (SSDE) give more reliable results
accounting for the patient size as well. This parameter uses CTDIvol and size dependent conversion factors (fDw) which are calculated by means of water equivalent diameter (Dw) of the patient cross section in every slice of image. Purpose. To develop software to automatically calculate SSDE and to assess the impact of variations in Dw along the z axis on SSDE for CT examinations of the torso in pediatric patients. Materials and methods. 55 consecutive CT exams of the combined chest, abdomen and pelvis (CAP) have been examined. SSDE has been calculated for 6 hypothetical scan ranges: chest alone, abdomen alone, pelvis alone, chest and abdomen, abdomen and pelvis, and CAP. Two methods were used in mean SSDE approach: (1) mean SSDE over each scan range; (2) SSDE value at the middle of the scan range. Results. For scan ranges 1 to 6, the average of the difference in maximal and minimal Dw accross patients was 3.7, 3.8, 2.6, 4.1, 4.4 and 4.5 cm. The mean SSDE values calculated using methods (1) and (2) were highly compatible, with root mean square differences of 0.4, 0.5, 0.3, 1.0, 1.5 and 0.7 mGy or 3%, 4%, 2%, 7%, 10%, 5%. Conclusion. Using the mean CTDIvol and the water equivalent diameter at the middle of the scan range provides a reasonable estimation of patient dose in pediatric exams. http://dx.doi.org/10.1016/j.ejmp.2016.07.307
THE ESTABLISHMENT OF LOCAL DIAGNOSTIC REFERENCE LEVELS FOR PEDIATRIC CT Birute Griciene a,b, Milda Petkelyte a,b, Arijanda Neverauskiene a,c, Linas Petkevicius d,a. aVilnius University, Faculty of Medicine, Lithuania b
Department of Clinical Radiation Surveillance, Vilnius University Hospital Santariskiu Klinikos, Lithuania c Centre of Radiology, Children’s Hospital, Affiliate of Vilnius University Hospital Santariskiu Klinikos, Lithuania d Vilnius University, Faculty of Mathematics and Informatics, Lithuania Introduction. Computed tomography (CT delivers more than a half of collective effective dose received at medical diagnostic procedures. It is recommended that routine procedures have diagnostic reference levels (DRLs) set and kept up-to-date, especially for pediatric examinations. Purpose. The main objective of this study is to analyse dose trends in 2010–2014, identify future optimisation targets and set local DRLs for most common pediatric CT examinations. Materials and methods. A retrospective study of pediatric (<18 y) patients that underwent CT examinations in 2010, 2012 and 2014 was done. Effective dose was calculated. The mean DLP, CTDIvol values were estimated for age groups, body area scanned and compared to national and European DRLs. Results. 2042 examinations were analysed, most of them (57.9%) head CT scans. Head dose decreased in all age groups from 2,9 to 1,6 mSv. In 2014 the mean DLP for head was 267, 293, 313 and 371 mGy⁄ cm for patients aged 0–1, 1–5, 5–10 and 10–18 years respectively; the mean DLP for chest was 74, 199 and 303 mGy⁄ cm for patients aged 1–5, 5–10 and 10–18 years; the mean DLP for pelvis was 69, 91, 159 and 284 mGy⁄ cm for patients aged 0–1, 1–5, 5– 10 and 10–18 years. The local DRLs for head, chest and pelvis CT were set. Conclusion. For CT procedures the comparison between local DRLs and the national DRLs shows that doses don’t exceed the recommended levels. While CT dose decreases, it is important to ensure that examinations are performed at optimised state. Disclosure. None. http://dx.doi.org/10.1016/j.ejmp.2016.07.308
Abstracts / Physica Medica 32 (2016) 179–183
UNBORN CHILDREN: RADIATION PROTECTION IN PREGNANCY John Damilakis. University of Crete, Greece A diagnostic or interventional X-ray examination of a pregnant patient is sometimes considered to be necessary. In these cases, conceptus dose estimation is needed to assess radiogenic risks to the unborn child. During extra-abdominal examinations, the unborn child is exposed to scattered radiation and in most cases its dose is lower than 1 mGy. A detailed embryo/fetus dose evaluation is not needed for these examinations. Abdominal and/or pelvis X-ray examinations may deliver higher radiation doses to the conceptus. An abdominal CT examination performed on the mother is associated with an embryo/ fetus dose of about 10–25 mGy. However, this is only a typical range of dose values. The actual dose depends on factors such as exposure parameters, x-ray tube filtration and use of dose reduction tools such as automatic exposure control. Doses to the unborn child below 100 mGy should not lead to therapeutic abortion. The risk to the embryo/fetus for stochastic effects is assessed on the basis of radiation dose using appropriate conversion coefficients provided by international organizations. Several methods have been developed to estimate doses to unborn children from X-ray examinations. CODE (COnceptus Dose Estimation) is a free web-based software tool (uploaded on embryodose.med.uoc.gr) developed for the estimation of conceptus radiation dose and risks in case of: a) pregnant patients subjected to radiological examinations and b) pregnant employees exposed during fluroscopically guided interventional procedures. http://dx.doi.org/10.1016/j.ejmp.2016.07.305
OPTIMIZATION OF PAEDIATRIC CT Mannudeep K. Kalra. Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA Children have a special place in the hearts of their parents and the same should be true for CT practices too! They have longer life expectancy, more dividing cells which have greater risk potential from radiation exposure. Plus, they can range from less than a kilogram to more than 100 kg with childhood obesity. Younger children also provide additional challenges when they cannot or do not cooperate during CT scanning, which can result in motion artifacts and suboptimal interpretations. These issues demand special attention to details during paediatric CT. The best way to optimize dose for children is to rationalize clinical indications for CT in children. Whenever possible and appropriate, non-ionizing radiation based imaging techniques should be used in children. When CT is appropriately indicated, careful attention must be given to patient positioning and counselling. Several scan techniques can help optimize radiation doses, and these must be liberally employed. Each paediatric CT should be tailored to personalize scan technique, image reconstruction and radiation doses to specific clinical indication, body region, and patient size. In this presentation, we will review strategies to optimize paediatric CT. http://dx.doi.org/10.1016/j.ejmp.2016.07.306
SIZE SPECIFIC DOSE ESTIMATES IN PEDIATRIC CHEST, ABDOMEN AND PELVIS CT EXAMINATIONS Aysegul Yurt a, Ismail Ozsoykal a, Kadir Akgungor K. b. aDokuz Eylul University, Department of Medical Physics, Turkey b
Dokuz Eylul University, Department of Physics, Turkey
Introduction. Volume computed tomography dose index (CTDIvol) does not contain any dose information regarding the patient size. Size specific dose estimates (SSDE) give more reliable results
accounting for the patient size as well. This parameter uses CTDIvol and size dependent conversion factors (fDw) which are calculated by means of water equivalent diameter (Dw) of the patient cross section in every slice of image. Purpose. To develop software to automatically calculate SSDE and to assess the impact of variations in Dw along the z axis on SSDE for CT examinations of the torso in pediatric patients. Materials and methods. 55 consecutive CT exams of the combined chest, abdomen and pelvis (CAP) have been examined. SSDE has been calculated for 6 hypothetical scan ranges: chest alone, abdomen alone, pelvis alone, chest and abdomen, abdomen and pelvis, and CAP. Two methods were used in mean SSDE approach: (1) mean SSDE over each scan range; (2) SSDE value at the middle of the scan range. Results. For scan ranges 1 to 6, the average of the difference in maximal and minimal Dw accross patients was 3.7, 3.8, 2.6, 4.1, 4.4 and 4.5 cm. The mean SSDE values calculated using methods (1) and (2) were highly compatible, with root mean square differences of 0.4, 0.5, 0.3, 1.0, 1.5 and 0.7 mGy or 3%, 4%, 2%, 7%, 10%, 5%. Conclusion. Using the mean CTDIvol and the water equivalent diameter at the middle of the scan range provides a reasonable estimation of patient dose in pediatric exams. http://dx.doi.org/10.1016/j.ejmp.2016.07.307
THE ESTABLISHMENT OF LOCAL DIAGNOSTIC REFERENCE LEVELS FOR PEDIATRIC CT Birute Griciene a,b, Milda Petkelyte a,b, Arijanda Neverauskiene a,c, Linas Petkevicius d,a. aVilnius University, Faculty of Medicine, Lithuania b
Department of Clinical Radiation Surveillance, Vilnius University Hospital Santariskiu Klinikos, Lithuania c Centre of Radiology, Children’s Hospital, Affiliate of Vilnius University Hospital Santariskiu Klinikos, Lithuania d Vilnius University, Faculty of Mathematics and Informatics, Lithuania Introduction. Computed tomography (CT delivers more than a half of collective effective dose received at medical diagnostic procedures. It is recommended that routine procedures have diagnostic reference levels (DRLs) set and kept up-to-date, especially for pediatric examinations. Purpose. The main objective of this study is to analyse dose trends in 2010–2014, identify future optimisation targets and set local DRLs for most common pediatric CT examinations. Materials and methods. A retrospective study of pediatric (<18 y) patients that underwent CT examinations in 2010, 2012 and 2014 was done. Effective dose was calculated. The mean DLP, CTDIvol values were estimated for age groups, body area scanned and compared to national and European DRLs. Results. 2042 examinations were analysed, most of them (57.9%) head CT scans. Head dose decreased in all age groups from 2,9 to 1,6 mSv. In 2014 the mean DLP for head was 267, 293, 313 and 371 mGy⁄ cm for patients aged 0–1, 1–5, 5–10 and 10–18 years respectively; the mean DLP for chest was 74, 199 and 303 mGy⁄ cm for patients aged 1–5, 5–10 and 10–18 years; the mean DLP for pelvis was 69, 91, 159 and 284 mGy⁄ cm for patients aged 0–1, 1–5, 5– 10 and 10–18 years. The local DRLs for head, chest and pelvis CT were set. Conclusion. For CT procedures the comparison between local DRLs and the national DRLs shows that doses don’t exceed the recommended levels. While CT dose decreases, it is important to ensure that examinations are performed at optimised state. Disclosure. None. http://dx.doi.org/10.1016/j.ejmp.2016.07.308