Computed tomography for pulmonary embolism: scan assessment of a one-year cohort and estimated cancer risk associated with diagnostic irradiation. Award: Poster No.: E-0004 Certificate of Merit Congress: ESTI 2012 Type: Authors: Keywords: Scientific Exhibit T. Niemann 1, I. Zbinden 1, H. W. Roser 1, J. Bremerich 1, M. Remy- Jardin 2, G. Bongartz 1 ; 1 Basel/CH, 2 Lille/FR Thorax, Radioprotection / Radiation dose, CT-Angiography, Radiation effects, Radiation safety, Biological effects Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. www.myesr.org Page 1 of 10
Objectives The objective of this study is to demonstrate a method applicable to larger populations to evaluate the additional lifetime attributable risk (LAR) of cancer incidence and cancer mortality due to a single diagnostic chest CT applicable to a larger population, namely a one-year cohort of consecutive patients referred for chest CT for suspected pulmonary embolism. Materials and Methods A one-year cohort of consecutive chest CT admitted to our service for suspected pulmonary embolism was analysed retrospectively. The cohort consisted of 691 patients (352 male, 339 female), mean age 66 years (SD 13 years). See fig. 1 for age distribution. All scans were peformed on a Siemens Sensation 10, 16 or 64 CT system (120 kv, 100 refmas, 0.5 s, pitch 1.3-1.4). For each CT system a standard scan was simulated using CT-Expo Version 2.0.1 (developed by G. Stamm and H. D. Nagel Hannover/ Hamburg, Germany, 2001-2001) [Stamm G, Nagel HD. CT-expo--a novel program for dose evaluation in CT. Rofo 2002; 174:1570-1576]. A standardized scan length was assumed from the lowest part of the lower pleural recessus to the apex of the lungs (fig. 2). Scanner specific organ doses derived were used for normalisation of patient data. To estimate patient specific organ doses we then applied a correction factor using CTDI vol (patient specific) that was derived from each examination and that was divided by CTDI vol (standard examination) that was estimated using the simulated CT protocol as described. The mean predicted cancer incidence and the predicted cancer mortality were calculated based on the BEIR VII results [National Research Council. Health Risks from Exposure to Low Levels of Ionizing Radiation: BEIR VII Phase 2. Washington, DC: The National Academies Press, 2006]. Natural occurring lifetime risks for the cancers were derived from the Surveillance, Epidemiology and End Results (SEER) data from the US National Cancer Institute [US Page 2 of 10
National Institutes of Health. Surveillance Epidemiology and End Results (SEER). http:// seer.cancer.gov/. 2011]. Images for this section: Fig. 1: age distribution Page 3 of 10
Fig. 2: simulation of standard scan using mean mas of patients concerned and assuming standardized scan length. Page 4 of 10
Results The mean effective dose for a chest CTA was 4.35 msv (SD 0.31) for both sexes based on an ICRP 60 calculation. See tab. 1 for detailled results of risk estimation of cancer incidence for the population analysed. The analysis shows, that the attributable risk of cancer incidence remains low for all specific cancer sites given in this patient cohort. Though, when calculating relative risks compared to natural estimates there is an increase of up to 1.03% for the thyroid, 0.61% for the lungs and 0.4% for the breasts in 20 year female patient. Adding up relative risks for all cancer sites analysed results in a cumulative increase of up to 2.76% in 20 year female patient (1.67% in 20 year male patient). See tab. 2 for detailled results of risk estimation of cancer mortality. Again, the absolute lifetime attributable risk of organ cancer associated mortality remains low. Relative risks increase accordingly to incidence estimates highest for 20 year female patient (0.67% for the lungs and 0.41% for the breasts). Cumulative relative risk was highest for 20 year females up to 1.85% (1.03% for 20 year male patient) for the cancer sites analysed. Images for this section: Page 5 of 10
Table 1: lifetime attributable risk of cancer incidence after one chest CTA examination in our population analysed per 100000 persons exposed. The naturally occurring lifetime attributable risks of developing cancer for the cancer sites analysed are derived from Surveillance, Epidemiology and End Results (SEER) data from the US National Cancer Institute. Page 6 of 10
Table 2: lifetime attributable risk of cancer mortality after one chest CTA in our population analysed per 100000 persons exposed. The natural occurring risks of cancer associated mortality for the cancer sites analysed are again derived from Surveillance, Epidemiology and End Results (SEER) data from the US National Cancer Institute. Page 7 of 10
Conclusions The absolute attributable organ specific risks of cancer incidence and cancer mortality for a single chest CTA for pulmonary embolism are low for all age groups and sex, but substantial in relative cumulative analysis for young patients (2.76% incidence LAR for 20 year females). Organs at highest relative risks are the thyroid, followed by the lungs and the breasts. Hence the risk for radiation induced organ cancers must be considered and outweighed both against the potential benefit of treatment and the potential risks of a missed and therefore untreated pulmonary embolism, especially in young patients. Thus basic knowledge of risk estimates associated with diagnostic irradiation is crucial when justifying CT scans for both radiologists and questioners. See fig. 3 for acknowledgement. Images for this section: Page 8 of 10
Fig. 3: acknowledgement Page 9 of 10
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