Transcript 등가선량
Radiation & Cardiac Diagnostic Imaging 전남대병원 핵의학과 김자혜 2013 전문의 시험 기출문제 • 통상적 용량으로 방사선피폭량이 최소인 것은? ① ② ③ ④ ⑤ Rubidium-82 PET Tl-201 SPECT Tc-99m tetrofosmin SPECT Tc-99m MIBI SPECT N-13 ammonia PET Exposure of the population of the US to ionizing radiation in early 1980s and in 2006. NCRP report No. 106 Collective effective dose as a percentage for all exposure categories in 2006 NCRP report No. 106 원자력안전위원회 공고 제2013-32호 방사선안전관리 등의 기술기준에 관한 규칙 일부개정안 행정예고 2013년 9월 3일 개정이유 및 주요내용 가. 방사선원의 시설기준과 취급기준에 혼재되어 있는 안전과 보안 관 련 기준에서 보안관련 기준을 분리․신설하여 개봉선원과 밀봉선원 시설기준과 취급기준에 방사선원에 대한 보안관리 기준을 개선하기 위함(안 제23조의2, 제29조의2, 제40조의2, 제46조의2) 나. 임신 또는 모유 수유중인 여성 환자․연구자원자 등 의료피폭대상과 방호요건 등을 정하고, 방사성동위원소 투여환자 관리․사고에 의한 의료피폭 최소화 등을 국내 의료피폭 안전규제 기준에 반영하기 위 함(안 제50조에서부터 제54조까지) 다. 전용 사용시설을 설치하지 않은 방사선투과검사 작업장에 대한 안 전기준을 강화하고 작업현장별로 방사선안전관리자 확보의무 등을 규정화하기 위함(안 제57조, 제58조, 제58조의2) 2013 전문의 시험 기출문제 • 통상적 용량으로 방사선피폭량이 최소인 것은? ① ② ③ ④ ⑤ Rubidium-82 PET Tl-201 SPECT Tc-99m tetrofosmin SPECT Tc-99m MIBI SPECT N-13 ammonia PET 50-60 3 mCi 10-30 10-30 15-20 mCi mCi mCi mCi Estimates of effective dose of standard MPI protocols Circulation 2007;116:1290-1350. Radiation dose to patients from cardiac diagnostic imaging • Nuclear scintigraphy • CT for calcium scoring and coronary angiography (CTCA) • Conventional coronary angiography 1. Nuclear Cardiology • 흡수선량 (absorbed dose, D) Gy, rad – 피폭하는 물체에 흡수되는 방사선 에너지의 양 • 등가선량 (equivalent dose, HT) Sv, rem – 조직 또는 장기의 평균흡수선량 D에 방사선가중치 (WR)의 곱 • 유효선량 (effective dose, E) Sv, rem – 같은 1 Sv의 등가선량을 받더라도 피폭부위가 유방이냐 피부냐 에 따라 영향이 다름 – 각 장기나 조직의 등가선량에 조직가중치 (WT)를 곱하고 이 결 과를 전신에 대해 합친 것. • 등가선량 (equivalent dose, HT) – 조직 또는 장기의 평균흡수선량 D에 방사선가중치 (WR)의 곱 Tissue dose coefficient • 유효선량 (effective dose, E) – 같은 1 Sv의 등가선량을 받더라도 피폭부위가 유방이냐 피부냐 에 따라 영향이 다름 – 각 장기나 조직의 등가선량에 조직가중치 (WT)를 곱하고 이 결 과를 전신에 대해 합친 것. Tissue dose coefficient Effective dose coefficient Estimates of effective dose of standard MPI protocols Using ICRP 60 tissue weighting factors Package inserts Tissue weighting factors in ICRP publication 26, 60 and 103 Effect of ICRP tissue weighting factors WT on estimates of effective dose E1 (mSv) Comparison of estimated effective doses, determined with the use of ICRP (60) and manufactureres’ PI dose coefficients Effective doses from standard nuclear cardiology procedures by ICRP 103 American Society of Nuclear Cardiology guidelines (Henzlova, 2009) European Council on Nuclear Cardiology guidelines (Hesse, 2005) ICRP publication 120 Strategies to minimize dose in cardiac nuclear imaging Tc-99m agents preferred when possible in SPECT Consider stress-first/stress-only protocol for patients with low pretest probability of stress perfusion defect Minimize activity (mCi) to that needed to obtain good image quality with high degree of confidence Consider lower activity (mCi) in smaller patients For CT attenuation correction, minimize tube current Hydrate after imaging and encourage early micturation 2. Cardiac CT • Three types of dosimetric quantities – CTDIW (weighted CT dose index) and CTDIvol (volume CT dose index) – DLP (dose length product) – Effective dose E = DLP x k k factor: 0.014 mSv mGy-1 cm-1 (cardiac study) • Factors affecting patient dose – Tube current current↑: image noise↓, radiation dose ↑ scan mode, reconstruction algorithms – Tube potential cardiac MDCT: 120 kV is common smaller patients: lower potential (100 kV) – Scan length 11-15 cm is typical greater cranicaudal coverage: CABG – Scan mode Helical scan Helical scan with ECTCM (ECG-controlled tube current modulation) Axial step-and-shoot (prospectively ECG-triggered) scan Studies reporting effective dose in CTCA Nuclear medicine imaging VS Cardiac CT Estimated effective dose and weighted organ equivalent dose CTCA: 0.6 mm slice thickness, 165 mAs ECTCM: 110 mAs CaSc: 20x1.2 mm collimation, 27 mAs Strategies to minimize dose from cardiac CT Employ ECG-controlled tube current modulation when possible (low heart rate, regular rhythm) Use beta blocker to lower heart rate, which improved efficacy of ECTCM Minimize scan length Prospective gate calcium scoring scan Match tube current to patient habitus for calcium scoring and CTCA 3. Coronary angiography In Europe, 1992-2001 Studies reporting effective dose of conventional CA UNSCEAR (UN scientific Committee on the Effects of Atomic Radiation) ≒ 7 mSv • Radial artery access > femoral access routes • Fluorography (cine) > 2 x fluoroscopy • Procedures involving right heart catheterization > 2 x fluoroscopy • Left anterior oblique view > posterior anterior or right anterior oblique view • Radiation-induced skin injury – Coronary interventions, electrophysiological procedures – Transient erythema ~ necrosis, malignancy 10 months after PCI 22 Gy Fluoroscopic time: 20 min. 5 months 3 weeks 6.5 months PCI time: 6 hours Strategies to minimize dose from fluoroscopy Employ slowest fluoroscopy and fluorography frame rates that maintain diagnostic image quality Minimize fluoroscopy and fluorography time Use least amount of image magnification needed for accurate interpretation Minimize distant from patient to image detector and x-ray tube Optimize beam collimation Minimize number of view Shield sensitive organs (eg. Gonads) Use highest acceptable kV to maintain lower possible mAs Omit left venticulography if the diagnostic information is available from other tests Circulation 2007;116:1290-1350. 다음의 심장영상의 방사선피폭에 대한 설명 중 옳은 것을 고르세요. 1. Tl-201와 Tc-99m제재를 동시에 사용한 심장핵의학 영상 은 cardiac CT angiography보다 방사선피폭량이 적다. 2. Tc-99m sestamibi의 결정장기는 lung이다. 3. N-13 ammonia PET은 Rb-82 PET보다 방사선피폭량이 낮으며, 영상의 질이 더 좋다. 4. Cardiac CT angiography촬영 시 prospective ECG gating 은, 방사선피폭량을 증가시킨다. 5. Fluoroscopy검사 시 left anterior oblique view에서 영상 을 얻으면 방사선피폭량을 감소시킨다. • Nuclear scintigraphy: 2.2 ~ 31.5 mSv • CTCA: 19 4 (or 2) mSv • CCA: 7 mSv Thank you for your attention References • ICRP publication 120, radiological protection in cardiology • Circulation 2007;116:1290-1305, radiation dose to patients from cardiac diagnostic imaging • Circulation 2009;119:1056-1065, ionizing radiation in cardiac imaging: a science advisory from the American Heart Committee on Cardiovascular Imaging and Intervention of the Council on Cardiovascular Radiology and Intervention • NCRP report No. 160 • Radiology 2010;254:326-341, Fluoroscopically Guided Interventional Procedures: A Review of Radiation Effects on Patients’ Skin and Hair • Radiology 2009;253:293-296, National Council on Radiation Protection and Measurements Report Shows Substantial Medical Exposure Increase