ABSTRACT
Objective:To study the feasibility that using size-specific dose estimation (SSDE) to estimate organ dose and effective dose in coronary CT angiography (CTA).Methods:Totally 421 consecutive patients with coronary artery CTA were included and retrospectively analized. All patients were scanned using the 3rd generation dual-source Force CT with prospectively ECG gated axis scan mode. The size specific dose estimation(SSDE) for each patient was conducted by calculate water equivalent diameters with Radimetrics. The organ doses of heart, lung, liver and breast, were estimated with Monte Carlo method. Patient-specific effective dose was calculated as a weighted sum of simulated organ doses with the coefficients from ICRP 103. Linear correlation analysis was used to validate the relationship between SSDE and organ doses as well as effective dose, and to derive coefficients for patient specific dose estimation. The mean error rate was used to evaluate estimation accuracy.Results:The CTDI vol, SSDE and effective dose were (16.8±8.7)mGy, (20.8±8.8)mGy and (4.4±2.9)mSv, respectively. The linear fitting formula for estimating organ dose based on SSDE were: Y=1.2 X-6.4 ( R2=0.91, P<0.05, mean error 0.1%) for heart, Y=1.4 X-7.4 ( R2=0.91, P<0.05, mean error 7.9%) for breast, Y=0.89 X-4.6 ( R2=0.86, P<0.05, mean error 8.3%) for lung, and Y=0.36 X-1.8 ( R2=0.64, P<0.05, mean error -17.9%) for liver. The linear fitting formula for estimating the individual effective dose based on SSDE were: Y=0.21 X-1.2 ( R2=0.92, P<0.05, mean error 0.2%) for men, Y=0.39 X-2.2 ( R2=0.93, P<0.05, mean error 1.7%) for women. Conclusions:In coronary artery CTA, the absorbed dose of the organs and patient specific effective dose could be estimated with SSDE and the corresponding conversion coefficients, which will help to achieve personalized assessment and precise management of patient radiation dose and risk in clinical practice.
ABSTRACT
Objective To estimate the lifetime attributable risk (LAR) of lung cancer,stomach cancer,liver cancer,thyroid cancer,breast cancer and leukemia for 1-,5-and 10-year old children undergoing chest CT scan.Methods Chest CT images of children was retrieved from the picture archiving and communication system (PACS) and the average CT number and area of the region of interest (ROI) were read on the CT work station.Water equivalent diameter were calculated according to the method recommended by the American Association of Physicists in Medicine (AAPM).Furthermore,the size-specific dose estimation (SSDE) was made based on the water equivalent diameter and the volume computed tomography dose index(CTDIvol).Based on the method recommended by Caro Franck,the SSDE then was converted into average organ doses to lung,stomach,liver,thyroid,breast and blood for children at different ages and of different sex undergoing chest CT scan.On the basis of average organ dose,the cancer risk prediction model from the National Academy of Science's Biological Effects of Ionizing Radiation-Ⅶ (BEIR-Ⅶ) was used to predict the LAR for different cancers mentioned above.For lung cancer,gastric cancer,liver cancer and leukemia,the calculating sequence was from average organ dose to excess relative risk (ERR) to LAR,whereas for the thyroid cancer and breast cancer,the sequence was from ERR to average organ dose to LAR.Results The average organ dose to lung,stomach,liver,thyroid,breast and blood for children at different age and of different sex undergoing chest CT scan was obtained.The age had a statistically significant impact on the SSDE (t =24.28,P ＜ 0.05),but sex has not (P ＞ 0.05).LAR for lung cancer,gastric cancer,liver cancer,thyroid cancer,breast cancer and leukemia for 1-,5-and 10-year old children undergoing chest CT scan was obtained,among whom the LAR for thyroid cancer and breast cancer was relatively high.The LAR for women breast cancer was 10.9 per 100 000 persons for 1 year old children,30.8 per 100 000 persons for 5 years old and 34.5 per 100 000 persons for 10 years old.Conclusions With introduction of new technologies,the radiation dose due to chest CT scan is on the decline.But the induced radiation dose is still significant compared with general diagnostic radiography.The risk of cancer still deserves more attention and should be taken into consideration in the justification of diagnostic radiology.