Female breast radiation exposure during thorax multidetector computed tomography and the effectiveness of bismuth breast shield to reduce breast radiation dose

OBJECTIVE: The purpose of our study was to determine the breast radiation dose when performing routine thoracic multidetector computed tomography (MDCT). We also evaluated dose reduction and the effect on image quality of using a bismuth breast shield when performing thoracic MDCT. MATERIAL AND METHODS: The dose reduction achievable by shielding the adult (18 years or older) female breasts was studied in 50 women who underwent routine thoracic MDCT. All examinations were performed with a 16-MDCT scanner (Sensation Cardiac 16; Siemens Medical Solutions). To compare the shielded/unshielded breast dose, the examination was performed with (right breast) and without (left breast) breast shielding in all patients. With this technique, the superficial breast doses were calculated. To determine the average glandular breast radiation dose, we imaged an anthropomorphic dosimetric phantom into which calibrated dosimeters were placed to measure the dose to breast. The phantom was imaged using the same protocol. Radiation doses to the breasts with and without the breast shielding were measured and compared using the Student t test. RESULTS: In the qualitative evaluation of the MDCT scans, all were considered to be of diagnostic quality. We did not see any differences in quality between the shielded and unshielded lung. The mean radiation doses to the breasts with the shield and to those without the shield were 8.6 +/- 2.33 versus 14.46 +/- 3.94 mGy, respectively. The breast shield enabled a 40.53% decrease in radiation dose to the breast. The difference between the dose received by the breasts with and that received by the breasts without bismuth shielding was significant, with a P value of less than 0.001. CONCLUSIONS: Bismuth in-plane shielding for routine thoracic MDCT decreased radiation dose to the breast without qualitative changes in image quality. The other radiosensitive superficial organs (eg, testes and thyroid gland) specifically must be protected with shielding.     

Assessment of the efficiency of new bismuth composite shields in radiation dose decline to breast during chest CT

Background

Bismuth shield has been recently introduced for radiation protection of patient radiosensitive organs such as breast during chest CT with image diagnosis capability. The purpose of this study was to evaluate the dose reduction and image quality conserve using new bismuth-silicon composite shields during chest CT.

Computer-simulated radiation dose reduction for abdominal multidetector CT of pediatric patients

OBJECTIVE. Limiting CT radiation dose is especially critical when imaging children. The purpose of our study was to modify and test an accurate and safe tool for evaluating systematic dose reduction for abdominal multidetector CT (MDCT) in pediatric patients. MATERIALS AND METHODS: After validating the computer-simulation technique with a water phantom, we subjected the original digital scanning data for 26 contrast-enhanced abdominal MDCT scans (120 mA) obtained in infants and children (age range, 1 month-9 years; mean age, 3.1 years) to simulated tube current reduction (100, 80, 60, and 40 mA) by adding noise. this procedure created four additional examinations per child that were identical to the originals except for image noise. The 130 examinations were scored randomly, independently, and without prior knowledge of the children's diagnoses by three radiologists for depiction of high-visibility structures, such as adrenal glands and fat in the intrahepatic falciform ligament, and low-visibility structures, such as the extrahepatic hepatic artery, small intrahepatic vessels, and common bile duct. Aligned rank and Wilcoxon's signed rank tests were used for statistical analyses. RESULTS. Simulated tube current reduction significantly affected the detection of low-visibility structures (p < 0.001). Reduced detection in low-visibility structures was evident at a level less than or equal to 80 mA. No loss of detection in high-visibility structures was found at any tube current level (p > 0.5). CONCLUSION. The results of this computer simulation suggest that accurate abdominal MDCT can be performed in pediatric patients using substantially reduced radiation, depending on the indication for imaging. (In our case, the reduction was between 33% and 67%, depending on whether a high-visibility or low-visibility structure was being assessed.) This simulation technology can be applied to MDCT of other organ systems for systematic evaluation of radiation dose reduction.     

Radiation dose reduction in chest CT: a review

OBJECTIVE: This article aims to summarize the available data on reducing radiation dose exposure in routine chest CT protocols. First, the general aspects of radiation dose in CT and radiation risk are discussed, followed by the effect of changing parameters on image quality. Finally, the results of previous radiation dose reduction studies are reviewed, and important information contributing to radiation dose reduction will be shared. CONCLUSION: A variety of methods and techniques for radiation dose reduction should be used to ensure that radiation exposure is kept as low as is reasonably achievable.     

Low-dose multidetector dynamic CT in the breast: preliminary study

This study investigated the feasibility of using low-dose multidetector dynamic computed tomography (CT) scan for imaging breast. We measured the radiation dose using a phantom at low- and standard-dose CT. To compare the image quality at low- and standard-dose CT, we evaluated normal breasts in 57 cases. In 44 cases with breast cancer, we assessed the staging and time-enhancement curves of breast cancer. In conclusion, the low-dose multidetector dynamic CT scan is feasible for the evaluation of the breast, with reduced radiation dose and with similar image quality when compared with standard-dose CT scan. In breast cancers, low-dose dynamic CT could be used for the staging of breast cancer before surgery.     

Fetal shielding combined with state of the art CT dose reduction strategies during maternal chest CT

Purpose

Custom bismuth-antimony shields were previously shown to reduce fetal dose by 53% on an 8DR (detector row) CT scanner without dynamic adaptive section collimation (DASC), automatic tube current modulation (ATCM) or adaptive statistical iterative reconstruction (ASiR). The purpose of this study is to compare the effective maternal and average fetal organ dose reduction both with and without bismuth-antimony shields on a 64DR CT scanner using DASC, ATCM and ASiR during maternal CTPA.

Materials and methods

A phantom with gravid prosthesis and a bismuth-antimony shield were used. Thermoluminescent dosimeters (TLDs) measured fetal radiation dose. The average fetal organ dose and effective maternal dose were determined using 100 kVp, scanning from the lung apices to the diaphragm utilizing DASC, ATCM and ASiR on a 64DR CT scanner with and without shielding in the first and third trimester. Isolated assessment of DASC was done via comparing a new 8DR scan without DASC to a similar scan on the 64DR with DASC.

Results

Average third trimester unshielded fetal dose was reduced from 0.22 mGy ± 0.02 on the 8DR to 0.13 mGy ± 0.03 with the conservative 64DR protocol that included 30% ASiR, DASC and ATCM (42% reduction, P < 0.01). Use of a shield further reduced average third trimester fetal dose to 0.04 mGy ± 0.01 (69% reduction, P < 0.01). The average fetal organ dose reduction attributable to DASC alone was modest (6% reduction from 0.17 mGy ± 0.02 to 0.16 mGy ± 0.02, P = 0.014).First trimester fetal organ dose on the 8DR protocol was 0.07 mGy ± 0.03. This was reduced to 0.05 mGy ± 0.03 on the 64DR protocol without shielding (30% reduction, P = 0.009). Shields further reduced this dose to below accurately detectable levels. Effective maternal dose was reduced from 4.0 mSv on the 8DR to 2.5 mSv on the 64DR scanner using the conservative protocol (38% dose reduction).

Conclusion

ASiR, ATCM and DASC combined significantly reduce effective maternal and fetal organ dose during CTPA. Shields continue to be an effective means of fetal dose reduction.     

使用自适应统计迭代重建技术降低胸部CT辐射剂量:一项初步研究

目的在一组采用不同的管电流时间乘积(40～150mAs)的CT检查中,比较自适应统计迭代重建技术(ASIR)和滤波反向投影技术(FBP)重建获得影像的病灶显示能力及影像质量。材料与方法在这项经机构审查委员会批准,符合HIPAA标准的研究中,共有23例病人接受了CT     

Radiation dose reduction to breast and thyroid during MDCT: effectiveness of an in-plane bismuth shield

PURPOSE: To evaluate dose reduction and image deterioration using in-plane bismuth breast-shielding and thyroid-shielding for MDCT. MATERIAL AND METHODS: Skin and organ doses of thyroid and breast were measured with thermoluminescent dosimeters in a female Alderson-Rando Phantom with and without a 4-ply in-plane bismuth shield. Routine neck (120 kVp, 150 mAs(eff); 16 x 1.5 mm) and chest (120 kVp, 100 mAs(eff); 16 x 1.5 mm) scan protocols were simulated on a 16-row MDCT scanner in three different settings: without shielding, with the shield directly on the surface, and with a 1-cm-thick cotton spacer between surface and shield. Image noise was quantified and compared using the t test. RESULTS: On average, shielding resulted in a 47% organ-dose reduction for the thyroid and 32% for the breast. Placement of the spacer between shield and surface had no significant impact on the measured doses, but significantly decreased the image noise (P < 0.05). CONCLUSION: In-plane bismuth breast and thyroid shielding significantly decreases radiation dose in MDCT without deteriorating image quality.     

Coronary calcium scoring with MDCT: the radiation dose to the breast and the effectiveness of bismuth breast shield

OBJECTIVE: The purpose of our study was to determine the breast radiation dose during coronary calcium scoring with multidetector computerized tomography (MDCT). We also evaluated the degree of dose reduction by using a bismuth breast shield when performing coronary calcium scoring with MDCT. MATERIALS AND METHODS: The dose reduction achievable by shielding the adult (35 years or older) female breasts was studied in 25 women who underwent coronary calcium scoring with MDCT. All examinations were performed with a 16-MDCT scanner. To compare the shielded versus unshielded breast dose, the examinations were performed with (right breast) and without (left breast) breast shielding in all patients. With this technique the superficial breast doses were calculated. To determine the average glandular breast radiation dose, we imaged an anthropomorphic dosimetric phantom into which calibrated dosimeters were placed to measure the dose to the breast. The phantom was imaged using the same protocol. Radiation doses to the breasts with and without the breast shielding were measured and compared using the Student's t-test. RESULTS: The mean radiation doses with and without the breast shield were 5.71+/-1.1 mGy versus 9.08+/-1.5 mGy, respectively. The breast shield provided a 37.12% decrease in radiation dose to the breast with shielding. The difference between the dose received by the breasts with and without bismuth shielding was significant, with a p-value of less than 0.001. CONCLUSION: The high radiation during MDCT greatly exceeds the recommended doses and should not be underestimated. Bismuth in plane shielding for coronary calcium scoring with MDCT decreased the radiation dose to the breast. We recommend routine use of breast shields in female patients undergoing calcium scoring with MDCT.     

80kV64排多层螺旋CT低辐射肺动脉成像

目的 研究80 kV 管电压64排多层螺旋CT低辐射肺动脉成像的可行性。方法 64名志愿者随机分为2组。观察组35例采用80kV管电压CT结合右头臂静脉作为团注追踪(bolus tracking) 监测点进行肺动脉成像,对照组29例采用120kV管电压,延迟时间采用团注测试峰值时间+0.7 s,进行肺动脉成像。测量容积CT剂量指数(CTDI_vol)、剂量长度乘积(DLP),计算加权CT剂量指数(CTDI_w)和有效剂量(E),测量肺动脉强化后CT值和背景噪声,计算信噪比(SNR)和对比噪声比(CNR)。5分法对两组图像质量进行目测评分。对DLP、E、SNR、CNR进行t检验;采用Mann-Whitney U检验比较两组图像目测评分结果。结果 观察组DLP和E分别为(146.5±7.6)mGy·cm和(2.5±0.1)mSv,对照组DLP和E分别为(313.4±13.5) mGy·cm和(5.3±0.2) mSv,两者差异有统计学意义(P＜0.001),观察组的辐射剂量低于对照组。图像质量量化评价:观察组和对照组的SNR分别为32.6±3.6和31.35±2.0,差异无统计学意义(P=0.089)。观察组和对照组CNR分别为28.5±3.4和27.6±1.1,差异无统计学意义(P=0.18)。目测评分结果:观察组为5分8例,4分26例,3分1例;对照组为5分5例,4分24例,差异无统计学意义(P=0.76)。结论 80 kV 64排多层螺旋CT结合右头臂静脉作为bolus tracking 监测点可以减少辐射剂量,同时不降低图像质量,是肺动脉造影的首选检查方法。     

80 kV 64排多层螺旋CT低辐射肺动脉成像

Objective To assess the feasibility of minimizing radiation doses using 80 kV 64-row muhidetector computed tomography on pulmonary angiography.Methods 64 volunteers were derided into 2 groups to undergo MDCT pulmonary angiography(collimation,64×0.625 mm;pitch,1.204).The observed group consisting of 35 patients were for pulmonary angiography with 80 kV voltage,300 mAs,0.75 s/roation.The control group consisting of 29 patients were for pulmonary angiography with the standard tube voltage (120 kV),200 mAs,0.5 s/roation and time delay using the peak time on bolus test added 0.7 s.Volume computed tomography dose index (CTDIvol),dose length product (DLP),pulmonary vessel enhancement and back noise were quantified.Signal-noise-ratio (SNR),contrast-to-noise-ratio (CNR),weighted computed tomography dose index (CTDIw) and effective dose (E) were calculated.Results of the two protocols were compared by using t test.Two radiologists used five-point scale to subjectively score arterial enhancement and depiction of small arterial detail.The scores were compared with Mann-Whitney U test.Results The 80 kV protocol had a significantly lower DLP and E than the 120 kV protocol[(146.5±7.6)mGy·cm vs(313.4±13.5)mGy·cm,P<0.001]and [(2.5m±0.1)mGy vs (5.3±0.2)mGy,P<0.001],respectively.The 80 kV protocol and the 120 kV protocol had identical SNR(32.6±3.6 vs 31.3±2.3;P=0.089) and CNR (28.5±3.4 vs 27.6±1.1;P=0.18).No significant difference was found between the two protocols on scores for arterial enhancement and depiction of small arterial detail ( P=0.76).Conclusions 80 kV 64 slices MDCT combined with right brachiocephalic vein as the monitoring site for bolus tracking could be the first choice of pulmonary angingraphy.It can reduce the radiation dose without sacrificing the image quality.     

Quality initiatives: CT radiation dose reduction: how to implement change without sacrificing diagnostic quality

The risks and benefits of using computed tomography (CT) as opposed to another imaging modality to accomplish a particular clinical goal should be weighed carefully. To accurately assess radiation risks and keep radiation doses as low as reasonably achievable, radiologists must be knowledgeable about the doses delivered during various types of CT studies performed at their institutions. The authors of this article propose a process improvement approach that includes the estimation of effective radiation dose levels, formulation of dose reduction goals, modification of acquisition protocols, assessment of effects on image quality, and implementation of changes necessary to ensure quality. A first step toward developing informed radiation dose reduction goals is to become familiar with the radiation dose values and radiation-associated health risks reported in the literature. Next, to determine the baseline dose values for a CT study at a particular institution, dose data can be collected from the CT scanners, interpreted, tabulated, and graphed. CT protocols can be modified to reduce overall effective dose by using techniques such as automated exposure control and iterative reconstruction, as well as by decreasing the number of scanning phases, increasing the section thickness, and adjusting the peak voltage (kVp setting), tube current-time product (milliampere-seconds), and pitch. Last, PDSA (plan, do, study, act) cycles can be established to detect and minimize negative effects of dose reduction methods on image quality.     

Model-based iterative reconstruction technique for radiation dose reduction in chest CT: comparison with the adaptive statistical iterative reconstruction technique

Objectives

To prospectively evaluate dose reduction and image quality characteristics of chest CT reconstructed with model-based iterative reconstruction (MBIR) compared with adaptive statistical iterative reconstruction (ASIR).

Methods

One hundred patients underwent reference-dose and low-dose unenhanced chest CT with 64-row multidetector CT. Images were reconstructed with 50?% ASIR-filtered back projection blending (ASIR50) for reference-dose CT, and with ASIR50 and MBIR for low-dose CT. Two radiologists assessed the images in a blinded manner for subjective image noise, artefacts and diagnostic acceptability. Objective image noise was measured in the lung parenchyma. Data were analysed using the sign test and pair-wise Student’s t-test.

Results

Compared with reference-dose CT, there was a 79.0?% decrease in dose–length product with low-dose CT. Low-dose MBIR images had significantly lower objective image noise (16.93?±?3.00) than low-dose ASIR (49.24?±?9.11, P?P?Conclusion Diagnostically acceptable chest CT images acquired with nearly 80?% less radiation can be obtained using MBIR. MBIR shows greater potential than ASIR for providing diagnostically acceptable low-dose CT images without severely compromising image quality.

Key Points

? Model-based iterative reconstruction (MBIR) creates high-quality low-dose CT images. ? MBIR significantly improves image noise and artefacts over adaptive statistical iterative techniques. ? MBIR shows greater potential than ASIR for diagnostically acceptable low-dose CT. ? The prolonged processing time of MBIR may currently limit its routine use in clinical practice.     

与自适应统计迭代重建技术相比,基于模型的迭代重建技术在减少胸部CT扫描辐射剂量中的应用

摘要目的前瞻性对比研究基于模型的迭代重建(MBIR)技术与自适应统计迭代重建(ASIR)技术在减少胸部CT辐射剂量和影像质量方面的特征。方法应用64层螺旋CT对100例病人分别进行参考剂量和低剂量的胸部CT平扫。采用50%自适应统计迭代重建过滤背景投影混合技术,将重建的影像作为参考剂量CT影像,低剂量CT影像采用ASIR50及MBIR技术进行重建。由2名放射科医生评价主观图像噪声、伪影及诊断的可接受性。客观影像噪声在肺实质中测得。