Dose Length Products for the 10 Most Commonly Ordered CT Examinations in Adults: Analysis of Three Years of the ACR Dose Index Registry

As CT use steadily rises, concern over potential risks of radiation exposure from medical imaging has received increasing attention. Since May 2011, the ACR Dose Index Registry (DIR) has been open for general participation and has been collecting CT radiation dose data from an increasing number of facilities of various types. In this introductory review, we analyze the first three years of ACR DIR data, categorize the 10 most commonly performed CT examinations nationwide, review the variability of the recorded radiation dose indices for each, and take preliminary steps toward identifying possible factors associated with variability in dose indices. We believe that disseminating such information will help prompt informed improvements in standardization of CT protocols with respect to radiation dose.     

Evaluation of Radiation Exposure of Medical Staff During CT-Guided Interventions

PurposeThe purpose of this prospective study was to investigate absolute radiation exposure values and factors that influence radiation exposure of interventionists during CT-guided interventions (CTGIs). To our knowledge, no data exist regarding the radiation dose to which the interventionist is exposed during these procedures.MethodsAbsolute radiation dose values from a total of 131 CTGIs were analyzed. Radiation dose values were collected by thermoluminescent dosimeters that were positioned above the lead protection being worn, on the forehead, thyroid, chest, gonads, and right and left hand and foot.The radiation doses were analyzed with respect to the experience level of the person performing the procedure, the degree of difficulty measured on a 4-point Likert scale, the lesion size measured on a 3-point Likert scale, and the CT system used.ResultsMedian whole-body dose was 12 μSv. With the exception of the forehead, all whole-body radiation doses were statistically significantly lower in CTGIs performed using the modern dual-source CT system compared with the 16-slice multi-detector CT. For CTGIs rated as more complex, the radiation exposure of the radiologist performing the procedure was statistically significantly higher, with the exception of the left hand. A statistically significantly lower median whole-body dose was measured for inexperienced compared with experienced radiologists. However, a few dose measurements of more than 1 mSv were found at the right hand.ConclusionsRadiation exposure measured during CTGIs is low (<50 μSv). Because the radiation dose was higher in more-complex interventions and for 16-slice multi-detector row CT, inexperienced radiologists should focus on less-complex procedures.     

Physicians’ Perceptions of Radiation Dose Quantity Depend on the Language in Which It Is Expressed

PurposeRadiation dose information is increasingly requested by nonradiology providers, but there are no standard methods for communicating dose. The aim of this study was to compare physicians’ perceptions of the amount of radiation associated with similar dose quantities expressed using different dose terms to evaluate the impact of word choice on physicians’ understanding of radiation dose.MethodsInternal medicine and pediatric residents were surveyed online for 42 days. After obtaining demographics and training levels, respondents were asked to rank five different radiation dose quantities, each corresponding to one of the five ACR relative radiation levels (RRLs) expressed using different dose terms. Respondents ranked the choices from least to greatest (ie, from 1 to 5) or indicated if all five were equal. For the final question, the same dose quantity was expressed five different ways.ResultsFifty-one medicine and 45 pediatric residents responded (a 44% response rate). Mean differences in rankings were as follows: for chest x-rays, 0.109 (95% confidence interval [CI], −0.018 to 0.236); for cross-country flights, 0.462 (95% CI, 0.338 to 0.585); for natural background radiation, −0.672 (95% CI, −0.793 to −0.551); for cancer risk, −0.294 (95% CI, −0.409 to −0.178); and for ACR RRL, 0.239 (95% CI, 0.148 to 0.329). Statistically significant differences were found in the distributions of rankings (P < .001) and percentage of correct rankings across each radiation dose term (P < .001), with the ACR RRL having the highest percentage of correct rankings (61.2%).ConclusionsAdult and pediatric physicians consistently over- or underestimated radiation dose quantities using different terms to express radiation dose. These results suggest that radiation dose information should be communicated using standard terminology such as the ACR RRL scale to foster consistency and improve the accuracy of physicians’ radiation risk perceptions.     

Reducing Variability of Radiation Dose in CT: The New Frontier in Patient Safety

PurposeAlthough reducing radiation dose in CT examinations is an important goal, also important in the management of radiation dose is ensuring consistency of dose administered for a given type of examination. We have implemented an approach to reducing variance in CT radiation dose by standardizing protocols and implementing software that decreases variance.MethodsA multifaceted approach to reducing variance in CT radiation dose was utilized: (1) establishment of the Radiation Dose Optimization Committee, (2) standardization of protocols, and (3) implementation of scanner software. Two periods of data were collected: pre-intervention (January 1, 2013, to July 31, 2014) and postintervention (January 1, 2016, to December 31, 2016). The period from August 1, 2014, to December 31, 2015, represented the time the major interventions were performed.ResultsThe average radiation dose for all CT exams performed during the pre-intervention period (n = 39,314) was 22.3 CTDIvol with an SD of 17.0. The average radiation dose for all CT exams performed during the postintervention period (n = 49,863) was 13.6 CTDIvol with an SD of 9.01. The postintervention variance was significantly decreased (P < .0001).ConclusionsA significant decrease in the variability of our network CT radiation dose was achieved as a result of a combination of standardizing protocols across the network and implementation of advanced software that effectively managed radiation dose, all overseen by the Radiation Dose Optimization Committee.     

Radiation dose reduction in chest CT—Review of available options

Computed tomography currently accounts for the majority of radiation exposure related to medical imaging. Although technological improvement of CT scanners has reduced the radiation dose of individual examinations, the benefit was overshadowed by the rapid increase in the number of CT examinations. Radiation exposure from CT examination should be kept as low as reasonably possible for patient safety. Measures to avoid inappropriate CT examinations are needed. Principles and information on radiation dose reduction in chest CT are reviewed in this article.     

高端影像学体检中X线检查辐射危害的调查

 目的 探讨高端影像学体检人群历年X线检查辐射受照情况、可能带来的危害及防护策略。方法 分析研究对象X线检查数据,评估其年剂量以及累计辐射剂量;按年受照剂量分组,分析其重复照射部位阳性变化与受照剂量相关性。结果 研究对象X线年均人受照剂量4.59 mSv,达到中剂量辐射水平(3~20 mSv)。其中,116人至少接受了2次某个部位的CT重复检查,34人有阳性改变,中剂量组25人(占73.53%),低剂量组9人,检测阳性率、阴性率在两组间无统计学意义。低辐射组(43.33%)与中辐射组(56.67%)两组间性别、年龄比较差异无统计学意义。结论 该群体X线检查累计辐射剂量偏大;不少人接受了不必要的CT检查;重视和探讨体检人群辐射危害控制策略意义重大。     

Dual-Energy CT of the Abdomen and Pelvis: Radiation Dose Considerations

Dual-energy CT offers several new applications and opportunities for routine clinical practice. Increasing utilization in the context of both routine practice and clinical research raises questions about expected radiation dose when compared with conventional single-energy exams. Despite initial concerns, advanced iterative reconstruction techniques and creation of virtual unenhanced images in multiphase acquisitions offer methods for dose reduction. Although dose varies across patients and scanners, modern dual-energy exams allow for comparable and potentially decreased radiation dose when compared with single-energy CT. In this review, we examine dual-energy radiation dose considerations with discussion of accepted ACR diagnostic reference levels.     

Organizational Factors and Quality Improvement Strategies Associated With Lower Radiation Dose From CT Examinations

PurposeThe aim of this study was to identify organizational factors and quality improvement strategies associated with lower radiation doses from abdominal CT.MethodsCross-sectional survey was administered to radiology leaders, along with simultaneous measurement of CT radiation dose among 19 health care organizations with 100 imaging centers throughout the United States, Europe, and Japan, using a common dose management software system. After adjusting for patient age, gender, and size, quality improvement strategies were tested for association with mean abdominal CT radiation dose and the odds of a high-dose examination.ResultsCompleted surveys were received from 90 imaging centers (90%), and 182,415 abdominal CT scans were collected during the study period. Radiation doses varied considerably across organizations and centers. Univariate analyses identified eight strategies and systems that were significantly associated with lower average doses or lower frequency of high doses for abdominal CT examinations: tracking patient safety measures, assessing the impact of CT changes, identifying areas for improvement, setting specific goals, organizing improvement teams, tailoring decisions to sites, testing process changes before full implementation, and standardizing workflow. These processes were associated with an 18% to 37% reduction in high-dose examinations (P < .001-.03). In multivariate analysis, having a tracking system for patient safety measures, supportive radiology leaders, and obtaining clear images were associated with a 47% reduction in high-dose examinations.ConclusionsThis documentation of the relation between quality improvement strategies and radiation exposure from CT examinations has identified important information for others interested in reducing the radiation exposure of their patients.     

Estimation of the radiation exposure of a chest pain protocol with ECG-gating in dual-source computed tomography

The aim of the study was to evaluate radiation exposure of a chest pain protocol with ECG-gated dual-source computed tomography (DSCT). An Alderson Rando phantom equipped with thermoluminescent dosimeters was used for dose measurements. Exposure was performed on a dual-source computed tomography system with a standard protocol for chest pain evaluation (120 kV, 320 mAs/rot) with different simulated heart rates (HRs). The dose of a standard chest CT examination (120 kV, 160 mAs) was also measured. Effective dose of the chest pain protocol was 19.3/21.9 mSv (male/female, HR 60), 17.9/20.4 mSv (male/female, HR 80) and 14.7/16.7 mSv (male/female, HR 100). Effective dose of a standard chest examination was 6.3 mSv (males) and 7.2 mSv (females). Radiation dose of the chest pain protocol increases significantly with a lower heart rate for both males (p = 0.040) and females (p = 0.044). The average radiation dose of a standard chest CT examination is about 36.5% that of a CT examination performed for chest pain. Using DSCT, the evaluated chest pain protocol revealed a higher radiation exposure compared with standard chest CT. Furthermore, HRs markedly influenced the dose exposure when using the ECG-gated chest pain protocol.     

CT辐射剂量所面临的挑战

尽管CT检查仅占所有检查的2%,而对于公众诊断性成像的接收剂量,CT却占20%左右。具有10mSy有效剂量的成人腹部检查会增加致癌风险1/2000。儿童对于放射线影响的灵敏度是中年人的10倍多,女孩比男孩更敏感。剂量增加的原因有:CT应用的偏差、使用方便的结果、多层CT的危机、未意识到"非耦合效应"。医护人员要进行很好的培训,要意识到不断涌现的资料及实践中潜在的变化,根据进展修正方案。像进行传统X射线摄影一样,"合理使用低剂量(as low as reasonably achievable,ALARA)"原则也很适合于CT的应用。     

Patient Radiation Exposure: Imaging During Radiation Oncology Procedures: Executive Summary of NCRP Report No. 184

The National Council on Radiation Protection and Measurements (NCRP) recently assessed patient radiation exposure in the United States, which was summarized in its 2019 NCRP Report No. 184. This work involved an estimation of the number of medical procedures using ionizing radiation, as well as the associated effective doses from these procedures. The NCRP Report No. 184 committee elected to not incorporate radiation dose from radiotherapy into its calculated population dose exposures, as the assessment of effective dose for the population undergoing radiotherapy is more complex than that for other medical radiation exposures. However, the aim of NCRP Report No. 184 was to raise awareness of ancillary radiation exposures to patients undergoing radiotherapy. Overall, it was estimated that annually, in 2016, approximately 800,000 patients received approximately 1 million courses of radiation therapy. Each of these treatments includes various types of imaging that may not be familiar to radiologists or others. Exposures from radiotherapy planning and delivery are reviewed in the report and summarized in this executive summary. The imaging techniques, use of this imaging, and associated tissue doses are described. Imaging can contribute a few percent to the planned treatment doses (which are prescribed to specified target volumes) as well as exposing patients to radiation outside of the target volume (in the imaging field of view).     

CT Radiation Dose Optimization and Estimation: an Update for Radiologists

In keeping with the increasing utilization of CT examinations, the greater concern about radiation hazards from examinations has been addressed. In this regard, CT radiation dose optimization has been given a great deal of attention by radiologists, referring physicians, technologists, and physicists. Dose-saving strategies are continuously evolving in terms of imaging techniques as well as dose management. Consequently, regular updates of this issue are necessary especially for radiologists who play a pivotal role in this activity. This review article will provide an update on how we can optimize CT dose in order to maximize the benefit-to-risk ratio of this clinically useful diagnostic imaging method.     

Radiation dose in dental radiology

The aim of this study was to compare radiation exposure in panoramic radiography (PR), dental CT, and digital volume tomography (DVT). An anthropomorphic Alderson-Rando phantom and two anatomical head phantoms with thermoluminescent dosimeters fixed at appropriate locations were exposed as in a dental examination. In PR and DVT, standard parameters were used while variables in CT included mA, pitch, and rotation time. Image noise was assessed in dental CT and DVT. Radiation doses to the skin and internal organs within the primary beam and resulting from scatter radiation were measured and expressed as maximum doses in mGy. For PR, DVT, and CT, these maximum doses were 0.65, 4.2, and 23 mGy. In dose-reduced CT protocols, radiation doses ranged from 10.9 to 6.1 mGy. Effective doses calculated on this basis showed values below 0.1 mSv for PR, DVT, and dose-reduced CT. Image noise was similar in DVT and low-dose CT. As radiation exposure and image noise of DVT is similar to low-dose CT, this imaging technique cannot be recommended as a general alternative to replace PR in dental radiology.     

Radiation exposure in X-ray-based imaging techniques used in osteoporosis

Recent advances in medical X-ray imaging have enabled the development of new techniques capable of assessing not only bone quantity but also structure. This article provides (a) a brief review of the current X-ray methods used for quantitative assessment of the skeleton, (b) data on the levels of radiation exposure associated with these methods and (c) information about radiation safety issues. Radiation doses associated with dual-energy X-ray absorptiometry are very low. However, as with any X-ray imaging technique, each particular examination must always be clinically justified. When an examination is justified, the emphasis must be on dose optimisation of imaging protocols. Dose optimisation is more important for paediatric examinations because children are more vulnerable to radiation than adults. Methods based on multi-detector CT (MDCT) are associated with higher radiation doses. New 3D volumetric hip and spine quantitative computed tomography (QCT) techniques and high-resolution MDCT for evaluation of bone structure deliver doses to patients from 1 to 3 mSv. Low-dose protocols are needed to reduce radiation exposure from these methods and minimise associated health risks.     

RADIANCE: An automated, enterprise-wide solution for archiving and reporting CT radiation dose estimates

There is growing interest in the ability to monitor, track, and report exposure to radiation from medical imaging. Historically, however, dose information has been stored on an image-based dose sheet, an arrangement that precludes widespread indexing. Although scanner manufacturers are beginning to include dose-related parameters in the Digital Imaging and Communications in Medicine (DICOM) headers of imaging studies, there remains a vast repository of retrospective computed tomographic (CT) data with image-based dose sheets. Consequently, it is difficult for imaging centers to monitor their dose estimates or participate in the American College of Radiology (ACR) Dose Index Registry. An automated extraction software pipeline known as Radiation Dose Intelligent Analytics for CT Examinations (RADIANCE) has been designed that quickly and accurately parses CT dose sheets to extract and archive dose-related parameters. Optical character recognition of information in the dose sheet leads to creation of a text file, which along with the DICOM study header is parsed to extract dose-related data. The data are then stored in a relational database that can be queried for dose monitoring and report creation. RADIANCE allows efficient dose analysis of CT examinations and more effective education of technologists, radiologists, and referring physicians regarding patient exposure to radiation at CT. RADIANCE also allows compliance with the ACR's dose reporting guidelines and greater awareness of patient radiation dose, ultimately resulting in improved patient care and treatment.     

Tracking and Resolving CT Dose Metric Outliers Using Root-Cause Analysis

PurposeThe aim of this study was to examine the frequency and type of outlier dose metrics for three common CT examination types on the basis of a root-cause analysis (RCA) approach.MethodsInstitutional review board approval was obtained for this retrospective observational study. The requirement to obtain informed consent was waived. Between January 2010 and December 2013, radiation dose metric data from 34,615 CT examinations, including 26,878 routine noncontrast CT head, 2,992 CT pulmonary angiographic (CTPA), and 4,745 renal colic examinations, were extracted from a radiation dose index monitoring database and manually cleaned. Dose outliers were identified on the basis of the statistical distribution of volumetric CT dose index and dose-length product for each examination type; values higher than the 99th percentile and less than the 1st percentile were flagged for RCA.ResultsThere were 397 noncontrast CT head, 52 CTPA, and 80 renal colic outliers. Root causes for high-outlier examinations included repeat examinations due to patient motion (n = 122 [31%]), modified protocols mislabeled as “routine” (n = 69 [18%]), higher dose examinations for patients with large body habitus (n = 27 [7%]), repeat examinations due to technical artifacts (n = 20 [5%]), and repeat examinations due to suboptimal contrast timing (CTPA examinations) (n = 18 [5%]). Root causes for low-outlier examinations included low-dose protocols (n = 112 [29%]) and aborted examinations (n = 8 [2%]). On the basis of examination frequency over a 3-month period, the 90th and 10th percentile values were set in the radiation dose index monitoring database as thresholds for sending notifications to staff members responsible for outlier investigations.ConclusionsSystematic RCA of dose outliers identifies sources of variation and dose excess and pinpoints specific protocol and technical shortcomings for corrective action.     

Radiation exposure during midfacial imaging using 4- and 16-slice computed tomography, cone beam computed tomography systems and conventional radiography

OBJECTIVES: Radiation doses were determined to balance risks against usefulness of the different modalities available for the imaging of the facial skeleton. METHODS: An Alderson Rando Phantom, armed with lithium fluoride thermoluminescent dosemeters (TLDs) was exposed using a set of four conventional radiographs (orbital view, modified Waters view, orthopantomography, skull posterior--anterior 0 degrees ), two different cone beam computed tomography (CBCT) (NewTom 9000 and Siremobil Iso-C3D), and multislice computed tomography (CT) modalities (Somatom VolumeZoom and Somatom Sensation 16). TLDs from 14 well defined anatomical sites lying within the primary beam as well as the TLD corresponding to the thyroid gland were evaluated. RESULTS: Multislice CT showed the highest exposure values. Exposure levels of the CBCT systems lay between CT and conventional radiography. Dose measurement for the 16-slice CT revealed nearly the same radiation exposure as the 4-slice system when adapted examination protocols were used. CONCLUSIONS: Selection of the most appropriate imaging modality should be performed in view of the delivered doses, required image quality and information and the clinical circumstances.     

Management of Incidental Adnexal Findings on CT and MRI: A White Paper of the ACR Incidental Findings Committee

The ACR Incidental Findings Committee (IFC) presents recommendations for managing adnexal masses incidentally detected on CT and MRI. These recommendations represent an update of those provided in our previous JACR 2013 white paper. The Adnexal Subcommittee, which included six radiologists with subspecialty expertise in abdominal imaging or ultrasound and one gynecologist, developed this algorithm. The recommendations draw from published evidence and expert opinion and were finalized by iterative consensus. Algorithm branches successively categorize adnexal masses based on patient characteristics (eg, pre- versus postmenopausal) and imaging features. They terminate with a management recommendation. The algorithm addresses most, but not all, pathologies and clinical scenarios. Our goal is to improve quality of care by providing guidance on how to manage incidentally detected adnexal masses.     

Effect of multislice scanners on patient dose from routine CT examinations in East Anglia

As part of the dose optimization process, the Ionising Radiation (Medical Exposure) Regulations 2000 include requirements relating to the assessment of patient dose, and the setting and subsequent review of diagnostic reference levels. In East Anglia, audits of effective dose in CT have been carried out in 1996, 1999 and 2002. In the 2002 audit, nine of the 14 scanners assessed had been replaced since the previous audit. Eight of the new scanners were multislice scanners, acquiring up to 16 slices in a single rotation. The objective of the 2002 audit was to investigate the effect of the introduction of these multislice scanners on patient doses from routine CT examinations. Exposure parameters were collected for 10 different types of routine CT examination. In excess of 550 sets of patient data were obtained. For each of these, effective doses were calculated using the results of Monte Carlo simulations published by the National Radiological Protection Board. Averaged across all 10 examinations, regional mean effective doses are 34% higher than in 1999. The multislice scanners in the region give, on average, 35% more effective dose than the single-slice scanners. The effect of collimation in multislice scanners makes these effective dose differences most notable for examinations that use narrow slice widths. Further optimization of exposures on multislice scanners has the potential to reduce the differences observed between single-slice and multislice doses. However, when taken in combination with the increased use of CT in many hospitals, the effective dose increases observed are likely to result in a significant increase in the already substantial collective radiation dose from CT.