International variation in radiation dose for computed tomography examinations: prospective cohort study.

OBJECTIVE: To determine patient, institution, and machine characteristics that contribute to variation in radiation doses used for computed tomography (CT). DESIGN: Prospective cohort study. SETTING: Data were assembled and analyzed from the University of California San Francisco CT International Dose Registry. PARTICIPANTS: Standardized data from over 2.0 million CT examinations of adults who underwent CT between November 2015 and August 2017 from 151 institutions, across seven countries (Switzerland, Netherlands, Germany, United Kingdom, United States, Israel, and Japan). MAIN OUTCOME MEASURES: Mean effective doses and proportions of high dose examinations for abdomen, chest, combined chest and abdomen, and head CT were determined by patient characteristics (sex, age, and size), type of institution (trauma center, care provision 24 hours per day and seven days per week, academic, private), institutional practice volume, machine factors (manufacturer, model), country, and how scanners were used, before and after adjustment for patient characteristics, using hierarchical linear and logistic regression. High dose examinations were defined as CT scans with doses above the 75th percentile defined during a baseline period. RESULTS: The mean effective dose and proportion of high dose examinations varied substantially across institutions. The doses varied modestly (10-30%) by type of institution and machine characteristics after adjusting for patient characteristics. By contrast, even after adjusting for patient characteristics, wide variations in radiation doses across countries persisted, with a fourfold range in mean effective dose for abdomen CT examinations (7.0-25.7 mSv) and a 17-fold range in proportion of high dose examinations (4-69%). Similar variation across countries was observed for chest (mean effective dose 1.7-6.4 mSv, proportion of high dose examinations 1-26%) and combined chest and abdomen CT (10.0-37.9 mSv, 2-78%). Doses for head CT varied less (1.4-1.9 mSv, 8-27%). In multivariable models, the dose variation across countries was primarily attributable to institutional decisions regarding technical parameters (that is, how the scanners were used). CONCLUSIONS: CT protocols and radiation doses vary greatly across countries and are primarily attributable to local choices regarding technical parameters, rather than patient, institution, or machine characteristics. These findings suggest that the optimization of doses to a consistent standard should be possible. STUDY REGISTRATION: Clinicaltrials.gov NCT03000751.

Optimizing Radiation Doses for Computed Tomography Across Institutions: Dose Auditing and Best Practices.

Importance: Radiation doses for computed tomography (CT) vary substantially across institutions. Objective: To assess the impact of institutional-level audit and collaborative efforts to share best practices on CT radiation doses across 5 University of California (UC) medical centers. Design, Setting, and Participants: In this before/after interventional study, we prospectively collected radiation dose metrics on all diagnostic CT examinations performed between October 1, 2013, and December 31, 2014, at 5 medical centers. Using data from January to March (baseline), we created audit reports detailing the distribution of radiation dose metrics for chest, abdomen, and head CT scans. In April, we shared reports with the medical centers and invited radiology professionals from the centers to a 1.5-day in-person meeting to review reports and share best practices. Main Outcomes and Measures: We calculated changes in mean effective dose 12 weeks before and after the audits and meeting, excluding a 12-week implementation period when medical centers could make changes. We compared proportions of examinations exceeding previously published benchmarks at baseline and following the audit and meeting, and calculated changes in proportion of examinations exceeding benchmarks. Results: Of 158 274 diagnostic CT scans performed in the study period, 29 594 CT scans were performed in the 3 months before and 32 839 CT scans were performed 12 to 24 weeks after the audit and meeting. Reductions in mean effective dose were considerable for chest and abdomen. Mean effective dose for chest CT decreased from 13.2 to 10.7 mSv (18.9% reduction; 95% CI, 18.0%-19.8%). Reductions at individual medical centers ranged from 3.8% to 23.5%. The mean effective dose for abdominal CT decreased from 20.0 to 15.0 mSv (25.0% reduction; 95% CI, 24.3%-25.8%). Reductions at individual medical centers ranged from 10.8% to 34.7%. The number of CT scans that had an effective dose measurement that exceeded benchmarks was reduced considerably by 48% and 54% for chest and abdomen, respectively. After the audit and meeting, head CT doses varied less, although some institutions increased and some decreased mean head CT doses and the proportion above benchmarks. Conclusions and Relevance: Reviewing institutional doses and sharing dose-optimization best practices resulted in lower radiation doses for chest and abdominal CT and more consistent doses for head CT.

Renal cell carcinoma attenuation values on unenhanced CT: importance of multiple, small region-of-interest measurements.

OBJECTIVE: Since it has been suggested that benign renal cysts can be diagnosed at unenhanced CT on the basis of homogeneity and attenuations of 20 HU or less, we determined the prevalence of renal cell carcinomas (RCCs) with these characteristics using two different methods of measuring attenuation. MATERIALS AND METHODS: After IRB approval, two radiologists obtained unenhanced attenuation values of 104 RCCs (mean size 5.6 cm) using a single, large region of interest (ROI), two-thirds the size of the mass. They were then determined if the masses appeared heterogeneous. Of RCCs measuring 20 HU or less, those which appeared homogeneous were re-measured with multiple (6 or more), small (0.6 cm2 or smaller) ROIs dispersed throughout the lesion. Masses with attenuations 20 HU or less were compared to those with masses with HU greater than 20 for any differences in demographic data. RESULTS: Of 104 RCCS, 24 RCC had HU less than 20 using a large ROI. Of these, 21 appeared heterogeneous and 3 appeared homogeneous. Using multiple small ROIs, these three RCCs revealed maximum attenuation values above 20 HU (Range: 26-32 HU). A greater portion of RCCs measuring 20 HU or less using a large ROI were clear cell sub-type. There were no other differences. CONCLUSIONS: Renal cell carcinoma can measure 20 HU or less at unenhanced CT when a single large ROI is used. While most appear heterogeneous, some may appear homogeneous, but will likely reveal attenuations greater than 20 HU when multiple, small ROIs are used. This knowledge may prevent some RCCs from being misdiagnosed as cysts on unenhanced CT.

Predictors of CT Radiation Dose and Their Effect on Patient Care: A Comprehensive Analysis Using Automated Data.

Purpose To determine patient, vendor, and institutional factors that influence computed tomography (CT) radiation dose. Materials and Methods The relevant institutional review boards approved this HIPAA-compliant study, with waiver of informed consent. Volume CT dose index (CTDIvol) and effective dose in 274 124 head, chest, and abdominal CT examinations performed in adult patients at 12 facilities in 2013 were collected prospectively. Patient, vendor, and institutional characteristics that could be used to predict (a) median dose by using linear regression after log transformation of doses and (b) high-dose examinations (top 25% of dose within anatomic strata) by using modified Poisson regression were assessed. Results There was wide variation in dose within and across medical centers. For chest CTDIvol, overall median dose across all institutions was 11 mGy, and institutional median dose was 7-16 mGy. Models including patient, vendor, and institutional factors were good for prediction of median doses (R2 = 0.31-0.61). The specific institution where the examination was performed (reflecting the specific protocols used) accounted for a moderate to large proportion of dose variation. For chest CTDIvol, unadjusted median CTDIvol was 16.5 mGy at one institution and 6.7 mGy at another (adjusted relative median dose, 2.6 mGy [95% confidence interval: 2.5, 2.7]). Several variables were important predictors that a patient would undergo high-dose CT. These included patient size, the specific institution where CT was performed, and the use of multiphase scanning. For example, while 49% of patients (21 411 of 43 696) who underwent multiphase abdominal CT had a high-dose examination, 8% of patients (4977 of 62 212) who underwent single-phase CT had a high-dose examination (adjusted relative risk, 6.20 [95% CI: 6.17, 6.23]). If all patients had been examined with single-phase CT, 69% (18 208 of 26 388) of high-dose examinations would have been eliminated. Patient size, institutional-specific protocols, and multiphase scanning were the most important predictors of dose (change in R2 = 8%-32%), followed by manufacturer and iterative reconstruction (change in R2, 0.2%-15.0%). Conclusion CT doses vary considerably within and across facilities. The primary factors that influenced dose variation were multiphase scanning and institutional protocol choices. It is unknown if the variation in these factors influenced diagnostic accuracy. © RSNA, 2016.

Radiation Doses in Consecutive CT Examinations from Five University of California Medical Centers.

PURPOSE: To summarize data on computed tomographic (CT) radiation doses collected from consecutive CT examinations performed at 12 facilities that can contribute to the creation of reference levels. MATERIALS AND METHODS: The study was approved by the institutional review boards of the collaborating institutions and was compliant with HIPAA. Radiation dose metrics were prospectively and electronically collected from 199 656 consecutive CT examinations in 83 181 adults and 3871 consecutive CT examinations in 2609 children at the five University of California medical centers during 2013. The median volume CT dose index (CTDIvol), dose-length product (DLP), and effective dose, along with the interquartile range (IQR), were calculated separately for adults and children and stratified according to anatomic region. Distributions for DLP and effective dose are reported for single-phase examinations, multiphase examinations, and all examinations. RESULTS: For adults, the median CTDIvol was 50 mGy (IQR, 37-62 mGy) for the head, 12 mGy (IQR, 7-17 mGy) for the chest, and 12 mGy (IQR, 8-17 mGy) for the abdomen. The median DLPs for single-phase, multiphase, and all examinations, respectively, were as follows: head, 880 mGy · cm (IQR, 640-1120 mGy · cm), 1550 mGy · cm (IQR, 1150-2130 mGy · cm), and 960 mGy · cm (IQR, 690-1300 mGy · cm); chest, 420 mGy · cm (IQR, 260-610 mGy · cm), 880 mGy · cm (IQR, 570-1430 mGy · cm), and 550 mGy · cm (IQR 320-830 mGy · cm); and abdomen, 580 mGy · cm (IQR, 360-860 mGy · cm), 1220 mGy · cm (IQR, 850-1790 mGy · cm), and 960 mGy · cm (IQR, 600-1460 mGy · cm). Median effective doses for single-phase, multiphase, and all examinations, respectively, were as follows: head, 2 mSv (IQR, 1-3 mSv), 4 mSv (IQR, 3-8 mSv), and 2 mSv (IQR, 2-3 mSv); chest, 9 mSv (IQR, 5-13 mSv), 18 mSv (IQR, 12-29 mSv), and 11 mSv (IQR, 6-18 mSv); and abdomen, 10 mSv (IQR, 6-16 mSv), 22 mSv (IQR, 15-32 mSv), and 17 mSv (IQR, 11-26 mSv). In general, values for children were approximately 50% those for adults in the head and 25% those for adults in the chest and abdomen. CONCLUSION: These summary dose data provide a starting point for institutional evaluation of CT radiation doses.

Accuracy and radiation dose reduction of a limited abdominopelvic CT in the diagnosis of acute appendicitis.

PURPOSE: To determine the accuracy and radiation dose reduction of a limited abdominopelvic CT from the bottom of T10 to the top of the pubic symphysis in patients with suspected acute appendicitis. METHODS: We performed a HIPAA compliant and IRB-approved retrospective study of adult patients who underwent CT abdomen/pelvis for suspected appendicitis. The Z-axis length and whole body effective doses of the original full scan and theoretical limited scan from the bottom of T10 to the top of the pubic symphysis were recorded. Images were reviewed to determine if the appendix or entire cecum would be visualized and if any cases of appendicitis or alternative diagnoses would be missed with the limited scan. RESULTS: 235 patients (89 male, mean age 44.6 years) were included. The limited scan resulted in a mean Z-axis length reduction of 5.1 cm superiorly, 6.1 cm inferiorly, and a total reduction of 11.2 cm (24%). The mean whole body effective dose was 11.8 and 9.1 mSv for the original and limited scans, respectively (23% reduction). The entire appendix or cecum was visualized in all cases. Appendicitis was present in 24 cases and an alternative diagnosis was made in 75. No cases of appendicitis or alternative diagnoses were missed using the limited scan. CONCLUSIONS: A limited range CT from the bottom of T10 to the top of the pubic symphysis is as accurate as full abdominopelvic CT in evaluating patients with suspected acute appendicitis and results in approximately 23% dose reduction.

Optimizing bone surveys performed for suspected non-accidental trauma with attention to maximizing diagnostic yield while minimizing radiation exposure: utility of pelvic and lateral radiographs.

BACKGROUND: Skeletal surveys for non-accidental trauma (NAT) include lateral spinal and pelvic views, which have a significant radiation dose. OBJECTIVE: To determine whether pelvic and lateral spinal radiographs should routinely be performed during initial bone surveys for suspected NAT. MATERIALS AND METHODS: The radiology database was queried for the period May 2005 to May 2011 using CPT codes for skeletal surveys for suspected NAT. Studies performed for skeletal dysplasia and follow-up surveys were excluded. Initial skeletal surveys were reviewed to identify fractures present, including those identified only on lateral spinal and/or pelvic radiographs. Clinical information and MR imaging was reviewed for the single patient with vertebral compression deformities. RESULTS: Of the 530 children, 223 (42.1%) had rib and extremity fractures suspicious for NAT. No fractures were identified solely on pelvic radiographs. Only one child (<0.2%) had vertebral compression deformities identified on a lateral spinal radiograph. This infant had rib and extremity fractures and was clinically paraplegic. MR imaging confirmed the vertebral body fractures. CONCLUSION: Since no fractures were identified solely on pelvic radiographs and on lateral spinal radiographs in children without evidence of NAT, nor in nearly all with evidence of NAT, inclusion of these views in the initial evaluation of children for suspected NAT may not be warranted.

Consuming fructose-sweetened, not glucose-sweetened, beverages increases visceral adiposity and lipids and decreases insulin sensitivity in overweight/obese humans.

Studies in animals have documented that, compared with glucose, dietary fructose induces dyslipidemia and insulin resistance. To assess the relative effects of these dietary sugars during sustained consumption in humans, overweight and obese subjects consumed glucose- or fructose-sweetened beverages providing 25% of energy requirements for 10 weeks. Although both groups exhibited similar weight gain during the intervention, visceral adipose volume was significantly increased only in subjects consuming fructose. Fasting plasma triglyceride concentrations increased by approximately 10% during 10 weeks of glucose consumption but not after fructose consumption. In contrast, hepatic de novo lipogenesis (DNL) and the 23-hour postprandial triglyceride AUC were increased specifically during fructose consumption. Similarly, markers of altered lipid metabolism and lipoprotein remodeling, including fasting apoB, LDL, small dense LDL, oxidized LDL, and postprandial concentrations of remnant-like particle-triglyceride and -cholesterol significantly increased during fructose but not glucose consumption. In addition, fasting plasma glucose and insulin levels increased and insulin sensitivity decreased in subjects consuming fructose but not in those consuming glucose. These data suggest that dietary fructose specifically increases DNL, promotes dyslipidemia, decreases insulin sensitivity, and increases visceral adiposity in overweight/obese adults.

Computer-assisted image analysis of bronchioloalveolar carcinoma.

In clinical trials, response rate is an important endpoint for assessing the efficacy of an anticancer drug. The Response Evaluation Criteria for Solid Tumors (RECIST) has been widely used as a standard method to assess response. The RECIST requires only 1-dimensional measurement of tumor size. However, bronchioloalveolar carcinoma (BAC), which commonly presents as infiltrative or micronodular lesions, is not always readily assessable by RECIST. During the past 2 years, we have been developing computer-based programs to more accurately measure tumor size on chest computed tomography (CT) scans. In a first-generation computer-assisted image analysis (CAIA) system, we were able to capture and quantify lesions on CT scans by linking the software programs of eFilm, HyperSnap, and Scion. We have applied this CAIA approach to measuring BAC response to gefitinib in the Southwest Oncology Group (S0126) trial. However, this first-generation CAIA system involves multiple manual steps and is therefore labor intensive. We are now developing a fully automated CAIA program based on a versatile software platform, ImageJ, created at the National Institutes of Health. Taking theoretical and physical considerations into account, Java plug-in programs for ImageJ are created to automatically analyze CT scans in the Digital Imaging and Communications in Medicine format. We have demonstrated the feasibility of an ImageJ-based automated CAIA program for measuring BAC bidimensionally on CT scans. This automated CAIA system will be applied in a prospective clinical trial of the GVAX vaccine in patients with BAC.