Aaron Sodickson

Recurrent CT, Cumulative Radiation Exposure, and Associated Radiation-induced Cancer Risks from CT of Adults

PURPOSE To estimate cumulative radiation exposure and lifetime attributable risk (LAR) of radiation-induced cancer from computed tomographic (CT) scanning of adult patients at a tertiary care academic medical center. MATERIALS AND METHODS This HIPAA-compliant study was approved by the institutional review board with waiver of informed consent. The cohort comprised 31,462 patients who underwent diagnostic CT in 2007 and had undergone 190,712 CT examinations over the prior 22 years. Each patients cumulative CT radiation exposure was estimated by summing typical CT effective doses, and the Biological Effects of Ionizing Radiation (BEIR) VII methodology was used to estimate LAR on the basis of sex and age at each exposure. Billing ICD9 codes and electronic order entry information were used to stratify patients with LAR greater than 1%. RESULTS Thirty-three percent of patients underwent five or more lifetime CT examinations, and 5% underwent between 22 and 132 examinations. Fifteen percent received estimated cumulative effective doses of more than 100 mSv, and 4% received between 250 and 1375 mSv. Associated LAR had mean and maximum values of 0.3% and 12% for cancer incidence and 0.2% and 6.8% for cancer mortality, respectively. CT exposures were estimated to produce 0.7% of total expected baseline cancer incidence and 1% of total cancer mortality. Seven percent of the cohort had estimated LAR greater than 1%, of which 40% had either no malignancy history or a cancer history without evidence of residual disease. CONCLUSION Cumulative CT radiation exposure added incrementally to baseline cancer risk in the cohort. While most patients accrue low radiation-induced cancer risks, a subgroup is potentially at higher risk due to recurrent CT imaging.

Effect of Computerized Clinical Decision Support on the Use and Yield of CT Pulmonary Angiography in the Emergency Department

PURPOSE To determine the effect of evidence-based clinical decision support (CDS) on the use and yield of computed tomographic (CT) pulmonary angiography for acute pulmonary embolism (PE) in the emergency department (ED). MATERIALS AND METHODS Institutional review board approval was obtained for this HIPAA-compliant study, which was performed between October 1, 2003, and September 30, 2009, at a 793-bed quaternary care institution with 60,000 annual ED visits. Use (number of examinations per 1000 ED visits) and yield (percentage of examinations positive for acute PE) of CT pulmonary angiography were compared before and after CDS implementation in August 2007. The authors included all adult patients presenting to the ED and developed and validated a natural language processing tool to identify acute PE diagnoses. Linear trend analysis was used to assess for variation in CT pulmonary angiography use. Logistic regression was used to determine variation in yield after controlling for patient demographic and clinical characteristics. RESULTS Of 338,230 patients presenting to the ED, 6838 (2.0%) underwent CT pulmonary angiography. Quarterly CT pulmonary angiography use increased 82.1% before CDS implementation, from 14.5 to 26.4 examinations per 1000 patients (P<.0001) between October 10, 2003, and July 31, 2007. After CDS implementation, quarterly use decreased 20.1%, from 26.4 to 21.1 examinations per 1000 patients between August 1, 2007, and September 30, 2009 (P=.0379). Overall, 686 (10.0%) of the CT pulmonary angiographic examinations performed during the 6-year period were positive for PE; subsequent to CDS implementation, yield by quarter increased 69.0%, from 5.8% to 9.8% (P=.0323). CONCLUSION Implementation of evidence-based CDS in the ED was associated with a significant decrease in use, and increase in yield, of CT pulmonary angiography for the evaluation of acute PE.

Cumulative Radiation Exposure and Cancer Risk Estimates in Emergency Department Patients Undergoing Repeat or Multiple CT

OBJECTIVE The purpose of our study was to define a conservative estimate of the number of patients undergoing repeat or multiple emergency department CT studies and to quantify their cumulative CT radiation doses and lifetime attributable risk of developing cancer. MATERIALS AND METHODS We identified all patients at a tertiary care adult academic medical center with at least three emergency department visits within a 1-year period that included CT of the neck, chest, abdomen, or pelvis. For this cohort, we identified all diagnostic CT studies over the previous 7.7 years. We calculated cumulative radiation doses by summing typical effective doses of the anatomic regions scanned, and we calculated lifetime attributable risk using the population-averaged dose-to-risk conversion factor of one cancer per 1,000 patients receiving a 10-mSv dose, in accordance with the seventh Biologic Effects of Ionizing Radiation (BEIR VII) report. RESULTS One hundred thirty emergency department patients met the inclusion criteria. Over the 7.7-year period, median, mean, and maximum values for the study count were 10, 13, and 70 with cumulative CT doses of 91, 122, and 579 mSv and lifetime attributable risk of one in 110, one in 82, and one in 17, respectively. Emergency department studies comprised 55% of those captured. Repeat imaging of the same study type represented at least half of the imaging for 72% of the cohort and all of the imaging for 12%. CONCLUSION A small proportion (1.9%) of emergency department patients undergoing CT of the neck, chest, abdomen, or pelvis have high cumulative rates of multiple or repeat imaging. Collectively, this patient subgroup may have a heightened risk of developing cancer from cumulative CT radiation exposure.

Outside Imaging in Emergency Department Transfer Patients: CD Import Reduces Rates of Subsequent Imaging Utilization

PURPOSE To test the hypothesis that among emergency department (ED) transfer patients, CD import of outside examinations into the picture archiving and communication system (PACS) decreases imaging utilization in the subsequent 24 hours. MATERIALS AND METHODS Institutional review board approval was obtained for this HIPAA-compliant study, with waiver of informed consent for retrospective medical records review. In 1487 consecutive ED patients, CD import to PACS was attempted between February 1 and August 31, 2009. Subsequent rates of imaging performed within 24 hours of any CD import attempt were extracted from the electronic medical record and compared between two patient groups: those with successful CD import and those for whom CD import had failed. Rates of all subsequent imaging and of computed tomographic (CT) imaging alone were compared by using the Wilcoxon rank sum test. ED CT utilization in the successful-import group was compared with that in a historical control group of 254 consecutive ED patients transferred with outside hospital CDs between August 2007 and January 2008, prior to implementation of import procedures. RESULTS CD import to PACS was successful in 78% (1161 of 1487) of patients. Successful CD import produced a 17% reduction (P < .001) in mean rates of all subsequent diagnostic imaging, from 3.30 to 2.74 examinations per patient in the failed-import and successful-import groups, respectively, and a 16% reduction (P = .01) in subsequent CT utilization from mean of 1.41 to 1.19 scans per patient in those respective groups. Compared with the historical control group, posttransfer utilization of CT in the ED was reduced by 29% (P < .001) from 1.18 (historical control group) to 0.84 (successful-import group) scans per patient. CONCLUSION Among ED transfer patients, CD import of outside imaging from the sending institution into the receiving institutions PACS significantly decreased the rates of subsequent imaging utilization.

Strategies for Reducing Radiation Exposure in Multi-Detector Row CT

Many tools and strategies exist to enable the reduction of radiation exposure from computed tomography (CT). The common CT metrics of x-ray output, CTDI(vol) and DLP, are explained and serve as the basis for monitoring radiation exposure from CT scans. Many strategies to dose optimize CT protocols are explored that, in combination with available hardware and software tools, allow robust diagnostic quality CT scans to be performed with a radiation exposure appropriate for the clinical scenario and the size of the patients. Specific emergency department example protocols are used to demonstrate these techniques.

Variation in Use of Head Computed Tomography by Emergency Physicians

OBJECTIVE Variation in emergency department head computed tomography (CT) use in patients with atraumatic headaches between hospitals is being measured nationwide. However, the magnitude of interphysician variation within a hospital is currently unknown. We hypothesized that there was significant variation in the rates of physician head CT use, both overall and for patients diagnosed with atraumatic headaches. METHODS This cross-sectional study was conducted in the emergency department of a large urban academic hospital, and institutional review board approval was obtained. All emergency department visits from 2009 were analyzed, and the primary outcome measure was whether or not head CT was performed. Logistic regression was used to control for patient, physician, and visit characteristics potentially associated with head CT ordering. The degree of interphysician variability was tested, both before and after controlling for these variables. RESULTS Of 55,286 emergency department patient encounters, 4919 (8.9%) involved head CT examinations. Unadjusted head CT ordering rates per physician ranged from 4.4% to 16.9% overall and from 15.2% to 61.7% in patients diagnosed with atraumatic headaches, with both rates varying significantly between physicians. Two-fold variation in head CT ordering overall (6.5%-13.5%) and approximately 3-fold variation in head CT ordering for atraumatic headaches (21.2%-60.1%) persisted even after controlling for pertinent variables. CONCLUSION Emergency physicians vary significantly in their use of head CT both overall and in patients with atraumatic headaches. Further studies are needed to identify strategies to reduce interphysician variation in head CT use.

Effect of clinical decision support on documented guideline adherence for head CT in emergency department patients with mild traumatic brain injury

Imaging utilization in emergency departments (EDs) has increased significantly. More than half of the 1.2 million patients with mild traumatic brain injury (MTBI) presenting to US EDs receive head CT. While evidence-based guidelines can help emergency clinicians decide whether to obtain head CT in these patients, adoption of these guidelines has been highly variable. Promulgation of imaging efficiency guidelines by the National Quality Forum has intensified the need for performance reporting, but measuring adherence to these imaging guidelines currently requires labor-intensive and potentially inaccurate manual chart review. We implemented clinical decision support (CDS) based on published evidence to guide emergency clinicians towards appropriate head CT use in patients with MTBI and automated data capture needed for unambiguous guideline adherence metrics. Implementation of the CDS was associated with a 56% relative increase in documented adherence to evidence-based guidelines for imaging in ED patients with MTBI.

Effects of patient size on radiation dose reduction and image quality in low-kVp CT pulmonary angiography performed with reduced IV contrast dose

The purpose of the study is to evaluate image quality and radiation exposure as a function of patient size for CT pulmonary angiography (CTPA) performed at reduced tube voltage and reduced intravenous (IV) contrast dose. We reviewed consecutive CTPAs performed between 9/1/2010 and 10/31/2010 on a 128-slice Siemens AS+ scanner using automated tube current modulation with quality reference mAs 200 and IV contrast concentration 370 mg I/ml followed by a saline flush: 99 scans at 120 kVp using 75 ml of contrast at 5 ml/s and 53 scans on patients lighter than 175 lbs at 100 kVp using 50 ml of contrast at 4 ml/s. We measured patient size (mean water-equivalent diameter) using a topogram analysis tool, signal (mean CT density) and noise (standard deviation) in the main pulmonary artery (MPA) on axial images, and calculated local CTDIvol from the kVp and mAs. Linear regression models were created for dependent variables ln(CTDIvol), signal, noise, and signal to noise ratio (SNR) as a function of independent variables size, age, gender, and kVp. After controlling for other variables, scanning at 100 kVp yielded CTDIvol reduction of 33 % (p < 0.0001), signal increase of 96 HU (p < 0.0001), and increased image noise (p < 0.0001), but without significant difference in SNR (p = 0.99). Relative to 120 kVp, 100-kVp CTPA allows simultaneous reduction of radiation exposure by 33 % and IV contrast dose by 33 % while maintaining image quality. Scanning at 100 kVp is recommended in all patients for whom the required mAs does not exceed maximum X-ray tube output.

Radiology utilization in the emergency department: trends of the past 2 decades.

OBJECTIVE The objective of our study was to assess radiology utilization trends for emergency department (ED) patients from 1993 through 2012. MATERIALS AND METHODS For this retrospective study, we reviewed radiology utilization at a 793-bed quaternary care academic medical center from January 1, 1993, through December 31, 2012, during which time the number of ED patient visits increased from approximately 48,000 to 61,000, and determined the number of imaging studies by modality (radiography, sonography, CT, MRI, other) and associated relative value units (RVUs). We used linear regression to assess for trends in the number of imaging RVUs and imaging accession numbers, our primary and secondary outcomes, respectively. RESULTS The total RVUs attributable to ED imaging per 1000 ED visits increased 208% from 1993 to 2007 (p < 0.0001) and then decreased 24.7% by 2012 (p = 0.0019). The total number of imaging accession numbers per 1000 ED visits increased 47.8% from 1993 until 2005 (p = 0.0003) and then decreased 26.9% by 2012 (p < 0.0001). CT RVUs per 1000 ED visits increased 493% until 2007 (p < 0.0001) and then decreased 33.4% (p < 0.0001), and MRI RVUs increased 2475% until 2008 (p < 0.0001) and then decreased 20.6% (p < 0.0032). Sonography RVUs increased 75.7% over the study period (p < 0.0001), whereas radiography RVUs decreased 28.1% (p = 0.0009). CONCLUSION After a period of substantial increase from 1993 to 2007, volume-adjusted ED imaging RVUs declined from 2007 through 2012, largely because of the decreasing use of CT and MRI. Additional studies are needed to determine the causes of this decline, which may include quality improvement activities, advocacy for appropriateness by leadership, concerns regarding radiation exposure and cost, and health information technology interventions.

Exposing Exposure: Automated Anatomy-specific CT Radiation Exposure Extraction for Quality Assurance and Radiation Monitoring

PURPOSE To develop and validate an informatics toolkit that extracts anatomy-specific computed tomography (CT) radiation exposure metrics (volume CT dose index and dose-length product) from existing digital image archives through optical character recognition of CT dose report screen captures (dose screens) combined with Digital Imaging and Communications in Medicine attributes. MATERIALS AND METHODS This institutional review board-approved HIPAA-compliant study was performed in a large urban health care delivery network. Data were drawn from a random sample of CT encounters that occurred between 2000 and 2010; images from these encounters were contained within the enterprise image archive, which encompassed images obtained at an adult academic tertiary referral hospital and its affiliated sites, including a cancer center, a community hospital, and outpatient imaging centers, as well as images imported from other facilities. Software was validated by using 150 randomly selected encounters for each major CT scanner manufacturer, with outcome measures of dose screen retrieval rate (proportion of correctly located dose screens) and anatomic assignment precision (proportion of extracted exposure data with correctly assigned anatomic region, such as head, chest, or abdomen and pelvis). The 95% binomial confidence intervals (CIs) were calculated for discrete proportions, and CIs were derived from the standard error of the mean for continuous variables. After validation, the informatics toolkit was used to populate an exposure repository from a cohort of 54 549 CT encounters; of which 29 948 had available dose screens. RESULTS Validation yielded a dose screen retrieval rate of 99% (597 of 605 CT encounters; 95% CI: 98%, 100%) and an anatomic assignment precision of 94% (summed DLP fraction correct 563 in 600 CT encounters; 95% CI: 92%, 96%). Patient safety applications of the resulting data repository include benchmarking between institutions, CT protocol quality control and optimization, and cumulative patient- and anatomy-specific radiation exposure monitoring. CONCLUSION Large-scale anatomy-specific radiation exposure data repositories can be created with high fidelity from existing digital image archives by using open-source informatics tools.