D Zamora

Effective and Organ Specific Radiation Doses from Videourodynamics in Children

PURPOSE Effective and organ specific doses of ionizing radiation during videourodynamics are unknown. We estimated radiation exposure in children undergoing videourodynamics, and identified patient and examination factors that contribute to higher dosing. MATERIALS AND METHODS Fluoroscopy data were collected from consecutive patients undergoing videourodynamics. Documented dose metrics were used to calculate entrance skin dose after applying a series of correction factors. Effective doses and organ specific doses (ovaries/testes) were estimated from entrance skin dose using Monte Carlo methods on a mathematical anthropomorphic phantom (ages 0, 1, 5, 10 and 15 years). Regression analysis was performed to determine patient and procedural factors associated with higher dosing. RESULTS A total of 100 children (45% male, mean ± SD age 9.3 ± 5.7 years) were studied. Diagnoses included neurogenic bladder (73%), anatomical abnormality (14%) and functional/nonneurogenic disorder (13%). Mean fluoroscopy time was 0.17 ± 0.12 minutes. Mean age adjusted entrance skin dose, effective dose, and testis and ovary doses were 2.18 ± 2.00 mGy, 0.07 ± 0.05 mSv, 0.09 ± 0.10 mGy and 0.20 ± 0.13 mGy, respectively. On univariate analysis age, height, weight, body mass index, bladder capacity and fluoroscopy time were associated with effective dose. On multivariate adjusted analysis, body mass index, bladder capacity and fluoroscopy time were independently associated with effective dose. CONCLUSIONS The average effective dose of ionizing radiation from videourodynamics was less compared to voiding cystourethrogram dose reported in the literature. Greater fluoroscopy time, body mass index and bladder capacity are independently associated with higher dosing.

Estimated Skin Dose Look-Up Tables and Their Effect on Dose Awareness in the Fluoroscopy-Guided Imaging Suite

OBJECTIVE The displayed air kerma during a fluoroscopy-guided procedure often does not represent the entrance skin dose. The purpose of this work is to develop a system-specific air kerma-to-entrance skin dose look-up table (LUT) for immediate reference and to evaluate its clinical utility. MATERIALS AND METHODS Physicists are often involved in retrospective dosimetry and risk estimates. Conservative dosimetry conversion factors, represented by the total conversion factor, prospectively estimate the maximum potential skin dose from the displayed air kerma. Air kerma-to-skin dose LUTs with corresponding tissue reactions and approximate time-of-onset can be posted for reference. By developing skin dose LUTs, physicians can actively evaluate during the procedure the potential for deterministic skin reactions. System user surveys evaluated the impact of LUTs on dose awareness. RESULTS The range of the total conversion factor to the displayed air kerma for the nine systems evaluated was 0.8-1.6 for frontal x-ray tubes. Skin dose LUTs were posted in all imaging suites, and two surveys reported user feedback. Radiology technologists indicated that LUTs improved user dose awareness. Twelve of 14 physician respondents indicated an understanding that entrance skin dose is not equal to the displayed air kerma. CONCLUSION Our efforts focused on educating fluoroscopy users about differences between displayed air kerma and the entrance skin dose while increasing dose awareness using an accessible and easy-to-understand tool. Skin dose LUTs provide physicians and staff an immediate reference for the maximum estimated entrance skin dose and the associated deterministic skin effects, allowing appropriate patient management.

Targeted CT Dose Reduction Using a Novel Dose Metric and the American College of Radiology Dose Index Registry: Application to Thoracic CT Angiography.

OBJECTIVE The purpose of this article is to illustrate the use of the American College of Radiology Dose Index Registry data with a novel measurement of exposure to guide quality improvement efforts. MATERIALS AND METHODS Using information from the Dose Index Registry report covering July through December 2012, we examined our relative ranking compared with the national median CT dose for the 20 most frequently performed examinations at our institution. The total exposure variance, defined as the difference between institutional and median national dose multiplied by the local examination frequency and expressed in units of mGy-persons, was calculated. Using this metric, two examinations were selected for investigation: pulmonary and thoracic CT angiography (CTA). Protocol modifications were implemented, and postintervention dose data were assessed from the report 1 year later. RESULTS As indicated by size-specific dose estimates (SSDEs), the 2012 pulmonary CTA was within the national interquartile range; however, total exposure variance analysis showed that it presented the greatest opportunity for improvement on a population basis. Thoracic CTA was a top quartile examination and offered the second highest potential savings. After protocol modification, the average pulmonary CTA SSDEs decreased by 16%, for a population exposure savings of 1776 mGy-persons in the 2013 report. Average thoracic CTA SSDEs decreased by 44%, for a population exposure savings of 1050 mGy-persons. CONCLUSION Total exposure variance analysis can increase the usefulness of Dose Index Registry data by relating per-examination dose differences to the local examination frequency. This study exhibited reduction of dose metrics for two commonly performed examinations.

MO-F-16A-06: Implementation of a Radiation Exposure Monitoring System for Surveillance of Multi-Modality Radiation Dose Data

PURPOSE We have implemented a commercially available Radiation Exposure Monitoring System (REMS) to enhance the processes of radiation dose data collection, analysis and alerting developed over the past decade at our sites of practice. REMS allows for consolidation of multiple radiation dose information sources and quicker alerting than previously developed processes. METHODS Thirty-nine x-ray producing imaging modalities were interfaced with the REMS: thirteen computed tomography scanners, sixteen angiography/interventional systems, nine digital radiography systems and one mammography system. A number of methodologies were used to provide dose data to the REMS: Modality Performed Procedure Step (MPPS) messages, DICOM Radiation Dose Structured Reports (RDSR), and DICOM header information. Once interfaced, the dosimetry information from each device underwent validation (first 15-20 exams) before release for viewing by end-users: physicians, medical physicists, technologists and administrators. RESULTS Before REMS, our diagnostic physics group pulled dosimetry data from seven disparate databases throughout the radiology, radiation oncology, cardiology, electrophysiology, anesthesiology/pain management and vascular surgery departments at two major medical centers and four associated outpatient clinics. With the REMS implementation, we now have one authoritative source of dose information for alerting, longitudinal analysis, dashboard/graphics generation and benchmarking. REMS provides immediate automatic dose alerts utilizing thresholds calculated through daily statistical analysis. This has streamlined our Closing the Loop process for estimated skin exposures in excess of our institutional specific substantial radiation dose level which relied on technologist notification of the diagnostic physics group and daily report from the radiology information system (RIS). REMS also automatically calculates the CT size-specific dose estimate (SSDE) as well as provides two-dimensional angulation dose maps for angiography/interventional procedures. CONCLUSION REMS implementation has streamlined and consolidated the dosimetry data collection and analysis process at our institutions while eliminating manual entry error and providing immediate alerting and access to dosimetry data to both physicists and physicians. Brent Stewart has funded research through GE Healthcare.

SU‐E‐E‐01: ABR Diagnostic Radiology Core Exam: Was Our Redesigned Physics Course Successful in Teaching Physics to Radiology Residents?

PURPOSE Our purpose is to evaluate the effectiveness of our two year physics course in preparing radiology residents for the American Board of Radiology (ABR) diagnostic radiology exam. METHODS We designed a new two-year physics course that integrates radiology clinical content and practice and is primarily based on the AAPM curriculum and RSNA/AAPM physics modules. Biweekly classes focus on relevant concepts from assigned reading and use audience response systems to encourage participation. Teaching efficiency is optimized through lecturer rotations of physicists, radiologists, and guest speakers. An emphasis is placed on clinical relevance by requiring lab work and providing equipment demonstrations. Periodic quiz were given during the course. The course website was also redesigned for usability, and physics review lectures were conducted two weeks before the board exam to refresh key concepts. At the completion of our first two-year course, we conducted a confidential evaluation of the faculty and course. The evaluation assessed metrics such as overall organization, clinical relevance of content, and level of difficulty, with a rating scale from poor to excellent. RESULTS Our evaluation indicated that the redesigned course provided effective board exam preparation, with most responses between good and excellent. There was some criticism on the course length and on chronological discontinuity, but the review lectures were appreciated by the residents. All of our residents passed the physics component of the ABR exam with scores exceeding the minimum passing score by a significant margin. CONCLUSION The course evaluation and board exam results indicate that our new two-year course format provides valuable board exam preparation. This is possible thanks to the time and effort taken by the physics faculty on ensuring the residents get quality physics education.

MO‐F‐213CD‐07: Implementation of Dose Monitoring in a Cardiology Department with Independent Medical Reporting Systems

Purpose: Not all clinical service sections within a large hospital system are incorporated into the main radiology information system (RIS) and picture archiving and communication system (PACS); attaining and analyzingdose data for a cardiology department at our institution is challenging. The aim is to implement a dose monitoring program in a cardiology department whose medical recording systems are independent of the institutional systems. Methods: During a cardiac case the technologist documents the activities (catheterization, biometrics, biopsy, valve replacement, etc.) performed by the medical staff. Physics worked with the cardiology staff to identify what standard notations would indicate the procedure type, and where to reliably enter cumulative air kerma (AK). This information was compiled into a report, and the data was manually classified into seven pertinent procedure types. For a particular procedure and quarter, cases exceeding a z_score of 5 (indicating >5 SD above mean) were excluded and catalogued. Basic statistics (mean/SD/median/percentiles/min/max) were calculated for the purpose of observing longitudinal trends. A list of flagged studies ‐ cases exceeding the 95 th percentile for a given data subset ‐ was generated for the purpose of clinical review. Result: Preliminary analysis shows that common low dosecardiac procedures such as heart biopsies, intra‐arterial balloon pump insertions, and right heart catheterizations (RHC) exhibit stable median AK of approximately 200 mGy over the last two quarters. Higher dose procedures include left heart catheterizations (LHC), combination LHC/RHCs (both with median AK approximately 900 mGy), and the more complex interventional LHC (median AK approximately 3000 mGy). Cases exceeding the 95th percentile for a given procedure are currently being used to develop a follow‐up process for potential deterministic effects. Conclusions: A robust system of analyzingdose data from an RIS/PACS‐independent cardiology system has been developed. The results are being used to improve physician training and fluoroscopic practice.

TU-FG-209-08: Distribution of the Deviation Index (DI) in Digital Radiography Practices Across the United States

PURPOSE To characterize the distribution of the deviation index (DI) in digital radiography practices across the United States. METHODS DI data was obtained from 10 collaborating institutions in the United States between 2012 and 2015. Each institution complied with the requirements of the Institutional Review Board at their site. DI data from radiographs of the body parts chest, abdomen, pelvis and extremity were analyzed for anteroposterior, posteroanterior, lateral, and decubitus views. The DI data was analyzed both in aggregate and stratified by exposure control method, image receptor technology, patient age, and participating site for each body part and view. The number of exposures with DI falling within previously published control limits for DI and descriptive statistics were calculated. RESULTS DI data from 505,930 radiographic exposures was analyzed. The number of exposures with DI falling within published control limits for DI varied from 10 to 20% for adult patients and 10 to 23% for pediatric patients for different body parts and views. Mean DI values averaged over other parameters for radiographs of the abdomen, chest, pelvis, and extremities ranged from 0.3 to 1.0, -0.6 to 0.5, 0.8, and -0.9 to 0.5 for the different adult views and ranged from -1.6 to -0.1, -0.3 to 0.5, -0.1, -0.2 to 1.4 for the different pediatric views, respectively (DI data was solicited only for anteroposterior view of pelvis). Standard deviation values of DI from individual sites ranged from 1.3 to 3.6 and 1.3 to 3.0 for the different adult and pediatric views, respectively. Also of interest was that target exposure indicators varied by up to a factor of 6 between sites for certain body parts and views. CONCLUSION Previously published DI control limits do not reflect the state of clinical practice in digital radiography. Mean DI and target exposure indicators are targets for quality improvement efforts in radiography.

SU-D-209-03: Radiation Dose Reduction Using Real-Time Image Processing in Interventional Radiology

PURPOSE To characterize changes in radiation dose after introducing a new real-time image processing technology in interventional radiology systems. METHODS Interventional radiology (IR) procedures are increasingly complex, at times requiring substantial time and radiation dose. The risk of inducing tissue reactions as well as long-term stochastic effects such as radiation-induced cancer is not trivial. To reduce this risk, IR systems are increasingly equipped with dose reduction technologies.Recently, ClarityIQ (Philips Healthcare) technology was installed in our existing neuroradiology IR (NIR) and vascular IR (VIR) suites respectively. ClarityIQ includes real-time image processing that reduces noise/artifacts, enhances images, and sharpens edges while also reducing radiation dose rates. We reviewed 412 NIR (175 pre- and 237 post-ClarityIQ) procedures and 329 VIR (156 preand 173 post-ClarityIQ) procedures performed at our institution pre- and post-ClarityIQ implementation. NIR procedures were primarily classified as interventional or diagnostic. VIR procedures included drain port, drain placement, tube change, mesenteric, and implanted venous procedures. Air Kerma (AK in units of mGy) was documented for all the cases using a commercial radiation exposure management system. RESULTS When considering all NIR procedures, median AK decreased from 1194 mGy to 561 mGy. When considering all VIR procedures, median AK decreased from 49 to 14 mGy. Both NIR and VIR exhibited a decrease in AK exceeding 50% after ClarityIQ implementation, a statistically significant (p<0.05) difference. Of the 5 most common VIR procedures, all median AK values decreased, but significance (p<0.05) was only reached in venous access (N=53), angio mesenteric (N=41), and drain placement procedures (N=31). CONCLUSION ClarityIQ can reduce dose significantly for both NIR and VIR procedures. Image quality was not assessed in conjunction with the dose reduction.

SU-E-I-30: Effect of Automatic Tube Voltage Selection and Reconstruction Method On CT Dose Reduction

Purpose: To study the effect of automatic tube voltage selection and reconstruction method on CT dose reduction. Methods: A retrospective study was conducted to gather data from 126 CT exams among 80 patients from 3 different CT scanners. Data on scan parameters was collected and categorized for 3 different patient sizes: small, medium and large. For each patient group, exams using manual selection of tube voltage and automatic selection of tube voltage were compared for dose reduction. The influence of reconstruction method and automatic or manual tube voltage selection was also studied. Results: Dose reduction was observed in all patient size categories with the largest dose reduction of 55% seen in the medium sized patients and 35% reduction in the small and large patients. The patients who underwent both a manual and automatic tube voltage selection for their CT study also showed similar dose reduction. Use of iterative reconstruction method and automatic tube voltage selection also showed a 30% dose reduction when compared with manual tube voltage selection and filtered back projection reconstruction method. Dose reduction of up to 45% was observed for both automatic and manual tube voltage selection irrespective of which reconstruction method was used. Conclusion: Using automatic tube voltage selection and iterative reconstruction demonstrated significant dose reduction compared to manual tube voltage selection and filtered back reconstruction method. Between the different generation CT scanners used in this study, the scanner with the most advanced technology demonstrated the most significant dose reduction.

TH‐EF‐BRA‐06: A Novel Method of ACR Dose Index Registry Report Interpretation: Population Dose Reduction for Thoracic CT Angiography

Purpose: To identify a method of ACR Dose Index Registry (DIR) report analysis and interpretation that focuses dose reduction efforts on exams that most affect our patient population. Methods: In place of a direct interpretation of the DIR report, a proposed additional metric — the Total Exposure Variance (TEV) — was calculated for each of the most frequently performed institutional exams. TEV was defined as the product of exam frequency (N) and the difference between institutional and national median dose (CTDIvol or SSDE). TEV indicated total excess institution population dose beyond the equivalent national benchmark. TEV analysis focused investigation of two exams from the 2012 DIR report: 1) CT pulmonary angiography (CTPA), which had SSDE between the median and third quartile; and, 2) CT thoracic angiography (CTTA), optimized for the aorta, which had SSDE in the top quartile. Results: CT scan parameter changes were implemented lowering the quality reference mAs by 20% and limiting the automatic kV selection range to 100–120. DIR data from July–December 2012 were compared to same time period for 2013. CTPA showed a decrease of median CTDIvol and SSDE of 14% and 16%, respectively, representing a realized decrease in TEV of 1776 mGy-persons. Data for CTTA showed a decrease of median CTDIvol and SSDE of 38% and 44%, respectively, representing a realized decrease in TEV of 1050 mGy-persons. In both cases, the incremental and population dose metrics moved down toward national benchmarks. Conclusion: TEV analysis used DIR data to shift the paradigm toward reducing population dose instead of frequency-independent interpretation of the report. The TEV metric highlighted exams that would have otherwise been overlooked with direct DIR report interpretation. Recent modifications to the DIR report contents may avail additional approaches to dose reduction.