Patient Radiation Doses in IR Procedures: The American College of Radiology Dose Index Registry-Fluoroscopy Pilot.

PURPOSE: To update normative data on fluoroscopy dose indices in the United States for the first time since the Radiation Doses in Interventional Radiology study in the late 1990s. MATERIALS AND METHODS: The Dose Index Registry-Fluoroscopy pilot study collected data from March 2018 through December 2019, with 50 fluoroscopes from 10 sites submitting data. Primary radiation dose indices including fluoroscopy time (FT), cumulative air kerma (Ka,r), and kerma area product (PKA) were collected for interventional radiology fluoroscopically guided interventional (FGI) procedures. Clinical facility procedure names were mapped to the American College of Radiology (ACR) common procedure lexicon. Distribution parameters including the 10th, 25th, 50th, 75th, 95th, and 99th percentiles were computed. RESULTS: Dose indices were collected for 70,377 FGI procedures, with 50,501 ultimately eligible for analysis. Distribution parameters are reported for 100 ACR Common IDs. FT in minutes, Ka,r in mGy, and PKA in Gy-cm2 are reported in this study as (n; median) for select ACR Common IDs: inferior vena cava filter insertion (1,726; FT: 2.9; Ka,r: 55.8; PKA: 14.19); inferior vena cava filter removal (464; FT: 5.7; Ka,r: 178.6; PKA: 34.73); nephrostomy placement (2,037; FT: 4.1; Ka,r: 39.2; PKA: 6.61); percutaneous biliary drainage (952; FT: 12.4; Ka,r: 160.5; PKA: 21.32); gastrostomy placement (1,643; FT: 3.2; Ka,r: 29.1; PKA: 7.29); and transjugular intrahepatic portosystemic shunt placement (327; FT: 34.8; Ka,r: 813.0; PKA: 181.47). CONCLUSIONS: The ACR DIR-Fluoro pilot has provided state-of-the-practice statistics for radiation dose indices from IR FGI procedures. These data can be used to prioritize procedures for radiation optimization, as demonstrated in this work.

Patient Radiation Doses in Interventional Radiology Procedures: Comparison of Fluoroscopy Dose Indices between the American College of Radiology Dose Index Registry-Fluoroscopy Pilot and the Radiation Doses in Interventional Radiology Study.

PURPOSE: To compare radiation dose index distributions for fluoroscopically guided interventions in interventional radiology from the American College of Radiology (ACR) Fluoroscopy Dose Index Registry (DIR-Fluoro) pilot to those from the Radiation Doses in Interventional Radiology (RAD-IR) study. MATERIALS AND METHODS: Individual and grouped ACR Common identification numbers (procedure types) from the DIR-Fluoro pilot were matched to procedure types in the RAD-IR study. Fifteen comparisons were made. Distribution parameters, including the 10th, 25th, 50th, 75th, and 95th percentiles, were compared for fluoroscopy time (FT), cumulative air kerma (Ka,r), and kerma area product (PKA). Two derived indices were computed using median dose indices. The procedure-averaged reference air kerma rate (Ka,r¯) was computed as Ka,r / FT. The procedure-averaged x-ray field size at the reference point (Ar) was computed as PKA / (Ka,r × 1,000). RESULTS: The median FT was equally likely to be higher or lower in the DIR-Fluoro pilot as it was in the RAD-IR study, whereas the maximum FT was almost twice as likely to be higher in the DIR-Fluoro pilot than it was in the RAD-IR study. The median Ka,r was lower in the DIR-Fluoro pilot for all procedures, as was median PKA. The maximum Ka,r and PKA were more often higher in the DIR-Fluoro pilot than in the RAD-IR study. Ka,r¯ followed the same pattern as Ka,r, whereas Ar was often greater in DIR-Fluoro. CONCLUSIONS: The median dose indices have decreased since the RAD-IR study. The typical Ka,r rates are lower, a result of the use of lower default dose rates. However, opportunities for quality improvement exist, including renewed focus on tight collimation of the imaging field of view.

AAPM Task Group Report 272: Comprehensive acceptance testing and evaluation of fluoroscopy imaging systems.

Modern fluoroscopes used for image guidance have become quite complex. Adding to this complexity are the many regulatory and accreditation requirements that must be fulfilled during acceptance testing of a new unit. Further, some of these acceptance tests have pass/fail criteria, whereas others do not, making acceptance testing a subjective and time-consuming task. The AAPM Task Group 272 Report spells out the details of tests that are required and gives visibility to some of the tests that while not yet required are recommended as good practice. The organization of the report begins with the most complicated fluoroscopes used in interventional radiology or cardiology and continues with general fluoroscopy and mobile C-arms. Finally, the appendices of the report provide useful information, an example report form and topics that needed their own section due to the level of detail.

The American College of Radiology Fluoroscopy Dose Index Registry Pilot: Technical Considerations and Dosimetric Performance of the Interventional Fluoroscopes.

PURPOSE: To characterize the accuracy and consistency of fluoroscope dose index reporting and report rates of occupational radiation safety hardware availability and use, trainee participation in procedures, and optional hardware availability at pilot sites for the American College of Radiology (ACR) Fluoroscopy Dose Index Registry (DIR). MATERIALS AND METHODS: Nine institutions participated in the registry pilot, providing fluoroscopic technical and clinical practice data from 38 angiographic C-arm-type fluoroscopes. These data included measurements of the procedure table and mattress transmission factors and accuracy measurements of the reference-point air kerma (Ka,r) and air kerma-area product (PKA). The accuracy of the radiation dose indices were analyzed for variation over time by 1-way analysis of variance (ANOVA). Sites also self-reported information on availability and use of radiation safety hardware, hardware configuration of fluoroscopes, and trainee participation in procedures. RESULTS: All Ka,r and PKA measurements were within the ±35% regulatory limit on accuracy. The mean absolute difference between correction factors for a given system in fluoroscopic and acquisition mode was 0.03 (95% confidence interval, 0.03-0.03). For the 28 fluoroscopic imaging planes that provided data for 3 time points, ANOVA yielded an F value of 0.134 with an F-critical value of 3.109 (P = .875). CONCLUSIONS: This publication provides the technical and clinical framework pertaining to the ACR Fluoroscopy DIR pilot and offers necessary context for future analysis of the clinical procedure radiation-dose data collected.

Technical Note: Characterization of x-ray beam profiles for a fluoroscopic system incorporating copper filtration.

PURPOSE: The goal of this study was to investigate x-ray beam profiles at various water depths to characterize the two-dimensional x-ray dose distribution, allowing for off-axis and out-of-field radiation dose estimation for a wide range of x-ray beam spectra commonly encountered in fluoroscopically guided interventional procedures. METHODS: A Siemens Artis interventional fluoroscope was operated in a service mode to generate a continuous x-ray beam at fixed x-ray beam spectra, defined by their kVp and the thickness of additional copper filtration. A PTW scanning water tank with a diode detector was used to measure the x-ray beam profiles at several depths in water at various fields of view and x-ray beam spectra, both parallel and perpendicular to the anode-cathode axis direction. RESULTS: X-ray beam profiles, including out-of-field tails, were characterized for a wide range of beam qualities. The anode heel effect was pronounced even at depth, resulting in large dose variations across the x-ray field; this effect was even more definite at large fields of view, at higher kVps, and in the absence of additional copper filtration. CONCLUSIONS: This study investigated and characterized 2D radiation dose deposition in water from x-ray beam spectra commonly used by modern fluoroscopes in interventional procedures. This knowledge can be applied to manual dosimetry calculations or can be used to refine the accuracy of automated dose mapping tools or Monte Carlo simulations of the radiation dose to soft tissue within the x-ray field and to tissue adjacent to the primary beam. Additionally, this study illustrates a substantial reduction of the anode heel effect by using moderate amounts of additional copper filtration to harden the x-ray beam spectrum.

Occupational and patient radiation doses in a modern cardiac electrophysiology laboratory.

PURPOSE: Technological advancements have greatly expanded the field of cardiac electrophysiology, requiring greater demands on imaging systems and potentially delivering higher radiation doses to patients and operators. With little contemporary research on occupational and patient radiation risk in the electrophysiology laboratory, the aim of this study was to analyze radiation doses, including occupational fetal doses, over approximately the last decade. We benchmarked the occupational data to our patient radiation dose data to allow for comparison and to put into perspective the associated radiation risks. METHODS: Occupational radiation dosimetry analyzed included data from an 11-year period for physicians, a 7-year period for nurses, and a 9-year period for fetal doses. Patient-related dose metrics over an 8-year period were also analyzed. RESULTS: In the physician and nursing groups, there was a nearly 70% decrease in the average occupational radiation doses over the given periods. Within the electrophysiology department, the average fetal occupational doses were very low, close to 0 µSv. The average reference point air kerma per patient for all electrophysiology procedures decreased from nearly 600 mGy/procedure in 2010 to just over 100 mGy/procedure in 2017. CONCLUSIONS: Patient and occupational radiation doses in our laboratories significantly decreased over the periods analyzed as a result of clinical and technical staff efforts as well as advances in imaging technology. The radiation-related risk to individuals working in our electrophysiology laboratories, including pregnant women, is very low. Data reported herein could be used by other institutions to evaluate their occupational and patient radiation safety practices.

Percent depth doses and X-ray beam characterizations of a fluoroscopic system incorporating copper filtration.

PURPOSE: In this investigation, we sought to characterize X-ray beam qualities and quantitate percent depth dose (PDD) curves for fluoroscopic X-ray beams incorporating added copper (Cu) filtration, such as those commonly used in fluoroscopically guided interventions (FGI). The intended application of this research is for dosimetry in soft tissue from FGI procedures using these data. METHODS: All measurements in this study were acquired on a Siemens (Erlangen, Germany) Artis zeego fluoroscope. X-ray beam characteristics of first half-value layer (HVL), second HVL, homogeneity coefficients (HCs), backscatter factors (BSFs) and kVp accuracy and precision were determined to characterize the X-ray beams used for the PDD measurements. A scanning water tank was used to measure PDD curves for 60, 80, 100, and 120 kVp X-ray beams with Cu filtration thicknesses of 0.0, 0.1, 0.3, 0.6, and 0.9 mm at 11 cm, 22 cm, and 42 cm nominal fields of view, in water depths of 0 to 150 mm. RESULTS: X-ray beam characteristics of first HVLs and HCs differed from previous published research of fluoroscopic X-ray beam qualities without Cu filtration. PDDs for 60, 80, 100, and 120 kVp with 0 mm of Cu filtration were comparable to previous published research, accounting for differences in fluoroscopes, geometric orientation, type of ionization chamber, X-ray beam quality, and the water tank used for data collection. PDDs and X-ray beam characteristics for beam qualities with Cu filtration are presented, which have not been previously reported. CONCLUSIONS: The data sets of X-ray beam characteristics and PDDs presented in this study can be used to estimate organ or soft tissue doses at depth involving similar beam qualities or to compare with mathematical models.

Effect of fluoroscopic X-ray beam spectrum on air-kerma measurement accuracy: implications for establishing correction coefficients on interventional fluoroscopes with KAP meters.

The first goal of this study was to investigate the accuracy of the displayed reference plane air kerma (Ka,r) or air kerma-area product (Pk,a) over a broad spectrum of X-ray beam qualities on clinically used interventional fluoroscopes incorporating air kerma-area product meters (KAP meters) to measure X-ray output. The second goal was to investigate the accuracy of a correction coefficient (CC) determined at a single beam quality and applied to the measured Ka,r over a broad spectrum of beam qualities. Eleven state-of-the-art interventional fluoroscopes were evaluated, consisting of eight Siemens Artis zee and Artis Q systems and three Philips Allura FD systems. A separate calibrated 60 cc ionization chamber (external chamber) was used to determine the accuracy of the KAP meter over a broad range of clinically used beam qualities. For typical adult beam qualities, applying a single CC deter-mined at 100 kVp with copper (Cu) in the beam resulted in a deviation of < 5% due to beam quality variation. This result indicates that applying a CC determined using The American Association of Physicists in Medicine Task Group 190 protocol or a similar protocol provides very good accuracy as compared to the allowed ± 35% deviation of the KAP meter in this limited beam quality range. For interventional fluoroscopes dedicated to or routinely used to perform pediatric interventions, using a CC established with a low kVp (~ 55-60 kVp) and large amount of Cu filtration (~ 0.6-0.9 mm) may result in greater accuracy as compared to using the 100 kVp values. KAP meter responses indicate that fluoroscope vendors are likely normalizing or otherwise influencing the KAP meter output data. Although this may provide improved accuracy in some instances, there is the potential for large discrete errors to occur, and these errors may be difficult to identify.

Approaches to interventional fluoroscopic dose curves.

Modern fluoroscopes used for image-based guidance in interventional procedures are complex X-ray machines, with advanced image acquisition and processing systems capable of automatically controlling numerous parameters based on defined protocol settings. This study evaluated and compared approaches to technique factor modulation and air kerma rates in response to simulated patient thickness variations for four state-of-the-art and one previous-generation interventional fluoroscopes. A polymethyl methacrylate (PMMA) phantom was used as a tissue surrogate for the purposes of determining fluoroscopic reference plane air kerma rates, kVp, mA, and variable copper filter thickness over a wide range of simulated tissue thicknesses. Data were acquired for each fluoroscopic and acquisition dose curve within each vendor's default abdomen or body imaging protocol. The data obtained indicated vendor- and model-specific variations in the approach to technique factor modulation and reference plane air kerma rates across a range of tissue thicknesses. However, in the imaging protocol evaluated, all of the state-of-the-art systems had relatively low air kerma rates in the fluoroscopic low-dose imaging mode as compared to the previous-generation unit. Each of the newest-generation systems also employ Cu filtration within the selected protocol in the acquisition mode of imaging; this is a substantial benefit, reducing the skin entrance dose to the patient in the highest dose-rate mode of fluoroscope operation. Some vendors have also enhanced the radiation output capabilities of their fluoroscopes which, under specific conditions, may be beneficial; however, these increased output capabilities also have the potential to lead to unnecessarily high dose rates. Understanding how fluoroscopic technique factors are modulated provides insight into the vendor-specific image acquisition approach and may provide opportunities to optimize the imaging protocols for clinical practice.

Accuracy and calibration of integrated radiation output indicators in diagnostic radiology: A report of the AAPM Imaging Physics Committee Task Group 190.

Due to the proliferation of disciplines employing fluoroscopy as their primary imaging tool and the prolonged extensive use of fluoroscopy in interventional and cardiovascular angiography procedures, "dose-area-product" (DAP) meters were installed to monitor and record the radiation dose delivered to patients. In some cases, the radiation dose or the output value is calculated, rather than measured, using the pertinent radiological parameters and geometrical information. The AAPM Task Group 190 (TG-190) was established to evaluate the accuracy of the DAP meter in 2008. Since then, the term "DAP-meter" has been revised to air kerma-area product (KAP) meter. The charge of TG 190 (Accuracy and Calibration of Integrated Radiation Output Indicators in Diagnostic Radiology) has also been realigned to investigate the "Accuracy and Calibration of Integrated Radiation Output Indicators" which is reflected in the title of the task group, to include situations where the KAP may be acquired with or without the presence of a physical "meter." To accomplish this goal, validation test protocols were developed to compare the displayed radiation output value to an external measurement. These test protocols were applied to a number of clinical systems to collect information on the accuracy of dose display values in the field.

Radiation recall after a transarterial hepatic chemoembolization.

Radiation recall is a rare side effect observed in patients treated with certain medications after radiation therapy. This effect mimics a radiation-induced tissue reaction in expression; however, it occurs outside of the traditional time course and only in the presence of a catalyzing agent. The authors report a case of radiation recall resulting from an interaction between radiation delivered during a fluoroscopically guided hepatic chemoembolization for treatment of metastatic carcinoid tumor and the oral chemotherapeutic agents capecitabine and temozolomide administered 7 weeks later.