Stephen Balter

The management of imaging dose during image-guided radiotherapy: Report of the AAPM Task Group 75

Radiographic image guidance has emerged as the new paradigm for patient positioning, target localization, and external beam alignment in radiotherapy. Although widely varied in modality and method, all radiographic guidance techniques have one thing in common--they can give a significant radiation dose to the patient. As with all medical uses of ionizing radiation, the general view is that this exposure should be carefully managed. The philosophy for dose management adopted by the diagnostic imaging community is summarized by the acronym ALARA, i.e., as low as reasonably achievable. But unlike the general situation with diagnostic imaging and image-guided surgery, image-guided radiotherapy (IGRT) adds the imaging dose to an already high level of therapeutic radiation. There is furthermore an interplay between increased imaging and improved therapeutic dose conformity that suggests the possibility of optimizing rather than simply minimizing the imaging dose. For this reason, the management of imaging dose during radiotherapy is a different problem than its management during routine diagnostic or image-guided surgical procedures. The imaging dose received as part of a radiotherapy treatment has long been regarded as negligible and thus has been quantified in a fairly loose manner. On the other hand, radiation oncologists examine the therapy dose distribution in minute detail. The introduction of more intensive imaging procedures for IGRT now obligates the clinician to evaluate therapeutic and imaging doses in a more balanced manner. This task group is charged with addressing the issue of radiation dose delivered via image guidance techniques during radiotherapy. The group has developed this charge into three objectives: (1) Compile an overview of image-guidance techniques and their associated radiation dose levels, to provide the clinician using a particular set of image guidance techniques with enough data to estimate the total diagnostic dose for a specific treatment scenario, (2) identify ways to reduce the total imaging dose without sacrificing essential imaging information, and (3) recommend optimization strategies to trade off imaging dose with improvements in therapeutic dose delivery. The end goal is to enable the design of image guidance regimens that are as effective and efficient as possible.

Fluoroscopically guided interventional procedures: a review of radiation effects on patients' skin and hair.

Most advice currently available with regard to fluoroscopic skin reactions is based on a table published in 1994. Many caveats in that report were not included in later reproductions, and subsequent research has yielded additional insights. This review is a consensus report of current scientific data. Expected skin reactions for an average patient are presented in tabular form as a function of peak skin dose and time after irradiation. The text and table indicate the variability of reactions in different patients. Images of injuries to skin and underlying tissues in patients and animals are provided and are categorized according to the National Cancer Institute skin toxicity scale, offering a basis for describing cutaneous radiation reactions in interventional fluoroscopy and quantifying their clinical severity. For a single procedure performed in most individuals, noticeable skin changes are observed approximately 1 month after a peak skin dose exceeding several grays. The degree of injury to skin and subcutaneous tissue increases with dose. Specialized wound care may be needed when irradiation exceeds 10 Gy. Residual effects from radiation therapy and from previous procedures influence the response of skin and subcutaneous tissues to subsequent procedures. Skin irradiated to a dose higher than 3-5 Gy often looks normal but reacts abnormally when irradiation is repeated. If the same area of skin is likely to be exposed to levels higher than a few grays, the effects of previous irradiation should be included when estimating the expected tissue reaction from the additional procedure.

Radiation Doses in Interventional Radiology Procedures: The RAD-IR Study Part I: Overall Measures of Dose

PURPOSE To determine patient radiation doses for interventional radiology and neuroradiology procedures, to identify procedures associated with higher radiation doses, and to determine the effects of various parameters on patient doses. MATERIALS AND METHODS A prospective observational study was performed at seven academic medical centers. Each site contributed demographic and radiation dose data for subjects undergoing specific procedures in fluoroscopic suites equipped with built-in cumulative dose (CD) and dose-area-product (DAP) measurement capability compliant with International Electrotechnical Commission standard 60601-2-43. The accuracy of the dosimetry was confirmed by comprehensive measurements and by frequent consistency checks performed over the course of the study. RESULTS Data were collected on 2,142 instances of interventional radiology procedures, 48 comprehensive physics evaluations, and 581 periodic consistency checks from the 12 fluoroscopic units in the study. There were wide variations in dose and statistically significant differences in fluoroscopy time, number of images, DAP, and CD for different instances of the same procedure, depending on the nature of the lesion, its anatomic location, and the complexity of the procedure. For the 2,142 instances, observed CD and DAP correlate well overall (r = 0.83, P <.000001), but correlation in individual instances is poor. The same is true for the correlation between fluoroscopy time and CD (r = 0.79, P <.000001). The correlation between fluoroscopy time and DAP (r = 0.60, P <.000001) is not as good. In 6% of instances (128 of 2,142), which were principally embolization procedures, transjugular intrahepatic portosystemic shunt (TIPS) procedures, and renal/visceral artery stent placements, CD was greater than 5 Gy. CONCLUSIONS Most procedures studied can result in clinically significant radiation dose to the patient, even when performed by trained operators with use of dose-reducing technology and modern fluoroscopic equipment. Embolization procedures, TIPS creation, and renal/visceral artery stent placement are associated with a substantial likelihood of clinically significant patient dose. At minimum, patient dose data should be recorded in the medical record for these three types of procedures. These data should include indicators of the risk of deterministic effects as well as the risk of stochastic effects.

Guidelines for Patient Radiation Dose Management

Michael S. Stecker, MD, Stephen Balter, PhD, Richard B. Towbin, MD, Donald L. Miller, MD, Eliseo Vano, PhD,Gabriel Bartal, MD, J. Fritz Angle, MD, Christine P. Chao, MD, Alan M. Cohen, MD, Robert G. Dixon, MD,Kathleen Gross, MSN, RN-BC, CRN, George G. Hartnell, MD, Beth Schueler, PhD, John D. Statler, MD,Thierry de Baere, MD, and John F. Cardella, MD, for the SIR Safety and Health Committee and the CIRSEStandards of Practice Committee

Radiation Doses in Interventional Radiology Procedures: The RAD-IR Study Part II: Skin Dose

PURPOSE To determine peak skin dose (PSD), a measure of the likelihood of radiation-induced skin effects, for a variety of common interventional radiology and interventional neuroradiology procedures, and to identify procedures associated with a PSD greater than 2 Gy. MATERIALS AND METHODS An observational study was conducted at seven academic medical centers in the United States. Sites prospectively contributed demographic and radiation dose data for subjects undergoing 21 specific procedures in a fluoroscopic suite equipped with built-in dosimetry capability. Comprehensive physics evaluations and periodic consistency checks were performed on each unit to verify the stability and consistency of the dosimeter. Seven of 12 fluoroscopic suites in the study were equipped with skin dose mapping software. RESULTS Over a 3-year period, skin dose data were recorded for 800 instances of 21 interventional radiology procedures. Wide variation in PSD was observed for different instances of the same procedure. Some instances of each procedure we studied resulted in a PSD greater than 2 Gy, except for nephrostomy, pulmonary angiography, and inferior vena cava filter placement. Some instances of transjugular intrahepatic portosystemic shunt (TIPS) creation, renal/visceral angioplasty, and angiographic diagnosis and therapy of gastrointestinal hemorrhage produced PSDs greater than 3 Gy. Some instances of hepatic chemoembolization, other tumor embolization, and neuroembolization procedures in the head and spine produced PSDs greater than 5 Gy. In a subset of 709 instances of higher-dose procedures, there was good overall correlation between PSD and cumulative dose (r = 0.86; P <.000001) and between PSD and dose-area-product (r = 0.85, P <.000001), but there was wide variation in these relationships for individual instances. CONCLUSIONS There are substantial variations in PSD among instances of the same procedure and among different procedure types. Most of the procedures observed may produce a PSD sufficient to cause deterministic effects in skin. It is suggested that dose data be recorded routinely for TIPS creation, angioplasty in the abdomen or pelvis, all embolization procedures, and especially for head and spine embolization procedures. Measurement or estimation of PSD is the best method for determining the likelihood of radiation-induced skin effects. Skin dose mapping is preferable to a single-point measurement of PSD.

Radiation safety program for the cardiac catheterization laboratory

The Society of Cardiovascular Angiography and Interventions present a practical approach to assist cardiac catheterization laboratories in establishing a radiation safety program. The importance of this program is emphasized by the appropriate concerns for the increasing use of ionizing radiation in medical imaging, and its potential adverse effects. An overview of the assessment of radiation dose is provided with a review of basic terminology for dose management. The components of a radiation safety program include essential personnel, radiation monitoring, protective shielding, imaging equipment, and training/education. A procedure based review of radiation dose management is described including pre‐procedure, procedure and post‐procedure best practice recommendations. Specific radiation safety considerations are discussed including women and fluoroscopic procedures as well as patients with congenital and structural heart disease.

Occupational Radiation Doses To Operators Performing Cardiac Catheterization Procedures

Cardiac catheterization procedures using fluoroscopy reduce patient morbidity and mortality compared to operative procedures. These diagnostic and therapeutic procedures require radiation exposure to patients and physicians. The objectives of the present investigation were to provide a systematic comprehensive summary of the reported radiation doses received by operators due to diagnostic or interventional fluoroscopically-guided procedures, to identify the primary factors influencing operator radiation dose, and to evaluate whether there have been temporal changes in the radiation doses received by operators performing these procedures. Using PubMed, we identified all English-language journal articles and other published data reporting radiation exposures to operators from diagnostic or interventional fluoroscopically-guided cardiovascular procedures from the early 1970s through the present. We abstracted the reported radiation doses, dose measurement methods, fluoroscopy system used, operational features, radiation protection features, and other relevant data. We calculated effective doses to operators in each study to facilitate comparisons. The effective doses ranged from 0.02–38.0 &mgr;Sv for DC (diagnostic catheterizations), 0.17–31.2 &mgr;Sv for PCI (percutaneous coronary interventions), 0.24–9.6 &mgr;Sv for ablations, and 0.29–17.4 &mgr;Sv for pacemaker or intracardiac defibrillator implantations. The ratios of doses between various anatomic sites and the thyroid, measured over protective shields, were 0.9 ± 1.0 for the eye, 1.0 ± 1.5 for the trunk, and 1.3 ± 2.0 for the hand. Generally, radiation dose is higher on the left side of an operators body, because the operators left side is closer to the primary beam when standing at the patients right side. Modest operator dose reductions over time were observed for DC and ablation, primarily due to reduction in patient doses due to decreased fluoroscopy/cineradiography time and dose rate by technology improvement. Doses were not reduced over time for PCI. The increased complexity of medical procedures appears to have offset dose reductions due to improvements in technology. The large variation in operator doses observed for the same type of procedure suggests that optimizing procedure protocols and implementing general use of the most effective types of protective devices and shields may reduce occupational radiation doses to operators. We had considerable difficulty in comparing reported dosimetry results because of significant differences in dosimetric methods used in each study and multiple factors influencing the actual doses received. Better standardization of dosimetric methods will facilitate future analyses aimed at determining how well medical radiation workers are being protected.

Occupational hazards of Interventional cardiologists: Prevalence of orthopedic health problems in contemporary practice

Invasive cardiologists generally consider radiation to be the chief occupational hazard. Heavy leaded aprons worn to reduce this risk may be associated with orthopedic complications. This study was designed to characterize the prevalence of these occupational health problems. The Interventional Committee of the Society for Cardiac Angiography and Interventions (SCAI) sent to its Internet‐registered members a Web‐based survey. Inquiries included age, years of invasive practice, and diagnostic/interventional cases/year. Questions (yes/no) focused on orthopedic (spine, hips, knees, and ankles) and radiation‐associated problems (cataracts and cancers). The survey was sent to over 1,600 members with 424 responses. Responders were on average busy and experienced, performing catheterization > 10 years in 62% of cases and > 20 years in 24% others. Average annual diagnostic‐only case load was > 200/year in 72%, > 300/year in 43%, and > 500/year in 18% of responders. Reported annual interventional caseload was > 100/year in 83%, > 200/year in 37%, and > 300/year in 15% of operators. Orthopedic problems included spine problems in 42% of responders (of these, 70% were lumbosacral and 30% cervical). Hip, knee, or ankle problems were noted in 28% of operators. Spine problems were related to the annual procedural caseload and the number of years in practice. Over one‐third reported spine problems had caused them to miss work. The results of the radiation queries were inconclusive. These results document that interventional cardiologists commonly suffer orthopedic disease, frequently leading to lost work days. Catheter Cardiovasc Interv 2004;63:407–411.

Multiple testing, cumulative radiation dose, and clinical indications in patients undergoing myocardial perfusion imaging.

CONTEXT Myocardial perfusion imaging (MPI) is the single medical test with the highest radiation burden to the US population. Although many patients undergoing MPI receive repeat MPI testing, or additional procedures involving ionizing radiation, no data are available characterizing their total longitudinal radiation burden and relating radiation burden with reasons for testing. OBJECTIVES To characterize procedure counts, cumulative estimated effective doses of radiation, and clinical indications for patients undergoing MPI. DESIGN, SETTING, AND PATIENTS A retrospective cohort study of 1097 consecutive patients undergoing index MPI during the first 100 days of 2006 (January 1-April 10) at Columbia University Medical Center, New York, New York, that evaluated all preceding medical imaging procedures involving ionizing radiation undergone beginning October 1988, and all subsequent procedures through June 2008, at the center. MAIN OUTCOME MEASURES Cumulative estimated effective dose of radiation, number of procedures involving radiation, and indications for testing. RESULTS Patients underwent a median of 15 (interquartile range [IQR], 6-32; mean, 23.9) procedures involving radiation exposure; of which 4 (IQR, 2-8; mean, 6.5) were high-dose procedures (≥3 mSv; ie, 1 years background radiation), including 1 (IQR, 1-2; mean, 1.8) MPI study per patient. A total of 344 patients (31.4%) received cumulative estimated effective dose from all medical sources of more than 100 mSv. Multiple MPIs were performed in 424 patients (38.6%), for whom cumulative estimated effective dose was 121 mSv (IQR, 81-189; mean, 149 mSv). Men and white patients had higher cumulative estimated effective doses. More than 80% of initial and 90% of repeat MPI examinations were performed in patients with known cardiac disease or symptoms consistent with it. CONCLUSION In this institution, multiple testing with MPI was common and in many patients associated with high cumulative estimated doses of radiation.

Radiation doses in interventional radiology procedures: The RAD-IR study. Part III: Dosimetric performance of the interventional fluoroscopy units

PURPOSE To present the physics data supporting the validity of the clinical dose data from the RAD-IR study and to document the performance of dosimetry-components of these systems over time. MATERIALS AND METHODS Sites at seven academic medical centers in the United States prospectively contributed data for each of 12 fluoroscopic units. All units were compatible with International Electrotechnical Commission (IEC) standard 60601-2-43. Comprehensive evaluations and periodic consistency checks were performed to verify the performance of each units dosimeter. Comprehensive evaluations compared system performance against calibrated ionization chambers under nine combinations of operating conditions. Consistency checks provided more frequent dosimetry data, with use of each units built-in dosimetry equipment and a standard water phantom. RESULTS During the 3-year study, data were collected for 48 comprehensive evaluations and 581 consistency checks. For the comprehensive evaluations, the mean (95% confidence interval range) ratio of system to external measurements was 1.03 (1.00-1.05) for fluoroscopy and 0.93 (0.90-0.96) for acquisition. The expected ratio was 0.93 for both. For consistency checks, the values were 1.00 (0.98-1.02) for fluoroscopy and 1.00 (0.98-1.02) for acquisition. Each system was compared across time to its own mean value. Overall uncertainty was estimated by adding the standard deviations of the comprehensive and consistency measurements in quadrature. The authors estimate that the overall error in clinical cumulative dose measurements reported in RAD-IR is 24%. CONCLUSION Dosimetric accuracy was well within the tolerances established by IEC standard 60601-2-43. The clinical dose data reported in the RAD-IR study are valid.