Trends in Percutaneous Embolization Procedures by Radiologists and Other Specialists

PurposeTo evaluate utilization trends in percutaneous embolization among radiologists and nonradiologist providers.Materials and MethodsThe nationwide Medicare Part B fee-for-service databases for 2005–2016 were used to evaluate percutaneous embolization codes. Six codes describing embolization procedures were reviewed. Physician providers were grouped as radiologists, vascular surgeons, cardiologists, nephrologists, other surgeons, and all others.ResultsThe total volume of Medicare percutaneous embolization procedures increased from 20,262 in 2005 to 45,478 in 2016 (+125%). Radiologists performed 13,872 procedures in 2005 (68% of total volume) and 33,254 in 2016 (73% of total volume), a 140% increase in volume. While other specialists also increased the number of cases performed from 2005 to 2016, radiologists strongly predominated, performing 87% of arterial and 30% of venous procedures in 2016, more than any other single specialty. In 2014 and 2015, a sharp increase in venous embolization cases performed by nonradiologists preceded a sharp decrease in 2016, likely the result of complicated billing codes for venous procedures. Radiologists maintained a steady upward trend in the number of cases they performed during those years.ConclusionsThe volume of percutaneous embolization procedures performed in the Medicare population increased from 2005 to 2016, reflecting a trend toward minimally invasive intervention. In 2016, radiologists performed nearly 10 times more arterial embolization procedures than the second highest specialty and more venous embolization procedures than any other single specialty.     

National Trends in Inferior Vena Cava Filter Placement and Retrieval Procedures in the Medicare Population Over Two Decades

PurposeTo assess trends in inferior vena cava (IVC) filter placement and retrieval procedures in Medicare beneficiaries over the last two decades.MethodsUsing Physician/Supplier Procedure Summary Master Files from 1994 through 2015, we calculated utilization rates for IVC filter placement and retrieval procedures in Medicare fee-for-service beneficiaries. Services were stratified by provider specialty group and site of service.ResultsIVC filter placement rates increased from 1994 to 2008 (from 65.0 to 202.1 per 100,000 beneficiaries, compound annual growth rate [CAGR] +8.4%) and then decreased to 128.9 by 2015 (CAGR −6.2%). This decrease was observed across all specialty groups and sites of service. From 1994 to 2015, placement procedure market share increased for radiologists (from 45.1% to 62.7%) and cardiologists (from 2.5% to 6.7%) but decreased for surgeons (from 46.6% to 27.9%). Overall, procedures shifted slightly from the inpatient (from 94.5% to 86.5% of all procedures) to outpatient hospital (from 4.9% to 14.9%) settings. Between 2012 and 2015, retrieval rates increased from 12.0 to 17.7 (CAGR +13.9%). Retrievals as a percentage of placement procedures were similar across specialties in 2015 (range 13.0%-13.8%).ConclusionDespite prior dramatic growth, the utilization of IVC filters in Medicare beneficiaries markedly declined over the last decade, likely relating to evolving views regarding efficacy and long-term safety. This decline was accompanied by several filter-related market shifts, including increasing placement by radiologists and cardiologists, increasing outpatient placement procedures, and increasing retrieval rates.     

Nationwide Trends in Use of Catheter-Directed Therapy for Treatment of Pulmonary Embolism in Medicare Beneficiaries from 2004 to 2016

PurposeTo evaluate changes in the use of catheter-directed therapy (CDT) for pulmonary embolism (PE) treatment with attention to primary operator specialty in the Medicare population.MethodsUsing a 5% national sample of Medicare claims data from 2004 to 2016, all claims associated with PE were identified. The annual volume of 2 billable CDT services—arterial mechanical thrombectomy and transcatheter arterial infusion for thrombolysis—were determined to evaluate changes in CDT use and primary CDT operator specialty over time.ResultsThe total number of CDT procedures increased over the course of the study period, representing 0.457 and 5.057 service counts per 100,000 Medicare beneficiaries in 2004 and 2016, respectively. The proportion of PEs treated with CDT increased 10-fold from 2004 to 2016, increasing from 0.1% to 1.0%. Interventional radiologists performed most CDT therapies each year, with the exception of 2010 when vascular surgeons performed more. In 2016, interventional radiologists performed 3.54 CDT services for PE per 100,000 Medicare beneficiaries, which was 70% of total CDT for PE procedures, followed by interventional cardiologists and vascular surgeons performing 0.92 services (18%) and 0.60 services (12%), respectively.ConclusionsCDT is an increasingly used treatment for PE, with a 10-fold increase from 2004 to 2016. Interventional radiologists are the dominant providers of these services, followed by interventional cardiologists and vascular surgeons.     

Hemodialysis Access Maintenance in the Medicare Population: An Analysis Over a Decade of Trends by Provider Specialty and Site of Service

Purpose

To evaluate annual national trends in hemodialysis access maintenance procedures in the Medicare population by specialty and setting.

Lower-extremity endovascular interventions for Medicare beneficiaries: comparative effectiveness as a function of provider specialty

PurposeLower-extremity endovascular interventions are increasingly being performed by vascular surgeons (VSs) and interventional cardiologists (ICs) in addition to interventional radiologists (IRs). Regardless of specialty, well trained, experienced, and dedicated operators are expected to offer the best outcomes. To examine specialty-specific trends, outcomes of percutaneous lower-extremity revascularizations in Medicare beneficiaries were compared according to physician specialty types providing the service.Materials and MethodsMedicare Standard Analytical Files that contain longitudinal data of all services (physician, inpatient, outpatient) provided to a 5% sample of Medicare beneficiaries were studied. All claims for percutaneous angioplasty, atherectomy, and stent implantation of lower-extremity arteries during the years 2005–2007 were extracted, and the following outcomes were assessed: mortality, transfusion, intensive care unit (ICU) use, length of stay, and subsequent revascularization or amputation. Outcomes were compared by using regression models adjusted for age, sex, race, emergency department admission, and comorbid conditions.ResultsMost outcomes were significantly worse if the service was provided by vascular surgeons compared with other vascular specialists. The in-hospital mortality rate for procedures performed by VSs was 19% higher than for those performed by others, but this difference was not significant (P =.351). Adjusted average 1-year procedure costs were significantly lower for IRs ($17,640) than for VSs ($19,012) or ICs ($19,096).ConclusionsMedicare data show that endovascular lower-extremity revascularization by vascular surgeons results in more transfusion and ICU use, longer hospital stay, more repeat revascularization procedures or amputations, and higher costs compared with procedures performed by interventional radiologists.     

Interventional Radiology-Operated Endoscopy as an Adjunct to Image-Guided Interventions

Purpose

Interventional radiology-operated endoscopy is an underused technique, which may have a significant impact on the ability to treat patients with a variety of conditions. The purpose of this article is to discuss the setup, equipment, and potential clinical uses of interventional radiology-operated endoscopy.

Inferior Vena Cava Filter Placement and Retrieval Rates among Radiologists and Nonradiologists

Purpose

To evaluate inferior vena cava (IVC) filter placement and retrieval rates among radiologists, vascular surgeons, cardiologists, other surgeons, and all other health care providers for Medicare fee-for-service beneficiaries in the years 2012–2015.

Nationwide Trends in Catheter-Directed Therapy Utilization for the Treatment of Lower Extremity Deep Vein Thrombosis in Medicare Beneficiaries

PurposeTo determine overall and provider specialty trends in the use of catheter-directed therapy for lower extremity deep vein thrombosis (DVT) treatment in the Medicare population.Materials and MethodsUsing data obtained from 2007–2017 Centers for Medicare & Medicaid Services 5% research identifiable files, all claims associated with acute and chronic lower extremity DVT were identified. The annual volume of 2 services—venous percutaneous transluminal thrombectomy (current procedural terminology [CPT] code 37187) and venous infusion for thrombolysis (CPT code 37201 from 2007 to 2012 and CPT code 37212 from 2013 to 2017)—was examined for trends in DVT intervention. Utilization rates based on region and the place of service were calculated. The results were further categorized based on primary operator type (radiology, cardiology, surgery, and other).ResultsThe total number of DVT interventions increased over time, with 4.27 service counts per 100,000 beneficiaries in 2007 increasing to 13.4 by 2017, a growth rate of 12.09%. Radiologists performed the majority of interventions each year, except in 2013, in which they performed 46.6% of interventions, whereas surgeons and cardiologists combined performed the other 53.4%. In 2017, radiologists performed 7.56 services per 100,000 beneficiaries, which was 56.8% of the total count, more than those performed by surgeons, cardiologists, and unspecified providers combined.ConclusionsCatheter-directed therapy is increasingly being used for the treatment of DVT, with its use undergoing a nearly 12-fold increase from 2007 to 2017 in the Medicare population. Radiologists remained the dominant provider of these services throughout the majority of study period, with a relative reduction in market share from 72% in 2007 to 57% in 2017.     

Trends in the Use of Percutaneous Versus Open Surgical Breast Biopsy: An Update

PurposeDespite the emergence of core-needle (percutaneous) biopsy as the standard of breast care, open surgical breast biopsies continue to be performed with variable frequency. The aim of this study was to compare trends in the use of percutaneous and open surgical breast biopsies and the relative roles of radiologists and surgeons in performing them.MethodsThe nationwide Medicare Part B Physician/Supplier Procedure Summary Master Files for 2004 to 2016 were reviewed, and trends were studied in the total volume of breast biopsies performed in the Medicare fee-for-service population and in volumes of imaging-guided percutaneous biopsies (IGPBs) and open surgical biopsies. Using Medicare’s physician specialty codes, the numbers of procedures performed by different specialties were determined. Trends in the type of imaging used for IGPBs were analyzed using the relevant Current Procedural Terminology codes, introduced in 2014.ResultsBetween 2004 and 2016, utilization of IGPBs increased from 124,423 to 187,914 (+51%), whereas the use of open surgical breast biopsies declined from to 6,605 to 2,373 (−64%). IGPBs performed by radiologists increased from 89,493 to 160,485 (+79%), and IGPBs by surgeons declined from 30,264 to 24,703 (−18%). Among IGPBs from 2014 to 2016, ultrasound-guided and MRI-guided percutaneous biopsies increased, whereas stereotactic biopsies declined.ConclusionsThere is a steady upward trend in the utilization of imaging-guided breast biopsies, and a majority are performed by radiologists. Ultrasound is the primary guidance technique used in percutaneous breast biopsies.     

Clinical IR in Canada: The Evolution of a Revolution

Purpose

To investigate the current status and evolution of both the interventional radiologist’s role as a clinician and the practice of interventional radiology (IR) over the past decade in Canada.

Day of Week,Site of Service,and Patient Complexity Differences in Venous Ultrasound Interpreted by Radiologists Versus Nonradiologists

ObjectiveNationally, nonradiologists interpret an increasing proportion of lower extremity venous duplex ultrasound (LEVDU) examinations. We aimed to study day of week, site of service, and patient complexity differences in LEVDU services interpreted by radiologists versus nonradiologists.Materials and MethodsUsing carrier claims files for a 5% national sample of Medicare beneficiaries from 2012 to 2015, we retrospectively classified all LEVDU examinations by physician specialty (radiologist versus nonradiologist), day of week (weekday versus weekend), site of service, and patient Charlson Comorbidity Index (CCI) scores. Pearson’s χ² was used to test statistical significance.ResultsOf 760,433 LEVDU examinations for which provider specialty could be determined, 439,964 (58%) were interpreted by radiologists and 320,469 (42%) by nonradiologists. On weekends, radiologists interpreted 75% (66,094 of 88,244) and nonradiologists 25% (22,150 of 88,244) (P < .0001). Of LEVDU examinations interpreted by radiologists, 57% were performed in the inpatient or emergency department settings, and 70% of LEVDU examinations interpreted by nonradiologists were performed in the private office or outpatient hospital setting. Radiologists interpreted a slightly larger proportion (17%) of their examinations on patients with more comorbidities (CCI of ≥3) than nonradiologists (15%) (P < .0001).ConclusionCompared with nonradiologists, radiologists interpret a disproportionately larger share of weekend (versus weekday) LEVDU examinations and a considerably larger proportion in higher acuity settings. Additionally, the patients on whom they render services have more comorbidities. To optimize around-the-clock patient access to necessary imaging, emerging quality payment programs should consider the timing and sites of service, as well as patient complexity.     

Disparities over Time in Volume,Day of the Week,and Patient Complexity between Paracentesis and Thoracentesis Procedures Performed by Radiologists versus Those Performed by Nonradiologists

PurposeTo compare the disparities between the paracenteses and thoracenteses performed by radiologists with those performed by nonradiologists over time. Variables included the volume of procedures, the days of the week, and the complexity of the patient’s condition.Materials and MethodsUsing carrier claims files for a 5% national sample of Medicare beneficiaries from 2004 to 2016, paracentesis and thoracentesis examinations were retrospectively classified by physician specialty (radiologist vs nonradiologist), day of the week (weekday vs weekend), and the complexity of the patient’s condition (using Charlson comorbidity index scores). The Pearson chi-square and independent samples t-test were used for statistical analysis.ResultsBetween 2004 and 2016, the proportion of all paracentesis and thoracentesis procedures performed by radiologists increased from 70% to 80% and from 47% to 66%, respectively. Although radiologists increasingly performed more of both services on both weekends and weekdays, the share performed by radiologists was lower on weekends. For most of the first 9 years across the study period, radiologists performed paracentesis in patients with more complex conditions than those treated by nonradiologists, but the complexity of patients’ conditions was similar during recent years. For thoracentesis, the complexity of patients’ conditions was similar for both specialty groups across the study period.ConclusionsThe proportion of paracentesis and thoracentesis procedures performed in Medicare beneficiaries by radiologists continues to increase, with radiologists increasingly performing most of both services on weekends. Nonetheless, radiologists perform disproportionately more on weekdays than on weekends. Presently, radiologists and nonradiologists perform paracentesis and thoracentesis procedures in patients with similarly complex conditions. These interspecialty differences in timing and complexity of the patient’s condition differ from those recently described for several diagnostic imaging services, reflecting the unique clinical and referral patterns for invasive versus diagnostic imaging services.     

National Trends in the Utilization of Skeletal Radiography From 2003 to 2015

PurposeExamine recent trends in the use of skeletal radiography and assess the roles of various nonradiologic specialties in the interpretations.MethodsMedicare Part B fee-for-service claims data files from 2003 to 2015 were analyzed for all Current Procedural Terminology, version 4 (CPT-4) procedure codes related to skeletal radiography. The files provide examination volume, and we calculated utilization rates per 1,000 Medicare beneficiaries. Medicare’s physician specialty codes were used to determine the specialties of the providers. Total utilization rate trends were analyzed, as well as those for radiologists and nonradiologists. We determined which nonradiologist specialties were the highest users of skeletal radiography. Medicare place-of-service codes were used to identify the locations where the services were provided.ResultsThe total utilization rate per 1,000 of skeletal radiography within the Medicare population increased 9.5% from 2003 to 2015. The utilization rate for radiologists increased 5.5% from 2003 to 2015 versus 11.1% for nonradiologists as a group. Among nonradiologist specialties in all health care settings over the study period, orthopedic surgeons increased 10.6%, chiropractors and podiatrists together increased 14.4%, nonphysician providers (primarily nurse practitioners and physician assistants) increased 441%, and primary care physicians’ rate decreased 33.5%. Although radiologists do almost all skeletal radiography interpretation in hospital settings, nonradiologists do the majority in private offices. There has been strong growth in skeletal radiography in emergency departments, but a substantial drop in inpatient settings.ConclusionsThe utilization of skeletal radiography has increased more rapidly among nonradiologists than among radiologists. This raises concerns about self-referral and quality.     

Trends in Outpatient MRI Seem to Reflect Recent Reimbursement Cuts

PurposeTo determine whether recent reimbursement cuts have resulted in a shift of outpatient MRI from private offices to hospital outpatient departments (HOPDs); and to study office MRI utilization trends among radiologists and other specialists.MethodsThe Medicare Part B Physician/Supplier Procedure Summary Master Files were used. MRI codes were aggregated, and total MRI volumes from 2002 to 2012 were studied. Medicare place-of-service codes were used to identify studies performed in private offices and HOPDs and create trend lines. Specialty codes were used to categorize private office MRI users as radiologists, orthopedic surgeons, other physicians, and independent diagnostic testing facilities.ResultsMedicare office and HOPD utilization of MRI (all specialties) rose rapidly from 2002 to 2006, reaching 2,727,807 in offices and 2,355,641 in HOPDs. Thereafter, office volume steadily declined, whereas HOPD volume steadily increased. By 2012, more studies were done in HOPDs than in offices. Over the entire period from 2002 and 2012, office MRI volume among radiologists increased 27%, compared with 216% among orthopedic surgeons and 124% among other physicians.ConclusionsAlthough the majority of Medicare outpatient MRI studies had previously been performed in private offices, recent years brought a shift, with more now being performed in HOPDs. This change will increase costs to payers, because reimbursements to HOPDs are generally higher than those to offices. Although radiologists perform the majority of MRI exams that are conducted in private offices, the rate of growth for such exams from 2002 to 2012 was considerably higher among orthopedic surgeons and other physicians than among radiologists.     

Relative Roles of Radiologists and Other Physicians in Percutaneous Endovascular Neurointerventions

PurposeCerebral catheter angiography and endovascular neurointerventions (ENIs) were developed and refined by early pioneers in neuroradiology. Recently, with developments in the safety and efficacy of ENIs, other physician specialists have expressed strong interest in performing these procedures. Our purpose was to compare volume and utilization of ENIs, among the various specialties, from 2000 to 2013.MethodsData from the Medicare Part B Physician/Supplier Procedure Summary Master Files for 2000 to 2013 were used to study ENI volume and utilization rates, by radiologists, neurosurgeons, neurologists, vascular surgeons, cardiologists, and other physicians.ResultsFrom 2000 to 2013, the volume of intracranial ENIs increased: overall, from 2,439 to 7,424; for radiologists, from 1,956 to 3,993; and for neurosurgeons, from 237 to 2,900. Although cardiologists did not perform many intracranial ENIs in these years, they performed most of the carotid artery stenting procedures (4,097, which is 51% of the total 8,201 performed in 2013).ConclusionsRadiologists continue to maintain a strong presence in the field of neurointerventional radiology, particularly in percutaneous intracranial interventions, performing 51% of all intracranial procedures in 2013, down from 80% in 2000. However, neurosurgeons have made substantial inroads into ENI procedures, with their volume increasing from 10% to 33%, from 2000 to 2013. The overall volume of ENIs rose steadily from 2000 to 2013.     

Predicted Cost Savings Achieved by the Radiology Support,Communication and Alignment Network from Reducing Medical Imaging Overutilization in the Medicare Population

ObjectiveThe Radiology Support, Communication and Alignment Network (R-SCAN) is a quality improvement program through which patients, referring clinicians, and radiologists collaborate to improve imaging appropriateness based on Choosing Wisely recommendations and ACR Appropriateness Criteria. R-SCAN was shown previously to increase the odds of obtaining an appropriate, higher patient or diagnostic value, imaging study. In the current study, we aimed to estimate the potential imaging cost savings associated with R-SCAN use for the Medicare population.Material and MethodsThe R-SCAN data set was used to determine the proportion of appropriate and lesser value imaging studies performed, as well as the percent change in the total number of imaging studies performed, before and after an R-SCAN educational intervention. Using a separate CMS data set, we then identified the total number of relevant imaging studies and associated total costs using a 5% sample of Medicare beneficiaries in 2017. We applied R-SCAN proportions to the CMS data set to estimate the potential impact of the R-SCAN interventions across a broader Medicare population.ResultsWe observed a substantial reduction in the costs associated with lesser value imaging in the R-SCAN cohort, totaling $260,000 over 3.5 months. When extrapolated to the Medicare population, the potential cost reductions associated with the decrease in lesser value imaging totaled $433 million yearly.ConclusionIf expanded broadly, R-SCAN interventions can result in substantial savings to the Medicare program.     

Professional Services Rendered by Nurse Practitioners and Physician Assistants Employed by Radiology Practices: Characteristics and Trends From 2017 Through 2019

PurposeWith radiology practices increasingly employing nonphysician practitioners (NPPs), we aimed to characterize specific NPP clinical roles.MethodsLinking 2017 to 2019 Medicare data sets, we identified all claims-submitting nurse practitioners and physician assistants (together NPPs) employed by radiologists. NPP-billed services were identified, weighted by work relative value units, and categorized as (1) clinical evaluation and management (E&M), (2) invasive procedures, and (3) noninvasive imaging interpretation. NPP practice patterns were assessed temporally and using frequency analysis.ResultsAs the number of radiologist-employed NPPs submitting claims increased 16.3% (from 523 in 2017 to 608 in 2019), their aggregate Medicare fee-for-service work relative value units increased 17.3% (+40.0% for E&M [from 79,540 to 111,337]; +5.6% for procedures [from 179,044 to 189,003]; and +74.0% for imaging [from 5,087 to 8,850]). The number performing E&M, invasive procedures, and imaging interpretation increased 7.6% (from 329 to 354), 18.3% (from 387 to 458), and 31.8% (from 85 to 112), with 58.2%, 75.3%, and 18.4% billing those services in 2019. Paracentesis and thoracentesis were the most frequently billed invasive procedures. Fluoroscopic swallowing and bone densitometry examinations were the most frequently billed imaging services. By region, NPPs practicing as majority clinical E&M providers were most common in the Midwest (33.5%) and South (33.0%), majority proceduralists in the South (53.1%), and majority image interpreters in the Midwest (50.0%).ConclusionsAs radiology practices employ more NPPs, radiologist-employed NPPs’ aggregate services have increased for E&M, invasive procedures, and imaging interpretation. Most radiologist-employed NPPs perform invasive procedures and E&M. Although performed by a small minority, imaging interpretation has shown the largest relative service growth.     

Utilization of and Outcomes Associated with Intravascular Ultrasound during Deep Venous Stent Placement among Medicare Beneficiaries

PurposeTo evaluate temporal trends, practice variation, and associated outcomes with the use of intravascular ultrasound (US) during deep venous stent placement among Medicare beneficiaries.Materials and MethodsAll lower extremity deep venous stent placement procedures performed between January 1, 2017, and December 31, 2019 among Medicare beneficiaries were included. Temporal trends in intravascular US use were stratified by procedural setting and physician specialty. The primary outcome was a composite of 12-month all-cause mortality, all-cause hospitalization, or repeat target vessel intervention. The secondary outcome was a composite of 12-month stent thrombosis, embolization, or restenosis.ResultsAmong the 20,984 deep venous interventions performed during the study period, 15,184 (72.4%) utilized intravascular US. Moderate growth in intravascular US use was observed during the study period in all clinical settings. There was a variation in the use of intravascular US among all operators (median, 77.3% of cases; interquartile range, 20.0%–99.2%). In weighted analyses, intravascular US use during deep venous stent placement was associated with a lower risk of both the primary (adjusted hazard ratio, 0.72; 95% confidence interval [CI], 0.69–0.76; P < .001) and secondary (adjusted hazard ratio, 0.32; 95% CI, 0.27–0.39; P < .001) composite end points.ConclusionsIntravascular US is frequently used during deep venous stent placement among Medicare beneficiaries, with further increase in use from 2017 to 2019. The utilization of intravascular US as part of a procedural strategy was associated with a lower cumulative incidence of adverse outcomes after the procedure, including venous stent thrombosis and embolization.     

Changing Medicare Utilization of Minimally Invasive Procedures for the Treatment of Chronic Venous Insufficiency

Purpose

To examine changes in the utilization of procedures related to treatment of chronic venous insufficiency (CVI) in the Medicare population.

Geographic Variations in Growth of Radiologists and Medicare Enrollees From 2012 to 2019

ObjectiveAnalyze changes in the number of Medicare-serving radiologists and Medicare enrollees nationwide and by geographic region and state from 2012 to 2019 to understand variations in allocation of imaging health care services over the past decade.MethodsThe number of radiologists submitting claims to Medicare was extracted from the CMS Physician and Other Supplier Public Use File Database. The number of Medicare enrollees by state was obtained from the Kaiser Family Foundation. National-, regional-, and state-level changes in rates of growth of radiologists, Medicare enrollees, and radiologists per 100,000 Medicare enrollees from 2012 to 2019 were tabulated.ResultsThe overall number of radiologists per 100,000 Medicare enrollees was 79.7 in 2012, increasing to 79.9 in 2019. In 2012, the number of radiologists per 100,000 enrollees was lower than the national average in the South (66.9; 16% lower) and Midwest (79.1; 0.7% lower) and higher in the Northeast (98.3; 23% higher) and West (88.8; 11% higher). In 2019, the number of radiologists per 100,000 enrollees was lower than the national average in the South (69.8; 12% lower) only and was higher in the Midwest (81.4; 1.9% higher), Northeast (99.3; 24% higher), and West (80.2; 0.4% higher). By state, there was a 4.2-fold variation in the number of radiologists per 100,000 Medicare enrollees, ranging from 38.8 in Wyoming to 161.4 in Minnesota (200.5 in Washington, DC).DiscussionThe growth of Medicare-serving radiologists and Medicare enrollees was stable nationally and demonstrated tremendous variations by US region and state. These variations bring to light potential implications for patient access to care and distribution of health care resources.