Medicare Utilization of CT Angiography from 2001 through 2014: Continued Growth by Radiologists

A fully automated machine learning-based methodology for personalized radiation dose assessment in thoracic and abdomen CT

PURPOSE

To develop a machine learning-based methodology for patient-specific radiation dosimetry in thoracic and abdomen CT.

METHODS

Three hundred and thirty-one thoracoabdominal radiotherapy-planning CT examinations with the respective organ/patient contours were collected retrospectively for the development and validation of segmentation 3D-UNets. Moreover, 97 diagnostic thoracic and 89 diagnostic abdomen CT examinations were collected retrospectively. For each of the diagnostic CT examinations, personalized MC dosimetry was performed. The data derived from MC simulations along with the respective CT data were used for the training and validation of a dose prediction deep neural network (DNN). An algorithm was developed to utilize the trained models and perform patient-specific organ dose estimates for thoracic and abdomen CT examinations. The doses estimated with the DNN were compared with the respective doses derived from MC simulations. A paired t-test was conducted between the DNN and MC results. Furthermore, the time efficiency of the proposed methodology was assessed.

RESULTS

The mean percentage differences (range) between DNN and MC dose estimates for the lungs, liver, spleen, stomach, and kidneys were 7.2 % (0.2-24.1 %), 5.5 % (0.4-23.0 %), 7.9 % (0.6-22.3 %), 6.9 % (0.0-23.0 %) and 6.7 % (0.3-22.6 %) respectively. The differences between DNN and MC dose estimates were not significant (p-value = 0.12). Moreover, the mean processing time of the proposed workflow was 99 % lower than the respective time needed for MC-based dosimetry.

CONCLUSIONS

The proposed methodology can be used for rapid and accurate patient-specific dosimetry in chest and abdomen CT.

Detection of Low Blood Hemoglobin Levels on Pulmonary CT Angiography: A Feasibility Study Combining Dual-Energy CT and Machine Learning

OBJECTIVES

To evaluate if dual-energy CT (DECT) pulmonary angiography (CTPA) can detect anemia with the aid of machine learning.

METHODS

Inclusion of 100 patients (mean age ± SD, 51.3 ± 14.8 years; male-to-female ratio, 42/58) who underwent DECT CTPA and hemoglobin (Hb) analysis within 24 h, including 50 cases with Hb below and 50 controls with Hb ≥ 12 g/dL. Blood pool attenuation was assessed on virtual noncontrast (VNC) images at eight locations. A classification model using extreme gradient-boosted trees was developed on a training set (n = 76) for differentiating cases from controls. The best model was evaluated in a separate test set (n = 24).

RESULTS

Blood pool attenuation was significantly lower in cases than controls (p-values < 0.01), except in the right atrium (p = 0.06). The machine learning model had sensitivity, specificity, and accuracy of 83%, 92%, and 88%, respectively. Measurements at the descending aorta had the highest relative importance among all features; a threshold of 43 HU yielded sensitivity, specificity, and accuracy of 68%, 76%, and 72%, respectively.

CONCLUSION

VNC imaging and machine learning shows good diagnostic performance for detecting anemia on DECT CTPA.

Increasing Utilization of Emergency Department Neuroimaging from 2007 to 2017

Background: The volume of emergency department (ED) visits and neuroimaging have grown since the start of the century. Little is known about this growth in the commercially insured and Medicare Advantage populations. Objective: To evaluate changing emergency department utilization of neuroimaging from 2007 to 2017 in both commercially insured and Medicare Advantage enrollees. Methods: Using patient-level claims from Optum's De-identified Clinformatics Data Mart database, which annually includes approximately 12 to 14 million commercial and Medicare Advantage health plan enrollees, annual ED utilization of head computed tomography (CT), head magnetic resonance (MR), head CT angiography (CTA), neck CTA, head MR angiography (MRA), neck MRA, and carotid duplex ultrasound (CDUS) were assessed from 2007 through 2017. To account for an aging sample population, utilization rates were adjusted using annual relative proportions of age groups and stratified by patient demographics, payer type, and provider state. Results: Between 2007 and 2017, age-adjusted ED neuroimaging utilization rates per 1000 ED visits increased 72% overall (compound annual growth rate [CAGR] 5%). This overall increase corresponded to an increase of 69% for head CT (CAGR 5%); 67% for head MRI (CAGR 5%); 1100% for head CTA (CAGR 25%); 1300% for neck CTA (CAGR 27%); 36% for head MRA (CAGR 3%); 52% for neck MRA (CAGR 4%); and a decrease of 8% for CDUS (CAGR -1%). The utilization of head CT and CTA of the head and neck per 1000 ED visits continuously increased in those 65 or older by 48% (CAGR 4%) and 1011% (CAGR 24%). Conclusion: Neuroimaging utilization in the ED grew considerably between 2007 and 2017, with growth of head and neck CTA far outpacing other modalities. Unenhanced head CT remains by far the dominant ED neuroimaging examination. Clinical Impact: The rapid growth of head and neck CTA observed in the fee-for-service Medicare population is also observed in the commercially insured and Medicare Advantage populations. The appropriateness of this growth should be monitored as the indications for CTA expand.

Acute Kidney Injury in Acute Ischemic Stroke Patients in Clinical Trials

OBJECTIVES

Acute ischemic stroke patients are at risk of acute kidney injury due to volume depletion, contrast exposure, and preexisting comorbid diseases. We determined the occurrence rate and identified predictors associated with acute kidney injury in acute ischemic stroke patients.

SETTING

Multiple specialized ICUs within academic medical centers.

DESIGN

Post hoc analysis of pooled data from prospective randomized clinical trials.

PATIENTS

Acute ischemic stroke patients recruited within 3 hours or within 5 hours of symptom onset.

INTERVENTIONS

IV recombinant tissue plasminogen activator, endovascular treatment, IV albumin, or placebo.

MEASUREMENTS AND MAIN RESULTS

Serum creatinine levels from baseline and within day 5 or discharge were used to classify acute kidney injury classification into stages. Any increase in serum creatinine was seen in 697 (36.1%) and acute kidney injury was seen in 68 (3.5%) of 1,931 patients with acute ischemic stroke. Severity of acute kidney injury was grade I, II, and III in 3.1%, 0.4%, and 0.05% patients, respectively. Patients with albumin (5.5% compared with 2.6%; p = 0.001), preexisting hypertension (4.3% compared with 1.5%; p = 0.0041), and preexisting renal disease (9.1% compared with 3.0%; p < 0.0001) had higher risk of acute kidney injury. The risk of acute kidney injury was lower between those who either underwent CT angiography (2.0% compared with 4.7%; p = 0.0017) or endovascular treatment (1.6% compared with 4.2%; p = 0.0071). In the multivariate analysis, hypertension (odds ratio, 2.6; 95% CI, 1.2-5.6) and renal disease (odds ratio, 3.5; 95% CI, 1.9-6.5) were associated with acute kidney injury. The risk of death was significantly higher among patients with acute kidney injury (odds ratio, 2.7; 95% CI, 1.4-4.9) after adjusting for age and National Institutes of Health Stroke Scale score strata.

CONCLUSIONS

The occurrence rate of acute kidney injury in acute ischemic stroke patients was low and was not higher in patients who underwent CT angiogram or those who received endovascular treatment. Occurrence of acute kidney injury increased the risk of death within 3 months among acute ischemic stroke patients.

Nationwide Trends in Tube-Related Genitourinary Interventions for Medicare Beneficiaries

PURPOSE

To evaluate national trends in tube-related genitourinary interventions, with specific attention to primary operator specialty.

METHODS

Using a 5% national sample of Medicare claims data from 2005 to 2015, all claims associated with nephrostomy tube, nephro-ureteral tube, and ureteral stent placement and exchange were identified. The annual volume of the nine billable procedures were analyzed to evaluate trends in the number of procedures performed and primary operator specialty over time. The Charleston Comorbidity Index (CCI) was used to evaluate patient comorbidities and to determine differences in patient populations treated by interventional radiologists and urologists.

RESULTS

The total volume of tube-related genitourinary interventions has increased over the course of the study period, representing 455.0 services per 100,000 Medicare Fee-for-Service beneficiaries in 2005 to 607.2 services in 2015, an increase of 33.4%. Interventional radiologists performed the majority of all procedures in all procedure types and for each year (>90%) with the exception of nephro-ureteral catheter placement or ureteral stent placement, for which urologists performed the overwhelming majority of procedures each year (>85%). Interventional radiologists performed 63% of their total number of procedures on patients with a CCI = 3 or higher, and urologists performed 42% of their total number of procedures on patients with a CCI = 3 or higher (P < .01).

CONCLUSION

Tube-related genitourinary interventions have demonstrated persistent growth over the 2005 to 2015 decade. Interventional radiologists are the dominant providers for the majority of these interventions compared with urologists while delivering care to a patient population with a higher number of comorbidities.

Appropriate utilization of cardiac computed tomography for the assessment of stable coronary artery disease

Background

Appropriate use criteria (AUC) have been developed in response to growth in cardiac imaging utilization and concern regarding associated costs. Cardiac computed tomography angiography (CCTA) has emerged as an important modality in the evaluation of coronary artery disease, however its appropriate utilization in actual practice is uncertain. Our objective was to determine the appropriate utilization of CCTA in a large quaternary care institution and to compare appropriate utilization pre and post publication of the 2013 AUC guidelines. We hypothesized that the proportion of appropriate CCTA utilization will be similar to those of other comparable cardiac imaging modalities and that there would be a significant increase in appropriate use post AUC publication.

Methods

We employed a retrospective cohort study design of 2577 consecutive patients undergoing CCTA between January 1, 2012 and December 30, 2016. An appropriateness category was assigned for each CCTA. Appropriateness classifications were compared pre- and post- AUC publication via the chi-square test.

Results

Overall, 83.5% of CCTAs were deemed to be appropriate based on the AUC. Before the AUC publication, 75.0% of CCTAs were classified as appropriate whereas after the AUC publication, 88.0% were classified as appropriate (p < 0.001). The increase in appropriate utilization, when extrapolated to the Medicare population of the United States, was associated with potential cost savings of approximately $57 million per year.

Conclusions

We report a high rate of appropriate use of CCTA and a significant increase in the proportion of CCTAs classified as appropriate after the AUC publication.

Trends in Cardiovascular MRI and CT in the U.S. Medicare Population from 2012 to 2017

Purpose

To assess the characteristics and trends of cardiovascular MRI and CT practitioners and practice in the United States.

Materials and Methods

A retrospective cross-sectional analysis of 2012-2017 Medicare Part B physician payments from the Provider Utilization and Payment Data Physician and Other Supplier Public Use Files (POSPUF) was performed. Characteristics of cardiovascular MRI and CT, including the number of providers and examinations, provider sex and location, and physician reimbursement were analyzed. Variable means, standard deviations, and changes per year were reported and compared.

Results

In 2017, 582 physicians provided cardiovascular MRI services in 45 states, a 16.6% increase from 2016 and an 84.8% increase from 2012. A total of 1645 physicians provided cardiovascular CT services in 49 states, a 14.2% increase from 2016 and a 77.3% increase from 2012. Of the providers, 18.0% and 13.3% of cardiovascular MRI and CT providers were women, respectively, similar to providers' respective medical specialties. Only 1.0% of radiologists and 0.2% of cardiologists provided cardiovascular MRI services. A total of 3.2% of radiologists and 0.5% of cardiologists provided cardiovascular CT services. Both cardiovascular MRI use (+75.5%) and cardiovascular CT use (+97.4%) increased markedly over the 6-year study period.

Conclusion

Although the availability of cardiovascular MRI and CT is increasing, both are used less frequently in comparison with other cardiovascular imaging modalities.See also the commentary by Bierhals in this issue.Supplemental material is available for this article.© RSNA, 2021.

Changing National Medicare Utilization of Catheter, Computed Tomography, and Magnetic Resonance Extremity Angiography: A Specialty-focused 16-Year Analysis

To assess changing utilization of extremity angiography from 2001 to 2016, focusing on modalities and provider specialties. Medicare PSPS Master Files from 2001-2016 and POSPUF from 2016 were used to determine overall and specialty utilization of diagnostic catheter angiography (DCA), CT angiography (CTA), and MR angiography (MRA). From 2001 to 2016, extremity angiography increased from 1107 to 1590 extremities imaged per 100,000 beneficiaries, with rapid expansion of CTA (22 in 2001 to 619 in 2009; plateau of 645 in 2016), but declines in DCA (1039 to 914) and MRA (45 to 30). Over time, extremity angiography shifted from 94% DCA, 4% MRA, and 2% CTA to 58% DCA, 41% CTA, and 2% MRA. For radiologists, extremity angiography increased slightly (741 to 767) with increases in CTA (20 to 595) and large decreases in DCA (681 to 145), with MRA remaining low (40 to 27). Extremity angiography increased for cardiologists (197 to 349) and vascular surgeons (87 to 351), both overwhelmingly performing DCA. Radiologists' share of all extremity angiography shifted from 67% to 48%, with interventionalists (47%), generalists (43%), and abdominal radiologists (7.4%) providing most radiologist services in 2016. Throughout, radiologists were the dominant providers of CTA (89% to 92%) and MRA (89% to 90%). Extremity angiography utilization in Medicare beneficiaries increased nearly 50% from 2001 to 2016, largely related to CTA performed by radiologists. Of radiologists, interventionalists and generalists together render most services. Cardiologists and surgeons assumed a large share of DCA previously performed by radiologists.

Diagnostic and Interventional Imaging Services are Significant Sources of Medicare Revenue for Highly Reimbursed Nonradiologist Providers

INTRODUCTION

Nonradiologist providers increasingly perform diagnostic imaging examinations and imaging-guided interventions traditionally performed by radiologists, which have raised concerns regarding appropriate utilization and self-referral. The purpose of this study was to assess the contribution of imaging studies to Medicare reimbursements for highly compensated nonradiologist providers in specialties often performing imaging studies.

METHODS

The Medicare Provider Utilization and Payment Database was queried for provider information regarding overall reimbursement for providers in anesthesiology, cardiology, emergency medicine, neurology, obstetrics and gynecology, orthopedic surgery, neurology, and vascular surgery. Information regarding imaging studies reported and payment amounts were extracted for the 25 highest-reimbursed providers. Data were analyzed for relative contribution of imaging payments to overall medical Medicare payments.

RESULTS

Significant differences between numbers of imaging studies, types of imaging, and payment amounts were noted based on provider specialty (p < 0.001). Highest-reimbursed cardiologists received the greatest percentage of Medicare payments from imaging (18.3%) followed by vascular surgery (11.6%), obstetrics and gynecology (10.9%), orthopedic surgery (9.6%), emergency medicine (8.7%), neurology (7.8%), and anesthesiology (3.2%) providers. Mean imaging payments amongst highly reimbursed nonradiologists were greatest for cardiology ($578,265), vascular surgery ($363,912), and orthopedic surgery ($113,634). Amongst highly reimbursed specialists, most common nonradiologist imaging payments were from ultrasound (45%) and cardiac nuclear medicine studies (40%).

CONCLUSIONS

Nonradiologist performed imaging payments comprised substantial proportions of overall Medicare reimbursement for highly reimbursed physicians in several specialties, especially cardiology, vascular surgery, and orthopedic surgery. Further investigation is needed to better understand the wider economic implications of nonradiologist imaging study performance and self-referral beyond the Medicare population.

Characteristics of MR Neuroimaging Services Billed by Radiologists versus Nonradiologists

BACKGROUND AND PURPOSE

Although most neuroimaging examinations are interpreted by radiologists, many nonradiologists provide interpretation services. We studied day of the week, site of service, and patient complexity differences for common Medicare MR neuroimaging examinations interpreted by radiologists versus nonradiologists.

MATERIALS AND METHODS

Using carrier claims files for a 5% sample of Medicare beneficiaries from 2012 to 2014, we identified all claims for brain and lumbar spine MR imaging examinations. Services were categorized by physician specialty, day of the week, and the site of service. Patient complexity was calculated using Charlson Comorbidity Indices. The χ² was performed to test statistical significance.

RESULTS

A provider specialty could be identified for 568,423 brain and lumbar spine MR imaging examinations. Of weekday examinations, radiologists interpreted 475,288 (92.3%), and nonradiologists, 39,510 (7.7%). Of weekend examinations, radiologists interpreted 52,028 (97.0%) and nonradiologists 1597 (3.0%). Radiologists interpreted 145,904 (98.7%) examinations in the inpatient hospital and emergency department settings versus 1882 (1.3%) by nonradiologists. Of all examinations, 44,547 of those interpreted by radiologists (8.4%) were on the most clinically complex patients versus 2139 (5.2%) for nonradiologists. All interspecialty differences for day of the week, the site of service, and patient complexity were statistically significant (P < .001).

CONCLUSIONS

Although radiologists interpret most common MR neuroimaging examinations for Medicare beneficiaries, in contrast to nonradiologists, they disproportionately render those services on weekends, in higher acuity sites, and on more complex patients. To optimize access and minimize disparities in necessary neuroimaging, quality metrics should consider such service characteristics.