Summary: A 2022 study by the Harvey L. Neiman Health Policy Institute revealed that radiologists interpreted 72.1% of Medicare imaging studies, with non-radiologists performing 27.9%, and highlighted economic incentives and practice settings as key factors influencing market share, particularly in non-cardiac and advanced imaging modalities.

Key Takeaways:

  1. Radiologists’ Dominance in Imaging Interpretation: In 2022, radiologists interpreted 72.1% of all imaging studies for Medicare fee-for-service beneficiaries, including the vast majority of CT (97.3%) and MRI (91.0%) scans, but had a lower share in ultrasound (33.9%).
  2. Economic and Practical Influences: Non-radiologists performed 27.9% of imaging studies, particularly X-ray and ultrasound, driven by economic incentives and self-referral practices, despite the Stark Law’s intent to limit such self-referrals.
  3. Variation by Imaging Setting and Type: Radiologists dominated non-cardiac imaging in hospital settings but had less market share in office settings for X-ray (43.1%) and ultrasound (29.2%), while cardiologists primarily interpreted cardiac imaging, except for cardiac CT.


A new study by the Harvey L. Neiman Health Policy Institute revealed that in 2022, radiologists interpreted 72.1% of all imaging studies for Medicare fee-for-service beneficiaries. The remaining 27.9% were performed by other clinicians. The market share by imaging modality showed radiologists interpreted 97.3% of CT scans, 91.0% of MRIs, 76.6% of radiology/fluoroscopy studies, 50.9% of nuclear medicine scans, and 33.9% of ultrasounds. This research, published in the Journal of the American College of Radiology (JACR), was based on 123 million Medicare Part B imaging claims from 2022.

Non-Radiologists Lead in Office X-Ray and Ultrasound

For non-cardiac imaging, the study found that radiologists interpreted nearly all imaging in the hospital outpatient, inpatient, and emergency department settings: 99.5% for CT, 99.4% for MR, 98.9% for NM, 97.9% for XR, and 79.3% for ultrasound. Even in the office setting, radiologists interpreted a majority of non-cardiac advanced imaging (84.4% of CT, 78.7% of MR, 85.4% of nuclear medicine) but a minority of X-ray (43.1%) and ultrasound (29.2%).

“There are economic benefits to non-radiologists that likely contribute to their majority market share of X-ra and ultrasound imaging. These providers have financial incentives for self-referral of imaging,” says Eric Christensen, PhD, research director at the Neiman Institute. “The Stark Law, which was designed in part to prohibit self-referral of imaging to facilities in which the referring physician had a financial interest, have largely been ineffective. The literature shows that even after the passage of the Stark Law, self-referring non-radiologists ordered 1.2 to 6.4 times more imaging studies than those who do not self-refer.”

“Non-radiologists have likely been more successful with capturing market share with X-ray and ultrasound than with advanced modalities because imaging volume from their practice’s patients alone may be sufficient for a positive return on investment for providing these services,” adds coauthor Jeffrey Newhouse, MD, Professor Emeritus of Radiology, Columbia University Medical Center. “However, advanced imaging involves substantially higher capital and operational costs, making the economics impractical for most practices.”

Cardiologists Dominate Cardiac Imaging

The study found that radiologist market share also varied by the focus body region, and in particular for cardiac imaging. For non-cardiac imaging, radiologists interpreted 97.6% of CT, 91.4% of MR, 95.6% of nuclear medicine, 76.6% of X-ray and 53% of ultrasound. In contrast, radiologists’ share of cardiac imaging was 67.6% of CT, 42.2% of MR, 11.8% of nuclear medicine, and 0.4% of ultrasound.

“Cardiologists interpret most cardiac imaging, and a greater share than radiologists for all modalities except cardiac CT,” says. Christensen. “Cardiology is the only non-radiology specialty that interprets a large percentage of advanced imaging—CT, MR, and nuclear medicine—but only cardiac imaging.”