Study: Picking US over MRI for MSK imaging could save billions

The U.S. could save up to $736 million annually -- and billions over the course of the next 15 years -- if physicians used ultrasound rather than MRI for musculoskeletal imaging when clinically indicated.

That's according to a new study published in the Journal of the American College of Radiology by a multicenter group that includes imaging utilization watchdogs Dr. David C. Levin and Dr. Vijay Rao of Thomas Jefferson University in Philadelphia (JACR, March 2008, Vol. 5:3, pp. 182-188). The lead author on the study was Laurence Parker, Ph.D., also of Thomas Jefferson.

MRI has become the standard of care for imaging a wide range of musculoskeletal disorders, the researchers noted. That preference has been reflected in growth rates for MRI in musculoskeletal imaging: MRI use increased 354% from 1996 to 2005, from 708 studies per 100,000 Medicare beneficiaries to 3,210 studies per 100,000 beneficiaries in 2005.

At the same time, however, growth rates for ultrasound musculoskeletal imaging have been far lower, with the modality usage growing 157.1% over the study period. This is despite the fact that that ultrasound is far cheaper than MRI, with a cost difference of $336 per exam in 2005, according to the researchers. See chart below for a list of growth rates by modality in musculoskeletal imaging.

MSK imaging growth rate, 1996-2005
(per 100,000 Medicare beneficiaries)
Modality 1996 2005 Growth
CT 138 589 326.5%
MRI 708 3,210 353.5%
US 147 379 157.1%
X-ray 44,153 52,586 19.1%
Total 45,146 56,765 25.7%

Despite ultrasound's lower growth rate, clinical studies have indicated that for many musculoskeletal applications, ultrasound may offer diagnostic accuracy comparable to that of MRI, according to the researchers. The modality even has certain advantages over MRI, such as the ability to perform dynamic studies.

The researchers sought to examine how much money could be saved if ultrasound were substituted for MRI for a range of musculoskeletal imaging applications in which clinical evidence indicates that ultrasound is at least comparable to MRI. They examined data from the U.S. Centers for Medicare and Medicaid Services Physician/Supplier Procedure Summary Master Files (PSPSMF) from 1996 to 2005, as well as data from its own radiology information systems (RIS).

The study included five components:

  1. Computing musculoskeletal imaging use by modality from 1996 to 2005
  2. Predicting future use rates from 2006 to 2020
  3. Estimating the cost of MSK imaging by modality
  4. Estimating the proportion of MSK MRI procedures for which MSK ultrasound could be substituted
  5. Computing the cost savings that would result

To assess the percentage of cases in which MRI exams could have been replaced by ultrasound, the group relied on cases extracted from its RIS over a one-year period, due to the detail of clinical information available in these cases relative to those in the Medicare database. These cases were then analyzed by a panel of three academic attending radiologists, who "examined the body part/diagnosis combinations and made retrospective judgments of what prospectively would have been the best test to answer each clinical question," based on their experience and knowledge of evidence-based imaging literature.

Substitution rates were calculated, both for primary diagnosis and all diagnoses in the report. They found that 45.4% of primary diagnoses and 30.6% of primary and secondary diagnoses could have been made by ultrasound.

The group then calculated cost savings to the U.S. healthcare system by decreasing the MRI utilization rate by the number of substituted cases, and increasing the ultrasound utilization rate. The numbers were extrapolated by multiplying the use rate per 100,000 Medicare beneficiaries by U.S. Census Bureau population estimates for future years.

In calculating average cost factors for each modality, the researchers came up with the following numbers for 2005:

  • CT:      $276.72
  • MRI:    $424.73
  • US:        $88.26
  • X-ray:   $29.82

Medicare MSK imaging payments in 2020
with and without US substitution and savings
Modality 2020 predicted cost 2020 substituted cost 2020 savings
MRI $2.046 billion         $1.117 billion            $929 million
US   $40 million         $233 million            -$193 million
    Total net savings $736 million

The researchers concluded by acknowledging the challenges that may have impeded the wider use of ultrasound for musculoskeletal applications: it's operator-dependent and has a longer learning curve than MRI, and referring physicians typically find MR images easier to understand.

Ultrasound scanners also tend to produce less revenue than MRI machines if both are fully used, due to different reimbursement levels and the increased physician interpretation time for US images. MRI also holds the advantage when symptoms are nonspecific, and a single scan can help depict regional anatomy and depict primary and secondary disease, they stated.

But the authors noted that typical imaging workflow involves starting with a less expensive modality initially and working up to more expensive technologies if clinical questions remain. The clinical evidence is growing to support ultrasound in MSK applications, and if this knowledge were applied to technology usage patterns, it could benefit the healthcare system as a whole, the researchers stated.

"There is some complexity to determining when US is an appropriate substitute, but if that problem is addressed, enormous cost savings may be produced," they wrote.

By Brian Casey staff writer
March 6, 2008

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Ultrasound shows promise as a screening tool for wrist pain, February 5, 2008

Comprehensive musculoskeletal US exam offers most value, January 3, 2008

Making the most of MRI to assess the rotator cuff pre- and postinjury, November 9, 2007

Copyright © 2008

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