A win for high-value care: CMS approves new measure of CT radiation quality

Editor’s Note: This blog was updated on November 30th to clarify the drivers of variations in doses of radiation.

Last month signified a victory for high-value care with the approval of a new patient safety metric, Excessive Radiation Dose or Inadequate Image Quality for Diagnostic Computed Tomography in Adults. Starting in 2025, the measure will be integrated into the Centers for Medicare and Medicaid Services (CMS)’s Merit-based Incentive Payment System (MIPS) and Hospital Inpatient and Outpatient Quality Reporting Programs, with the goal of regulating patients’ exposure to radiation during computed tomography (CT) scans. 

This new measure of radiation quality sheds light on an important potential harm of imaging overuse. Here’s what it means for the future of provider accountability and patient safety.

Radiation exposure during CT scans

Each year, it is estimated that more than 80 million CT scans are performed in the United States. The computerized x-ray imaging procedure has the power to inform diagnostic decisions for everything from tumors and lesions to heart disease and pneumonia. 

While CT scans are an essential diagnostic tool in doctors’ medical toolkits, it’s important they be used carefully. Each time a CT scan is performed, the patient is exposed to ionizing radiation, which is required to produce an internal image for the physician to review and make diagnostic and treatment-related decisions. However, in large doses, exposure to such radiation can damage genetic and cellular material, increasing the risk for mutations and consequently, cancer. 

“Many patients still routinely receive radiation doses two or three times what they should. That will lead to cancer in a small percentage of patients, approximately thirty-six thousand cancers every year. This means that CT causes two percent of annual cancers, and we can reduce that risk substantially without reducing the value of the scans.”

Dr. Rebecca Smith-Bindman, UCSF

Given how common CT scans are and the potential risks of radiation exposure, it seems obvious that there would be standard measures for how much radiation doctors can use. But in fact, the amount of radiation that a patient gets in a CT scan varies widely, largely due to differences in the ways in which physicians use CT machines across institutions. The results of studies exploring the implications of this are alarming, with one citing a 13-fold mean variation between the lowest and highest dosages used across different CT scans. 

Measuring what matters in imaging

To tackle the widespread variation and lack of regulation surrounding CT radiation dosage, UCSF Professor in Residence Dr. Rebecca Smith-Bindman and her team developed a new measure, Excessive Radiation Dose or Inadequate Image Quality for Diagnostic Computed Tomography in Adults. The measure sets lower and upper thresholds for radiation dose based on patient characteristics and type of CT scan. The radiation dose floor ensures that enough radiation is used to create an image of acceptable quality, while the ceiling prevents over-radiation that could increase cancer risk. 

Here’s an example from researchers at UCSF:

If a physician suspected that a patient had kidney stones and referred him to radiology, the radiologist would then decide how to perform the scan. She could perform a single-phase, low-dose scan that delivered roughly 2 milli-Sieverts (mSv), which is considered the correct scan to look for kidney stones. Alternatively, she could do a multi-phase, high-dose scan that might impart 25 times that amount of radiation, but which would be far higher than necessary. Because the measure will judge the scan based on the reason it was ordered, the 25 mSv dose would be considered out of range and unacceptable. 

The measure is implemented through software that links to providers’ electronic health records, so clinicians can get real-time feedback on their performance. CMS will evaluate providers based on “the percentage of CT exams that are out-of-range based on having either excessive radiation dose or inadequate image quality.”

The future of overuse metrics

The new radiation quality metric is a great example of how overuse measures can help improve quality and reduce patient harm. CMS estimates this measure could prevent nearly 14,000 cancers among Medicare beneficiaries and save as much as $5 billion to Medicare each year.

This overuse metric is one of many that deserve broader use among providers. Through our research on the Lown Hospitals Index, we’ve seen how common unnecessary imaging and procedures can be in U.S. hospitals. For example, a Lown Institute report from October 2023 found that US hospitals delivered nearly 230,000 unnecessary coronary stents from 2019-2021– that’s a rate of one every seven minutes. The Lown Hospitals Index for Social Responsibility evaluates hospitals on 11 other low-value services, including unnecessary imaging like CT scans for fainting and procedures like spinal fusion for lower back pain. We look forward to incorporating the new metric of CT radiation quality into the Index as data becomes available.