CT at RSNA: Dose dominates, but clinical value persists

Lisa Fratt, Editor

For more than two decades, CT has been hailed as the life-saving, game-changing modality that it is. However, in the last few years, CT has born increasing scrutiny from the medical community, regulatory agencies, lawmakers, media and patients. Visitors to RSNA 2011 will have the opportunity to consider the larger framework, learning about current topics in dose management as well as examining clinical advances.

The top issue is, of course, radiation dose. Although the medical community has not yet agreed on the actual carcinogenic effects of ionizing radiation, it has united around the ALARA (or, as low as reasonably achievable) principle.

While initiatives like the Image Gently campaign--organized by the Society for Pediatric Radiology (SPR), the American College of Radiology (ACR), the American Society of Radiologic Technologists (ASRT), and the American Association of Physicists in Medicine (AAPM)--have gained traction, critics continue to fan the flames of the dose fire. A recent analysis published in the Journal of the National Cancer Institute, for example, estimates that adults may be more vulnerable to the radiation dose than previously believed.

As a partial response to the Cedars Sinai Medical Center debacle, where more than 200 patients were exposed to radiation doses eight times higher than expected, the Golden State passed SB 1237, requiring protocols and safeguards to protect patients from excess exposure.

The radiology community is doing its part, too. Recent industry-wide initiatives aim to improve process. The Medical Imaging and Technology Alliance’s Dose Check safeguard alerts techs to potential overdoses, and DICOM Dose Structured Reporting offers a format for reporting dose data to PACS and EMRs. Although vendors are collaborating on such critical initiatives, CT dose is the new differentiator in the market.

Advances in reconstruction, like adaptive statistical iterative reconstruction (ASIR), slash CT dose up to 50 percent. Earlier this year, separate studies estimated potential dose drop at 50 percent for CT colonography dose (from 5 mSv to 2.5 mSv) and 33 percent for abdominal CT imaging. Estimates for Iterative Reconstruction in Image Space (ISIR) peg the dose drop at up to 60 percent depending on the exam and the patient. Other versions of the algorithm could trim coronary CT angiography dose to 0.25 mSv to 1 mSv.

At the same time, CT imaging use continues to spike. Order for advanced imaging in the ED, which includes CT, MRI and ultrasound, swelled by 367.6 percent for chest pain and 122.6 percent for abdominal pain in the last decade, according to the Centers for Disease Control and Prevention. A study published in the October issue of the Journal of the American Medical Association identified CT as the dominating contributor to three-fold increase in injury-related imaging in the ED.

Pioneers are searching for a new model. An August study published in Radiology suggested that a brief risk assessment could more accurately target CT angiography for emergency department patients with suspected pulmonary emboli. And Children’s Hospital of Wisconsin now subs fast MRI for CT imaging to measure ventricular size in patients with shunts.

Still, CT is radiology’s powerhorse. In the most recent news, cardiac CT angiography was deemed acceptable for screening of patients at low to intermediate risk of coronary artery disease in new appropriate use criteria. Although screening CT colonography has yet to gain reimbursement, study after study demonstrates its value. Multiple studies have shown that it improves reader sensitivity and also boosts screening compliance.

RSNA 2011 is exploring these issues and much more later this month in Chicago. Read on for the Health Imaging & IT editorial staff’s top picks.

Lisa Fratt
lfratt@healthimaging.com
Editor of Health Imaging & IT