Whole-body imaging survives era of undirected screening to emerge as tool for specific indications

March 13, 2007

Few controversies in radiology have generated as much interest as that of whole-body imaging. But niche-specific indications for the technique may quell the controversy.

Few controversies in radiology have generated as much interest as that of whole-body imaging. But niche-specific indications for the technique may quell the controversy.

"It's a perfect topic for the meeting as it has been so controversial, with people advocating whole-body imaging and others with very strong feelings against it," said session moderator Dr. Gabriel P. Krestin, radiology chair at Erasmus University Medical Center in Rotterdam, the Netherlands.

There is no question that whole-body imaging is more feasible than ever given technological advances in both CT and MRI. The question then becomes in which patient population it makes the most sense to apply the technique.

Examining the topic from an epidemiological point of view, Dr. Myriam G. Hunink from the department of epidemiology and biostatistics and the department of radiology at Erasmus focused on whether whole-body imaging is beneficial and whether those benefits are cost-effective.

"The decision to perform whole-body imaging depends on the probability of disease, the trade-off between the expected net gain of correctly identifying patients with disease versus the expected net harm of incorrectly labelling a healthy individual as diseased, and the associated costs," she said.

False-positive test results and incidental findings, which are often underestimated, carry an increased risk to the patient stemming from need for further workup and anxiety. Additionally, they could put a strain on healthcare finances.

"In Europe, where we have many countries with socialized medicine, we are concerned about the effect whole-body imaging will have on the finances of the healthcare system," Krestin told Diagnostic Imaging.

Many people came to this special focus session expecting to hear about undirected screening of asymptomatic people, he said. What they got instead were two very strong advocates of whole-body imaging, but for clearly specified indications.

Dr. Geoffrey Rubin, chief of cardiovascular imaging at Stanford University in Palo Alto, CA, described the current evidence for and against whole-body imaging for vascular disease.

It is known that atherosclerosis is a systemic disease, he said. If it is found in one vessel area, it is most likely to be in other vessel areas. But there is scant peer-reviewed evidence that treating asymptomatic lesions results in better survival.

"Technologically, we have the capability to scan the entire arterial system with CT and MRI. Clinically, we haven't proven it has a real benefit in whole populations," he said.

Many outcome studies need to be conducted to determine the path of preclinical lesions. Until then, clinicians run the risk of putting in stents or performing surgery when it's not really needed, according to Rubin.

He favours using whole-body imaging to investigate atherosclerosis as a disease, to better understand the diversity of its manifestations. He does not advocate screening asymptomatic vascular territories with the intent to treat lesions when they're found.

"There is very little evidence to support doing so," he said.

There are a few preliminary reports for whole-body MRI, but no outcome studies comparing treatment based on 64-slice CT to the reference standard of catheter angiography. This is a recognized deficiency, and some outcome studies are in the works, particularly looking at the acute chest pain patient, Rubin said.

The final presenter, Dr. Stephen J. Eustace, a professor of musculoskeletal radiology at Cappagh National Orthopaedic and Mater Misericordiae Hospitals in Dublin, advocates using whole-body MRI for staging cancer patients. He says it is a much more efficient approach than a bone scan for proving or ruling out metastatic disease. Whole-body MRI also provides additional diagnostic information.

Evidence of MRI's superior sensitivity in detecting bone metastases has been available for over a decade. Researchers held back from recommending that scintigraphy surveys be discontinued, however, until head-to-toe MRI examinations became clinically viable.

Whole-body MRI can identify sclerotic metastases, which are common to prostate and breast cancers, and the bone marrow disease multiple myeloma. Eustace also favors MRI over PET for staging skeletal metastases. Regarding soft-tissue metastatic disease, PET-CT currently holds an edge, but diffusion-weighted MRI techniques hold promise. Additionally, whole-body MRI staging of cancer will only grow with the development of targeted contrast agents.

Whether these lectures will put an end to the swirling controversy remains to be seen.

"Physicians, radiologists, entrepreneurs, and a large portion of the population were, and still are, attracted to the idea of whole-body imaging. Yes, there is a place for whole-body imaging, but only for very clear indications. In this setting, it is feasible," Krestin said.