Diagnostic ultrasound: who pulled the plug?

Ultrasound has in effect become a "second-class citizen" in diagnostic imaging, despite the fact that all radiologists are trained in the technique. Competing against MRI and CT has levelled its importance, while the lack of an ultrasound contrast material has hampered its availability as a true diagnostic tool. At the same time, diagnostic ultrasound is also migrating into general medicine where, much like the stethoscope, it is utilized by many yet understood by few. As a result, the refinement and rapid development of ultrasound has ended, and very few advances will now occur.

Several factors have led us to this situation in the US. A shortage of radiologists, combined with a skewed reimbursement system, which heavily rewards MRI and CT, mean that ultrasound has become less valued as a diagnostic tool. In addition, ultrasound is a time-intensive modality that, more often than not, requires the involvement of a physician to obtain a good study.

No contrast

In truth, ultrasound has been held back by the lack of a contrast material approved by the US Food and Drug Administration. A technique that must distinguish tissue textures is emasculated without the utilization of contrast. Alternative imaging techniques like MRI and CT have contrast, and as a result they have leaped ahead. Even if a contrast agent were to be released soon, one wonders about its acceptance. The incorporation of MRI and CT into contemporary imaging is now so strong that an ultrasound contrast material is not likely to have much success, at least in the US.

Second-class citizen

The bottom line is this: MRI and CT are contrast-enhanced, protocol-driven, technologist-operated tools that produce images without direct physician involvement. As a result, radiologists are focusing their efforts on these modalities and devote little attention to ultrasound.

Looking across the field of diagnostic radiology in the US, it's evident that no one is participating in post-residency/fellowship training in ultrasound. We are having difficulty finding leaders in ultrasound to replace the present ultrasound experts, and most residency programmes lack radiologists with specialist training in ultrasound to direct the training of the new residents. The demise of ultrasound is becoming a self-fulfilling prophecy; further promulgating the fact that ultrasound soon will not have any real refinements, expertise or devotion to it.

Outside radiology, meanwhile, many other physicians are seeking to exploit ultrasound. The modality presents a great opportunity to be able to bill for additional studies, and because of its wide safety margin, parameters for watching and controlling it are minimal. In an office practice where credentialing is often non-existent, ultrasound can be set up for well under $30,000.

Smaller, cheaper

This is bad news. Technological innovation in ultrasound has traditionally been driven by R&D and then implemented initially on the most expensive units. Over time, those advances have migrated to less expensive systems. But with the diffusion of ultrasound into general medicine, and the lack of development and integration of new techniques by radiologists, ultrasound will probably not show significant technological advance beyond the realization of cheaper, smaller units.

This trend is illustrated by the development of hand-held ultrasound devices. On the face of it, this would seem to be a great advance. The reality, however, is that these devices further undermine the support structure for ultrasound within diagnostic imaging. Cheaper and of lower quality, these units are marketed primarily to non-radiologists, who in turn utilize them to provide imaging quality that is adequate but less than that which could be achieved with dedicated high-end units.

As it disperses into general medicine, ultrasound will be utilized, but perhaps not to its full potential. The writing is on the wall and I fully expect ultrasound to gradually assume an increasingly marginalized position in diagnostic radiology, at least in the US. This is ironic, given the growing concern about high radiation doses produced by multi-detector CT. These days, in spite of the fact that diagnostic ultrasound has no known side-effects, a patient entering an emergency room will most likely get a CT for abdominal or pelvic pain even if the patient is a female of reproductive age.

It is hard to see how this situation could be corrected without a realignment of the reimbursement structure to make ultrasound more profitable. Help could come from the research community, however, in the form of developments in basic ultrasound technology. For ultrasound to be a more attractive option to radiologists we need automated scanning techniques, which enable volume imaging, and which yield data that can be interpreted in any plane. Only then might ultrasound be able to compete with CT and MRI in the US.