Ultrasound in the spotlight

Ultrasound is an attractive imaging option due to the absence of ionizing radiation and low cost relative to other modalities. Because of this, researchers have been investigating ultrasound as a superior alternative for a number of indications, and this week’s top stories were dominated by these efforts.

Take kidney stones, for example. The most common initial imaging test for suspected stones, or nephrolithiasis, is CT because of its high sensitivity. However, if ultrasound could be used instead, patients would be spared exposure to radiation.

Rebecca Smith-Bindman, MD, of the University of California in San Francisco, and colleagues set out to compare outcomes when ultrasound is used instead of CT as the initial imaging method for suspected nephrolithiasis, and published their findings in The New England Journal of Medicine. More than 2,700 patients were randomized to either point-of-care ultrasonography, radiology ultrasonography or CT, and results showed no significant differences in high-risk diagnoses with complications, serious adverse events, pain scores or hospitalizations. As would be expected, radiation exposure for the ultrasound groups was much lower, though more than zero since some patients received follow-up CT.

Ultrasound also could spare patients from having multiple fine-needle aspiration (FNA) procedures, according to another study featured this week from Radiology. Although current guidelines recommend a second FNA if an initial FNA comes back with non-diagnostic results, Thomas J. T. Anderson, MD, of Rhode Island Hospital in Providence, and colleagues sought to determine what features may predict malignancy in order to clarify the role of repeat FNA.

After examining almost 400 nodules that had non-diagnostic FNA results but adequate cytologic, surgical and ultrasound follow-up, they found that just 2.3 percent of the nodules were subsequently diagnosed as malignancies. Patients with malignancies were older (median age of 64 years) and more likely to be men. Odds of malignancy also increased significantly for each 1-cm increase in anteroposterior, minimum and mean nodule diameter. Based on these findings, Anderson and colleagues suggested that clinical and ultrasound follow-up may be more appropriate than repeat FNA following an initial non-diagnostic result.

Ultrasound also showed its versatility in a pilot study presented at International Contrast Ultrasound Society annual conference in Chicago. Norwegian researchers found that ultrasound microbubbles typically used as a contrast agent could enhance the delivery and absorption of cancer drugs in patients with pancreatic cancer. After patients received infusions of both a chemotherapy drug and a microbubble contrast agent, an ultrasound scanner was used to induce “sonoporation,” which causes cell membranes to open and reseal to allow for enhanced delivery of the cancer drug. Preliminary results showed tumor sizes were reduced or growth was slowed in the small group of initial trial subjects.

The catch here is that the FDA has only approved ultrasound contrast agents for cardiac imaging in the U.S., and while additional diagnostic uses are currently being considered, no therapeutic applications have been submitted for review. Hopefully studies like the ones highlighted this week will bring more attention to the potential of the ultrasound alternative.

-Evan Godt
Editor – Health Imaging