Doctors cut nuclear stress test dose in half

Posted on Jun 20, 2011 in Uncategorized

Image processing software lets doctors cut the radiation dose in half for nuclear stress tests without a clinically meaningful drop in image quality, according to new research.

The results of the late-breaking study were presented at the International Conference of Non-Invasive Cardiovascular Imaging in Amsterdam this week.

“It’s our view that myocardial perfusion imaging is feasible with significant radiation dose reduction,” said lead author Dr. Nili Zafrir, director of nuclear cardiology at the Rabin Medical Center in Petah Tikva, Israel, in a statement.

Myocardial perfusion studies are performed to check for disease or abnormalities of the heart. To do it, doctors inject patients with a radioactive dye, technetium-99m. Patients typically then receive two scans from a SPECT unit: one of their heart at rest, and another when it’s “stressed” — that is, after exercise or excitation by drugs.

But in the their presentation, the doctors said that thanks to special software, they could inject only a half-dose of Tc-99m and get nearly the same clinical results.

The software, called “evolution for cardiac,” reconstructs and processes images for SPECT machines.

In the prospective, randomized trial patients described in the abstract, 109 patients were injected with a full dose, or 12-32 millicuries, and another 109 patients received a half-dose, between 5 and 17 mSCi. (Exact dose varied by patient weight.)

Total effective dose for the stress-rest tests were 7.19 mSv for the half-dose protocol, and 14.4 mSv for the conventional protocol, the doctors said. About 94 percent of the images in the half-dose protocol were deemed “excellent to good,” Zafrir said.

Also, about one-third of patients in the half-dose group got a single, stress-only investigation, so they were exposed to a mean dose of 1.9 mSv, “far below the dose range we see in conventional perfusion scanning,” Zafrir said.

“Clearly, we cannot be certain what the long-term benefit of reducing radiation exposure might be, but theoretically it would seem important,” she observed.

As the study was presented at a conference, the results should be considered preliminary.

May 19, 2011
by Brendon Nafziger, DOTmed News Associate Editor