Researchers in Japan have demonstrated a way to modify a coronary CT technique such that it significantly cuts the time patients have to hold their breath while being scanned both with and without contrast, according to a study published online July 14 in Academic Radiology.
Cardiovascular radiologist Kunihiro Yoshioka, MD, and colleagues at Iwate Medical University in Morioka, Japan, used their modified version of subtraction coronary CT angiography (CCTA) to acquire high-quality images of 12 patients with severe calcifications of the coronary arteries—“still a major challenge in coronary CT,” the authors point out—in less than 15 seconds.
If replicable, the method holds promise for boosting the success rate of subtraction CCTA by reducing artifacts while also opening the exam to patients who cannot hold their breath for the 20 to 40 seconds demanded by conventional subtraction CCTA.
In setting up the small study, Yoshioka and team hypothesized that the breath-holding time for subtraction CCTA could be shortened if the pre-contrast (mask) scan could be acquired after the post-contrast scan rather than before.
They enrolled a dozen patients who had coronary calcium scores over 400 and were unable to hold their breath for more than 20 seconds.
Performing modified subtraction CCTA using bolus tracking, the researchers adjusted the image-acquisition protocol so that the mask scan was acquired 10 seconds after the post-contrast scan during a single breath-hold.
Upon obtaining the subtraction image by removing the mask-image data from the post-contrast image data, they analyzed the results and found:
- The mean breath-holding time was 12.8 ± 0.8 seconds (range, 12 to 14 seconds).
- Average image quality was significantly increased, rising from 2.1 ± 0.9 on a scale of 0 to 4 with conventional CCTA to 3.1 ± 0.7 with subtraction CCTA.
- With subtraction CCTA, the number of non-diagnostic segments was cut some 34 percent (from 53 percent to 19 percent).
“The purpose of this small investigation was to obtain initial experience with our modified subtraction CCTA protocol and demonstrate its feasibility in patients unable to perform long breath-holds,” the authors write.
They say their next step will be to compare the diagnostic accuracy of their modified subtraction CCTA with that of invasive coronary angiography.
Academic Radiology publisher Elsevier has posted the full study for free.