Free breathing, made possible by the use of a high-pitch technique at dual-source CT (DSCT), has the potential to improve results in patients with suspected pulmonary embolism in several ways, Dr. Ralf Bauer wrote in an email to AuntMinnie.com.
"A regular CT scanner, even a 64- or 128-slice machine, requires at least a breath-hold period of a couple of seconds to image the pulmonary structures without breathing artifacts," he explained. "Most departments would use inspiratory breath-hold."
Unfortunately, there are many problems with breathing commands. Some patients don't understand the instructions and continue to breathe. Also, if a patient takes a deep breath and holds it in, changes of the intrathoracic and intravascular pressure gradients occur, which alters the blood flow to and from the heart, he said. The high-pitch scan is so fast that it stops patient motion, providing sharply delineated pulmonary vessels.
Patients were scanned in dual-source, high-pitch mode (pitch 3.0, 100 kV, 180 mAs, and 50 mL of contrast material) without any breathing commands.
Mean central and peripheral pulmonary arterial attenuation in the first 67 patients was measured at 404 ± 104 HU and 453 ± 119 HU, respectively, with mean image noise of 11 ± 2 HU. Scans took less than a second. The aortic root was pictured without any motion artifact in more than 80% of scans, and the use of contrast was reduced, the authors wrote in an abstract.
"This protocol has become our standard protocol for CTPA," Bauer stated.
