CT software aids stroke diagnosis and preserves patient comfort

The accuracy, safety, and patient comfort of perfusion studies conducted on CT scanners are improved by a new GE Medical Systems software package, according to the company.

The image analysis software, simply called CT Perfusion, delivers a quantitative measure of perfusion disturbances found in patients’ brains, thereby providing physicians with an objective means for assessing brain damage and determining treatment. Other software packages have focused mostly on qualitative interpretations of the images.

The GE software currently runs only on the company’s Advantage Windows workstation. By the third quarter of this year, however, it will be able to run on the consoles of GE’s top-of-the-line multislice scanner, LightSpeed QX/i, as well as its HiSpeed X/i series CT scanners.

GE claims that CT Perfusion boosts reproducibility, decreasing the margin for user error by providing a quantitative assessment rather than requiring qualitative interpretation of images. The company says the software promotes patient safety and comfort by reducing the speed with which the contrast medium must be administered. Whereas other packages may require injection of 10 to 20 mL of contrast medium per second, CT Perfusion requires a rate of just 4 mL.

Fast injection rates can pose serious risks to patients, said Dr. Michael Lev, director of emergency neuroradiology at Massachusetts General Hospital. These rates, ironically, present the greatest risk to patients most likely to need the test.

“Higher injection rates are not only more difficult to routinely achieve in elderly or critically ill patients, who may have small or hard-to-find veins, but carry a greater risk of contrast extravasation into surrounding tissues,” Lev said.

Quantitative advantages are achieved through the use of algorithms that automatically calculate specific values. The ability of CT Perfusion to deliver these measurements sets this package apart from its competitors, some of which have been designed to work with MRI, rather than CT. Use of this modality has resulted in significant strides in neurological assessment over the last several years, largely on the basis of new tools designed to help physicians assess stroke.

“There is MR software that provides perfusion and diffusion information that is clearly highly qualified information,” said Pieter van der Poel, product manager of CT Perfusion in GE’s Premium Segment Global CT Business Unit. “It is not, however, quantitative, as is the CT information.”

GE’s CT Perfusion utilizes a bolus injection of contrast material to measure local cerebral blood volume, blood flow, mean transit time, and time to peak concentration. Algorithms written into the software analyze both arterial inflow and venous outflow to precisely calculate any brain disturbance that may have resulted from brain insult of the type that occurs during stroke. By providing exact quantitative measurement, variability in data interpretation can be reduced.

“Because CT is available around the clock, trauma patients are often sent to CT first,” van der Poel said. “A logical follow-up step now in assumed stroke cases would be to further work up the patient using CT Perfusion.”

In addition to detecting severe cases requiring immediate and aggressive treatment, CT Perfusion is sensitive enough to detect even mild brain disturbances. These are reflected in measurements of cerebral blood volume, cerebral blood flow, and mean transit time. This information reportedly allows physicians to scale treatment to the individual needs of patients.