New multiphase CT aids stroke imaging

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When imaging acute ischemic stroke (AIS) patients, a new CT angiography imaging method proved to be a reliable tool for imaging selection, according to a Canadian study published online Jan. 29 in Radiology.

Treatment for AIS patients has shifted over the past few years, according to the research team, including lead author Bijoy K. Menon, MD, with the Calgary Stroke Program at the University of Calgary. Current imaging techniques include unenhanced CT, single-phase CT, perfusion CT and MRI.

While all current modes of stroke imaging are effective, many leave much to be desired by the radiologist, including sensitivity to patient motion in unenhanced and perfusion CT and MRI and the invasive nature of conventional angiography, which is not feasible as a fast diagnostic tool for stroke patients.

“With acute stroke treatment, every minute counts. If you delay treatment by 30 minutes, you reduce the chances of the patient doing well by nearly 15 percent,” Menon told Health Imaging. “This is a big problem as most strokes can incapacitate the person for life. In the past, imaging techniques would take time to acquire and interpret. This time can often be around 15 to 30 minutes in some cases.”

In light of these stroke imaging needs, Menon and colleagues developed a multiphase CT angiography imaging tool that gives clinicians information on degree and extent of pial arterial filling in the brain.

“Our technique is easy to do, very fast to interpret even by a less trained physician and significantly resistant to patient motion,” Menon said.  “It is also inexpensive when compared to techniques like MRI and CT Perfusion. These qualities make us believe that it will improve patient care in stroke significantly.”

To study the effectiveness of the new imaging technique, the authors scanned 147 patients using baseline unenhanced CT, single-phase CT angiography of the head and neck, multi-phase CT angiography and perfusion CT. Mean patient age was 72 and the patient cohort was 49.7 percent male.

The ability of multiphase CT angiography to predict clinical outcome was modest but better than that of models using single-phase CT angiography and perfusion CT. Additionally, multiphase CT models decreased National Institute of Health Stroke Scores by 50 percent over a 24 hour period.

“Our study shows that multiphase CT angiography has good interrater reliability,” Menon and colleagues wrote. “It reduces uncertainty in clinical decision making and may be slightly better in the prediction of clinical outcome than currently used techniques, such as unenhanced CT, single-phase CT angiography, and perfusion CT.”

Menon said another major strength of multiphase CT angiography is its relative low cost.

“It’s inexpensive when compared to techniques like MRI and CT perfusion,” he said. “These qualities make us believe that it will improve patient care in stroke significantly.”

This new imaging method, Menon concluded, will be a boon to both stroke patients and their clinicians.

“The ease of use of the tool together with the time it saves when treating stroke patients will result in the technique being used more and more in stroke patients not just in major stroke centers but also in smaller ones. It has the capability of improving outcomes further in patients with this debilitating disease,” he said.