Good imaging is critical to focusing on a stroke patient's core and preumbral areas for treatment. An Ottawa research group looked at how computed tomography angiography source images (CTASI) and cerebral blood volume (CBV) could be used to understand outcomes and predict 24-hour infarct in stroke patients undergoing recanalization, according to a paper published online Aug. 7 in Stroke.

Researchers from the Ottawa Stroke Research Group assessed the Alberta Stroke Program Early CT Score (ASPECTS) and compared nonenhanced computed tomography (NECT) to CTASI and CT perfusion to determine which would provide the best prediction for outcomes. Out of 46 acute anterior stroke imaging studies, 78 percent revealed successful thrombectomy.

Lead author Cheemun Lum, MD, FRPC, of The Ottawa Hospital and colleagues found that the clearest picture of patient outcomes came from the images acquired through a combination of CTASI and CT perfusion. CT perfusion allowed the team to get an accurate prediction of cerebral blood volume while CTASI allowed them to get a clear picture of how much of the brain could potentially recover, highlighting the ischemic core in sharper detail.

The ASPECTS relating to CTASI had high specificity and sensitivity, 82 percent and 71 percent respectively.

In those patients where CT perfusion led to capturing CBV, CBV-ASPECTS revealed a specificity of 84 percent and a sensitivity of 54 percent, which was combined with a CTASI-ASPECTS specificity of 81 percent and sensitivity of 64 percent.

NECT had generally low sensitivity, even when specificity was high. NECT sensitivity was only 20 percent when it came to early infarct changes, even if it had a specificity of 97 percent. Hypodensity changes had only a 5 percent sensitivity through NECT, although specificity was 100 percent.

Lum et al wrote “Interestingly, our study also demonstrated a significant difference in median CTASI-ASPECTS [8 versus 5] in patients with good outcomes, suggesting a possible close relationship between baseline CBV and CTASI for estimating ischemic core.”

However, they went on to note, “that although CTASI and CBV can reliably identify ischemic core, the core will not always predict poor outcome.”

In a small number of patients where stroke was not acute, MRIs were performed. The MRI showed ischemic core patterns similar to the ones shown via CTASI. For some of these patients, even though the CTASI scores had predicted poor outcomes based on the core, they still experienced good outcomes. This was in line with other studies in the field.

Lum et al, regardless, considered CTASI and CBV a greater success in determining outcomes than NECT. With a need for improved imaging techniques to ensure best possible outcomes for stroke patients, the recommended combination is CTASI and CT perfusion as an “imaging biomarker of cerebrovascular disease.”