Perfusion computed tomography: 4 cm versus 8 cm coverage size in subjects with chronic carotid artery stenosis

The impact of coverage size on global cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT) and time to peak (TTP) parameters has not been investigated in patients with chronic carotid artery stenosis.

63 patients with stenosis of >70% within a single internal carotid artery and neurological symptoms were randomly assigned to two well-matched groups. Differences in CT perfusion scan over a 4 cm or 8 cm range of the brain were compared between the two groups.

The CBF and CBV values were higher in the 4 cm coverage size than in the 8 cm coverage size (by 14.7 and 10.7% on the ipsilateral side and 17.2 and 7.8% on the contralateral side, respectively; all p < 0.001). The MTT value was higher in the 4 cm coverage size than in the 8 cm coverage size on the ipsilateral side (9.6%; p < 0.001). There was no difference between MTT values in the contralateral size. There were no differences between TTP values on the ipsilateral and contralateral sides. The relative indices rMTT and rTTP were higher in the 4 cm coverage size than in the 8 cm coverage size (8.2%, p < 0.001, and 1.1%, p < 0.005, respectively).

Absolute CBF and CBV values and relative rMTT and rTTP indices in patients with low CBF and low CBV are highly dependent on coverage size. We recommend using a 4 cm coverage size to assess global cerebral perfusion parameters owing to better accuracy and quicker post-processing.

To the best of our knowledge, this is the first article to compare the influence of 4 cm vs 8 cm coverage size on cerebral perfusion parameters such as CBF, CBV, MTT and TTP in subjects with chronic carotid artery stenosis.