CT angiographic source images with modern multisection CT scanners: appropriate injection protocol is crucial.

Multisection CT Scanners: Appropriate Injection Protocol Is Crucial I have read with great interest the recently published article of Sharma et al. The study compared CT angiographic source imaging (CTASI) performed by a modern multisection CT scanner with cerebral blood flow (CBF) and cerebral blood volume (CBV) maps derived from dynamic CT perfusion in patients with acute ischemic stroke. The results demonstrate the strong correlation between the lesion volume of CTA-SI and CBF (r 0.89, P .001) in contrast to the weak correlation between the lesion volume of CTA-SI and CBV (r 0.5, P .001). The authors concluded that CTA-SI is CBFrather than CBV-weighted. Although it was probably not the intention of the authors, this conclusion suggests that CTA source data with modern multisection CT scanners somehow include CBF information. CBF can be calculated only from dynamic CT data acquired during the first pass of a contrast bolus. Hence, I consider the conclusion of Sharma et al critical, and it is the opposite of those of previous reports of the blood volume basis of CTA-SI. In my opinion, the reported results of apparent CBF-weighted CTA-SI in the article of Sharma et al need further discussion and detailed consideration of the underlying principle of CTA-SI. CBV relates to the area under the curve and is expressed by the following equation: