This article draws my interest due to the advancement of Flat Panel Detector CT (FPCT) utility in clinical stroke practice. Measurement of cerebral blood volume (CBV) by using of FPCT is a challenging technique to advance endovascular work in stroke business. Weakness in temporal resolution of C-arm makes it clinically unable to assess cerebral blood flow (CBF) or mean transit time (MTT).

From my analysis, this study has some limitations and arguments.

1) Incomplete comparison: It might be the reasons of time and contrast limitations; the initial FPCT CBV was skipped in the protocol. Complete comparison between perfusion CT (PCT) and FPCT in pre- and post- treatment would be interesting to see the difference.

2) Steady state issue: Regarding “steady state” of the brain by contrast bolus watching, this might not represent “steady state” of the ischemic tissue especially when it supplied by cortical collaterals which we have usually seen the significant delay on diagnostic angiography. This might explain the result of patient 9 in figure 2. The decreased area of CBV in right frontal operculum seems to be larger than the following PCT. CBV normally should represent the infarct core and not reversible by the treatment. In this case, partial CBV acquisition when tissue is not in steady state (some confounding from CBF or MTT mapping) might explain this finding.

Regarding patient 2 in figure 3, the authors performed endovascular treatment under sedation within 1 hour after initial imaging; the effect of hemodynamic change would be minimized. Immediate progression in area of decreased CBV would not be expected by the treatment alone. It would be interesting if the authors could demonstrate number of cases with this finding related to the successfulness of treatment and the initial CBF mapping to make this point clear.

3) CBV volume variation: There is a high range of CBV volumes among cases observed on the graph in figure 1 (high SD). It would be better if authors could explain in case-by-case comparison rather than in mean value.

4) Contrast extravasation effect: There are 2 cases in the hyperemic group which FPCT could not detect infarction. Additionally, there is no correlation of the hyperemic volume between post FPCT and post multisection CT (MSCT). Contrast extravasation is a key of these findings. Exact timing between post FPCT and post MSCT should be clarified since most of contrast extravasation would be cleared if the follow MSCT was performed close to 24 hours.

5) Correlation of absolute CBV value: The authors selectively compared absolute values of CBV after treatment in 6 cases, which could be possibly correlated only in the oligemic group as presented in this study. Since in the hyperemic group, the effect of contrast extravasation should be in concern. However, in oligemic group (n=10) there are 6 cases with successful treatment and 4 cases with failure treatment mixing in. There might be some effect of treatment confounding in these selected 6 cases.