Perfusion CT in Acute Ischemic Stroke: A Qualitative and Quantitative Comparison of Deconvolution and Maximum Slope Approach

B. Abels; E. Klotz; B.F. Tomandl; S.P. Kloska; M.M. Lell

doi:10.3174/ajnr.A2151

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Fig 1.
Overview of the qualitative results of 42 examinations. Detailed information on the quality aspects is provided by the diagrams on the right.
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Fig 2.
Color maps of a 63-year-old man with right middle cerebral artery infarction. CBF_DC and CBV_DC as well as CBF_MS and CBV_MS color maps are of high quality. The ischemic lesion is more clearly delineated on TTD and TTP maps compared with MTT. TTD provides the highest contrast of all temporal parameter maps.
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Fig 3.
Examinations with lower source-data quality. CBF_MS and CBV_MS maps are of reduced quality (category II, see rectangles). Whereas TTP and MTT quality is markedly reduced, TTD quality is good. The case was still considered to be interpretable with both DC and MS.
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Fig 4.
Box-and-whisker and Bland-Altman plots demonstrate that rCBF_DC is ≤rCBF_MS in suspected penumbra (TAR) regions of interest and rCBV_DC is ≥rCBV_MS in suspected core (NVT) regions of interest. While there is no slope (no significant relationship between method difference and size of measurement) for CBF, for CBV, there is a positive slope in all regions of interest (proportional difference).
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Fig 5.
Comparison of PCT lesion sizes (DC versus MS). All units are in cubic centimeters. Scatterplots show excellent agreement: NVT_DC = 1.03 × NVT_MS (R² = 0.998), TAR_DC = 1.02 × TAR_MS (R² = 0.989), and (NVT_DC + TAR_DC) = 1.03 × (NVT_MS + TAR_MS) (R² = 0.997). On the lower right, screenshots of 2 cases are shown as examples. Red indicates NVT; yellow, TAR.

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Table 1:
Results of the qualitative analysis^a
CBF_DC CBF_MS CBV_DC CBV_MS MTT TTD TTP
Quality score (mean + SD) 6.2 ± 1.3 5.9 ± 1.8 6.3 ± 1.1 6.0 ± 1.2 3.4 ± 2.1 7.0 ± 1.1 5.8 ± 1.2

a The average score is on a scale from 0 to 8 points.

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Table 2:

Results of the quantitative analysis

ROI^a	GM	WM	Suspected Penumbra		Suspected Core
ROI^a	Absolute	Absolute	Relative	Absolute	Relative	Absolute
CBF_DC(mL/100 g/min)	65 ± 4.7	30 ± 2.7	.48 ± .11	29 ± 6.6	.21 ± .08	12 ± 4.2
CBF_MS(mL/100 g/min)	61 ± 2.4	29 ± 1.7	.59 ± .12	32 ± 6.2	.18 ± .08	9 ± 4.0
Relative difference DC-MS	+6%^b	+5%^b	−.11^b	−12%^b	+.03^b	+24%^b
Bland-Altman plot slope	Yes^c	Yes^c	No	No	No	No
Potentially relevant differences	5%	5%	17%	7%	10%	10%

CBV_DC(mL/100 g)	3.5 ± .2	1.9 ± .2	.92 ± .16	2.9 ± .6	.37 ± .15	1.1 ± .44
CBV_MS(mL/100 g)	3.6 ± .2	1.9 ± .1	.80 ± .11	2.6 ± .3	.30 ± .12	.9 ± 0.35
Relative difference DC-MS	−4%^b	−2%	+.12^b	+11%^b	+.17^b	+20%^b
Bland-Altman plot slope	Yes^c	Yes^c	Yes^c	Yes^c	Yes^c	Yes^c
Potentially relevant differences	7%	5%	26%	12%	12%	14%

MTT	3.3 ± .3s	4.0 ± .6s	2.3 ± .67	7.6 ± 2.2s	2.1 ± .66	6.9 ± 2.1s
TTD	3.7 ± .6s	4.8 ± 1.0s	2.9 ± .87	10.6 ± 3.1s	3.7 ± 1.0	13.1 ± 3.5s
TTP	8.1 ± 2.4s	9.3 ± 2.5s	1.7 ± .33	13.4 ± 3.3s	1.8 ± .37	14.2 ± 3.7s

a ROI values are mean ± SD.
b Statistically significant difference of DC and MS medians (Wilcoxon signed rank test, P < .05).
c Statistically significant relationship of the method difference (DC − MS) versus the size of the measurement (DC + MS)/2 (Wilcoxon test, P < .05). “Yes” indicates a proportional difference; “no” indicates a systematic nonproportional or random difference.

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Table 3:
Results of PCT lesion scores^a
Score NVT_DC NVT_MS NVT_DC+ TAR_DC NVT_MS+ TAR_MS
Mean ± SD [interquartile range] 7.6 ± 1.9 [7.0–9.0] 7.6 ± 1.9 [7.0–9.0] 6.0 ± 2.1 [4.0–7.9] 6.0 ± 2.2 [4.0–7.5]

a Scores for 1 brain section in orientation to ASPECTS (minimum = 0, maximum = 10).