Automated Method for Generating the Arterial Input Function on Perfusion-Weighted MR Imaging: Validation in Patients with Stroke

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Fig 1.
Manual and automated choice of the best AIF.
A, Manual choice, based on visual estimation of the overall shape of the curve, high signal intensity, early peak time, and small width.
B, Automatically computed AIF is identified as the one with the optimal combination of Gaussian-fit parameters (maximum A₀ combined with A₁ and A₂ in the predefined limits) and the one satisfying the goodness-of-fit test.
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Fig 2.
AIF identified at voxels 24 mm apart.
A, Manual.
B, Automated.
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Fig 3.
Tmax and CBF maps, created on the basis of the manual (A, C) and automated (B, D) AIFs from Figure 1, have spatial pattern correlations of r = 0.87 and r = 0.86, respectively. Distance between corresponding AIF voxels, or d, is 30.6 mm.
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Fig 4.
Tmax and CBF maps (A, C) and (B, D) corresponding to Figure 2 have spatial pattern correlations of r = 0.74 and r = 0.60, respectively.

Comparison of automated and manual AIF parameters

Subject	ΔA₀ (sec⁻¹)	ΔA₁ (sec)	ΔA₂ (sec)	d (mm)	Correlation r^*
Subject	ΔA₀ (sec⁻¹)	ΔA₁ (sec)	ΔA₂ (sec)	d (mm)	Tmax	CBF
1	21.52	0.69	0.34	11.3	0.91	0.94
2	17.09	1.32	−0.17	15.9	0.87	0.92
3	0	0	0	0.9	1.00	1.00
4	19.75	−0.59	−0.37	7.1	0.82	0.66
5	47.48	−2.98	−1.23	11.4	0.70	0.60
6	11.39	0.32	−0.88	32.2	0.82	0.72
7	29.06	−0.39	−1.28	18.9	0.68	0.74
8	37.22	0.57	−0.68	18.2	0.76	0.83
9	12.83	0.12	0.76	6.0	0.75	0.72
10	32.61	1.30	−0.39	18.2	0.81	0.87
11	25.22	−0.79	−0.17	30.6	0.87	0.86
12	−4.32	−2.65	−2.15	35.9	0.81	0.82
13	1.24	−0.24	−0.30	37.8	0.73	0.82
14	27.30	−2.46	−0.24	24.0	0.74	0.60
15	15.26	−0.19	−0.07	3.0	0.85	0.88
16	17.83	0.36	1.36	2.7	0.80	0.77
17	2.71	−5.25	−2.18	35.0	0.54	0.68
18	0	0	0	1.3	1.00	1.00
19	19.27	−0.62	−0.09	16.9	0.87	0.87
20	11.78	0.71	−0.87	44.5	0.82	0.89
21	10.17	−0.19	−0.30	11.6	0.85	0.87
22	0	0	0	1.3	1.00	1.00
Mean	16.16	−0.50	−0.41	17.5	0.82	0.82
SD	13.49	NA	NA	13.45	0.11	0.12
P value	<0.001	0.374	0.018	NA	NA	NA

Note.—Differences were computed as the automated AIF parameter − manual AIF parameter. A₀ = curve height (maximum concentration of contrast agent), A₁ = curve center (time to peak), A₂ = curve width, d = distance between automated and manual AIF pixels, NA = not applicable.
* Between automated and manual maps.