Tracer Delay–Insensitive Algorithm Can Improve Reliability of CT Perfusion Imaging for Cerebrovascular Steno-Occlusive Disease: Comparison with Quantitative Single-Photon Emission CT

M. Sasaki; K. Kudo; K. Ogasawara; S. Fujiwara

doi:10.3174/ajnr.A1274

American Journal of Neuroradiology

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Fig 1.
CBF and MTT maps of a 70-year-old woman with occlusion of the right MCA. A and E, CTP with bSVD. B and F, CTP with sSVD. C and G, CTP with bMTF. D, Quantitative SPECT with ¹²³I-IMP. A–D, CBF. E–G, MTT. AIF was obtained from the second portion of the left MCA. A–C, E–G, CBF and MTT color maps on CTP appear different among the different deconvolution algorithms. B–D, Images obtained by using sSVD (B) and bMTF (C) overestimate the decrease in CBF of the right MCA territory, compared with that generated by SPECT (D), whereas images using bSVD (A) correspond well with those using SPECT (D).
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Fig 2.
Absolute CBF values of the unaffected and affected MCA territories with different algorithms and different locations of AIFs. The ranges of the CBF obtained by bSVD in any conditions and those obtained by sSVD with the AIF on the unaffected MCA are significantly smaller than the corresponding ranges obtained by quantitative SPECT. However, those obtained by bMTF are significantly larger than those obtained by SPECT, particularly when the AIF is on the affected MCA. The CBF ranges obtained by sSVD with the AIF on the affected MCA are compatible with those generated by SPECT. †P < .01.
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Fig 3.
The CBF ratios of the affected MCA territory to the contralateral corresponding area with different algorithms and different locations of AIFs. When comparing the CBF ratios with SPECT, we observed that the CBF ratios were underestimated in many patients on CTP with sSVD and bMTF but not with bSVD, regardless of the location (affected or unaffected side) of the AIF on the MCA.

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Correlation of the CBF values between CTP and SPECT

CBF	AIF Unaffected Side			AIF Affected Side
CBF	Unaffected Side	Affected Side	Ratio	Unaffected Side	Affected Side	Ratio
bSVD
r²	0.58^*	0.46^†	0.70^‡	0.44	0.36	0.60^*
ICC	−0.31	−0.42	0.64^‡	−0.22	−0.30	0.58^*
sSVD
r²	0.52^†	0.22	0.50^†	0.46^†	0.08	0.40
ICC	0.25	−0.36	0.02	0.43^†	0.02	0.03
bMTF
r²	0.40	0.25	0.57^*	0.22	0.22	0.11
ICC	0.21	0.26	−0.04	−0.31	−0.30	−0.23

Note:—CBF indicates cerebral blood flow; CTP, CT perfusion; SPECT, single-photon emission CT; AIF, arterial input function; bSVD, block-circulant singular value decomposition; SSVD, standard SVD; bMTF, box-modulation transfer function: ICC, intraclass correlation coefficient.
* P < .01.
† P < .05.
‡ P < .001.