TY - JOUR
T1 - Effects of tissue heterogeneity on cerebral vascular response to acetazolamide stress measured by an I-123-IMP autoradiographic method with single-photon emission computed tomography
AU - Ito, Hiroshi
AU - Shidahara, Miho
AU - Inoue, Kentaro
AU - Goto, Ryoui
AU - Kinomura, Shigeo
AU - Taki, Yasuyuki
AU - Okada, Ken
AU - Kaneta, Tomohiro
AU - Sato, Kazunori
AU - Sato, Tachio
AU - Fukuda, Hiroshi
N1 - Funding Information:
This work was supported by a Grant-in-Aid for Scientific Research (C) (No. 15591314) from the Japan Society for the Promotion of Science, a 21st Century COE Program Special Research Grant for "Future Medical Engineering Based on Bio-nanotechnology", and Health and Labour Science Research Grants for Research on Advanced Medical Technology (H 14-Nano-020). The assistance of members of the Tohoku University Hospital staff in performing the SPECT experiments is also gratefully acknowledged.
PY - 2005/6
Y1 - 2005/6
N2 - Objectives: Single-photon emission computed tomography (SPECT) with iodine-123 (123I)-labeled N-isopropyl-p-iodoamphetamine (IMP) is widely used in measuring the cerebral blood flow (CBF) response to acetazolamide stress for assessment of cerebral vascular reserve. To quantitate CBF by means of SPECT with IMP, an autoradiographic (ARG) method has been developed and is widely used. Because the relation between the brain counts on the SPECT scan and CBF is not linear in the ARG method, a mixture of gray and white matter in a pixel causes errors in the calculation of CBF. In the present study, errors in the calculation of CBF and vascular response to acetazolamide stress by the ARG method due to tissue heterogeneity were estimated by simulation study. Correction for effects of tissue heterogeneity in SPECT data was also attempted. Methods: Images of gray and white matter fraction were obtained by voxel-based morphometry analysis of magnetic resonance (MR) imaging data set. Ideal CBF images, which were generated from gray and white matter fraction images with assumed blood flow values for gray and white matter, were compared to CBF images generated by the ARG method. Correction for effects of tissue heterogeneity in SPECT data was performed with gray and white matter fraction data obtained from MR images. Results: Systematic underestimation of CBF due to tissue heterogeneity was observed in all brain regions. In the neocortical regions, underestimation by -21% to -16%, -26% to -20%, -31% to -24%, and -35% to -27% was observed for gray and white matter blood flow of 80 and 20, 100 and 25, 120 and 30, and 140 and 35 ml/100 ml/min, respectively. Vascular response was also systematically underestimated in most brain regions. Vascular responses in the neocortical regions ranged from 17% to 20%, from 31% to 37%, and from 42% to 52% when ideal vascular responses were 25%, 50%, and 75%, respectively. After correction for the effects of tissue heterogeneity, values of vascular response to acetazolamide stress ranged from 64% to 116% in the neocortical regions, whereas values obtained by the ARG method ranged from 48% to 52%. Conclusion: Underestimation of the vascular response to acetazolamide stress due to tissue heterogeneity should be considered in the estimation of cerebral vascular reserve.
AB - Objectives: Single-photon emission computed tomography (SPECT) with iodine-123 (123I)-labeled N-isopropyl-p-iodoamphetamine (IMP) is widely used in measuring the cerebral blood flow (CBF) response to acetazolamide stress for assessment of cerebral vascular reserve. To quantitate CBF by means of SPECT with IMP, an autoradiographic (ARG) method has been developed and is widely used. Because the relation between the brain counts on the SPECT scan and CBF is not linear in the ARG method, a mixture of gray and white matter in a pixel causes errors in the calculation of CBF. In the present study, errors in the calculation of CBF and vascular response to acetazolamide stress by the ARG method due to tissue heterogeneity were estimated by simulation study. Correction for effects of tissue heterogeneity in SPECT data was also attempted. Methods: Images of gray and white matter fraction were obtained by voxel-based morphometry analysis of magnetic resonance (MR) imaging data set. Ideal CBF images, which were generated from gray and white matter fraction images with assumed blood flow values for gray and white matter, were compared to CBF images generated by the ARG method. Correction for effects of tissue heterogeneity in SPECT data was performed with gray and white matter fraction data obtained from MR images. Results: Systematic underestimation of CBF due to tissue heterogeneity was observed in all brain regions. In the neocortical regions, underestimation by -21% to -16%, -26% to -20%, -31% to -24%, and -35% to -27% was observed for gray and white matter blood flow of 80 and 20, 100 and 25, 120 and 30, and 140 and 35 ml/100 ml/min, respectively. Vascular response was also systematically underestimated in most brain regions. Vascular responses in the neocortical regions ranged from 17% to 20%, from 31% to 37%, and from 42% to 52% when ideal vascular responses were 25%, 50%, and 75%, respectively. After correction for the effects of tissue heterogeneity, values of vascular response to acetazolamide stress ranged from 64% to 116% in the neocortical regions, whereas values obtained by the ARG method ranged from 48% to 52%. Conclusion: Underestimation of the vascular response to acetazolamide stress due to tissue heterogeneity should be considered in the estimation of cerebral vascular reserve.
KW - ARG method
KW - Acetazolamide
KW - IMP
KW - SPECT
KW - Tissue heterogeneity
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U2 - 10.1007/BF02984616
DO - 10.1007/BF02984616
M3 - Article
C2 - 16097633
AN - SCOPUS:23344439141
VL - 19
SP - 251
EP - 260
JO - Annals of Nuclear Medicine
JF - Annals of Nuclear Medicine
SN - 0914-7187
IS - 4
ER -