用单光子发射计算机断层扫描的I-123-IMP放射自显影法测量组织异质性对乙酰唑胺应激时脑血管反应的影响。

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.

作者信息

Ito Hiroshi, Shidahara Miho, Inoue Kentaro, Goto Ryoi, Kinomura Shigeo, Taki Yasuyuki, Okada Ken, Kaneta Tomohiro, Sato Kazunori, Sato Tachio, Fukuda Hiroshi

机构信息

Department of Nuclear Medicine and Radiology, Division of Brain Sciences, Institute of Development, Aging and Cancer, Tohoku University, Sendai 980-8575, Japan.

出版信息

Ann Nucl Med. 2005 Jun;19(4):251-60. doi: 10.1007/BF02984616.

DOI:10.1007/BF02984616

PMID:16097633

Abstract

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.

摘要

目的

利用碘 - 123（¹²³I）标记的N - 异丙基 - p - 碘安非他明（IMP）进行单光子发射计算机断层扫描（SPECT），广泛用于测量脑血流（CBF）对乙酰唑胺负荷的反应，以评估脑血管储备。为了通过IMP - SPECT定量CBF，已开发并广泛使用了一种放射自显影（ARG）方法。由于在ARG方法中，SPECT扫描上的脑计数与CBF之间的关系不是线性的，像素中灰质和白质的混合会导致CBF计算出现误差。在本研究中，通过模拟研究估计了ARG方法因组织异质性导致的CBF计算误差以及对乙酰唑胺负荷的血管反应。还尝试对SPECT数据中组织异质性的影响进行校正。

方法

通过对磁共振（MR）成像数据集进行基于体素的形态学分析，获得灰质和白质分数图像。将根据灰质和白质分数图像以及假设的灰质和白质血流值生成的理想CBF图像与ARG方法生成的CBF图像进行比较。利用从MR图像获得的灰质和白质分数数据对SPECT数据中组织异质性的影响进行校正。

结果

在所有脑区均观察到由于组织异质性导致的CBF系统性低估。在新皮质区域，当灰质和白质血流分别为80和20、100和25、120和30以及140和35 ml/100 ml/min时，低估分别为 - 21%至 - 16%、 - 26%至 - 20%、 - 31%至 - 24%以及 - 35%至 - 27%。大多数脑区的血管反应也被系统性低估。当理想血管反应分别为25%、50%和75%时，新皮质区域的血管反应分别为17%至20%、31%至37%以及42%至52%。在校正组织异质性的影响后，新皮质区域对乙酰唑胺负荷的血管反应值在64%至116%之间，而ARG方法获得的值在48%至52%之间。