Peer-Review ReportTime-Course Analysis of Brain Perfusion Single Photon Emission Computed Tomography Using a Three-Dimensional Stereotactic Region-of-Interest Template in Patients with Moyamoya Disease
Introduction
Moyamoya disease is a chronic, progressive cerebrovascular disease that is characterized by stenosis or occlusion of the terminal portion of the internal carotid artery. The syndrome involves the proximal portion of the anterior cerebral artery and the middle cerebral artery, with compensatory development of a collateral vascular network known as “moyamoya vessels” (10). Cerebral angiography, magnetic resonance angiography and magnetic resonance imaging (MRI) are usually performed to assist with the diagnosis of moyamoya disease. The angiographic staging of moyamoya disease indicates the progression of the disease, but it does not reflect the clinical severity because the decreased cerebral perfusion caused by steno-occlusion of the circle of Willis can be compensated by the development of moyamoya vessels (5, 10, 16).
The assessment of cerebral hemodynamics is indispensable for decisions regarding treatment strategy, including revascularization surgery. Brain perfusion single photon emission computed tomography (SPECT) is commonly used to assess the cerebral blood flow (CBF) at rest and the cerebrovascular reserve (CVR). The quantitative evaluation of changes in cerebral hemodynamics is important to predict the risk of future stroke in patients with moyamoya disease who present with a chronic and progressive clinical course (2, 3, 5, 8, 9, 11, 15, 16). However, the poor spatial resolution of SPECT images made it difficult to measure regional CBF with high reproducibility. The three-dimensional stereotactic region-of-interest template (3DSRT) is an automated region-of-interest analysis software that is designed to estimate the regional CBF objectively and reproducibly by establishing identical regions of interest on anatomically standardized SPECT images (7, 12, 13, 14).
In the present study, CBF and CVR in patients with moyamoya disease were examined during conservative therapy or before and after revascularization surgery using technetium-99m ethyl cysteinate dimer (Tc-99m ECD) SPECT. We verified the usefulness of the time-course analysis of regional CBF and CVR estimated quantitatively using the 3DSRT to assess clinical status in patients with moyamoya disease.
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Study Patients
The study comprised 12 patients (5 men and 7 women), with 21 hemispheres with the diagnosis of moyamoya disease. The patients underwent initial and follow-up Tc-99m ECD SPECT during the period 2005–2009 at our institution (Table 1). The median age at the initial SPECT study was 35.1 years ± 14.7 (range 15–55 years). Clinical diagnosis of moyamoya disease was accomplished using criteria prepared by the Research Committee on Spontaneous Occlusion of the Circle of Willis (moyamoya disease) in
Results
In the initial SPECT study, CBF of the hemispheres without ischemic events (n = 11) were estimated at 52.6 mL/100 g/min ± 7.0, and CBF of the hemispheres with ischemic events (n = 10) were estimated at 44.8 mL/100 g/min ± 10.6 (Figure 1A). CBF of the hemispheres with ischemic events was significantly lower than CBF of the hemispheres without ischemic events in the initial SPECT study (P = 0.001). In the follow-up SPECT study, CBF of 11 hemispheres without ischemic events, all of which did not
Discussion
An ideal method to measure cerebral hemodynamics has been pursued over the years using many modalities, including SPECT, positron emission tomography, computed tomography (xenon–computed tomography, perfusion computed tomography) and MRI (perfusion MRI, dynamic susceptibility MRI, arterial spin labeling MRI). These previous investigations revealed the strengths and limitations of these modalities by considering invasion, quantification, reproduction, availability, and cost (2, 3, 5, 6, 7, 8, 9,
Conclusions
Time-course brain perfusion SPECT was useful to evaluate changes in regional cerebral hemodynamics during the study period. The quantitative assessment of regional CBF using the 3DSRT reflected the impaired cerebral hemodynamics of hemispheres with disease progression and the efficacy of revascularization surgery. Regular hemodynamic studies are needed for patients with hemodynamic disorders to determine whether revascularization surgery should be performed to reduce the risk of future stroke.
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Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.