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Imaging of cerebral blood flow-to-volume distribution using SPECT
Insights
This study introduces a new SPECT imaging method to assess cerebrovascular disease (CVD) by measuring the ratio of cerebral blood flow (CBF) to cerebral blood volume (CBV). The findings support its use in evaluating cerebral perfusion reserve.
Area of Science:
- Neurology
- Radiology
- Medical Imaging
Background:
- Cerebrovascular disease (CVD) evaluation often relies on assessing cerebral blood flow (CBF) and cerebral blood volume (CBV).
- The ratio of CBF to CBV is a potential parameter for CVD assessment, but its use with SPECT has not been established.
- Existing methods lack comprehensive assessment of cerebral perfusion reserve in CVD.
Purpose of the Study:
- To assess the ratio of cerebral blood flow (CBF) to cerebral blood volume (CBV) using SPECT imaging in patients with cerebrovascular disease (CVD).
- To evaluate the utility of this CBF/CBV ratio for assessing cerebral perfusion reserve in CVD.
- To establish a novel SPECT imaging protocol for quantitative analysis of CBF and CBV.
Main Methods:
- Utilized [123I]IMP for cerebral blood flow (CBF) and [99mTc]erythrocytes for cerebral blood volume (CBV) imaging via SPECT.
- Implemented corrections for radionuclide cross-contamination between 123I and 99mTc tomograms.
- Quantified CBF/CBV distribution by comparing affected and non-symptomatic hemispheres and specific CVD-affected territories.
Main Results:
- In patients with CVD, affected territories showed reduced CBF (85% +/- 19%) and CBF/CBV ratio (60% +/- 32%) compared to the contralateral side.
- In unilateral internal carotid artery stenoses (>50%), segmental CBF was 81.1% +/- 10.1% and CBF/CBV was 49.6% +/- 15.5% relative to the unaffected side.
- Hemispheric CBF and CBF/CBV ratios were also significantly reduced in affected areas, reflecting autoregulation and vasodilation.
Conclusions:
- The developed SPECT imaging technique for CBF/CBV ratio is effective in assessing cerebrovascular disease (CVD).
- The results demonstrate the method's ability to reflect cerebral autoregulation mechanisms, such as vasodilation.
- This SPECT-based CBF/CBV assessment provides a valuable tool for evaluating cerebral perfusion reserve in patients with CVD.
Abstract:
The ratio between cerebral blood flow (CBF) and cerebral blood volume (CBV) has been proposed as an adequate parameter for the evaluation of cerebrovascular disease (CVD), but to date it has not been assessed with SPECT. We have chosen [123I]IMP for CBF and [99mTc] erythrocytes for CBV imaging. The distribution of both nuclides was investigated in succession using corrections for the contamination of the 99mTc tomograms by 123I. The ratio between 123I and 99mTc tomograms yielded the CBF/CBV distribution. Quantitation was obtained by side-to-side comparison of both hemispheres and of segments containing the territories affected by CVD. In 16 patients with CVD, CBF of the affected territories was 85 +/- 19% (s.d.) when related to the nonsymptomatic contralateral side (100%). When the regions of interest defined within one slice encompassed the entire affected hemisphere, the average CBF was 95 +/- 9%, again related to the nonsymptomatic side. The corresponding CBF/CBV data in 15 of these 16 patients were 60 +/- 32% and 81 +/- 16%. In unilateral internal carotid artery stenoses greater than 50% (N = 10), segmental CBF averaged 81.1 +/- 10.1% and CBF/CBV 49.6 +/- 15.5% relative to the contralateral side. The figures for the hemispheres were 92.8 +/- 5.8 and 75.8 +/- 12.6, respectively. These clinical findings mirror the characteristics of CBF autoregulation, namely the vasodilation of small vessels in decreased arterial perfusion pressure. They, therefore, substantiate SPECT imaging of CBF/CBV for the assessment of cerebral perfusion reserve in CVD.