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Published on: March 14, 2013
Human cerebral blood volume (CBV) measured by dynamic susceptibility contrast MRI and 99mTc-RBC SPECT
Christian Engvall1, Erik Ryding, Ronnie Wirestam
1Department of Anesthesiology, University Hospital, Lund, Sweden. christian.engvall@skane.se
Insights
Dynamic susceptibility contrast (DSC) MRI accurately measures cerebral blood volume (CBV), correlating well with 99mTc-RBC SPECT. This validates DSC-MRI as a tool for assessing CBV in percent of brain volume.
Area of Science:
- Neuroimaging
- Cerebrovascular Physiology
- Medical Physics
Background:
- Elevated intracranial pressure can compromise cerebral blood flow, leading to ischemia.
- Measuring cerebral blood volume (CBV) is crucial for managing intracranial pressure but is challenging.
- Established methods like 99mTc-RBC SPECT exist, with dynamic susceptibility contrast (DSC) MRI emerging as a new option.
Purpose of the Study:
- To validate dynamic susceptibility contrast (DSC) magnetic resonance imaging (MRI) for measuring cerebral blood volume (CBV).
- To investigate the correlation between regional CBV measurements from DSC-MRI and 99mTc-RBC SPECT in humans.
- To determine a conversion factor for interpreting DSC-MRI derived CBV values as a percentage of brain volume.
Main Methods:
- Cerebral blood volume (CBV) was measured in 8 volunteers under normocapnic and hypocapnic conditions.
- Both 99mTc-RBC SPECT and DSC-MRI were utilized for CBV quantification.
- Regional CBV distributions were compared between the two imaging modalities.
Main Results:
- Significant correlations were found between regional CBV distributions measured by 99mTc-RBC SPECT and DSC-MRI under both resting and hypocapnic states.
- A conversion factor of 0.0059+/-0.0013 was derived for DSC-MRI voxel values to SPECT CBV (percent of brain volume) at rest.
- Global CBV decreased significantly under hypocapnia in both SPECT (4.3% to 3.9%) and MRI (4.5% to 3.5%) groups.
Conclusions:
- Dynamic susceptibility contrast (DSC) MRI demonstrates a strong correlation with 99mTc-RBC SPECT for measuring cerebral blood volume (CBV).
- DSC-MRI is validated as a useful method for quantifying CBV as a percentage of brain volume.
- The findings support the clinical utility of DSC-MRI in managing conditions involving intracranial pressure.
Background:
Patients with elevated intracranial pressure risk compromising their cerebral blood flow, resulting in ischemia. Lowering of the raised intracranial pressure, is therefore, mandatory. Reduction of the cerebral blood volume (CBV) might be target. In finding ways to do so, one has to be able to measure CBV. Measurement of CBV is, however, difficult. Radio(99mTc-)labeled erythrocytes (99mTcRBC) single photon emission computer-aided tomography (SPECT) is one established method used for CBV measurement. Recently, dynamic susceptibility contrast (DSC) magnetic resonance imaging (MRI), has also been successfully used for this purpose. The aim of this study was to validate the use of DSC-MRI for the measurement of CBV by the investigation of the correlation between the regional distributions of 99mTc-RBC SPECT and DSC-MRI measurement of CBV in humans. If possible, the aim was also to find a conversion constant that will enable the DCS-MRI to be interpreted as CBV (percent of brain volume).
Methods:
CBV of 8 volunteers were studied under normocapnic and hypocapnic conditions. CBV was measured with both 99mTc-RBC SPECT and DSC-MRI.
Results:
There were significant correlations between the regional distributions of CBV measured by 99mTc-RBC SPECT and DSC-MRI (rest: F=4.53, P<0.05; hypocapnia: F=9.61, P<0.005). The derived conversion factor between DSC-MRI voxel values and 99mTc-RBC SPECT CBV (percent of brain volume) at rest was 0.0059+/-0.0013. Global CBV during normocapnia was 4.3%+/-0.6% of brain volume as measured by SPECT of brain volume and 4.5%+/-0.9% as measured by MRI. Decreasing the end-tidal pCO2 by 1.8 kPa by spontaneous hyperventilation reduced the global CBV significantly to 3.9%+/-0.5% in the SPECT group and to 3.5%+/-0.6% in the MRI group.
Conclusions:
The comparison of 99mTc-RBC SPECT and DSC-MRI measurements in our study indicates that DSC-MRI can be a useful method to measure CBV as a percent of brain volume.
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