Engvall Christian, Ryding Erik, Wirestam Ronnie, Holtås Stig, Ljunggren Kaj, Ohlsson Tomas, Reinstrup Peter
Department of Anesthesiology, University Hospital, Lund, Sweden.
J Neurosurg Anesthesiol. 2008 Jan;20(1):41-4. doi: 10.1097/ANA.0b013e31815d4c70.
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).
CBV of 8 volunteers were studied under normocapnic and hypocapnic conditions. CBV was measured with both 99mTc-RBC SPECT and DSC-MRI.
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.
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.
颅内压升高的患者有损害脑血流量并导致缺血的风险。因此，降低升高的颅内压是必须的。减少脑血容量（CBV）可能是目标。在寻找实现此目标的方法时，必须能够测量CBV。然而，CBV的测量很困难。放射性（99mTc-）标记的红细胞（99mTcRBC）单光子发射计算机断层扫描（SPECT）是一种用于CBV测量的既定方法。最近，动态磁敏感对比（DSC）磁共振成像（MRI）也已成功用于此目的。本研究的目的是通过研究99mTc-RBC SPECT和DSC-MRI测量的CBV在人体中的区域分布之间的相关性，验证DSC-MRI用于CBV测量的有效性。如果可能的话，目标还包括找到一个转换常数，使DCS-MRI能够被解释为CBV（脑体积的百分比）。
在正常碳酸血症和低碳酸血症条件下研究了8名志愿者的CBV。使用99mTc-RBC SPECT和DSC-MRI测量CBV。
99mTc-RBC SPECT和DSC-MRI测量的CBV区域分布之间存在显著相关性（静息状态：F = 4.53，P < 0.05；低碳酸血症：F = 9.61，P < 0.005）。静息状态下DSC-MRI体素值与99mTc-RBC SPECT CBV（脑体积的百分比）之间的推导转换因子为0.0059±0.0013。通过脑体积SPECT测量，正常碳酸血症期间的总体CBV为脑体积的4.3%±0.6%，通过MRI测量为4.5%±0.9%。通过自主过度通气使呼气末pCO2降低1.8 kPa，显著降低了总体CBV，SPECT组降至3.9%±0.5%，MRI组降至3.5%±0.6%。
我们研究中99mTc-RBC SPECT和DSC-MRI测量结果的比较表明，DSC-MRI可作为一种有用的方法来测量作为脑体积百分比的CBV。
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