Wirestam R, Knutsson L, Risberg J, Börjesson S, Larsson E-M, Gustafson L, Passant U, Ståhlberg F
Department of Medical Radiation, Lund University, Lund, Sweden.
Acta Radiol. 2007 Jun;48(5):550-6. doi: 10.1080/02841850701280825.
Attempts to retrieve absolute values of cerebral blood flow (CBF) by dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI) have typically resulted in overestimations.
To improve DSC-MRI CBF estimates by calibrating the DSC-MRI-based cerebral blood volume (CBV) with a corresponding T1-weighted (T1W) steady-state (ss) CBV estimate.
17 volunteers were investigated by DSC-MRI and 133Xe SPECT. Steady-state CBV calculation, assuming no water exchange, was accomplished using signal values from blood and tissue, before and after contrast agent, obtained by T1W spin-echo imaging. Using steady-state and DSC-MRI CBV estimates, a calibration factor K = CBV(ss)/CBV(DSC) was obtained for each individual. Average whole-brain CBF(DSC) was calculated, and the corrected MRI-based CBF estimate was given by CBF(ss) = K x CBF(DSC).
Average whole-brain SPECT CBF was 40.1+/-6.9 ml/min x 100 g, while the corresponding uncorrected DSC-MRI-based value was 69.2+/-13.8 ml/min x 100 g. After correction with the calibration factor, a CBF(ss) of 42.7+/-14.0 ml/min x 100 g was obtained. The linear fit to CBF(ss)-versus-CBF(SPECT) data was close to proportionality (R = 0.52).
Calibration by steady-state CBV reduced the population average CBF to a reasonable level, and a modest linear correlation with the reference 133Xe SPECT technique was observed. Possible explanations for the limited accuracy are, for example, large-vessel partial-volume effects, low post-contrast signal enhancement in T1W images, and water-exchange effects.
通过动态磁敏感对比磁共振成像（DSC-MRI）获取脑血流量（CBF）绝对值的尝试通常会导致高估。
通过用相应的T1加权（T1W）稳态（ss）脑血容量（CBV）估计值校准基于DSC-MRI的CBV来改进DSC-MRI CBF估计值。
对17名志愿者进行DSC-MRI和133Xe单光子发射计算机断层扫描（SPECT）检查。通过T1W自旋回波成像获得造影剂前后血液和组织的信号值，在假设无水交换的情况下完成稳态CBV计算。利用稳态和基于DSC-MRI的CBV估计值，为每个个体获得校准因子K = CBV(ss)/CBV(DSC)。计算全脑平均CBF(DSC)，基于MRI的校正CBF估计值由CBF(ss) = K×CBF(DSC)给出。
全脑平均SPECT CBF为40.1±6.9 ml/min×100 g，而相应的未校正的基于DSC-MRI的值为69.2±13.8 ml/min×100 g。用校准因子校正后，获得的CBF(ss)为42.7±14.0 ml/min×100 g。CBF(ss)与CBF(SPECT)数据的线性拟合接近正比关系（R = 0.52）。
通过稳态CBV校准将总体平均CBF降低到了合理水平，并且观察到与参考133Xe SPECT技术存在适度的线性相关性。准确性有限的可能解释例如大血管部分容积效应、T1W图像中造影剂后信号增强低以及水交换效应。
