Heiss W D, Herholz K, Podreka I, Neubauer I, Pietrzyk U
Max-Planck-Institut für Neurologische Forschung, Universität zu Köln, F.R.G.
J Cereb Blood Flow Metab. 1990 Sep;10(5):687-97. doi: 10.1038/jcbfm.1990.122.
Positron emission tomography (PET) of [18F]fluoromethane (FM) and single-photon emission tomography (SPECT) of [99mTc]hexamethylpropyleneamine oxime (HMPAO) were performed under identical conditions within 2 h in 22 patients suffering from cerebrovascular disease (8 ischemic infarction, 2 intracerebral hemorrhages, 7 transient ischemic attacks, and 5 multi-infarct syndrome). While gross pathological changes could be seen in the images of either procedure, focal abnormalities corresponding to transient ischemic deficits or to lesions in multi-infarct syndrome and areas of functional deactivation were sometimes missed on SPECT images. Overall, HMPAO SPECT images showed less contrast between high and low activity regions than the FM PET images, and differences between lesions and contralateral regions were less pronounced (6.4 vs 13.3% difference). Regional cerebral blood flow (rCBF) was calculated from FM PET studies in 14 large territorial regions and the pathological lesion, and the regional values relative to mean flow were compared to the relative HMPAO uptake in an identical set of regions defined on the SPECT images. Among individual patients, the Spearman rank-correlation coefficient between relative rCBF and HMPAO uptake varied between 0.48 and 0.89, with a mean of 0.70. While an underestimation of high flow with SPECT--which was demonstrated in a curvilinear relationship between all relative regional PET and SPECT values--could be corrected by linearization taking into account HMPAO efflux from the brain before metabolic trapping, correspondence of SPECT data with PET rCBF values was not improved since this procedure also increased the variance in high flow areas. In the cerebellum, however, a high HMPAO uptake in SPECT always overestimated CBF in relation to forebrain values; this finding might be due to high capillary density in the cerebellum. The differences observed between SPECT and PET data may be explained by technical and physical properties of the methods and by the incomplete first-pass extraction of HMPAO. Additionally, HMPAO or its metabolites may leak through a damaged blood-brain barrier (as observed in one infarct and in the surrounding of hemorrhages), impairing the contrast between lesion and normal tissue. The presented data indicate that the quantification of rCBF by HMPAO SPECT is limited.
在22例脑血管疾病患者（8例缺血性梗死、2例脑出血、7例短暂性脑缺血发作和5例多发梗死综合征）中，在相同条件下于2小时内进行了[18F]氟甲烷（FM）的正电子发射断层扫描（PET）和[99mTc]六甲基丙烯胺肟（HMPAO）的单光子发射断层扫描（SPECT）。虽然两种检查的图像中都能看到明显的病理变化，但SPECT图像有时会遗漏与短暂性缺血性缺损、多发梗死综合征中的病变或功能失活区域相对应的局灶性异常。总体而言，HMPAO SPECT图像中高活性区域和低活性区域之间的对比度低于FM PET图像，病变与对侧区域之间的差异也不那么明显（差异分别为6.4%和13.3%）。从14个大的脑区和病理病变的FM PET研究中计算局部脑血流量（rCBF），并将相对于平均血流量的局部值与在SPECT图像上定义的同一组区域中的HMPAO相对摄取量进行比较。在个体患者中，相对rCBF与HMPAO摄取之间的Spearman等级相关系数在0.48至0.89之间，平均为0.70。虽然SPECT对高血流量的低估——这在所有相对局部PET和SPECT值之间的曲线关系中得到了证实——可以通过考虑HMPAO在代谢捕获前从脑内流出的线性化来校正，但SPECT数据与PET rCBF值的对应性并未得到改善，因为该过程也增加了高血流量区域的方差。然而，在小脑中，SPECT中高HMPAO摄取相对于前脑值总是高估了CBF；这一发现可能是由于小脑毛细血管密度高。SPECT和PET数据之间观察到的差异可能由方法的技术和物理特性以及HMPAO的首过提取不完全来解释。此外，HMPAO或其代谢产物可能会通过受损的血脑屏障泄漏（如在1例梗死和出血周围观察到的），从而损害病变与正常组织之间的对比度。所呈现的数据表明，HMPAO SPECT对rCBF的定量是有限的。
