Dormehl I C, Oliver D W, Langen K J, Hugo N, Croft S A
AEC Institute for Life Sciences, University of Pretoria, South Africa.
J Nucl Med. 1997 Dec;38(12):1897-901.
Technetium-99m-bicisate ethyl cysteinate dimer (ECD) presents a different pattern from cerebral blood flow (CBF) in the subacute phase of cerebral infarction, as measured by PET, perhaps due to lack of oxygen and enzyme activity; this pattern is contrary to that of hexamethyl-propyleneamine oxime (HMPAO) but similar to that of N-isopropyl-[123I]beta-iodoamphetamine ([123I]IMP). This study explores possible CBF differences among HMPAO, ECD and IMP, with various relevant drug interventions.
Anesthetized adult baboons were used in these SPECT studies. Four studies (n = 6 baboons for each study), one control study and three intervention studies involving intravenous acetazolamide, nimodipine infusion and intramuscular sumatriptan, were followed with 99mTc-HMPAO, 99mTc-ECD and [123I]IMP. The split-dose method was used as follows. For each tracer, intervention data from the second SPECT (SPECT-2) after the second tracer injection (444 MBq) reflected a change in CBF with respect to the baseline SPECT (SPECT-1) data from the initial injection (222 MBq). These changes as a ratio, R (R = SPECT-2/SPECT-1), for each study, and the R values for each tracer were compared to R values from the corresponding control studies, yielding a quantitative estimate of drug effects.
There were no significant differences (p > 0.05) between HMPAO and ECD for the control, acetazolamide and sumatriptan studies, but there was indeed a difference between the two for the nimodipine study, indicating a nimodipine-dependent underestimation of CBF with ECD (and also with IMP), with respect to HMPAO. A further significant difference was that larger CBF increases were observed with acetazolamide, as measured with [123I]IMP.
This is a crucial observation for the clinical interpretation of CBF SPECT data and should direct the choice of tracer for a specific examination.
用正电子发射断层扫描（PET）测量，锝-99m-双半胱乙酯（ECD）在脑梗死亚急性期的脑血流（CBF）表现与CBF不同，这可能是由于缺氧和酶活性缺乏所致；这种表现与六甲基丙烯胺肟（HMPAO）相反，但与N-异丙基-[123I]β-碘安非他明（[123I]IMP）相似。本研究探讨了在各种相关药物干预下，HMPAO、ECD和IMP之间可能存在的CBF差异。
在这些单光子发射计算机断层扫描（SPECT）研究中使用了麻醉的成年狒狒。进行了四项研究（每项研究n = 6只狒狒），一项对照研究和三项干预研究，干预研究分别涉及静脉注射乙酰唑胺、输注尼莫地平和肌肉注射舒马曲坦，随后分别使用99mTc-HMPAO、99mTc-ECD和[123I]IMP进行检查。采用分剂量法如下。对于每种示踪剂，第二次注射示踪剂（444 MBq）后第二次SPECT（SPECT-2）的干预数据反映了相对于初始注射（222 MBq）的基线SPECT（SPECT-1）数据的CBF变化。将每项研究的这些变化作为比值R（R = SPECT-2/SPECT-1），并将每种示踪剂的R值与相应对照研究的R值进行比较，从而对药物效果进行定量评估。
在对照、乙酰唑胺和舒马曲坦研究中，HMPAO和ECD之间无显著差异（p > 0.05），但在尼莫地平研究中两者确实存在差异，表明与HMPAO相比，ECD（以及IMP）对CBF的估计存在尼莫地平依赖性低估。另一个显著差异是，用[123I]IMP测量时，乙酰唑胺使CBF增加幅度更大。
这对于CBF SPECT数据的临床解释是一项关键观察结果，应指导特定检查中示踪剂的选择。
