Siebelink H M, Natale D, Sinusas A J, Wackers F J
Department of Diagnostic Radiology, Yale University School of Medicine, New Haven, CT 06520-8042, USA.
J Nucl Cardiol. 1996 Nov-Dec;3(6 Pt 1):483-93. doi: 10.1016/s1071-3581(96)90058-6.
Dual-isotope rest/stress single-photon emission computed tomographic (SPECT) imaging is a time-saving imaging protocol. However, the stress radiotracer, technetium 99m-labeled sestamibi, and the rest radiotracer, thallium 201, have different physical properties and myocardial kinetics. In patients with abnormal resting myocardial perfusion, these differences may affect quantification of rest defect size and defect reversibility. The purpose of the study was to compare myocardial perfusion defect reversibility quantitatively by single-isotope (rest/stress sestamibi) and dual-isotope (rest thallium/stress sestamibi) SPECT.
Thirty patients with prior myocardial infarction underwent rest/stress sestamibi SPECT imaging and rest thallium SPECT imaging. Defects were quantified according to circumferential count profiles with a normal sestamibi database. The images of a subgroup of 21 patients were processed with radiotracer-specific normal databases. Defect size and defect reversibility were compared quantitatively for single-isotope and dual-isotope SPECT. Rest sestamibi defect size was significantly larger than rest thallium defect size (19 +/- 15 vs 14 +/- 16; p = 0.007). Defect reversibility was larger with thallium than with sestamibi (10 +/- 9 vs 6 +/- 6; p = 0.002). With radiotracer-specific normal databases, mean rest sestamibi and thallium defect sizes in 21 patients were not different (23 +/- 19 vs 21 +/- 17; difference not significant). With radiotracer-specific normal databases, mean defect reversibility was not different with either sestamibi or thallium (6 +/- 6 vs 8 +/- 9; difference not significant), although correlation among individual patients was only fair (r2 = 0.48).
In patients with prior myocardial infarction, stress-induced defect reversibility is quantitatively larger with dual-isotope imaging than with single-isotope imaging. Quantitative processing of dual-isotope images requires radiotracer-specific normal databases. Because of different characteristics of sestamibi and thallium, assessment of defect reversibility on dual-isotope images should be made with caution. Only relatively large defect reversibility can be assumed to represent true stress-induced myocardial ischemia.
双同位素静息/负荷单光子发射计算机断层扫描（SPECT）成像是一种节省时间的成像方案。然而，负荷放射性示踪剂锝99m标记的甲氧基异丁基异腈和静息放射性示踪剂铊201具有不同的物理特性和心肌动力学。在静息心肌灌注异常的患者中，这些差异可能会影响静息缺损大小和缺损可逆性的量化。本研究的目的是通过单同位素（静息/负荷甲氧基异丁基异腈）和双同位素（静息铊/负荷甲氧基异丁基异腈）SPECT定量比较心肌灌注缺损的可逆性。
30例有心肌梗死病史的患者接受了静息/负荷甲氧基异丁基异腈SPECT成像和静息铊SPECT成像。根据使用正常甲氧基异丁基异腈数据库的圆周计数轮廓对缺损进行量化。对21例患者亚组的图像使用放射性示踪剂特异性正常数据库进行处理。对单同位素和双同位素SPECT的缺损大小和缺损可逆性进行了定量比较。静息甲氧基异丁基异腈缺损大小显著大于静息铊缺损大小（19±15对14±16；p = 0.007）。铊的缺损可逆性大于甲氧基异丁基异腈（10±9对小6±6；p = 0.002）。使用放射性示踪剂特异性正常数据库时，21例患者的静息甲氧基异丁基异腈和铊的平均缺损大小无差异（23±19对21±17；差异不显著）。使用放射性示踪剂特异性正常数据库时，甲氧基异丁基异腈和铊的平均缺损可逆性无差异（6±6对8±9；差异不显著），尽管个体患者之间的相关性仅为中等（r2 = 0.48）。
在有心肌梗死病史的患者中，双同位素成像的负荷诱导缺损可逆性在定量上大于单同位素成像。双同位素图像的定量处理需要放射性示踪剂特异性正常数据库。由于甲氧基异丁基异腈和铊的特性不同，对双同位素图像上缺损可逆性的评估应谨慎进行。只有相对较大的缺损可逆性才能被认为代表真正的负荷诱导心肌缺血。
