Fukushima Kenji, Momose Mitsuru, Kondo Chisato, Kusakabe Kiyoko, Kasanuki Hiroshi
Department of Cardiology, Tokyo Women's Medical University, Tokyo, Japan.
Ann Nucl Med. 2007 Jul;21(5):267-73. doi: 10.1007/s12149-007-0019-x. Epub 2007 Jul 25.
(201)Thallium (TL), (99m)Tc-tetrofosmin (TF), and (99m)Tc-sestamibi (MIBI) are extensively used as myocardial perfusion agents. The objective of the present study was to evaluate their kinetics under acute ischemia-reperfusion.
Isolated rat hearts, perfused by the Langendorff method at a constant flow rate of 10 ml/min, were allotted to normal control, mild ischemia, and severe ischemia groups, in which 20-min tracer wash-in was conducted followed by a 25-min tracer washout. No-flow ischemia (15 min for mild ischemia groups; 30 min for severe ischemia groups) was induced before conducting wash-in and washout in the ischemia groups. Whole-heart radioactivity was determined with an external gamma detector. Myocardial flow rate (K (1), ml/min) and clearance rate (k (2), min(-1)) were calculated.
K (1TL), K (1TF), and K (1MIBI) decreased according to the severity of ischemia (K (1TL) 5.32 +/- 0.53, 4.76 +/- 0.70, and 1.44 +/- 0.59; K (1TF) 3.80 +/- 0.70, 2.73 +/- 0.99, and 1.09 +/- 0.45; and K (1MIBI) 3.45 +/- 1.10, 2.15 +/- 0.82, and 1.05 +/- 0.13, in the normal control, mild, and severe ischemia groups, respectively). K (1) was significantly higher for TL than for the (99m)Tc tracers (P < 0.05), but the (99m)Tc tracers had equivalent K (1) values. k (2TL) increased significantly (P < 0.05) in the ischemia groups (k (2TL) 0.062 +/- 0.013, 0.11 +/- 0.045, and 0.12 +/- 0.035), but showed no significant difference between the ischemia groups. k (2MIBI) and k (2TF) were significantly (P < 0.05) lower than k (2TL) and increased significantly (P < 0.05) in the severe ischemia group (k (2TF) 0.0056 +/- 0.0022, 0.0037 +/- 0.0015, and 0.024 +/- 0.015; and k (2MIBI) 0.00072 +/- 0.0011, 0.00038 +/- 0.00076, and 0.042 +/- 0.034). k (2MIBI) was significantly (P < 0.05) lower than k (2TF) in the normal control and mild ischemia groups.
Tracer extraction was higher for TL than for the (99m)Tc tracers and all tracers decreased according to the severity of ischemia-reperfusion in the three tracer groups. The clearance kinetics of not only MIBI but also TF is possibly useful for the evaluation of the severity of ischemia, and the Langendorff method and a methodological approach by continuous determinations of radioactivity may serve for the quantitative analysis of tracer kinetic profiles.
铊 - 201（²⁰¹Tl）、锝 - 99m - 替曲膦（⁹⁹ᵐTc - TF）和锝 - 99m - 甲氧基异丁基异腈（⁹⁹ᵐTc - MIBI）被广泛用作心肌灌注剂。本研究的目的是评估它们在急性缺血 - 再灌注情况下的动力学。
采用Langendorff法以10 ml/min的恒定流速灌注离体大鼠心脏，将其分为正常对照组、轻度缺血组和重度缺血组，每组先进行20分钟的示踪剂注入，随后进行25分钟的示踪剂洗脱。在缺血组进行注入和洗脱之前诱导无血流缺血（轻度缺血组15分钟；重度缺血组30分钟）。用外部γ探测器测定全心放射性。计算心肌流速（K₁，ml/min）和清除率（k₂，min⁻¹）。
K₁Tl、K₁TF和K₁MIBI根据缺血严重程度降低（正常对照组、轻度缺血组和重度缺血组中，K₁Tl分别为5.32±0.53、4.76±0.70和1.44±0.59；K₁TF分别为3.80±0.70、2.73±0.99和1.09±0.45；K₁MIBI分别为3.45±1.10、2.15±0.82和1.05±0.13）。Tl的K₁显著高于⁹⁹ᵐTc示踪剂（P < 0.05），但⁹⁹ᵐTc示踪剂的K₁值相当。缺血组中k₂Tl显著增加（P < 0.05）（k₂Tl为0.062±0.013、0.11±0.045和0.12±0.035），但缺血组之间无显著差异。k₂MIBI和k₂TF显著低于k₂Tl（P < 0.05），且在重度缺血组中显著增加（P < 0.05）（k₂TF为0.0056±0.0022、0.0037±0.0015和0.024±0.015；k₂MIBI为0.00072±0.0011、0.00038±0.00076和0.042±0.034）。在正常对照组和轻度缺血组中，k₂MIBI显著低于k₂TF（P < 0.05）。
Tl的示踪剂摄取高于⁹⁹ᵐTc示踪剂，且在三个示踪剂组中所有示踪剂均根据缺血 - 再灌注的严重程度而降低。不仅MIBI而且TF的清除动力学可能有助于评估缺血的严重程度，Langendorff法以及通过连续测定放射性的方法可能用于示踪剂动力学曲线的定量分析。
