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目的 本研究通过模型试验旨在评价18F-FDG及99mTc同时心肌显像(DISA)的准确性。方法应用标准心脏模型进行心肌断层采集。模型内部备有不同大小的缺损块,模拟心肌梗死,分别为整个心肌容积的3％、5％、10％及15％。模型内部注入99mTc-O4-74 MBq(2mCi)及18F-FDG 11.1MBq(300μCi)。使用配备超高能准直器的Varicam双探头SPECT,行双核素心肌DISA。采用滤波反投影法,进行重建,产生双核素图像(99mTc,18F-FDG)。采用5×5像素大小的感兴趣区,计算缺损区放射性计数,及与最大心肌计数的比值。结果所得图像中,缺损清晰可见。18F-FDG的图像中,缺损部位的放射性计数明显高于99mTc的图像,在小到中度缺损时尤其显著,而在大面积的缺损则差别减小。结论 此项技术可能高估存活心肌的大小,在灌注显像显示小或中等的缺损时,代谢显像可能会产生部分假的不匹配。因此,应考虑到此影响的存在,定量分析可能会提高DISA评价心肌灌注-代谢估价的准确性。
Objectives This study was designed to evaluate the accuracy of 18F-FDG and 99m Tc simultaneous myocardial imaging (DISA) through a model test. Methods The standard cardiac model was used to collect myocardial slices. The model has different sizes of internal defect block, simulating myocardial infarction, respectively, the entire myocardial volume of 3%, 5%, 10% and 15%. The model was injected with 99mTc-O4-74 MBq (2mCi) and 18F-FDG 11.1MBq (300μCi). Dual-isotope myocardial DISA was performed using a Varicam dual-probe SPECT with an ultra-high energy collimator. Filtered backprojection was used to reconstruct the bi-nuclide images (99mTc, 18F-FDG). Using a region of interest of 5 × 5 pixels, the radioactive counts in the defect area and the ratio to the maximum myocardial count were calculated. In the resulting image, the defect is clearly visible. In the 18F-FDG images, the radiological count of the defect site was significantly higher than that of the 99mTc image, especially in small to moderate defects, while the difference in large area defects was reduced. Conclusion This technique may overestimate the size of viable myocardium. Partial metabolic mismatch may occur in metabolic imaging when perfusion imaging shows small or moderate defects. Therefore, given this effect, quantitative analysis may improve the accuracy of the DISA assessment of myocardial perfusion-metabolism estimates.