Normal limits for transient ischemic dilation with 99mTc myocardial perfusion SPECT protocols
Normal limits for transient ischemic dilation with 99mTc myocardial perfusion SPECT protocols
复制标题
99mTc 心肌灌注 SPECT 方案短暂性缺血性扩张的正常限值
DOI：
10.1007/s12350-016-0582-4
复制
发表时间：
2017
影响因子：
2.4
通讯作者：
G. Germano
中科院分区：
文献类型：
--
作者：
P. Slomka;D. Berman;G. Germano
Transient ischemic dilation (TID) of the left ventricle—a ratio of the stress left ventricular (LV) volume to rest LV volume—on myocardial perfusion imaging has been described as a useful marker of severe and extensive coronary artery disease (CAD). TID measurement has also been shown to have distinct prognostic value, with abnormal TID indicating increased risk of myocardial infarction or cardiac death. TID is currently used in clinical practice and is routinely reported by most major quantitative software packages. The mechanisms of this relative increase of measured left ventricular volume at stress have been considered to be an apparent cavity size at stress due to subendocardial ischemia, a true increase in left ventricular volume persisting at the time of post-stress imaging due to stress-induced LV stunning, or a combination of both. In this issue of Journal of Nuclear Cardiology , Jameria et al. study in detail the TID derivation for the scans obtained with a new Cadmium Zinc Telluride (CZT) camera in the upright position. The TID measurements have not been studied yet on these new cameras. Potentially due to an increased resolution and different imaging position, the normal TID values could differ on these new systems. In regards to image resolution, it has been suggested that TID may be unreliable in small hearts, if reconstructed image resolution is too low. So how do the results presented by Jameria et al. compare to recent studies of TID? Table 1 lists several recent published reports with various Tc protocols, stress methods, software tools, criterions for cut-off, and definitions of normal population. Other studies have been published previously for dual-isotope protocols. In Table 1, it can be seen that normal cutoff values obtained by Jameria et al. are in fact remarkably similar to the values reported for exercise or pharmacological stress obtained with conventional imaging systems, including one previous report of TID in patients imaged in upright position. Similar to previous reports, the threshold defined as 2 standard deviations (SD) above the mean is indeed higher for the pharmacological stress studies than for the exercise studies. When comparing these recent reports, one can appreciate that there are several potential factors affecting the value of the normal threshold, such as imaging protocol, patient position, normal population definition, statistical threshold definition, and software used for TID computation. Nevertheless, despite these methodological differences, the abnormal TID cut-offs seem to be consistent across these reports. Some technical factors should be pointed out with regards to the study by Jameria et al. Does upright position affect the results? It is hard to tell since there are no paired supine TID measurements obtained in this report. In some clinical protocols, the upright and supine images are obtained both at stress and rest and therefore such comparison could be feasible in future studies. The normal TID cut-off values do not seem to differ from these reported by other studies despite the use of CZT camera. The number of normal regadenoson cases used for the derivation of normal limits is rather low, reflecting practical difficulty, since patients with low likelihood of disease are unlikely to undergo pharmacological stress. The authors Jameria et al. utilize the average of upright and supine perfusion results for the definition of the perfusion defect used in their analyses, See related article, pp. 1702-1708
