Bartlett M L, Srinivasan G, Barker W C, Kitsiou A N, Dilsizian V, Bacharach S L
Department of Nuclear Medicine, National Institutes of Health, Bethesda, Maryland 20892-1180, USA.
J Nucl Med. 1996 Nov;37(11):1795-9.
Global ejection fraction (EF) from planar gated blood-pool (GBP) imaging is a widely accepted measure of cardiac function. It has been suggested that planar GBP could be replaced by SPECT. In this article, we compare counts-based global EF measured from SPECT and planar images and investigate reasons for discrepancies between the two.
Twenty-three subjects were imaged with both planar and SPECT GBP. SPECT short-axis slices were projected to create reprojected images. Reprojected SPECT (rSPECT) images were created in both the true long-axis view and also in a view typical of planar studies (found to be 60 degrees from the true long-axis). Thus, angle of view effects on global EF could be investigated. In addition, we studied the effects of background and attenuation.
Long-axis rSPECT EF correlated well with planar EF (r = 0.89) but EF values were significantly higher for rSPECT than for planar (slope = 1.4, intercept = -8 EF units; p < 0.001). We found that background correction may not be necessary with rSPECT, but neither background nor attenuation explained the observed discrepancy between rSPECT and planar EFs. This discrepancy was found to be caused by atrial overlap in the planar image and disappeared when the SPECT slices were reprojected at the same angle of view as the planar images.
Global EF can be easily measured from rSPECT GBP images. Long-axis rSPECT EFs are, however, greater than planar EFs by a factor of 1.4 because atrial overlap causes a significant drop in planar EF in planar images. These results suggest that (long-axis) rSPECT EFs may be more accurate than planar EFs.
平面门控心血池（GBP）成像得出的整体射血分数（EF）是广泛认可的心脏功能指标。有人提出单光子发射计算机断层扫描（SPECT）可取代平面GBP。在本文中，我们比较了从SPECT和平面图像测得的基于计数的整体EF，并探究两者存在差异的原因。
对23名受试者进行了平面和SPECT GBP成像。将SPECT短轴切片进行投影以创建重投影图像。在真正的长轴视图以及平面研究的典型视图（发现与真正的长轴成60度）中均创建了重投影SPECT（rSPECT）图像。因此，可以研究视角对整体EF的影响。此外，我们研究了背景和衰减的影响。
长轴rSPECT EF与平面EF相关性良好（r = 0.89），但rSPECT的EF值显著高于平面EF（斜率 = 1.4，截距 = -8 EF单位；p < 0.001）。我们发现rSPECT可能无需进行背景校正，但背景和衰减均无法解释观察到的rSPECT与平面EF之间的差异。发现这种差异是由平面图像中的心房重叠引起的，当SPECT切片以与平面图像相同的视角进行重投影时，差异消失。
可以轻松地从rSPECT GBP图像测量整体EF。然而，长轴rSPECT EF比平面EF大1.4倍，因为心房重叠会导致平面图像中平面EF显著下降。这些结果表明（长轴）rSPECT EF可能比平面EF更准确。
