Vanhove Christian, Franken Philippe R, Defrise Michel, Deconinck Frank, Bossuyt Axel
Division of Nuclear Medicine, University Hospital, Free University of Brussels (AZ VUB), 101 Laarbeeklaan, 1090 Brussels, Belgium.
Eur J Nucl Med Mol Imaging. 2002 Apr;29(4):465-72. doi: 10.1007/s00259-002-0763-z. Epub 2002 Feb 19.
Reconstruction of gated single-photon emission tomography (gSPET) is intrinsically a four-dimensional (4D) problem. In practice, the time frames are reconstructed independently as a sequence of frame-by-frame reconstructions. This approach is not optimal since the strong signal correlations among the individual time frames are not exploited. In this study we propose a simple but efficient algorithm to improve the image quality of myocardial perfusion gSPET by incorporating the cyclic temporal information within the reconstruction using Fourier filtering. The gSPET images were reconstructed using the Ordered Subsets Expectation Maximisation (OSEM) algorithm employing six iterations with eight subsets. Temporal filtering was applied either before (PreOSEM) or after image reconstruction (PostOSEM) or was incorporated within the OSEM algorithm (OSEM4D). The effect of temporal filtering was compared with conventional frame-by-frame OSEM using clinical data. Image quality was evaluated by estimating the systematic and statistical error. The results indicated that temporal filtering introduces a small (<1%) systematic error, while the statistical error was reduced from 15.0%+/-3.1% when conventional frame-by-frame OSEM was applied to 12.6%+/-2.7%, 12.0%+/-2.5% and 9.3%+/-2.4% when PreOSEM, PostOSEM and OSEM4D were used, respectively. It is concluded that temporal filtering incorporated within OSEM reconstruction dramatically reduces noise in gated SPET myocardial images.
门控单光子发射断层扫描（gSPET）重建本质上是一个四维（4D）问题。在实际操作中，时间帧是作为一系列逐帧重建独立进行的。这种方法并非最优，因为各个时间帧之间的强信号相关性未得到利用。在本研究中，我们提出了一种简单而有效的算法，通过在重建过程中使用傅里叶滤波纳入循环时间信息，来提高心肌灌注gSPET的图像质量。使用有序子集期望最大化（OSEM）算法对gSPET图像进行重建，该算法采用八子集六次迭代。时间滤波在图像重建之前（PreOSEM）或之后（PostOSEM）应用，或者纳入OSEM算法（OSEM4D）。使用临床数据将时间滤波的效果与传统的逐帧OSEM进行比较。通过估计系统误差和统计误差来评估图像质量。结果表明，时间滤波引入的系统误差较小（<1%），而统计误差从应用传统逐帧OSEM时的15.0%±3.1%分别降低到使用PreOSEM、PostOSEM和OSEM4D时的12.6%±2.7%、12.0%±2.5%和9.3%±2.4%。得出的结论是，OSEM重建中纳入时间滤波可显著降低门控SPET心肌图像中的噪声。
