Department of Radiology, Charité-Universitätsmedizin Berlin, Berlin, Germany.
PLoS One. 2018 Oct 16;13(10):e0205922. doi: 10.1371/journal.pone.0205922. eCollection 2018.
Myocardial computed tomography perfusion (CTP) allows the assessment of the functional relevance of coronary artery stenosis. This study investigates to what extent the contour sharpness of sequences acquired by dynamic myocardial CTP is influenced by the following noise reduction methods: temporal averaging and adaptive iterative dose reduction 3D (AIDR 3D).
Dynamic myocardial CT perfusion was conducted in 29 patients at a dose level of 9.5±2.0 mSv and was reconstructed with both filtered back projection (FBP) and strong levels of AIDR 3D. Temporal averaging to reduce noise was performed as a post-processing step by combining two, three, four, six and eight original consecutive 3D datasets. We evaluated the contour sharpness at four distinct edges of the left-ventricular myocardium based on two different approaches: the distance between 25% and 75% of the maximal grey value (d) and the slope in the contour (m).
Iterative reconstruction reduced contour sharpness: both measures of contour sharpness performed better for FBP than for AIDR 3D (d = 1.7±0.4 mm versus 2.0±0.5 mm, p>0.059 at all edges; m = 255.9±123.9 HU/mm versus 160.6±123.5 HU/mm; p<0.023 for all edges). Increasing levels of temporal averaging degraded contour sharpness. When FBP reconstruction was applied, contour sharpness was best without temporal averaging (d = 1.7±0.4 mm, m = 255.9±123.9 HU/mm) and poorest for the strongest levels of temporal averaging (d = 2.1±0.3 mm, m = 142.2±104.9 HU/mm; comparison between lowest and highest temporal averaging level: for d p>0.052 at all edges and for m p<0.001 at all edges).
The use of both temporal averaging and iterative reconstruction degrades objective contour sharpness parameters of dynamic myocardial CTP. Thus, further advances in image processing are needed to optimise contour sharpness of 4D myocardial CTP.
心肌计算机断层灌注（CTP）可用于评估冠状动脉狭窄的功能相关性。本研究旨在探讨以下几种降噪方法对动态心肌 CTP 序列边缘轮廓锐利度的影响程度：时间平均法和自适应迭代剂量降低 3D（AIDR 3D）。
29 例患者行心肌 CTP 检查，剂量水平为 9.5±2.0mSv，重建时同时采用滤波反投影（FBP）和高强度 AIDR 3D。时间平均法作为一种后处理步骤，通过合并两个、三个、四个、六个和八个原始连续 3D 数据集来降低噪声。我们基于两种不同方法评估左心室心肌四个不同边缘的轮廓锐利度：最大灰度值 25%到 75%之间的距离（d）和轮廓斜率（m）。
迭代重建降低了轮廓锐利度：两种方法评估的轮廓锐利度，FBP 均优于 AIDR 3D（d=1.7±0.4mm 与 2.0±0.5mm，所有边缘均 p>0.059；m=255.9±123.9HU/mm 与 160.6±123.5HU/mm，所有边缘均 p<0.023）。时间平均法水平的增加降低了轮廓锐利度。当应用 FBP 重建时，无时间平均法时轮廓锐利度最佳（d=1.7±0.4mm，m=255.9±123.9HU/mm），时间平均法最强时轮廓锐利度最差（d=2.1±0.3mm，m=142.2±104.9HU/mm；最低和最高时间平均水平比较：d 在所有边缘均 p>0.052，m 在所有边缘均 p<0.001）。
时间平均法和迭代重建的使用降低了动态心肌 CTP 的客观轮廓锐利度参数。因此，需要进一步改进图像处理技术以优化 4D 心肌 CTP 的轮廓锐利度。
