Mizutani Asuka, Matsunari Ichiro, Kobayashi Masato, Nishi Kodai, Fujita Wataru, Miyazaki Yoshiharu, Nekolla Stephan G, Kawai Keiichi
School of Health Sciences, College of Medical, Pharmaceutical and Health Sciences, Kanazawa University, 5-11-80 Kodatsuno, Kanazawa, 920-0942, Japan.
Clinical Research Department, The Medical and Pharmacological Research Center Foundation, Wo 32, Inoyama, Hakui, Ishikawa, 925-0613, Japan.
EJNMMI Phys. 2015 Dec;2(1):7. doi: 10.1186/s40658-015-0111-6. Epub 2015 Mar 11.
The aims of this study were (1) to evaluate the impact of injection dose, post-reconstruction filtering, and collimator choice on image quality of myocardial perfusion single-photon emission computed tomography (SPECT) using cadmium-zinc telluride (CZT) detectors and (2) to determine how these factors affect measured infarct size in the in vivo rat.
Twenty-four healthy and eight myocardial infarct (MI) rats underwent myocardial perfusion SPECT imaging after injection of various doses (25 to 200 MBq) of (99m)Tc-tetrofosmin using a standard (STD) five-pinhole collimator and high-sensitivity (HS) five-pinhole collimator. Image quality score, contrast-to-noise ratio, sharpness index, coefficient of variation (CV), and measured defect size were assessed as measures of image quality.
The image quality score increased and CV decreased as a function of injection dose. The contrast-to-noise ratio increased and sharpness index decreased as a function of Gaussian kernel size. When STD and HS were compared, HS tended to show higher image quality score and lower CV than STD. The use of post-reconstruction filter significantly improved image quality score and lessened CV. The reproducibility of defect size measurements, as assessed by intraclass correlation coefficients (ICC), between the collimators was poor-to-moderate (ICC = -0.310.57) with low (25 MBq) injection dose and with no or light (1.5-mm kernel size) filtering, whereas it was good-to-excellent (ICC = 0.750.97) with high (200 MBq) dose or low dose with heavy (2.5-mm kernel size) filtering. The filtering-related reproducibility was poor (ICC = -0.180.17) for STD with low injection dose, whereas it was good-to-excellent (ICC = 0.790.89) for HS. Furthermore, there was a filtering-related underestimation of defect size particularly with the use of heavy smoothing.
Appropriate imaging setting is important to obtain high quality images and thereby reliable measurements using a preclinical myocardial SPECT in the rat. When only a low injection dose (25 MBq) is allowed, we would recommend to use HS with light (1.5-mm kernel size) filtering.
本研究的目的是：（1）评估注射剂量、重建后滤波以及准直器选择对使用碲化镉锌（CZT）探测器的心肌灌注单光子发射计算机断层扫描（SPECT）图像质量的影响；（2）确定这些因素如何影响体内大鼠梗死面积的测量。
24只健康大鼠和8只心肌梗死（MI）大鼠在注射不同剂量（25至200MBq）的（99m）Tc-替曲膦后，使用标准（STD）五针孔准直器和高灵敏度（HS）五针孔准直器进行心肌灌注SPECT成像。评估图像质量评分、对比度噪声比、锐度指数、变异系数（CV）和测量的缺损大小作为图像质量的指标。
图像质量评分随注射剂量增加而升高，CV随注射剂量增加而降低。对比度噪声比随高斯核大小增加而升高，锐度指数随高斯核大小增加而降低。比较STD和HS时，HS的图像质量评分往往高于STD，CV低于STD。重建后滤波的使用显著提高了图像质量评分并降低了CV。通过组内相关系数（ICC）评估，准直器之间缺损大小测量的可重复性在低（25MBq）注射剂量且无滤波或轻度（1.5mm核大小）滤波时为差到中等（ICC = -0.31至0.57），而在高（200MBq）剂量或低剂量且重度（2.5mm核大小）滤波时为好到优秀（ICC = 0.75至0.97）。对于低注射剂量的STD，与滤波相关的可重复性较差（ICC = -0.18至0.17），而对于HS则为好到优秀（ICC = 0.79至0.89）。此外，特别是在使用重度平滑时，存在与滤波相关的缺损大小低估。
合适的成像设置对于使用大鼠临床前心肌SPECT获得高质量图像并从而进行可靠测量很重要。当仅允许低注射剂量（25MBq）时，我们建议使用轻度（1.5mm核大小）滤波的HS。
