Nagayoshi Makoto, Murase Kenya, Fujino Kouichi, Uenishi Yusuke, Kawamata Minoru, Nakamura Yukio, Kitamura Keishi, Higuchi Ichiro, Oku Naohiko, Hatazawa Jun
Department of Medical Physics and Engineering, Graduate School of Medicine, Osaka University, Japan.
Ann Nucl Med. 2005 Sep;19(6):469-77. doi: 10.1007/BF02985574.
In positron emission tomography (PET) studies, shortening transmission (TR) scan time can improve patient comfort and increase scanner throughput. However, PET images from short TR scans may be degraded due to the statistical noise included in the TR image. The purpose of this study was to apply non-linear Gaussian (NLG) and noise adaptive NLG (ANLG) filters to TR images, and to evaluate the extent of noise reduction by the ANLG filter in comparison with that by the NLG filter using phantom and clinical studies.
In phantom studies, pool phantoms of various diameters and injected doses of 2-deoxy-2-[18F]fluoro-D-glucose (FDG) were used and the coefficients of variation (CVs) of the counts in the TR images processed with the NLG and ANLG filters were compared. In clinical studies, two normal volunteers and 13 patients with tumors were studied. In volunteer studies, the CV values in the liver were compared. In patient studies, the standardized uptake values (SUVs) of tumors in the emission images were obtained after processing the TR images using the NLG and ANLG filters.
In phantom studies, the CV values in the TR images processed with the ANLG filter were smaller than those in the images processed with the NLG filter. When using the ANLG filter, their dependency on the phantom size, injected dose of FDG and TR scan time was smaller than when using the NLG filter. In volunteer studies, the CV values in the images processed with the ANLG filter were smaller than those in the images processed with the NLG filter, and were almost constant regardless of the TR scan time. In patient studies, there was an excellent correlation between the SUVs obtained from the images with a TR scan time of 7 min processed with the NLG filter (x) and those obtained from the images with a TR scan time of 4 min processed with the ANLG filter (y) (r = 0.995, y = 1.034x - 0.075).
Our results suggest that the ANLG filter is effective and useful for noise reduction in TR images and shortening TR scan time while maintaining the quantitative accuracy of FDG-PET studies.
在正电子发射断层扫描（PET）研究中，缩短透射（TR）扫描时间可提高患者舒适度并增加扫描仪通量。然而，短TR扫描得到的PET图像可能会因TR图像中包含的统计噪声而质量下降。本研究的目的是将非线性高斯（NLG）滤波器和噪声自适应NLG（ANLG）滤波器应用于TR图像，并通过体模和临床研究评估ANLG滤波器与NLG滤波器相比的降噪程度。
在体模研究中，使用了不同直径和2-脱氧-2-[18F]氟-D-葡萄糖（FDG）注射剂量的液体体模，并比较了用NLG和ANLG滤波器处理后的TR图像中计数的变异系数（CV）。在临床研究中，对两名正常志愿者和13名肿瘤患者进行了研究。在志愿者研究中，比较了肝脏中的CV值。在患者研究中，在使用NLG和ANLG滤波器处理TR图像后，获取发射图像中肿瘤的标准化摄取值（SUV）。
在体模研究中，用ANLG滤波器处理的TR图像中的CV值小于用NLG滤波器处理的图像中的CV值。使用ANLG滤波器时，其对体模大小、FDG注射剂量和TR扫描时间的依赖性小于使用NLG滤波器时。在志愿者研究中，用ANLG滤波器处理的图像中的CV值小于用NLG滤波器处理的图像中的CV值，并且几乎与TR扫描时间无关。在患者研究中，用NLG滤波器处理的TR扫描时间为7分钟的图像获得的SUV（x）与用ANLG滤波器处理的TR扫描时间为4分钟的图像获得的SUV（y）之间存在极好的相关性（r = 0.995，y = 1.034x - 0.075）。
我们的结果表明，ANLG滤波器在降低TR图像噪声和缩短TR扫描时间方面是有效且有用的，同时能保持FDG-PET研究的定量准确性。
