Wells R G, Simkin P H, Judy P F, King M A, Pretorius H, Gifford H C
Division of Nuclear Medicine, University of Massachusetts Medical Center, Worcester 01655, USA.
Med Phys. 1999 Jul;26(7):1382-8. doi: 10.1118/1.598635.
Tumor detection can be significantly affected by filtering so determining an optimal filter is an important aspect of establishing a clinical reconstruction protocol. The purpose of this study was to identify the cut-off frequency of a Butterworth filter used in a filtered backprojection (FBP) reconstruction that maximized the detection and localization accuracy of 1 cm spherical lesions in Ga-67 citrate, thoracic SPECT images. Image quality was evaluated by means of a localization receiver operating characteristic (LROC) study using computer simulated images. Projection data were generated using the mathematical cardiac-torso digital phantom with a clinically realistic background source distribution. The images were reconstructed using FBP with multiplicative Chang attenuation correction and fifth-order Butterworth filtering. The cut-off frequencies considered were 0.25, 0.32, 0.47, and 0.79 cm(-1) for the case of three-dimensional (3D) post-filtering and 0.25, 0.32, and 0.47 cm(-1) for two-dimensional (2D) post-filtering. The images were read by three research scientists and one board certified nuclear medicine clinician. The area under the LROC curve and the localization accuracy for all test conditions were compared using Scheffé's multiple comparisons test. It was found that 3D post-filtering using filters with cut-off frequencies of 0.32 and 0.47 cm(-1) resulted in the highest lesion detectability and localization accuracy. These two test conditions did not differ significantly from each other but were significantly better (p<0.05) than all of the 2D, and the 3D 0.79 cm(-1) cut-off frequency cases.
滤波会对肿瘤检测产生显著影响，因此确定最佳滤波器是建立临床重建方案的一个重要方面。本研究的目的是确定在滤波反投影（FBP）重建中使用的巴特沃斯滤波器的截止频率，该截止频率能使枸橼酸镓Ga-67胸部单光子发射计算机断层扫描（SPECT）图像中1 cm球形病变的检测和定位准确性最大化。使用计算机模拟图像，通过定位接收者操作特征（LROC）研究来评估图像质量。使用具有临床现实背景源分布的数学心脏-躯干数字体模生成投影数据。图像采用带有乘法Chang衰减校正和五阶巴特沃斯滤波的FBP进行重建。对于三维（3D）后滤波情况，考虑的截止频率为0.25、0.32、0.47和0.79 cm⁻¹，对于二维（2D）后滤波情况，考虑的截止频率为0.25、0.32和0.47 cm⁻¹。由三位研究科学家和一位具备核医学专业认证的临床医生读取图像。使用谢费多重比较检验比较所有测试条件下LROC曲线下的面积和定位准确性。结果发现，使用截止频率为0.32和0.47 cm⁻¹的滤波器进行3D后滤波，可实现最高的病变可检测性和定位准确性。这两种测试条件之间没有显著差异，但比所有2D以及3D 0.79 cm⁻¹截止频率的情况显著更好（p<0.05）。
