Yamanashi PET Imaging Clinic, Shimokato, Chuo City, Yamanashi, 3046-2, Japan.
Department of Radiology, University of Yamanashi, Chuo City, Yamanashi, Japan.
Ann Nucl Med. 2021 May;35(5):608-616. doi: 10.1007/s12149-021-01604-9. Epub 2021 Mar 27.
This study aimed to determine the optimal β value of the relaxation control parameter and the post-smoothing filter in the list-mode dynamic row-action maximum likelihood algorithm (LM-DRAMA) to detect early stage breast cancer with high-resolution dedicated breast positron emission tomography (dbPET) in phantom and clinical studies.
A breast phantom containing four spheres (5, 7.5, 10, and 16 mm in diameter) was filled with F-fluorodeoxyglucose solution (sphere-to-background ratio, 8:1) and scanned on a dbPET scanner. The images were reconstructed using LM-DRAMA with different β values (5, 20, or 100) and Gaussian post-filters (0, 0.78, 1.17, 1.56, 1.95, or 2.34 mm). Other conditions were according to those routinely used (1 iteration and 128 subsets including attenuation and scatter correction). Image quality was evaluated visually and by computing the coefficient of variation of the background (CV), detectability index (DI), and contrast recovery coefficient. Parameters optimized in these phantom studies were applied to 25 clinical data sets. Variabilities for different reconstruction methods in visual scores, the maximum standardized uptake value of breast cancer, and the tumor-to-background uptake ratio were estimated.
The reconstruction images of the phantom with higher β values and smaller post-filters yielded higher visual scores for detectability and DI and lower smoothness and CV scores. Based on the phantom study, the β values and post-filter were optimized for clinical dbPET images except for β5 and 2.34 mm post-filter. Applying the other reconstructions to clinical studies showed that β100 provided higher quantitative parameter values. The detectability of lesions was similar for β100 and β20 and decreased with larger post-filters. The lesion detection rate was similar for β100 and β20 and decreased with larger post-filter.
The relaxation coefficient factor β20 and a 0.78- or 1.17-mm post-filter were optimal for dbPET image reconstruction with balanced spatial resolution and noise. However, they should be selected according to the impact on the dbPET image and the purpose of the examination.
本研究旨在确定松弛控制参数的最佳β值和后平滑滤波器，以便在体模和临床研究中使用高分辨率专用乳腺正电子发射断层扫描（dbPET）的动态行动作最大似然算法（LM-DRAMA）检测早期乳腺癌。
在一个包含四个球体（直径为 5、7.5、10 和 16 毫米）的乳腺体模中填充 F-氟脱氧葡萄糖溶液（球与背景比为 8:1），并在 dbPET 扫描仪上进行扫描。使用 LM-DRAMA 以不同的β值（5、20 或 100）和高斯后滤波器（0、0.78、1.17、1.56、1.95 或 2.34 毫米）进行图像重建。其他条件根据常规使用的条件设置（1 次迭代和 128 个子集，包括衰减和散射校正）。通过计算背景的变异系数（CV）、检测指数（DI）和对比恢复系数来评估图像质量。在这些体模研究中优化的参数应用于 25 个临床数据集。在视觉评分、乳腺癌最大标准化摄取值和肿瘤与背景摄取比值方面，估计了不同重建方法的可变性。
具有较高β值和较小后滤波器的体模重建图像具有更高的可检测性和 DI 的视觉评分，以及更低的平滑度和 CV 评分。基于体模研究，优化了临床 dbPET 图像的β值和后滤波器，除了β5 和 2.34 毫米后滤波器。将其他重建应用于临床研究表明，β100 提供了更高的定量参数值。病变的检测率β100 和β20 相似，随着后滤波器的增大而降低。β100 和β20 的病变检出率相似，随着后滤波器的增大而降低。
对于具有平衡空间分辨率和噪声的 dbPET 图像重建，松弛系数因子β20 和 0.78 或 1.17 毫米后滤波器是最佳选择。然而，它们的选择应根据对 dbPET 图像的影响和检查的目的而定。
