[论文解读] Quantitative investigation of low-dose PET imaging and post-reconstruction smoothing

Behnoush Sanaei, Reza Faghihi+1 more|arXiv (Cornell University)|Mar 18, 2021

Medical Imaging Techniques and Applications被引用 8

一句话总结

本研究定量评估了在50名头颈部癌患者脑部扫描中，将18F-FDG PET/CT剂量降低至标准剂量的1%–10%以及重建后高斯滤波对图像质量和SUV准确性的影响。研究发现，低剂量扫描显著增加了RMSE和SUVmax偏差，但高斯滤波能有效降低SUVmax偏差，同时增加SUVmean偏差，因此在低剂量扫描方案中需同时谨慎考虑这两项指标。

ABSTRACT

In this study, 18F-FDG PET/CT brain scans of 50 patients with head and neck malignant lesions were employed to systematically assess the relationship between the amount of injected dose (10%, 8%, 6%, 5%, 4%, 3%, 2%, and 1% of standard dose) and the image quality through measuring standard image quality metrics (peak-signal-to-noise-ration (PSNR), structural similarity index (SSIM), root mean square error (RMSE), and standard uptake value (SUV) bias) for the whole head region as well as within the malignant lesions, considering the standard-dose PET images as reference. Furthermore, we evaluated the impact of post-reconstruction Gaussian filtering on the PET images in order to reduce noise and improve the signal-to-noise ratio at different low-dose levels. Significant degradation of PET image quality and tumor detectability was observed with a decrease in the injected dose by more than 5%, leading to a remarkable increase in RMSE from 0.173 SUV (at 5%) to 1.454 SUV (at 1%). The quantitative investigation of the malignant lesions demonstrated that SUVmax bias greatly increased in low-dose PET images (in particular at 1%, 2%, 3% levels) before applying the post-reconstruction filter, while applying the Gaussian filter on low-dose PET images led to a significant reduction in SUVmax bias. The SUVmean bias within the malignant lesions was negligible (less than 1%) in low-dose PET images; however, this bias increased significantly after applying the post-reconstruction filter. In conclusion, it is strongly recommended that the SUVmax bias and SUVmean bias in low-dose PET images should be considered prior to and following the application of the post-reconstruction Guassain filter, respectively.

研究动机与目标

• 评估将18F-FDG PET/CT剂量降低至标准剂量的1%–10%对脑部扫描图像质量及SUV准确性的影响。
• 评估重建后高斯滤波对低剂量PET图像噪声降低及SUV偏差的影响。
• 确定在保持诊断准确性的同时最大限度减少辐射暴露的最优剂量与滤波策略。
• 比较低剂量与标准剂量参考图像之间的图像质量指标（PSNR、SSIM、RMSE）及SUV偏差。

提出的方法

• 对50名患者经系统性降低注射剂量（标准剂量的1%至10%）的18F-FDG PET/CT脑部扫描进行回顾性分析。
• 以标准剂量图像作为定量比较的参考，采用PSNR、SSIM、RMSE及SUV偏差指标。
• 对低剂量图像应用重建后高斯滤波，以评估其对噪声降低及SUV准确性的影响。
• 在恶性病灶及整个头颅区域量化SUVmax和SUVmean偏差。
• 针对每个剂量水平和滤波条件计算图像质量指标，以评估质量退化与改善情况。
• 对不同剂量水平及有无滤波条件下的指标进行统计比较，以识别关键阈值。

实验结果

研究问题

• RQ1 将18F-FDG注射剂量从100%降低至1%，对脑部PET/CT扫描的图像质量指标（如PSNR、SSIM和RMSE）有何影响？
• RQ2 重建后高斯滤波在低剂量PET图像中在多大程度上可降低噪声并提高信噪比？
• RQ3 在不同低剂量水平下，恶性病灶的SUVmax偏差在高斯滤波前后如何变化？
• RQ4 重建后滤波是否显著改变恶性病灶的SUVmean偏差，若显著，方向如何？
• RQ5 在何种剂量水平下，图像质量退化与SUV偏差变得对低剂量PET扫描方案具有临床关切意义？

主要发现

• RMSE从5%剂量时的0.173 SUV增加至1%剂量时的1.454 SUV，表明在极低剂量下图像质量显著退化。
• 在未进行滤波的情况下，低剂量图像中SUVmax偏差显著增加（尤其在1%、2%和3%剂量时），表明肿瘤摄取被低估。
• 重建后高斯滤波显著降低了低剂量图像中的SUVmax偏差，提高了SUV准确性。
• 在未滤波的低剂量图像中，SUVmean偏差保持在1%以下，但滤波后显著增加，表明平均摄取被高估。
• 低剂量成像与高斯滤波的结合需要对SUVmax和SUVmean偏差进行仔细评估，以避免诊断误判。
• 图像质量指标（PSNR、SSIM）随剂量降低而恶化，尤其在低于标准剂量5%时下降最为明显。