Department of Imaging Physics, UT MD Anderson Cancer Center, Houston, Texas, USA.
Mallinckrodt Institute of Radiology, Washington University in St. Louis, St. Louis, Missouri, USA.
Med Phys. 2024 Jul;51(7):4646-4654. doi: 10.1002/mp.17097. Epub 2024 Apr 22.
Data-driven gated (DDG) PET has gained clinical acceptance and has been shown to match or outperform external-device gated (EDG) PET. However, in most clinical applications, DDG PET is matched with helical CT acquired in free breathing (FB) at a random respiratory phase, leaving registration, and optimal attenuation correction (AC) to chance. Furthermore, DDG PET requires additional scan time to reduce image noise as it only preserves 35%-50% of the PET data at or near the end-expiratory phase of the breathing cycle.
A new full-counts, phase-matched (FCPM) DDG PET/CT was developed based on a low-dose cine CT to improve registration between DDG PET and DDG CT, to reduce image noise, and to avoid increasing acquisition times in DDG PET.
A new DDG CT was developed for three respiratory phases of CT images from a low dose cine CT acquisition of 1.35 mSv for a coverage of about 15.4 cm: end-inspiration (EI), average (AVG), and end-expiration (EE) to match with the three corresponding phases of DDG PET data: -10% to 15%; 15% to 30%, and 80% to 90%; and 30% to 80%, respectively. The EI and EE phases of DDG CT were selected based on the physiological changes in lung density and body outlines reflected in the dynamic cine CT images. The AVG phase was derived from averaging of all phases of the cine CT images. The cine CT was acquired over the lower lungs and/or upper abdomen for correction of misregistration between PET and FB CT as well as DDG PET and FB CT. The three phases of DDG CT were used for AC of the corresponding phases of PET. After phase-matched AC of each PET dataset, the EI and AVG PET data were registered to the EE PET data with deformable image registration. The final result was FCPM DDG PET/CT which accounts for all PET data registered at the EE phase. We applied this approach to 14 F-FDG lung cancer patient studies acquired at 2 min/bed position on the GE Discovery MI (25-cm axial FOV) and evaluated its efficacy in improved quantification and noise reduction.
Relative to static PET/CT, the SUV increases for the EI, AVG, EE, and FCPM DDG PET/CT were 1.67 ± 0.40, 1.50 ± 0.28, 1.64 ± 0.36, and 1.49 ± 0.28, respectively. There were 10.8% and 9.1% average decreases in SUV from EI and EE to FCPM DDG PET/CT, respectively. EI, AVG, and EE DDG PET/CT all maintained increased image noise relative to static PET/CT. However, the noise levels of FCPM and static PET were statistically equivalent, suggesting the inclusion of all counts was able to decrease the image noise relative to EI and EE DDG PET/CT.
A new FCPM DDG PET/CT has been developed to account for 100% of collected PET data in DDG PET applications. Image noise in FCPM is comparable to static PET, while small decreases in SUV were also observed in FCPM when compared to either EI or EE DDG PET/CT.
基于数据驱动门控（DDG）的 PET 已获得临床认可，并且已被证明可与外部设备门控（EDG）的 PET 相匹配或优于后者。然而，在大多数临床应用中，DDG PET 与在自由呼吸（FB）下获取的螺旋 CT 相匹配，而这些 CT 是在随机呼吸阶段获得的，这使得配准和最佳衰减校正（AC）都依赖于偶然因素。此外，DDG PET 需要额外的扫描时间来减少图像噪声，因为它仅在呼吸周期的呼气末阶段保留 35%-50%的 PET 数据。
基于低剂量电影 CT 开发了一种新的全计数、相位匹配（FCPM）DDG PET/CT，以改善 DDG PET 与 DDG CT 之间的配准，降低图像噪声，并避免在 DDG PET 中增加采集时间。
为了匹配 DDG PET 的三个数据相位：-10%到 15%、15%到 30%和 80%到 90%，从低剂量电影 CT 采集的 1.35 mSv 的三个呼吸阶段的 CT 图像中开发了一种新的 DDG CT：吸气末（EI）、平均（AVG）和呼气末（EE），并分别匹配相应的 DDG PET 数据相位：-10%到 15%、15%到 30%和 80%到 90%。DDG CT 的 EI 和 EE 相位是根据动态电影 CT 图像中反映的肺密度和身体轮廓的生理变化选择的。AVG 相位是从所有电影 CT 图像相位的平均值得出的。电影 CT 用于下肺和/或上腹部的采集，以校正 PET 与 FB CT 以及 DDG PET 与 FB CT 之间的配准错误。将这三个相位的 DDG CT 用于相应相位的 PET AC。在对每个 PET 数据集进行相位匹配 AC 后，使用变形图像配准将 EI 和 AVG PET 数据注册到 EE PET 数据。最终的结果是 FCPM DDG PET/CT，它可以处理所有在 EE 阶段注册的 PET 数据。我们将这种方法应用于 14 例在 GE Discovery MI（25-cm 轴向 FOV）上进行的 2 分钟/床位位置的 F-FDG 肺癌患者研究，并评估了其在改善定量和降低噪声方面的效果。
与静态 PET/CT 相比，EI、AVG、EE 和 FCPM DDG PET/CT 的 SUV 分别增加了 1.67±0.40、1.50±0.28、1.64±0.36 和 1.49±0.28。EI 和 EE 到 FCPM DDG PET/CT 的 SUV 平均分别降低了 10.8%和 9.1%。EI、AVG 和 EE DDG PET/CT 与静态 PET/CT 相比，图像噪声均有所增加。然而，FCPM 和静态 PET 的噪声水平在统计学上是等效的，这表明包含所有计数能够降低相对于 EI 和 EE DDG PET/CT 的图像噪声。
已经开发了一种新的 FCPM DDG PET/CT，用于处理 DDG PET 应用中收集的 100% PET 数据。FCPM 的图像噪声与静态 PET 相当，而与 EI 或 EE DDG PET/CT 相比，FCPM 中的 SUV 也略有下降。
