Department of Radiation Oncology, The Netherlands Cancer Institute, Antoni van Leeuwenhoek Hospital, Amsterdam, The Netherlands.
Int J Radiat Oncol Biol Phys. 2013 Oct 1;87(2):394-400. doi: 10.1016/j.ijrobp.2013.06.007. Epub 2013 Aug 1.
Four-dimensional positron emission tomography (4D PET) imaging of the thorax produces sharper images with reduced motion artifacts. Current radiation therapy planning systems, however, do not facilitate 4D plan optimization. When images are acquired in a 2-minute time slot, the signal-to-noise ratio of each 4D frame is low, compromising image quality. The purpose of this study was to implement and evaluate the construction of mid-position 3D PET scans, with motion compensated using a 4D computed tomography (CT)-derived motion model.
All voxels of 4D PET were registered to the time-averaged position by using a motion model derived from the 4D CT frames. After the registration the scans were summed, resulting in a motion-compensated 3D mid-position PET scan. The method was tested with a phantom dataset as well as data from 27 lung cancer patients.
PET motion compensation using a CT-based motion model improved image quality of both phantoms and patients in terms of increased maximum SUV (SUV(max)) values and decreased apparent volumes. In homogenous phantom data, a strong relationship was found between the amplitude-to-diameter ratio and the effects of the method. In heterogeneous patient data, the effect correlated better with the motion amplitude. In case of large amplitudes, motion compensation may increase SUV(max) up to 25% and reduce the diameter of the 50% SUV(max) volume by 10%.
4D CT-based motion-compensated mid-position PET scans provide improved quantitative data in terms of uptake values and volumes at the time-averaged position, thereby facilitating more accurate radiation therapy treatment planning of pulmonary lesions.
胸部四维正电子发射断层扫描（4D PET）成像可产生更清晰的图像，并减少运动伪影。然而，目前的放射治疗计划系统并不方便进行 4D 计划优化。当在 2 分钟的时间窗内采集图像时，每个 4D 帧的信噪比较低，从而影响图像质量。本研究旨在实施并评估使用 4D 计算机断层扫描（CT）衍生运动模型进行运动补偿的中置 3D PET 扫描的构建。
通过使用从 4D CT 帧中得出的运动模型，将所有 4D PET 体素配准到时间平均位置。配准后，扫描结果被求和，得到运动补偿的 3D 中置 PET 扫描。该方法在体模数据集以及 27 例肺癌患者的数据中进行了测试。
使用基于 CT 的运动模型进行 PET 运动补偿，提高了体模和患者的图像质量，表现为 SUV(max)值增加和表观体积减小。在均匀体模数据中，发现振幅与直径比与该方法的效果之间存在很强的相关性。在异质患者数据中，效果与运动幅度相关性更好。对于大的运动幅度，运动补偿可使 SUV(max)增加高达 25%，并使 50%SUV(max)体积的直径减小 10%。
基于 4D CT 的运动补偿中置 PET 扫描可在摄取值和平均位置体积方面提供更准确的定量数据，从而有利于更准确地对肺部病变进行放射治疗计划。
