Brynolfsson Patrik, Axelsson Jan, Holmberg August, Jonsson Joakim H, Goldhaber David, Jian Yiqiang, Illerstam Fredrik, Engström Mathias, Zackrisson Björn, Nyholm Tufve
Department of Radiation Sciences, Umeå University, Umeå, 901 87, Sweden.
GE Healthcare, Waukesha, WI, 53188, USA.
Med Phys. 2018 Jun 3. doi: 10.1002/mp.13032.
Simultaneous collection of PET and MR data for radiotherapy purposes are useful for, for example, target definition and dose escalations. However, a prerequisite for using PET/MR in the radiotherapy workflow is the ability to image the patient in treatment position. The aim of this work was to adapt a GE SIGNA PET/MR scanner to image patients for radiotherapy treatment planning and evaluate the impact on signal-to-noise (SNR) of the MR images, and the accuracy of the PET attenuation correction.
A flat tabletop and a coil holder were developed to image patients in the treatment position, avoid patient contour deformation, and facilitate attenuation correction of flex coils. Attenuation corrections for the developed hardware and an anterior array flex coil were also measured and implemented to the PET/MR system to minimize PET quantitation errors. The reduction of SNR in the MR images due to the added distance between the coils and the patient was evaluated using a large homogenous saline-doped water phantom, and the activity quantitation errors in PET imaging were evaluated with and without the developed attenuation corrections.
We showed that the activity quantitation errors in PET imaging were within ±5% when correcting for attenuation of the flat tabletop, coil holder, and flex coil. The SNR of the MRI images were reduced to 74% using the tabletop, and 66% using the tabletop and coil holders.
We present a tabletop and coil holder for an anterior array coil to be used with a GE SIGNA PET/MR scanner, for scanning patients in the radiotherapy work flow. Implementing attenuation correction of the added hardware from the radiotherapy setup leads to acceptable PET image quantitation. The drop in SNR in MR images may require adjustment of the imaging protocols.
为放射治疗目的同时采集PET和MR数据，例如对于靶区定义和剂量递增很有用。然而，在放射治疗工作流程中使用PET/MR的一个前提条件是能够对处于治疗体位的患者进行成像。本研究的目的是对GE SIGNA PET/MR扫描仪进行改造，以便对放射治疗计划的患者进行成像，并评估对MR图像信噪比（SNR）的影响以及PET衰减校正的准确性。
开发了一个平板台面和一个线圈固定器，以便对处于治疗体位的患者进行成像，避免患者轮廓变形，并便于对柔性线圈进行衰减校正。还对开发的硬件和前部阵列柔性线圈的衰减校正进行了测量，并应用于PET/MR系统，以尽量减少PET定量误差。使用一个大型均匀掺盐水水体模评估由于线圈与患者之间距离增加导致的MR图像SNR降低情况，并评估有无开发的衰减校正时PET成像中的活度定量误差。
我们表明，在校正平板台面、线圈固定器和柔性线圈的衰减时，PET成像中的活度定量误差在±5%以内。使用平板台面时，MRI图像的SNR降至74%，使用平板台面和线圈固定器时降至66%。
我们展示了一种用于前部阵列线圈的平板台面和线圈固定器，可与GE SIGNA PET/MR扫描仪配合使用，用于在放射治疗工作流程中扫描患者。对放射治疗设置中添加的硬件实施衰减校正可实现可接受的PET图像定量。MR图像中SNR的下降可能需要调整成像协议。
