Laboratory of Radiation Physics, Odense University Hospital, DK-5000 Odense, Denmark.
Acta Oncol. 2010;49(2):225-9. doi: 10.3109/02841860903386408.
In modern radiotherapy accelerators are equipped with 3D cone-beam CT (CBCT) which is used to verify patient position before treatment. The verification is based on an image registration between the CBCT acquired just before treatment and the CT scan made for the treatment planning. The purpose of this study is to minimise the scan time of the CBCT without compromising the accuracy of the image registration in IGRT.
Fast scans were simulated by reducing the number of acquired projection images, i.e. new reconstructions based on a subset of the original projections were made. The deviation between the registrations of these new reconstructions and the original registration was measured as function of the amount of reduction.
Twenty nine head and neck (H&N) and 11 stereotactic lung patients were included in the study. The mean of the registration deviation did not differ significantly from zero independently of the number of projections included in the reconstruction. Except for the smallest subset of reconstructions (10% and 25% of the original projection for the lung and H&N patients, respectively) the standard deviation of the registration differences was constant. The standard deviations were approximately 0.1 mm and 0.2 mm for the H&N and lung group, respectively. Based on these results an in-house developed solution, able to reduce the Cone-Beam CT scan time, has been implemented clinically.
现代放射治疗加速器配备有 3D 锥形束 CT（CBCT），用于在治疗前验证患者的位置。验证基于治疗前获取的 CBCT 与治疗计划 CT 扫描之间的图像配准。本研究的目的是在不影响图像配准精度的情况下，尽量减少 CBCT 的扫描时间。
通过减少获取的投影图像数量来模拟快速扫描，即根据原始投影的子集进行新的重建。测量这些新重建的注册偏差与原始注册之间的偏差作为减少量的函数。
本研究纳入了 29 例头颈部（H&N）和 11 例立体定向肺部患者。无论重建中包含的投影数量如何，注册偏差的平均值均与零无显著差异。除了最小的重建子集（分别为肺部和 H&N 患者原始投影的 10%和 25%）外，注册差异的标准差保持不变。对于 H&N 和肺部组，标准差分别约为 0.1mm 和 0.2mm。基于这些结果，开发了一种内部解决方案，能够减少锥形束 CT 的扫描时间，并已在临床中实施。
