ACRF Image X Institute, The University of Sydney Central Clinical School, Sydney, New South Wales, Australia.
ACRF Image X Institute, The University of Sydney Central Clinical School, Sydney, New South Wales, Australia.
Int J Radiat Oncol Biol Phys. 2018 Nov 15;102(4):932-940. doi: 10.1016/j.ijrobp.2018.04.056. Epub 2018 Apr 27.
Four-dimensional cone beam computed tomography (4DCBCT) facilitates verification of lung tumor motion before each treatment fraction and enables accurate patient setup in lung stereotactic ablative body radiation therapy. This work aims to quantify the real-time motion represented in 4DCBCT, depending on the reconstruction algorithm and the respiratory signal utilized for reconstruction.
Eight lung cancer patients were implanted with electromagnetic Calypso beacons in airways close to the tumor, enabling real-time motion measurements. 4DCBCT scans were reconstructed from projections for treatment setup CBCT for 1 to 2 fractions of 8 patients with the Feldkamp-Davis-Kress (FDK) algorithm or the prior image constrained compressed sensing (PICCS) method and internal real-time Calypso beacon trajectories or an external respiratory signal (bellows belt). The real-time beacon centroid ("target") motion was compared with beacon centroid positions segmented in the 4DCBCT reconstructions. We tested the hypotheses that (1) the actual target motion was accurately represented in the reconstructions and (2) the reconstruction/respiratory signal combinations performed similarly in the representation of the real-time motion.
On average the target motion was significantly underrepresented and exceeded the 4DCBCT motion for 48%, 25%, and 40% of the time in the left-right (LR), superior-inferior (SI), and anterior-posterior (AP) directions, respectively. The average underrepresentation for the LR, SI, and AP direction was 1.7 mm, 4.2 mm, and 2.5 mm, respectively. No difference could be shown between the reconstruction algorithms or respiratory signals in LR direction (FDK vs PICCS: P = .47, Calypso vs bellows: P = .19), SI direction (FDK vs PICCS: P = .49, Calypso vs bellows: P = .22), and AP direction (FDK vs PICCS: P = .62, Calypso vs bellows: P = .34).
The 4DCBCT scans all underrepresented the real-time target motion. The selection of the reconstruction algorithm and respiratory signal for the 4DCBCT reconstruction does not have an impact on the reconstructed motion range.
四维锥形束 CT（4DCBCT）有助于在每次分次治疗前验证肺肿瘤运动，并实现肺部立体定向消融体放射治疗中的精确患者摆位。本研究旨在根据重建算法和用于重建的呼吸信号，量化 4DCBCT 中实时运动的表示。
8 名肺癌患者在靠近肿瘤的气道中植入电磁 Calypso 信标，实现实时运动测量。从 8 名患者的 1 到 2 分次治疗计划 CBCT 的投影重建 Feldkamp-Davis-Kress（FDK）算法或先前图像约束压缩感知（PICCS）方法和内部实时 Calypso 信标轨迹或外部呼吸信号（波纹管带）的 4DCBCT 重建。将实时信标质心（“目标”）运动与 4DCBCT 重建中分割的信标质心位置进行比较。我们检验了以下两个假设：（1）实际目标运动在重建中得到了准确的表示；（2）重建/呼吸信号组合在实时运动的表示中表现相似。
平均而言，目标运动在左-右（LR）、上-下（SI）和前-后（AP）方向上分别有 48%、25%和 40%的时间显著小于 4DCBCT 运动，分别超过 4DCBCT 运动 48%、25%和 40%的时间。LR、SI 和 AP 方向的平均低估分别为 1.7mm、4.2mm 和 2.5mm。在 LR 方向上，重建算法或呼吸信号之间没有差异（FDK 与 PICCS：P=0.47，Calypso 与波纹管：P=0.19），SI 方向（FDK 与 PICCS：P=0.49，Calypso 与波纹管：P=0.22）和 AP 方向（FDK 与 PICCS：P=0.62，Calypso 与波纹管：P=0.34）。
4DCBCT 扫描均低估了实时目标运动。4DCBCT 重建中重建算法和呼吸信号的选择不会对重建运动范围产生影响。
