Interfractional variability of respiration-induced esophageal tumor motion quantified using fiducial markers and four-dimensional cone-beam computed tomography.

To investigate the interfractional variability of respiration-induced esophageal tumor motion using fiducial markers and four-dimensional cone-beam computed tomography (4D-CBCT) and assess if a 4D-CT is sufficient for predicting the motion during the treatment. Twenty-four patients with 63 markers visible in the retrospectively reconstructed 4D-CBCTs were included. For each marker, we calculated the amplitude and trajectory of the respiration-induced motion. Possible time trends of the amplitude over the treatment course and the interfractional variability of amplitudes and trajectory shapes were assessed. Further, the amplitudes measured in the 4D-CT were compared to those in the 4D-CBCTs. The amplitude was largest in the cranial-caudal direction of the distal esophagus (mean: 7.1mm) and proximal stomach (mean: 7.8mm). No time trend was observed in the amplitude over the treatment course. The interfractional variability of amplitudes and trajectory shapes was limited (mean: ≤1.4mm). Moreover, small and insignificant deviation was found between the amplitudes quantified in the 4D-CT and in the 4D-CBCT (mean absolute difference: ≤1.0mm). The limited interfractional variability of amplitudes and trajectory shapes and small amplitude difference between 4D-CT-based and 4D-CBCT-based measurements imply that a single 4D-CT would be sufficient for predicting the respiration-induced esophageal tumor motion during the treatment course.

Jin P ，Hulshof MCCM ，van Wieringen N ，Bel A ，Alderliesten T ... -  《-》

Setup strategies and uncertainties in esophageal radiotherapy based on detailed intra- and interfractional tumor motion mapping.

Detailed knowledge of target motion is important for improved accuracy and decreased toxicity of esophageal cancer radiotherapy. This study uses the 3D trajectories of implanted markers during setup CBCT scans to investigate the intra- and interfractional tumor motion in esophageal cancer radiotherapy. For 21 esophageal cancer patients with implanted fiducial markers, 60-s 3D marker trajectories were estimated from the 2D marker positions in the projections of daily setup CBCT scans by a probability-based method. The motion was separated into respiratory and cardiac components by frequency analysis and motion magnitude (2nd-98th percentile) was extracted for each marker. The mean motion was calculated over all markers. The daily mean setup interfraction error for bony-anatomy and soft-tissue setup was used to estimate the margin accounting for interfractional motion. A total of 1036 marker trajectories were extracted using 427 CBCT scans and 63 markers. The mean motion magnitude over all markers was 2.9 mm (left-right (LR)), 8.8 mm (cranio-caudal (CC)) and 4.1 mm (anterior-posterior (AP)) for the full motion during CBCT acquisition with mean magnitudes of 2.7 mm (LR), 8.4 mm (CC) and 3.5 mm (AP) for respiratory motion and 1.0 mm (LR), 1.5 mm (CC) and 1.4 mm (AP) for cardiac motion. Substantial daily marker shifts relative to bones resulted in margins of 8.9 mm (LR), 9.5 mm (CC), and 7.3 mm (AP). Soft-tissue based setup in and near the CTV combined with rescanning of patients with anatomical changes reduced the margins to 6.9 mm (LR), 6.8 mm (CC), and 5.6 mm (AP). Esophageal tumor motion was mapped with unprecedented detail throughout the radiotherapy course. Respiratory motion dominated and was largest in the CC direction. Soft-tissue matching and an adaptive strategy reduced interfractional margins by 2-3 mm compared to bony-anatomy matching.

Hoffmann L ，Poulsen PR ，Ravkilde T ，Bertholet J ，Kruhlikava I ，Helbo BL ，Schmidt ML ，Nordsmark M ... -  《-》

Differences in respiratory-induced pancreatic tumor motion between 4D treatment planning CT and daily cone beam CT, measured using intratumoral fiducials.

Lens E ，van der Horst A ，Kroon PS ，van Hooft JE ，Dávila Fajardo R ，Fockens P ，van Tienhoven G ，Bel A ... -  《-》

Tumor motion changes in stereotactic body radiotherapy for liver tumors: an evaluation based on four-dimensional cone-beam computed tomography and fiducial markers.

Shimohigashi Y ，Toya R ，Saito T ，Ikeda O ，Maruyama M ，Yonemura K ，Nakaguchi Y ，Kai Y ，Yamashita Y ，Oya N ，Araki F ... -  《Radiation Oncology》

Investigation of respiration induced intra- and inter-fractional tumour motion using a standard Cone Beam CT.

Gottlieb KL ，Hansen CR ，Hansen O ，Westberg J ，Brink C ... -  《-》