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 ... -  《-》

The use of tumour markers in oesophageal cancer to quantify setup errors and baseline shifts during treatment.

To prospectively evaluate the feasibility of solid gold marker placement in oesophageal cancer patients and to quantify inter-fractional and intra-fractional (baseline shift) marker motion during radiation treatment. Radiotherapy target margins and matching strategies were investigated. Thirty-four markers were implanted by echo-endoscopy in 10 patients. Patients received a planning 4D CT, daily pre-treatment cone-beam CT (CBCT) and a post-treatment CBCT for at least five fractions. For fractions with both pre- and post-treatment CBCT, marker displacement between planning CT and pre-treatment CBCT (inter-fractional) and between pre-treatment and post-treatment CBCT (intra-fractional; only for fractions without rotational treatment couch correction) were calculated in left-right (LR), cranio-caudal (CC) and anterior-posterior (AP) direction after bony-anatomy and soft-tissue matching. Systematic/random setup errors were estimated; treatment margins were calculated. No serious adverse events occurred. Twenty-three (67.6%) markers were visible during radiotherapy (n = 3 middle oesophagus, n = 16 distal oesophagus, n = 4 proximal stomach). Margins for inter-fractional displacement after bony-anatomy match depended on the localisation of the primary tumour and were 11.2 mm (LR), 16.4 mm (CC) and 8.2 mm (AP) for distal markers. Soft-tissue matching reduced the CC margin for these markers (16.4 mm to 10.5 mm). The mean intra-fractional shift of 12 distal markers was 0.4 mm (LR), 2.3 mm (CC) and 0.7 mm (AP). Inclusion of this shift resulted in treatment margins for distal markers of 12.8 mm (LR), 17.3 mm (CC) and 10.4 mm (AP) after bony-anatomy matching and 12.4 mm (LR), 11.4 mm (CC) and 9.7 mm (AP) after soft-tissue matching. This study demonstrated that the implantation of gold markers was safe, albeit less stable compared to other marker types. Inter-fractional motion was largest cranio-caudally for markers in the distal oesophagus, which was reduced after soft-tissue compared to bony-anatomy matching. The impact of intra-fractional baseline shifts on margin calculation was rather small.

Thomas M ，De Roover R ，van der Merwe S ，Lambrecht M ，Defraene G ，Haustermans K ... -  《Clinical and Translational Radiation Oncology》

Adaptive radiotherapy and the dosimetric impact of inter- and intrafractional motion on the planning target volume for prostate cancer patients.

Böckelmann F ，Putz F ，Kallis K ，Lettmaier S ，Fietkau R ，Bert C ... -  《-》

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 ... -  《-》

Liver motion during cone beam computed tomography guided stereotactic body radiation therapy.

Park JC ，Park SH ，Kim JH ，Yoon SM ，Song SY ，Liu Z ，Song B ，Kauweloa K ，Webster MJ ，Sandhu A ，Mell LK ，Jiang SB ，Mundt AJ ，Song WY ... -  《MEDICAL PHYSICS》