S2782
RTT - RTT contouring, target definition, and treatment planning
ESTRO 2026
[1] Andratschke N, Willmann J, Appelt A, Alaymani N, Balermpas P, Baumert B, et al. European Society for Radiotherapy and Oncology and European Organisation for Research and Treatment of Cancer consensus on re-irradiation: definition, reporting, and clinical decision making. Lancet Oncol 2022;23: e469– 478. Keywords: Reirradiation, Image Registration, Dose Mapping Poster Discussion 2534 Breathing Motion Measurement Accuracy of 4DCT Based on Diaphragm Motion using 5DCT Claudia R Miller, Michael V Lauria, Drew Moghanaki, Jie
The measured diaphragm dome end-exhale to end- inhale motion ranged from 7.9-28.9mm and 12.2- 30.2mm for the 4DCT and 5DCT images, respectively. The inter-protocol measured dome motion difference average was 6.1±5.1mm (range 0.2-18.9mm) with an example shown in the figure. The average 5DCT surrogate calibration error was 4.6±0.02 % (range 1.1- 10.0%). The average 5D model 95th percentile residual errors were 2.36±0.59mm (range 1.37-7.67mm). Conclusion: We have found that 5DCT can provide reliable, motion- compensated thoracic images for use in radiation therapy TP. In this study, 5DCT measured diaphragm dome motion differed from that measured using 4DCT by up to 18.9mm. Without a way to quantitatively quantify the performance of each 4DCT individually, 5DCT has the potential to serve as a new standard by which to quantify tumor motion during reparation. Further data collection is ongoing to more thoroughly compare the two imaging modalities and assess whether 4DCT remains an acceptable option for TP. References: 1.Kwong Y, Mel AO, Wheeler G, Troupis JM. Four- dimensional computed tomography (4DCT): A review of the current status and applications [published online ahead of print 20150603]. J Med Imaging Radiat Oncol. 2015;59(5):545-554.2.Zhang Y, Yang J, Zhang L, Court LE, Balter PA, Dong L. Erratum: "Modeling respiratory motion for reducing motion artifacts in 4D CT images" [Med. Phys. 40, 041716 (13pp.) (2013)]. Med Phys. 2015;42(11):6768.3.Low DA, Parikh PJ, Lu W, et al. Novel breathing motion model for radiotherapy. Int J Radiat Oncol Biol Phys. 2005;63(3):921-929. Keywords: Motion-Management, 4DCT, 5DCT Transitioning to a new Treatment Planning System: Using RapidPlan to obtain high quality prostate plans in Ethos. Sanne Janssen, Martijn Kusters, Erik Van der Bijl Radiation Oncology, Radboud University Medical Center, Nijmegen, Netherlands Purpose/Objective: Our institute is transitioning from Pinnacle Auto- Planning (Philips) for prostate cancer Digital Poster 2680
Deng, Alan Lee, Ryan Andosca, Daniel A Low Radiation Oncology, UCLA, Los Angeles, USA
Purpose/Objective: 4DCT is widely accepted as the clinical standard for managing respiratory motion in radiation oncology treatment planning (TP). Despite this, 4DCT images often suffer from sorting-induced artifacts caused by irregular breathing leaving the subsequent images unusable for TP1,2. 5-dimensional CT (5DCT), a type of model-based CT (MBCT), has been proposed as a replacement to commercial 4DCT to address these issues3. This modality can not only provide sharper images but also numerous quality assurance metrics that validate its performance. Our objective was to evaluate the difference in performance between 4DCT and 5DCT. Material/Methods: The 5DCT protocol uses a motion model with 25 deformably registered free-breathing CTs alongside a respiratory signal to generate patient images with a measurement of accuracy and precision for each voxel. 5DCT can be used to model tumor motion over user-specified breathing amplitudes from which an internal target volume can be created for TP. 4DCT and 5DCT images were acquired in the same CT session for 20 patients with lung cancer under an IRB- approved protocol (IRB-11-0620). The imaged diaphragm dome is used to calibrate the 25 scans to the respiratory breathing signal that is collected. The distance between diaphragm dome peaks from end- exhale to end-inhale were measured between the modalities and compared. The root mean squared error percentage of the accuracy of the diaphragm dome fit to the breathing signal for the 5D images were also calculated. Further, 5D accuracy statistics were calculated based on the motion model residual reported in mm of error. Results:
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