Dwi Seno Kuncoro Sihono1, Michael Ehmann2, Sigrun Heitmann2, Sandra von Swietochowski2, Mario Grimm2, Judit Boda-Heggemann2, Frank Lohr3, Frederik Wenz2, Hansjörg Wertz2. 1. Department of Radiation Oncology, Universitaetsmedizin Mannheim, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany; Department of Physics, Faculty of Mathematics and Sciences, University of Indonesia, Kampus UI Depok, Indonesia. Electronic address: sihono@stud.uni-heidelberg.de. 2. Department of Radiation Oncology, Universitaetsmedizin Mannheim, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany. 3. Struttura Complessa di Radioterapia, Dipartimento di Oncologia, Az. Ospedaliero-Universitaria di Modena, Modena, Italy.
Abstract
PURPOSE/ OBJECTIVE: To determine intrafraction prostate motion during volumetric modulated arc therapy (VMAT) using transperineal ultrasound (US) real-time tracking. METHODS AND MATERIALS: 770 US monitoring sessions in 38 prostate cancer patients' VMAT treatment series were retrospectively evaluated. Intrafraction motion assessment of the prostate was based on continuous position monitoring with a 4-dimensional US system along the 3 directions: left-right (LR), anterior-posterior (AP), and inferior-superior (SI). The overall mean values and standard deviations (SD) along with random and systematic errors were calculated. RESULTS: The mean duration of each monitoring session was 254 s. The mean (μ), the systematic error (Σ), and the random error (σ) of intrafraction prostate displacement were μ = (0.01, -0.08, 0.15) mm, Σ = (0.30, 0.34, 0.23) mm, and σ = (0.59, 0.73, 0.64) mm in the LR, AP and SI directions, respectively. The percentage of treatments for which prostate displacement was ≤2 mm was 97.01%, 92.24%, and 95.77% in the LR, AP, and SI directions, respectively. At 60 s, a vector length of prostate displacement >2 mm was present in 0.67% of the data. The percentage increased to 2.42%, 6.14%, and 9.35% at 120 s, 180 s, and 240 s, respectively. CONCLUSIONS: The magnitudes of intrafraction prostate motion along the SI and AP directions were comparable. On average, the smallest motion was in the LR direction and the largest in AP direction. Most of the prostate displacements were within a few millimeters. However, with increasing treatment time (eg, during hypofractionation), larger 3-dimensional prostate displacements up to 18.30 mm could be observed. Shortening treatment time can reduce the impact of intrafraction motion and potentially allows smaller safety margins.
PURPOSE/ OBJECTIVE: To determine intrafraction prostate motion during volumetric modulated arc therapy (VMAT) using transperineal ultrasound (US) real-time tracking. METHODS AND MATERIALS: 770 US monitoring sessions in 38 prostate cancerpatients' VMAT treatment series were retrospectively evaluated. Intrafraction motion assessment of the prostate was based on continuous position monitoring with a 4-dimensional US system along the 3 directions: left-right (LR), anterior-posterior (AP), and inferior-superior (SI). The overall mean values and standard deviations (SD) along with random and systematic errors were calculated. RESULTS: The mean duration of each monitoring session was 254 s. The mean (μ), the systematic error (Σ), and the random error (σ) of intrafraction prostate displacement were μ = (0.01, -0.08, 0.15) mm, Σ = (0.30, 0.34, 0.23) mm, and σ = (0.59, 0.73, 0.64) mm in the LR, AP and SI directions, respectively. The percentage of treatments for which prostate displacement was ≤2 mm was 97.01%, 92.24%, and 95.77% in the LR, AP, and SI directions, respectively. At 60 s, a vector length of prostate displacement >2 mm was present in 0.67% of the data. The percentage increased to 2.42%, 6.14%, and 9.35% at 120 s, 180 s, and 240 s, respectively. CONCLUSIONS: The magnitudes of intrafraction prostate motion along the SI and AP directions were comparable. On average, the smallest motion was in the LR direction and the largest in AP direction. Most of the prostate displacements were within a few millimeters. However, with increasing treatment time (eg, during hypofractionation), larger 3-dimensional prostate displacements up to 18.30 mm could be observed. Shortening treatment time can reduce the impact of intrafraction motion and potentially allows smaller safety margins.
Authors: Daan M de Muinck Keizer; Jochem R N van der Voort van Zyp; Eline N de Groot-van Breugel; Bas W Raaymakers; Jan J W Lagendijk; Hans C J de Boer Journal: Phys Imaging Radiat Oncol Date: 2021-07-25