Potential benefit of MRI-guided IMRT for flank irradiation in pediatric patients with Wilms’ tumor

Abstract

Purpose/Objective: Flank irradiation for Wilms' tumor (WT) is currently performed at our institute using a cone-beam computed tomography-guided volumetric modulated arc (VMAT CBCT ) workflow. By adding real-time magnetic resonance imaging (MRI) guidance to the treatment, safety margins could be reduced. The study purpose was to quantify the potential reduction of the planning target volume (PTV) margin and its dosimetric impact when using an MRI-guided intensity modulated radiation therapy (IMRT MRI ) workflow compared to the VMAT CBCT workflow. Material/Methods: 4D-CT, MRI and CBCT scans acquired during preparation and treatment of 15 patients, were used to estimate both geometric, motion and patient set-up systematic (∑) and random (σ) errors for VMAT CBCT and IMRT MRI workflows. The mean PTV (PTV mean ) expansion was calculated using the van Herk formula. Treatment plans were generated using five margin scenarios (PTV mean ± 0, 1 and 2 mm). Furthermore, the IMRT MRI plans were optimized with a 1.5T transverse magnetic field turned-on to realistically model an MRI-guided treatment. Plans were evaluated using dose-volume statistics (p