Deep learning-based 3D in vivo dose reconstruction with an electronic portal imaging device for magnetic resonance-linear accelerators: a proof of concept study

Abstract

Objective. To develop a novel deep learning-based 3D in vivo dose reconstruction framework with an electronic portal imaging device (EPID) for magnetic resonance-linear accelerators (MR-LINACs). Approach. The proposed method directly back-projected 2D portal dose into 3D patient coarse dose, which bypassed the complicated patient-to-EPID scatter estimation step used in conventional methods. A pre-trained convolutional neural network (CNN) was then employed to map the coarse dose to the final accurate dose. The electron return effect caused by the magnetic field was captured with the CNN model. Patient dose and portal dose datasets were synchronously generated with Monte Carlo simulation for 96 patients (78 cases for training and validation and 18 cases for testing) treated with fixed-beam intensity-modulated radiotherapy in four different tumor sites, including the brain, nasopharynx, lung, and rectum. Beam angles from the training dataset were further rotated 2–3 times, and doses were recalculated to augment the datasets. Results. The comparison between reconstructed doses and MC ground truth doses showed mean absolute errors <0.88% for all tumor sites. The averaged 3D γ-passing rates (3%, 2 mm) were 97.42%±2.66% (brain), 98.53%±0.95% (nasopharynx), 99.41%±0.46% (lung), and 98.63%±1.01% (rectum). The dose volume histograms and indices also showed good consistency. The average dose reconstruction time, including back projection and CNN dose mapping, was less than 3 s for each individual beam. Significance. The proposed method can be potentially used for accurate and fast 3D dosimetric verification for online adaptive radiotherapy using MR-LINACs.

Adoption of Hybrid MRI-Linac Systems for the Treatment of Brain Tumors: A Systematic Review of the Current Literature Regarding Clinical and Technical Features

“…Multiple experiences demonstrated excellent geometric accuracy 39 – 44 and dosimetric agreement 39 , 43 , 48 – 51 , 55 – 57 , 59 , 61 , 66 between simulation CTs and synCTs and the feasibility of adopting synCt to generate digitally reconstructed radiographs (DRRs) for IGRT. 46 , 47 , 59 , 66 , 69 Larger errors were identified at air and bone interfaces 44 , 55 – 57 , 67 possibly due to elevated intensity gradient and imperfect alignment between different imaging modalities.…”

“…Li et al 69 proposed a novel deep learning-based 3D in vivo dose reconstruction model using an electronic portal imaging device (EPID) for MRL: a pre-trained convolutional neural network (CNN) model yielded 3D-γ passing rates (3%, 2 mm) of 97.42% and MAE (%) of 0.88 for the brain.…”