Motion prediction in MRI-guided radiotherapy based on interleaved orthogonal cine-MRI

Abstract

In-room cine-MRI guidance can provide non-invasive target localization during radiotherapy treatment. However, in order to cope with finite imaging frequency and system latencies between target localization and dose delivery, tumour motion prediction is required. This work proposes a framework for motion prediction dedicated to cine-MRI guidance, aiming at quantifying the geometric uncertainties introduced by this process for both tumour tracking and beam gating. The tumour position, identified through scale invariant features detected in cine-MRI slices, is estimated at high-frequency (25 Hz) using three independent predictors, one for each anatomical coordinate. Linear extrapolation, auto-regressive and support vector machine algorithms are compared against systems that use no prediction or surrogate-based motion estimation. Geometric uncertainties are reported as a function of image acquisition period and system latency. Average results show that the tracking error RMS can be decreased down to a [0.2; 1.2] mm range, for acquisition periods between 250 and 750 ms and system latencies between 50 and 300 ms. Except for the linear extrapolator, tracking and gating prediction errors were, on average, lower than those measured for surrogate-based motion estimation. This finding suggests that cine-MRI guidance, combined with appropriate prediction algorithms, could relevantly decrease geometric uncertainties in motion compensated treatments.

Multislice motion modeling forMRI‐guided radiotherapy gating

“…Furthermore the 0.5‐s 3D cine acquisition period would introduce prohibitive gating latency and the 5‐mm spatial resolution of the cine imaging would potentially limit the accuracy of target tracking. Seregni et al . developed a feature tracking model with temporal prediction and, separately, an internal to external correlation model similar to the 5D model.…”

Characterization of spatial distortion in a 0.35 T MRI-guided radiotherapy system

“…On-line magnetic resonance imaging (MRI) guidance for radiation therapy provides a number of potential benefits including excellent soft tissue contrast for precise alignment, target tracking for respiratory and cardiac motion compensation, (Cervino et al 2011, Stam et al 2012, Seregni et al 2016) monitoring of tumor progression or regression and normal tissue response with on-board functional imaging, (Kupelian and Sonke 2014, Nguyen et al 2014, Yang et al 2016) and treatment plan adaptation (Dowling et al 2012). However, inhomogeneities in the magnetic field due to imperfect shimming, eddy currents and non-linear gradients will adversely affect the scanner’s spatial integrity resulting in reduced targeting accuracy and potentially reducing dose calculation accuracy (Spees et al 2011, Walker et al 2015).…”

Motion management in particle therapy

“…In recent years, with the development of combined MR‐linac machines, there has been a trend toward Magnetic Resonance imaging (MRI) guided radiotherapy. It is believed that online MRI can provide a feedback loop to enable gating and beam tracking in clinical routine . Crijns et al.…”