MRI-guided radiation therapy systems can acquire cine images to dynamically monitor in-treatment internal organ motion. The complex head and neck (H&N) structures and low-contrast/resolution of on-board cine MRI images make automatic motion tracking a very challenging task. In this study, we proposed an integrated model-driven method to automatically track the in-treatment motion of the H&N upper airway, a complex and highly deformable region wherein internal motion often occurs in an either voluntary or involuntary manner, from cine MRI images for the analysis of H&N motion patterns.

Methodology

We firstly built a set of linked statistical shapes (including face, face-jaw, and face-jaw-palate) using principal component analysis from clinically approved contours delineated on a set of training data. The linked statistical shapes integrate explicit landmarks and implicit shape representation. Then, a hierarchical model-fitting algorithm was developed to align the linked shapes on the first image frame of a to-be-tracked cine sequence and to localize the upper airway region. Finally, a multi-feature level set contour propagation scheme was performed to identify the upper airway shape change, frame-by-frame, on the entire image sequence. The multi-feature fitting energy, including the information of intensity variations, edge saliency, curve geometry, and temporal shape continuity, was minimized to capture the details of moving airway boundaries.

Flowchart of the proposed integrated model-driven motion tracking method.

Results

The tracking results on one test sequence.

Upper airway and trachea motion patterns (in breathing) quantified by the cross-sectional area and boundary displacement, respectively.

Related Publications:

Hua Li*, Hsin-Chen Chen, Steven Dolly, Harold Li, Benjamin Fischer-Valuck, James Victoria, James Dempsey, Su Ruan, Mark A. Anastasio, Rojano Kashani, Olga Green, Vivian Rodriguez, Hiram Gay, Wade Thorstad, Sasa Mutic, “An Integrated-Model Driven Method for In-treatment Upper Airway Motion Tracking using Cine MRI in Head & Neck Radiation Therapy“, Medical Physics, 2016, Vol.43, No. 8, pp: 4700-4710.