Super-resolution T2-weighted 4D MRI for image guided radiotherapy

Area of Science:

• Medical Imaging
• Radiotherapy Physics
• Image Reconstruction

Background:

• Four-dimensional T2-weighted MRI (4D-T2w MRI) offers superior soft-tissue contrast for radiotherapy planning.
• Current slice-selective implementations suffer from thick slices and artifacts due to data incompleteness and breathing motion.

Purpose of the Study:

• To develop a method for calculating midposition and 4D-T2w MRI of the whole thorax from continuously acquired 2D T2w MRI.
• To address limitations of current 4D-T2w MRI techniques in radiotherapy treatment planning.

Main Methods:

• A novel method was developed using image-derived respiratory surrogates, deformable image registration, and super-resolution reconstruction.
• Orthogonal 2D-T2w MRI data were continuously acquired and processed to generate whole-thorax midposition and 4D-T2w images.
• The minimum number of dynamic acquisitions required for representative midposition images was assessed through retrospective subsampling.

Main Results:

• Super-resolution 4D-T2w MRI (1.0 mm isotropic resolution, 8 respiratory phases) reduced data incompleteness and stitching artifacts.
• Experiments with a respiratory motion phantom showed a minor underestimation of motion range.
• Midposition diaphragm differences were <1.1 mm compared to the full dataset, with 10 dynamic acquisitions found sufficient.

Conclusions:

• A motion-modeling and super-resolution method was successfully developed.
• This method enables the calculation of high-quality 4D/midposition T2w MRI from orthogonal 2D T2w MRI.
• The technique improves image quality and potentially enhances radiotherapy treatment planning.