Simultaneous acquisition of orthogonal plane cine imaging and isotropic 4D-MRI using super-resolution.

Introduction: Effective management of intrafraction motion is critical to the success of MR-guided radiation therapy (MR-gRT) of abdominal or thoracic tumors. Recent developments have proposed the use of cine MRI to monitor motion and 4D-MRI to aid in the reconstruction of dose actually delivered to patients. The present work aims to develop and perform preliminary testing of an imaging framework capable of simultaneously acquiring orthogonal plane cine imaging and isotropic resolution 4D-MRI volumes using super-resolution methods.

Methods: A pulse sequence was developed to acquire time-locked cine imaging in sagittal and coronal planes while additionally acquiring 4D-MRIs in both planes simultaneously. Isotropic resolution 4D-MRIs were reconstructed by combining information from the orthogonal volumes using super-resolution methods. This method was tested in phantoms and in liver cancer patients.

Results: Simultaneous cine imaging in sagittal and coronal planes allowed monitoring of respiratory motion and an accurate binning of concurrently acquired 4D imaging slices into the appropriate respiratory phases. The super-resolution reconstruction methods improved the resolution of the 4D-MRI along both of the low-resolution slice-select dimensions.

Conclusions: The development and preliminary testing of an imaging framework capable of acquiring simultaneous orthogonal cine imaging and super-resolution 4D-MRI was performed. The promising results merit further investigation for use in dose reconstruction during MR-guided radiation therapy.