MRI sequence optimisation methods to identify cranial nerve course for radiotherapy planning.

Area of Science:

• Medical Imaging
• Radiation Oncology
• Neuroscience

Background:

• Magnetic resonance imaging (MRI) offers superior visualization of organs at risk compared to computed tomography (CT) in radiation therapy planning.
• Diagnostic MRI sequences, like T2-weighted 3D SPACE, are being adapted for radiation therapy planning, particularly for cranial nerve identification in head and neck cancer treatment.

Purpose of the Study:

• To adapt a 3D isotropic T2 SPACE MRI sequence for radiation therapy planning, focusing on cranial nerve identification.
• To minimize image distortion and validate the protocol for clinical use in radiation therapy.

Main Methods:

• A 3D isotropic T2 SPACE sequence was modified for radiation therapy, incorporating techniques to minimize distortion such as spin-echo sequences, 3D distortion correction, isocentre scanning, and increased readout bandwidth.
• Radiation therapy positioning was addressed using small flex, 4-channel coils.
• Protocol validation involved assessing cranial nerve identification and distortion minimization in clinical settings and with an MRI QA phantom.

Main Results:

• The adapted MRI protocol successfully visualized normal anatomy of cranial nerves (CI-CIX) and demonstrated clinical utility in cases involving tumors near the skull base.
• In-house testing confirmed that increased bandwidths (600 Hz) resulted in minimal image displacement (<1 mm).

Conclusions:

• MRI integration in radiation therapy planning enhances treatment individualization and outcome prediction.
• Accurate cranial nerve identification through MRI allows for dose reduction, potentially decreasing late side effects like cranial neuropathy.
• This technology holds promise for expanded applications in future radiation therapy treatments.