Technical developments for real-time MRI-guided HDR brachytherapy

Abstract

Magnetic resonance imaging (MRI) may be an ideal imaging modality for real-time guidance and verification of high dose rate (HDR) brachytherapy. MRI provides superior tissue contrast and is currently applied for manual catheter reconstruction and treatment planning. However, techniques for real-time treatment verification are not clinically available. MRI may be an ideal imaging modality for real-time guidance and verification of the treatment, as it allows visualization of the anatomy as well as visualization and detection of interventional devices. We have proposed an MRI-guided HDR brachytherapy workflow in which we apply MR-based source localization for reconstruction of the source dwell positions and for real-time treatment verification. In this scenario, the patient is positioned inside the MRI scanner during the full treatment. For this purpose, the impact of the magnetic field on the dose distribution was investigated. This impact was shown to be negligible, allowing the patient to be positioned inside the MRI scanner during irradiation. Furthermore, a prototype MR-conditional afterloader was developed and tested. Simultaneous functioning of the MR-conditional afterloader and a 1.5 T MRI system was demonstrated, allowing the acquisition of MR images while simultaneously using the afterloader. Additionally, a method for localization of the HDR brachytherapy source and a titanium needle was proposed. By simulating the MRI artifacts induced by the object, followed by template matching between the simulated artifact and the MRI artifact, the object position could be determined. This leads to an MRI-guided HDR brachytherapy workflow where we apply automatic reconstruction of the source dwell positions and real-time treatment verification.