T2 mapping as a predictor of nonperfused volume in MRgFUS treatment of desmoid tumors

Abstract

Objective: The objective of this study was to develop an alternative method of non-contrast monitoring of tissue ablation during focused ultrasound treatment. Desmoid tumors are benign but locally aggressive soft tissue tumors that arise from fibroblast cells. Magnetic resonance-guided focused ultrasound (MRgFUS) has emerged as an alternative to conventional therapies, showing promising results in reduction of tumor volume without significant side effects. The gold-standard assessment of the reduction of viable tumor volume post-treatment is non-perfused volume (NPV) and evaluation of NPV is typically performed with post-treatment gadolinium enhanced MR imaging. However, as gadolinium cannot be repeatedly administered during treatments, there is a need for alternative non-contrast monitoring of the tissue to prevent over and under treatment.

Methods: Double-echo and multi-echo images were acquired before, during and after the MRgFUS treatment. T2 maps were generated with an exponential fit and T2 maps were compared to post-treatment post-contrast images.

Results: In all five MRgFUS treatment sessions, T2 mapping showed excellent qualitative agreement with the post-contrast NPV.

Conclusions: T2 mapping may be used to visualize the extent of ablation with focused ultrasound and can be used as a predictor of NPV prior to the administration of contrast during the post-treatment assessment.

Keywords:

• Desmoid tumors
• T2 mapping
• MRgFUS
• HIFU
• thermal ablation

Acknowledgments

The authors would like to thank Misung Han for the help with protocol optimization and David Newitt for his help with multi-echo fitting parameters.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This study has been funded by NIH R00 HL097030 and by GE Healthcare.