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

Simona Morochnik,Eugene Ozhinsky,Viola Rieke,Matthew D Bucknor

doi:10.1080/02656736.2019.1698773

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.

Highlights

Magnetic resonance-guided focused ultrasound (MRgFUS), known as high-intensity focused ultrasound (HIFU), is a noninvasive ablation technique that has been successfully used for the treatment of uterine fibroids, bone metastases, and essential tremor.[1, 2]
MRgFUS is especially useful for desmoid tumors that are located in the lower extremity—this requires delicate technique as the tumors can grow to be quite large and often invade or grow proximally to neurovascular bundles
Five MRgFUS treatments of desmoid tumors were performed for this study with concurrent T2 acquisitions as outlined in the Materials and Methods

Summary

Introduction

Magnetic resonance-guided focused ultrasound (MRgFUS), known as high-intensity focused ultrasound (HIFU), is a noninvasive ablation technique that has been successfully used for the treatment of uterine fibroids, bone metastases, and essential tremor.[1, 2] More recently, focused ultrasound ablation has been investigated for indications such as treatment of focal breast lesions, osteoid osteomas, and desmoid tumors.[3, 4]Desmoid tumors are benign but locally aggressive monoclonal soft tissue tumors that arise from fibroblast cells. Magnetic resonance-guided focused ultrasound (MRgFUS), known as high-intensity focused ultrasound (HIFU), is a noninvasive ablation technique that has been successfully used for the treatment of uterine fibroids, bone metastases, and essential tremor.[1, 2] More recently, focused ultrasound ablation has been investigated for indications such as treatment of focal breast lesions, osteoid osteomas, and desmoid tumors.[3, 4]. MRgFUS is especially useful for desmoid tumors that are located in the lower extremity—this requires delicate technique as the tumors can grow to be quite large and often invade or grow proximally to neurovascular bundles

Methods

Results

Discussion

Conclusion