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.

MRI T2 mapping assessment of T2 relaxation time in desmoid tumors as a quantitative imaging biomarker of tumor response: preliminary results

“…Morochnik et al, described changes in T2 mapping values in desmoid tumors treated with cryoablation. In those cases, increases in T2 relaxation time were observed, reflecting the cryoablationinduced liquefactive tumor necrosis (23). Similar increases in T2 hyperintensity have been observed in DF treated locally with cryoablation.…”

MR Thermometry during Transcranial MR Imaging–Guided Focused Ultrasound Procedures: A Review

“…67,68 However, intraprocedural postcontrast NPV assessment is generally not performed due to safety concerns regarding heating of the contrast as well as potential errors of MRT. [69][70][71] In clinical practice, DWI is obtained postprocedurally to estimate the ablation zone.…”

“…Multiple additional MR imaging methods are being developed and evaluated to detect treatment effects after MRgFUS, including T1/T2 mapping, magnetization transfer ratio, amide proton transfer, and MR elastography. 70,73,74 A combination of emerging multiparametric MR imaging techniques may be needed to obtain a more comprehensive evaluation of tissue-level changes during and after MRgFUS.…”