Diffusion-weighted magnetic resonance imaging using different b-value combinations for the evaluation of treatment results after volumetric MR-guided high-intensity focused ultrasound ablation of uterine fibroids

Abstract

DWI could be useful for treatment evaluation after MR-HIFU of uterine fibroids. The ADC in fibroid tissue is influenced by the choice of b- values. Low b-values seem the best choice to emphasise perfusion effects after MR-HIFU.

Evaluation of Diffusion-Weighted Imaging and Apparent Diffusion Coefficient Mapping Using Different B-Values for Magnetic Resonanceguided Focused Ultrasound Surgery: A Preliminary Study for Uterine Fibroid and Adenomyoma

“…This observation was in agreement with previously published data, suggesting the lower b-value would have produced a better image contrast (17,23). The poorer image contrast of DWIs obtained with b-values of 600 s/mm² and 800 s/mm² can be ascribed to low signal-to-noise ratio due to shorter T2 relaxation times (25).…”

“…Since no significant difference was noticed between the contrast scores of DWIs and ADC maps of different b-values, there was no specified b-value to be considered as superior in delineating the ablated region at 12 months follow-up. Our results appear to contradict earlier reports (17,23) that suggested a better ADC map contrast was produced with higher b-values (400, 600 and 800 s/mm²) during 1 month follow-up due to the diffusion effects. Such differences noted can be ascribed to the different length of the follow-up period (1 month in the earlier reports against 12 months in our study).…”

“…Various studies have reported the use of DWI and apparent diffusion coefficient (ADC) mapping in monitoring and assessing the treatment outcomes of MRgFUS of the uterine fibroids and uterine artery embolization (17)(18)(19)(20)(21)(22)(23). However, the correlation between the quantitative volume measurements of the ablated fibroid or adenomyoma obtained from DWI or ADC map and post-contrast nonperfused volume (NPV) obtained from standard cT1WI are not known to be performed previously.…”

A feasibility study on monitoring the evolution of apparent diffusion coefficient decrease during thermal ablation

“…The origin of this decrease is still unknown. However, because this result was seen for both thermal and cryoablation lesions in the prostate, as well as in the treatment of other tissues such as uterine fibroids, 14,15 the decrease in ADC could be generalizable to loss of viability. Potential reasons for a decrease in ADC include decreased molecular activity due to protein denaturation, reduced cellular motility from loss of viability, and/or reduced perfusion from compromised vasculature.…”

“…Since this work was restricted to the treatment of healthy prostate tissue, treatments in different tissues, both healthy and cancerous, could help determine how generalizable this metric can be. Previous work in the fibroids 14,15 shows promise that ADC can also be a marker for thermal lesion formation in other organs.…”