Comparison between diffusion‐weighted imaging, ‐weighted, and postcontrast ‐weighted imaging after MR‐guided, high intensity, focused ultrasound treatment of uterine leiomyomata: Preliminary results

Abstract

Purpose:To investigate the comparison between diffusion-weighted imaging ͑DWI͒, T 2 -weighted imaging, ͑T 2 WI͒ and contrast T 1 -weighted imaging ͑cT 1 WI͒ in uterine leiomyoma following treatment by magnetic resonance imaging-guided, high intensity focused ultrasound surgery ͑MRg-HIFUS͒. Methods: Twenty one patients ͑45Ϯ 5 yrs͒ with clinical symptoms of uterine leiomyoma ͑fibroids͒ were treated by MRg-HIFUS using an integrated 1.5T MRI-HIFUS system. MRI parameters consisted of DWI, T 2 WI, and T 1 -weighted fast spoiled gradient echo before and after contrast. The post-MRg-HIFUS treatment volume in the fibroid was assessed by cT 1 WI and DWI. Trace apparent diffusion coefficient maps were constructed for quantitative analysis. The regions of the treated uterine tissue were defined by a semisupervised segmentation method called the "eigenimage filter," using both cT 1 WI and DWI. Signal-to-noise ratios were determined for the T 2 WI pretreatment images. Segmented regions were tested by a similarity index for congruence. Descriptive, regression, and Bland-Altman statistics were calculated. Results: All the patients exhibited heterogeneously increased DWI signal intensity localized in the treated fibroid regions and were colocalized with the cT 1 WI defined area. The mean pretreatment T 2 WI signal intensity ratios were T 2 WI/ muscle= 1.8Ϯ 0.7 and T 2 WI/ myometrium= 0.7Ϯ 0.4. The congruence between the regions was significant, with a similarity of 84% and a difference of 8% between the regions. Regression analyses of the cT 1 WI and DWI segmented treatment volumes were found to be significantly correlated ͑r 2 = 0.94, p Ͻ 0.05͒ with the linear equation, ͑cT 1 WI͒ = 1.1͑DWI͒ − 0.66. There is good agreement between the regions defined by cT1WI and DWI in most of the cases as shown from the Bland-Altman plots. Conclusions: Diffusion-weighted imaging exhibited excellent agreement, congruence, and correlation with the cT 1 WI-defined region of treatment in uterine fibroid. Therefore, DWI could be useful as an adjunct for assessing treatment of uterine fibroids by MRg-HIFUS.

MRI methods for the evaluation of high intensity focused ultrasound tumor treatment: Current status and future needs

“…Similar to the ex vivo study a significant ADC increase was observed instantly after HIFU treatment of subcutaneous mouse tumors and muscle tissue . In contrast, a significant decrease in ADC was found directly after treatment of uterine fibroids (Fig. A).…”

“…Jacobs et al used a multiparametric analysis using diffusion‐weighted and contrast‐enhanced T 1 ‐weighted images to segment successfully treated and nontreated tissue directly after HIFU treatment of uterine fibroids. Excellent agreement was observed between the segmentations based on both MRI methods . We have recently performed cluster analysis on multiparametric MRI data obtained after HIFU treatment of subcutaneous mouse tumors.…”

Development of a high-field MR-guided HIFU setup for thermal and mechanical ablation methods in small animals

“…Tissue response might become more apparent some hours after treatment [29]. Next to T2W MR imaging, other MR imaging techniques such as (dynamic) contrast-enhanced MR imaging, diffusion weighted, or T2* weighted MR imaging could be used for treatment evaluation and follow-up [21,[30][31][32][33]. It has previously been shown that the permeability of vessels increases, or the vessels are destroyed by mechanical destruction for example due to cavitation effects [8].…”

Assessment of acute thermal damage volumes in muscle using magnetization‐prepared 3D T2‐weighted imaging following MRI‐guided high‐intensity focused ultrasound therapy

“…Native T 1 ‐weighted images also have a zonal appearance that matches histology but has lower contrast . Diffusion‐weighted imaging (DWI) and apparent diffusion coefficient (ADC) mapping depict a mix of increased ADC due to disruption of cell membranes, and decreased ADC due to cell swelling and vascular shutdown . Intravoxel incoherent motion (IVIM) estimates tissue perfusion in addition to diffusion, and may improve specificity .…”