SU‐FF‐J‐145: Comparsion of Diffusion Weighted Imaging (DWI), T2‐Weighted and Post Contrast T1 Weighted Imaging After MR Guided High Intensity Focused Ultrasound Treatment of Uterine Leiomyomata: Preliminary Results

Purpose: To investigate the agreement between diffusion weighted imaging (DWI), T₂ weighted imaging(T₂WI), and contrast T₁ weighted imaging (cT₁WI) in uterine leiomyoma following treatment by magnetic resonance imaging guided high intensity focused ultrasound surgery (MRg‐HIFUS). Materials and Methods: Twenty‐one patients (45±3.8yrs) with clinical symptoms of uterine leiomyoma were treated by MRg‐HIFUS using an integrated 1.5T MRI‐FUS System. The post MRg‐HIFUS treatment volume in the leiomyoma was assessed by cT₁WI and DWI. MRI parameters consisted of DWI, T₂WI, and T₁ weighted fast spoiled gradient echo (FSPGR) before and after contrast. Trace apparent diffusion coefficient (ADC) maps were constructed for quantitative analysis. The regions of the treated uterine tissue were defined by a semi‐supervised segmentation method called the Eigenimage filter using both cT₁WI and DWI. Signal to noise ratios were determined for the T₂WI pretreatment images. Segmented regions were tested by similarity index for congruence. Descriptive, regression, and ANOVA statistics were completed. Results: All the patients exhibited heterogeneously increased DWI signal intensity localized in the treated leiomyoma regions and were colocalized with the cT₁WI defined area. The mean pretreatment T₂WI signal intensity ratios were T₂WI/muscle=1.8±0.7 and T₂WI/myometrium=0.7±0.4. The congruence between the regions was significant, with a similarity of 84% and a difference of 8% between the regions. Regression analysis of the cT₁WI and DWI segmented treatment volumes were found to be significantly correlated (r²=0.94,p<0.05) with the linear equation, (cT₁WI)=1.1(DWI)−0.66. Conclusion: Diffusion weighted imaging exhibited excellent correlation and agreement with the cT₁WI defined region of treatment in uterine leiomyoma. Therefore, DWI could be useful as an adjunct for assessing treatment of uterine leiomyomata by MRg‐HIFUS.