Proton, diffusion-weighted imaging, and Sodium( ²³Na) MRI of uterine leiomyomata after MR-guided high-intensity focused ultrasound: A preliminary study

Purpose: To determine the feasibility of using combined proton( ¹H), diffusion-weighted imaging(DWI), and sodium( ²³Na) magnetic resonance imaging(MRI) to monitor the treatment of uterine leiomyomata(fibroids). Materials and Methods: Eight patients with uterine leiomyomata were enrolled and treated using MRI-guided high-intensity frequency ultrasound surgery(MRg-HIFUS). MRI scans collected at baseline and posttreatment consisted of T2-, T1-, and ¹H DWI, as well as posttreatment ²³Na MRI. The ²³Na and ¹H MRi were coregistered using a replacement phantom method. Regions of interest in treated and untreated uterine leiomyoma tissue were drawn on ¹H MRI and DWI, wherein the tissue apparent diffusion coefficient of water(ADC) and absolute sodium concentrations were measured. Results: Regions of treated uterine tissue were clearly identified on both DWI and ²³Na images. The sodium concentrations in normal myometrium tissue were 35.8 ± 2.1 mmol(mM), in the fundus; 43.4 ± 3.8 mM, and in the bladder; 65.3 ± 0.8 mM with ADC in normal myometrium of 2.2 ± 0.3 × 10 ^-3mm ²/sec. Sodium concentration in untreated leiomyomata were 28 ± 5 mM, and were significantly elevated(41.6 ± 7.6 mM, P < 0.05) after treatment. Apparent diffusion coefficient values in the treated leiomyomata(1.30 ± 0.38 × 10 ^-3 mm ²/sec) were decreased compared to areas of untreated leiomyomata(1.75 ±-4048μ-4050μ36 × 10 ^-3 mm ²/sec; P = 0.04). Conclusion: Multiparametric imaging permits identification of uterine leiomyomata, revealing altered ²³Na MRI and DWI levels following noninvasive treatment that provides a mechanism to explore the molecular and metabolic pathways after treatment.