Therapeutic MRI-guided High Intensity Focused Ultrasound Ablation of Uterine Fibroids with Volumetric Heating Technique: Early Clinical Experience in South Korea

Introduction: A recent development in the treatment of uterine fibroids is the use of magnetic resonance guided high intensity focused ultrasound (MR-HIFU), which has been tested in several clinical trials and has been approved for clinical use in several countries In a traditional MR-HIFU treatment, a single focal point is iteratively sonicated at a time until the desired volume is ablated, with each sonication followed by a cooling period. The efficiency of this point-by-point method of ablation remains limited since a relatively large part of the energy deposited is lost via heat diffusion out of the small targeted region without being utilized for ablation. Recently, as an alternative sonication method in MR-HIFU treatment, Köhler et al demonstrated the applicability and usefulness of the volumetric sonication method under volumetric MRI thermometry in-vivo on a large animal model by comparing the resulting non-perfused volume of each sonication to the lethal thermal dose volume calculated on-line from MRI temperature maps. This method efficiently utilizes the inherent heat diffusion by electronically switching the focal point between a number of predetermined locations situated at outwards-moving concentric circles with diameters of upto 16 mm. The aim of this study was to describe our early experience using this volumetric sonication method with feedback control under volumetric MRI thermometry for the ablation of uterine fibroids.