Computer Simulations for Applications of Magnetic Resonance Guided Focused Ultrasound Surgery (MRgFUS) of Uterine Fibroids
Uterine fibroids (UF)s are extremely common growths of the uterus, which despite generally being benign impose a considerable health burden: several hundred thousand hysterectomies for UF treatment are performed annually in North America. Magnetic resonance guided focused ultrasound surgery (MRgFUS), a noninvasive modality utilizing ultrasound energy to perform thermal ablation, has been used clinically as an alternative to hysterectomy to treat UFs since receiving clinical approval in North America and Europe nearly two decades ago. Despite the advantages of MRgFUS being uterine sparing and having a shorter recovery time compared to hysterectomy, some fibroids are difficult to treat with MRgFUS, causing centres to limit patient eligibility. Treatments are generally also lengthy, typically requiring hours to complete, which is expensive in terms of cost and resources because treatments take place in a magnetic resonance imaging (MRI) suite where temperature imaging is interspersed throughout the treatment in intervals typically lasting up to several minutes.Additional biophysical insights into clinically relevant aspects of treatments, along with model-based treatment planning (MBTP) using simulations to predict clinical temperature distributions, may prove useful in shortening treatment durations and expanding patient eligibility for UF MRgFUS treatments. In this thesis, the potential of computer simulations for applications in MBTP of MRgFUS treatments of UFs is explored and simulations are used to gain biophysical insights into clinical treatments. In the first study, simulation results and clinical thermometry data are compared to explore the ability of the simulations to predict clinically relevant aspects of the temperature distribution. Ultrasound attenuation and absorption of UF were found to have an important role in explaining difficulty in clinical heating. In the second study, ultrasound absorption and attenuation of human UF were estimated, and correlations to MRI properties were obtained. In the third study, explanations for discrepancies between ablated volumes predicted from clinical thermometry measurement versus those visualized on post-treatment contrast-enhanced images were sought by performing a simulation-based assessment. The assessment found contributions from thermal buildup and inter-sonication temperature distributions not monitored with thermometry. Collectively, these findings may prove useful in further optimization of clinical treatment strategies for MRgFUS of UF.
clinical results, computer simulation, HIFU, MRgFUS, treatment planning, uterine fibroids
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