  A clinical case study of high-intensity focused ultrasound (HIFU) treatment
in the uterine fibroid was conducted. During the therapy, poor heating efficacy
was observed which could be attributed to several factors such as the local
perfusion rate, patient-specific anatomy or changes in acoustic parameters of
the ultrasound field. In order to determine the cause of the diminished
heating, perfusion analyses and ultrasound simulations were conducted using the
magnetic resonance imaging (MRI) data from the treatment. The perfusion
analysis showed high local perfusion rate in the myoma (301.0 +- 25.6 mL/100
g/min) compared to the surrounding myometrium (233.8 +- 16.2 mL/100 g/min). The
ultrasound simulations did not show large differences in the focal point shape
or the acoustic pressure (2.07 +- 0.06 MPa) when tilting the transducer.
However, a small shift (-2.2 +- 1.3 mm) in the axial location of the focal
point was observed. The main causes for the diminished heating were likely the
high local perfusion and ultrasound attenuation due to the deep location of the
myoma.
