How High Intensity Focused Ultrasound Works as a Treatment for Uterine Fibroids
MR guided focused ultrasound (MRgFUS) or Focused Ultrasound uses a combination of high-intensity focused ultrasound (hifu) and magnetic resonance (MR) Imaging to simultaneously image, treat and ablate uterine fibroid soft tissue. . Focused Ultrasound uses the ExAblateŽ 2000 system, which integrates high intensity focused ultrasound thermal ablation with the MR imaging capabilities.
Focused Ultrasound treatment is conducted while the patient lies on a patient table inside the Magnetic Resonance scanner. The patient is conscious, able to communicate with the physician during the treatment, and is provided with sedation medication prior to the first sonication. The entire procedure is planned and carried out from the Focused Ultrasound operator console located next to the MR workstation in the control room.
There are four major steps in the Focused Ultrasound treatment for uterine fibroids:
MR images are taken in three orientations to locate the target tissue and surrounding organs. These images are used to position the patient and determine the optimal path to the uterine fibroid tumor for the focused ultrasound beam.
The physician uses the MR images to identify the target anatomy and evaluates the structures surrounding the uterine fibroid to decide on a treatment region. Contours of the treatment area are drawn on the MR images and verified in three orientations. The ExAblateŽ 2000 system calculates the volume of the tissue to be treated and the number of treatment spots required. The beam path is visualized to verify that nothing interferes in any plane.
Treatment consists of multiple high-intensity focused ultrasound (hifu) "sonications" to ensure uterine fibroid tumor ablation. During each sonication, phase sensitive MR images are acquired, and real-time quantitative temperature maps are produced to confirm tissue heating. These temperature maps provide feedback to the physician who can then adjust treatment parameters to optimize thermal ablation. After each sonication, the transducer and MR scan plane are automatically directed to the succeeding point, and the process is repeated until the entire target volume has been treated.
At the end of treatment contrast enhanced MR images are acquired to measure the degree of contrast agent uptake. Regions without contrast agent uptake (non-perfused) have been destroyed by the thermal effects of the focused ultrasound. The physician can determine whether sufficient tissue has been treated, or if a repeat treatment is necessary.
