Discoveries During Use
Currently, the only proven imaging method to accurately quantify the heating produced during HIFU in vivo is Magnetic Resonance Imaging (MRI). MRI also has superior soft tissue contrast and can image in any orientation, making it the state of the art for guiding HIFU treatments. But MRI can't operate in real-time with HIFU, with the current state of the art being one image acquisition approximately every six seconds using a full scan of k-space. Researchers are working to reduce this image acquisition time through some of the speed enhancements common in other areas of MRI, including pulse sequences to scan a reduced k-space, constrained reconstruction, and model-based filtering using data from the bioheat equation.
The University of Minnesota produced a dual-mode ultrasound transducer that offers time resolution measured in milliseconds and offers closed-loop, real-time, intensity modulation based on continuous monitoring of tissue response to the HIFU beam. This method offers improved resolution over MRI.
Clinically, MRI-guided HIFU treatments have been tested for uterine fibroids, breast fibroadenomas, breast cancer, bone metastases, and liver tumors. The largest number of patients treated with MRI-guided HIFU have been with uterine fibroids.
USgFUS treatments have been approved with CE for wider range of benign and malignant tumors due to its higher power, precision and realtime monitoring system. The largest number of patients are uterine fibroids.
Ultrasound-guided HIFU treatments have been approved in Europe and Asia. MRI-guided treatments of uterine fibroids have been approved in Europe and Asia, and were granted FDA approval in the US in 2004.
Read more about this topic: High-intensity Focused Ultrasound
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