Thermal Ablation
Thermal ablation, the most clinically advanced bioeffect of focused ultrasound, produces cell death in a targeted area with minimal damage to the surrounding tissue.
Tissue damage can be accurately controlled using a range of focused ultrasound transducers with different sonication sizes. Magnetic resonance imaging allows for the monitoring of temperature rise in real time, allowing quantification of the therapeutic dose.
Alternatively, ultrasound imaging and tissue characterization techniques (e.g. elastography) can be used for treatment monitoring for many clinical applications. Depending on the equipment and parameters used, the volume of focused ultrasound lesions can be as small as a grain of rice (10 cubic millimeters). This allows for an extremely localized treatment and a sharp border between treated and untreated areas.
For treatment of larger structures such as tumors, multiple sonications can be combined to encompass the entire volume. A cooling period between sonications is often required to prevent unwanted heating of surrounding tissue. Therefore, the treatment of very large volumes can be time-consuming. However, optimized scanning algorithms and the use of spiral sonications are techniques that have been employed to reduce the time of treatments.
Focused ultrasound’s thermal ablation effect has been the most widely explored clinically, and may be used to noninvasively treat a variety of clinical conditions including symptomatic uterine fibroids; tumors in the prostate, breast, and liver; low back pain; and brain disorders such as essential tremor, Parkinson’s disease, and neuropathic pain among many other conditions.
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