Hyperthermia has been used extensively and successfully in the treatment of solid tumors. For accessible solid tumors with impressive efficacy not amenable to surgery, ablative hyperthermia (>55°C for 20 s to 15 min) has been used as a definitive treatment. By contrast, for both radiotherapy and chemotherapy, mild hyperthermia (40-45°C for up to 1 hour) has been shown useful as an adjuvant. It induces a multitude of changes to the physiology and biology of the target tumor that improve the effectiveness of other treatments and make mild hyperthermia synergistic with many chemotherapeutic agents and radiation therapies. Many currently available devices, including but not limited to radiofrequency (RF) applicators, microwave applicators, hot water baths, lasers, and magnetic fluids, can heat the target tissue to the mild hyperthermic range. However, these suffer from drawbacks: limited or superficial heating, hot and cold spots, inaccurate or spatially uneven heating, and a lack of spatiotemporal feedback control.
To resolve these challenges and safely heat anatomical regions with Magnetic Resource-Guided High-Intensity Focused Ultrasound (MR-HIFU), researchers at the National Institutes of Health Clinical Center (NIH CC) have developed a multi-foci sonication technology for sustained mild hyperthermia over an extended period. The multi-foci sonication approach controls temperature accuracy and uniformity, confines heated volumes, and lower peaks acoustic pressures in the heated region. The refined multi-foci sonication heating strategy is combined with a heating algorithm, and results in accurate and precise heating within the targeted region with significantly lower acoustic pressures and spatially more confined heating in the beam path direction (compared to the single focus sonication method). This multi-foci sonication hyperthermia technology may be implemented on a clinical MR-HIFU platform for oncology therapy.
The multi-foci heating strategy may also have other applications such as in MR-HIFU thermal ablations. The more even thermal profile may be utilized in drug delivery or gene therapy to obtain a more even drug release or gene expression, which can be combined with large area sonication strategies. Moreover, the multi-foci sonication approach can be combined with any control algorithm with an additional constraint on the allowed peak pressure which can be estimated based on quick Rayleigh integral evaluation or more sophisticated acoustic simulations in heterogeneous media.
This technology is currently available for licensing opportunities.
- Improved treatments for the target tumor
- Synergistic application with chemotherapeutic agents and radiation therapies
- Utilization in drug delivery or gene therapy
- Can be combined with any control algorithm
- Compared to the single focus approach, multi-foci sonications showed significantly lower, 67% reduction, peak acoustic pressures in simulations and hydrophone measurements
- Heated regions were significantly shorter in the beam path direction, 35% reduction, for multi-foci sonications
Matthew R Dreher (NIH CC)
Partanen A, et al. Reduction of peak acoustic pressure and shaping of heated region by use of multi-foci sonications in MR-guided high-intensity focused ultrasound mediated mild hyperthermia. [PMID 23298120]
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