A Preclinical System Prototype for Focused Microwave Thermal Therapy of the Breast

Abstract

A preclinical prototype of a transcutaneous thermal therapy system has been developed for the targeted treatment of breast cancer cells using focused microwaves as an adjuvant to radiation, chemotherapy, and high intensity focused ultrasound (HIFU). The prototype system employs a 2D array of tapered microstrip patch antennas operating at 915 MHz to focus continuous-wave microwave energy transcutaneously into the pendent breast suspended in a coupling medium. Prior imaging studies are used to ascertain the material properties of the breast tissue, and this data is incorporated into a multiphysics model. Time-reversal techniques are employed to find a solution (relative amplitudes and phase) for focusing at a given location. Modeling tests of this time-reversal focusing method have been performed which demonstrate good targeting accuracy within heterogeneous breast tissue. Experimental results using the laboratory prototype to perform focused heating in tissue-mimicking gelatin phantoms have demonstrated 1.5 cm diameter focal spot sizes and differential heating at the desired focus sufficient to achieve an antitumor effect confined to the target region.

Design of a compact antenna with flared groundplane for a wearable breast hyperthermia system

“…The chest wall, modelled as a 140 mm  140 mm layer of 15-mm thick fat adjacent to 5-mm thick muscle (with the same thermal properties as fibroglandular tissue as in [41] and dielectric properties as in [42]), terminated the top wall of the breast phantom, as shown in Figure 1. The temperature of the water was kept constant at 20 C. Frequency dependent dielectric and thermal properties for 1620 [21] 690 [41] 350 [41] water, skin, fibroglandular and fat tissue were implemented in the model, as listed in Table 1. Perfect electric conductor boundary conditions were applied on all copper surfaces.…”

“…Fenn et al [19] developed an approach for focused microwave hyperthermia involving multiple waveguides compressing the targeted breast. Stang et al have developed a rigid cylindrical array of patch antennas for non-invasive high-temperature thermal therapy and imaging of breast targets [20]. Ultra-wideband strategies for non-invasive delivery of microwave hyperthermia have also been explored [21].…”

Focusing microwave hyperthermia in realistic environment for breast cancer treatment

“…The impractical source for focusing microwave power has drawn researchers' attention recently [79,80]. In the most recent effort, instead of using point source, a circular array of antennas was placed around a realistic breast model [80].…”

“…In the most recent effort, instead of using point source, a circular array of antennas was placed around a realistic breast model [80]. This work presents a preclinical hyperthermia system for the targeted treatment of breast cancer using an image-based time-reversal focusing technique.…”

“…The simulated and experimental results of the preclinical system show the potential to improve non-invasive focusing microwave heating for thermal therapy. However the close inspection of the approach presented in [80] indicates that by operating at the low microwave frequency of 915 MHz, the system has a limited focusing capability. Thus, a high power (around 11 W per channel) was needed to achieve the required temperature of 42℃.…”