Focused microwave breast hyperthermia (FMBH) can provide accurate and cost-effective treatment of breast tumors with low side effect. A clinically feasible FMBH system requires a guidance technique to monitor the microwave power distribution in the breast. Although MRI has been used for monitoring hyperthermia, it is still hindered by high cost, low availability, long imaging time, and incompatibleness of the MRI equipment with the hyperthermia system. Microwave-induced compressive thermoacoustic tomography (CTT) is a suitable guidance approach for FMBH, which is more cost-effective and time-efficient than MRI and obviates the incompatible issue. However, no experimental validation based on a realized FMBH-CTT system has been reported, which greatly hinders the further advancement of this novel approach. In this work, we developed a preclinical system prototype for the FMBH-CTT technique, containing a microwave phased antenna array, a multi-channel microwave source, an ultrasound transducer array and associated data acquisition module. Experimental results employing homogeneous and inhomogeneous breast-mimicking phantoms demonstrate that the CTT technique can offer reliable guidance for the entire process of FMBH. This means the iterative microwave focusing process of FMBH, i.e., from unfocused to focused microwave power distribution, can be faithfully guided by CTT. In addition, small phase noises in the multi-channel microwave source do not deteriorate the overall guidance performance of the system prototype. The realized preclinical FMBH-CTT system prototype is capable for noninvasive, accurate and low-side-effect breast tumor treatment with effective guidance and monitoring. The experimentally validated FMBH-CTT system prototype provides a feasible paradigm for CTT guided FMBH, establishes a practical platform for future improvement of this technique, and paves the way for potential clinical translation. The CTT guidance mechanism also holds potential to be applied in other types of hyperthermia, such as liver cancer, prostate cancer and brain cancer.
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