Microwave-induced thermoacoustic imaging (MTAI) has emerged as a potential biomedical imaging modality with over 20-year growth. MTAI typically employs pulsed microwave as the pumping source, and detects the microwave-induced ultrasound wave via acoustic transducers. Therefore, it features high acoustic resolution, rich electromagnetic contrast, and large imaging depth. Benefiting from these unique advantages, MTAI has been extensively applied to various fields including pathology, biology, material and medicine. Till now, MTAI has been deployed for a wide range of biomedical applications, including cancer diagnosis, joint evaluation, brain investigation and endoscopy. This paper provides a comprehensive review on (1) essential physics (endogenous/exogenous contrast mechanisms, penetration depth and resolution), (2) hardware configurations and software implementations (excitation source, antenna, ultrasound detector and image recovery algorithm), (3) animal studies and clinical applications, and (4) future directions.

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