Generating and monitoring mild hyperthermia using a ring array ultrasound transducer

ObjectiveTo demonstrate the feasibility of using a ring array ultrasound (US) transducer, guided by ultrasound tomography (UST), for generating and monitoring mild hyperthermia (MHTh).MethodsIn silico and in vitro experiments were designed to evaluate the efficacy of a ring array US transducer for generating MHTh and monitoring changes in temperature. In a series of in silico studies, we compared the acoustic focal profiles produced by a ring array US transducer transmitting at different frequencies and further investigated the effectiveness of UST-guidance in implementing aberration correction to enhance the focal profile. In vitro experiments evaluated the capability of using a ring array US transducer to generate and maintain MHTh and the accuracy of using UST to monitor temperature changes.ResultsThe simulations demonstrated that a ring array US transducer achieves symmetrical and localized acoustic focusing. In a heterogenous tissue model, a ring array US transducer achieved a superior acoustic focus by implementing aberration correction with guidance from UST. In vitro experiments demonstrated the capability of a ring array US transducer to generate MHTh in a tissue-mimicking phantom in an average of 117 +/- 18 s and subsequently maintain MHTh. Lastly, a ring array US transducer utilized UST to track temperature changes in a preheated water-filled inclusion while it passively cooled from 45 degrees C to 25 degrees C, with a maximum error of 0.58 degrees C.ConclusionA ring array US transducer can noninvasively generate and monitor MHTh, overcoming many limitations of current clinical systems. The closed geometry of the transducer is optimal for acoustic focusing and UST-guidance allows for improved aberration correction in a heterogenous medium. Utilizing UST thermometry with the same ring array US transducer will allow for implementing an image-guided, temperature-controlled, all-acoustic MHTh system.