Photoacoustic-Based-Close-Loop Temperature Control for Nanoparticle Hyperthermia

Goal: Hyperthermia therapy requires tight temperature control to achieve selective killing of cancerous tissue with minimal damage on surrounding healthy tissues. Methods: To this end, accurate temperature monitoring and subsequent heating control are critical. However, an economic, portable, and real-time temperature control solution is currently lacking. To bridge this gap, we present a novel portable close-loop system for hyperthermia temperature control, in which photoacoustic technique is proposed for noninvasive real-time temperature measurement. Exploiting the high sensitivity of photoacoustics, the temperature is monitored with an accuracy of around 0.18 degrees C and then fed back to a controller implemented on field programmable gate array (FPGA) for temperature control. Dubbed as portable hyperthermia feedback controller (pHFC), it stabilizes the temperature at preset values by regulating the hyperthermia power with a proportional-integral-derivative (PID) algorithm; and to facilitate digital implementation, the pHFC further converts the PID output into switching values (0 and 1) with the pulse width modulation(PWM) algorithm. Results: Proof-of-concept hyperthermia experiments demonstrate that the pHFC system is able to bring the temperature from baseline to predetermined value with an accuracy of 0.3 degrees and a negligible temperature overshoot. Conclusion: The pHFC can potentially be translated to clinical applications with customized hyperthermia system design. Significance: This paper can facilitate future efforts in seamless integration of close-loop temperature control solution and various clinical hyperthermia systems.