Thermal Memory Based Photoacoustic Imaging of Temperature

Area of Science:

• Biomedical Optics
• Photoacoustic Imaging
• Thermal Therapy

Background:

• Accurate temperature mapping is critical for effective biomedical interventions.
• Conventional photoacoustic thermometry struggles with absolute temperature measurement in deep tissues due to unknown baseline temperatures and optical properties.

Purpose of the Study:

• To develop a novel photoacoustic thermometry method (TEMPT) for absolute temperature measurement.
• To overcome limitations of existing methods, particularly the need for baseline temperature and optical property information.

Main Methods:

• Utilized a thermal-energy-memory-based photoacoustic thermometry (TEMPT) approach.
• Employed nanosecond laser pulses and analyzed temperature-dependent thermal energy and Grüneisen parameter.
• Developed a self-normalized ratiometric measurement to cancel irrelevant factors and a mathematical model for temperature dependence.

Main Results:

• Demonstrated feasibility of TEMPT for temperature evaluation in tissue phantoms at 1.5 cm depth.
• Successfully applied TEMPT for *in vivo* temperature mapping during focused ultrasound treatment in mice at 2 mm depth.
• Validated TEMPT's ability to measure absolute temperature without requiring baseline temperature or optical properties.

Conclusions:

• TEMPT offers a robust method for absolute temperature mapping in biomedical applications.
• The technique is suitable for deep tissue imaging and *in vivo* studies.
• TEMPT holds promise for applications in thermotherapy, particularly in small animal models for cancer treatment.