Deep Tissues – Light, Sound Measure Temperature

As demonstrated by biomedical engineers, photoacoustic imaging can take the temperature of deep tissues more quickly and accurately than current techniques. This discovery could play a significant role in advancing thermal-based cancer therapies.

Because the efficiency of light-to-sound conversion varies with temperature, the temperature can be measured by listening to light-generated soundwaves. However, the process must know how many photons reach the tissue, which is technically challenging.

To compensate for the lack of information, the researchers used deep tissue heating with high-intensity focused ultrasound (HIFU). They developed a new technique known as thermal-energy-memory-based photoacoustic thermometry, or TEMPT. It employs photoacoustic imaging to assess tissue thermal memory.

Researchers use TEMPT to take a baseline temperature reading before blasting the tissue with a burst of nanosecond-long laser pulses. The pulses temporarily raise the temperature of the tissue, measured with another photoacoustic pulse. The research team could estimate the absolute temperature using these measurements and a mathematical model without knowing the number of photons delivered.

The ability to more precisely measure the temperature of deep tissues within the body has significant implications for cancer treatment using thermal ablation, which involves heating tumor cells with HIFU or radio waves until they die. Thermotherapy doesn’t cause the severe side effects associated with radiotherapy and chemotherapy.

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