Absolute photoacoustic thermometry in deep tissue

Abstract

Photoacoustic (PA) thermography is a promising tool for temperature measurement in deep tissue. Here, we propose an absolute temperature measurement method based on the dual temperature dependences of the Grüneisen parameter and the speed of sound in tissue. By taking ratiometric measurements at two adjacent temperatures, we can eliminate the factors that are temperature irrelevant but difficult to correct for in deep tissue. To validate our method, absolute temperatures of blood-filled tubes embedded ~9 mm deep in chicken tissue were measured in a biologically relevant range from 28 °C to 46 °C. The temperature measurement accuracy was ~0.6 °C. The results suggest that our method can be potentially used for absolute temperature monitoring in deep tissue during thermotherapy.

Red blood cell as a universal optoacoustic sensor for non-invasive temperature monitoring

“…[14][15][16] The presence of temperature dependent optoacoustic response (ThOR) measured from biological solutions, cells, and tissues provided the foundation for pioneering efforts in non-invasive temperature monitoring since over a decade ago. 17,18 Recent progress in this field of science demonstrated close correlation between local optoacoustic image intensity and temperature in tissue mimicking phantoms, [7][8][9][10]15,19 possibility to enhance the technique by combining laser optoacoustic and thermoacoustic sensing, 20 and optoacoustic temperature measurements in microscopy mode. 21,22 However, when considering in vivo applications, sample-to-sample and spatial variations of Gr€ uneisen parameter for different tissues negate all the advantages of the current methods, including high precision of the obtained temperature calibration curves.…”

“…[5][6][7] The potential advantages of optoacoustic temperature imaging techniques reside in enhanced spatial resolution, temperature sensitivity, and faster data acquisition. [8][9][10] During the past decade, optoacoustic imaging has attracted significant attention from researchers and clinicians due to its success in a variety of biomedical applications that involve high resolution deep tissue imaging of optical absorbers (blood, water, and near infrared contrast agents) unattainable with other modalities. [11][12][13] The premium quality of optoacoustic images, as compared to other imaging modalities based on tissue optical contrast, comes from the fact that optoacoustic energy conversion allows for tissue-specific information being encoded in and carried by acoustic rather than optical waves.…”

Catheter-based photoacoustic endoscope

“…PA tomography is expected to be a useful tool in the clinic because it enables high-resolution tomographic imaging at depths beyond the optical diffusion limit (∼1 mm in scattering tissue) and provides a wealth of functional and molecular information based on its strong spectroscopic imaging capability. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] So far, the clinical potential of the technique has been investigated in various endoscopic areas. [15][16][17][18][19][20][21][22][23][24][25][26] However, the development of associated imaging devices is still at an immature stage because of technical challenges.…”

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

“…These features, coupled further with its high sensitivity on temperature measurement [24]- [25], make photoacoustics particularly appealing for non-invasive temperature measurement. Indeed, preliminary deep tissue temperature measurement with sub-degree accuracy had been achieved by photoacoustics [26]. Though magnetic nanoparticles might possess weaker absorption at infrared wavelengths, strong signal to noise ratio (SNR) and hence good accuracy are still achievable by selecting judiciously the wavelength at the visible range [27].…”