Photoacoustic imaging and temperature measurement for photothermal cancer therapy

Abstract

Photothermal therapy is a noninvasive, targeted, laser-based technique for cancer treatment. During photothermal therapy, light energy is converted to heat by tumor-specific photoabsorbers. The corresponding temperature rise causes localized cancer destruction. For effective treatment, however, the presence of photoabsorbers in the tumor must be ascertained before therapy and thermal imaging must be performed during therapy. This study investigates the feasibility of guiding photothermal therapy by using photoacoustic imaging to detect photoabsorbers and to monitor temperature elevation. Photothermal therapy is carried out by utilizing a continuous wave laser and metal nanocomposites broadly absorbing in the near-infrared optical range. A linear array-based ultrasound imaging system is interfaced with a nanosecond pulsed laser to image tissue-mimicking phantoms and ex-vivo animal tissue before and during photothermal therapy. Before commencing therapy, photoacoustic imaging identifies the presence and spatial location of nanoparticles. Thermal maps are computed by monitoring temperature-induced changes in the photoacoustic signal during the

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.…”

“…It is also crucial that the measured optoacoustic response comes solely from the native optical absorption of hemoglobin compartmentalized inside red blood cells rather than external contrast agents. 7,8 Also, if optically absorbing substance is not forming chemical bonds with solvent, its ThOR would replicate the one of the pure solvent. The examples of such situations include suspensions of carbon microparticles 45 and gold nanospheres.…”

“…[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.…”

Microgels and Nanoparticles: Where Micro and Nano Go Hand in Hand

“…Nanoscale thermodynamics of a single Au NP heated by a laser source has gained attention from both experimental and theoretical points of view [50][51][52]. Nanoscale thermometry of Au NPs has been addressed by Raman spectroscopy [53], time-resolved X-ray spectroscopy [54] or by photo-acoustic experiments [55]. Fluorescent molecules [56], semiconductor NPs [57,58] and rareBrought to you by | MIT Libraries Authenticated Download Date | 5/11/18 4:03 AM earth compounds [59] exhibiting temperature-dependent spectra have also been used to estimate the temperature around excited Au NPs.…”

Intracellular temperature mapping with fluorescence-assisted photoacoustic-thermometry

“…Traditional photoacoustic thermometry [15][16][17] calculates the temperature map from Eq. (2) and Eq.…”