Characterization of multiphoton photoacoustic spectroscopy for subsurface brain tissue diagnosis and imaging

Abstract

The development and demonstration of a multiphoton photoacoustic imaging technique capable of providing high spatial resolution chemical images of subsurface tissue components as deep as 1.4 cm below the tissue surface is described. By combining multiphoton excitation in the diagnostic window (650 to 1100 nm), with ultrasonic detection of nonradiative relaxation events, it is possible to rapidly reconstruct three-dimensional, chemical specific, images of samples underneath overlying structures as well as chemical species of the same material. Demonstration of this technique for subsurface tissue differentiation is shown, with the ability to distinguish between grade III astrocytoma tissue and adjacent healthy tissue in blind studies. By employing photoacoustic signal detection, the high nonradiative relaxation rates of most biological tissue components (>90% >90% ) and the minimal signal attenuation of the resulting ultrasound compensate for excitation efficiency losses associated with two-photon absorption. Furthermore, the two-photon absorption process results in a highly localized excitation volume (ca., 60 μm 60 μm ). Characterization of the probing depth, spatial resolution, and ability to image through overlying structures is also demonstrated in this paper using tissue phantoms with well-characterized optical scattering properties, mimicking those of tissues.

Acoustic Steering Using Thermally Induced Optical Reflection of Sound (THORS)

“…Manipulation of acoustic waves is critical for many applications in science and engineering, including photoacoustic sensing, [1][2][3][4] sub-surface tissue imaging, [5][6][7] secure communications, acoustic design engineering, 8,9 and acoustic stealth technology. 10 Historically, the ability to guide and manipulate acoustic waves has typically required the use of physical material interfaces for this purpose.…”

Breakthroughs in modern cancer therapy and elusive cardiotoxicity: Critical research‐practice gaps, challenges, and insights

“…273,283 Various exogenous probes with high contrast have also been extensively developed, including inorganic and organic dyes, 274 magneto-optical and photochromic probes, 283 nanoparticles, 282,287 and genetically encoded probes, 281 to achieve improved resolution and sensitivity while providing multi-parametric photoacoustic imaging. 283 This imaging modality has proven its clinical and preclinical value in functional, structural, and molecular aspects of diseases and has been used for physiologically and pathologically imaging various organs and tissues, including breast cancer, [288][289][290][291][292] neural tissues, 277,287,[293][294][295] fingers, 296 sentinel lymph nodes, 277,292,297 the cardiovascular system, [298][299][300][301][302] the prostate, 303,304 skin, 305 cancer therapy, 273,274,306 muscle oxygenation, 307 metabolic status, 274,283 eyes, 308,309 plaque pathophysiology, 310 tumor microenvironment (pH, enzymes, radical oxidation species (ROS), and metal ions, among others), 274 and biomaterial-tissue interactions to assess the functions of the engineered tissue/organ constructs. <...>…”