There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

From bench to bedside

The life sciences can benefit greatly from imaging technologies that connect microscopic discoveries with macroscopic observations. One technology uniquely positioned to provide such benefits is photoacoustic tomography (PAT), a sensitive modality for imaging optical absorption contrast over a range of spatial scales at high speed. In PAT, endogenous contrast reveals a tissue's anatomical, functional, metabolic, and histologic properties, and exogenous contrast provides molecular and cellular specificity. The spatial scale of PAT covers organelles, cells, tissues, organs, and small animals. Consequently, PAT is complementary to other imaging modalities in contrast mechanism, penetration, spatial resolution, and temporal resolution. We review the fundamentals of PAT and provide practical guidelines for matching PAT systems with research needs. We also summarize the most promising biomedical applications of PAT, discuss related challenges, and envision PAT's potential to lead to further breakthroughs.

/pdf/a-practical-guide-to-photoacoustic-tomography-in-the-life-3ot96ziog0.pdf

A practical guide to photoacoustic tomography in the life sciences

Recent research in inverse problems seeks to develop a mathematically coherent foundation for combining data-driven models, and in particular those based on deep learning, with domain-specific knowledge contained in physical–analytical models. The focus is on solving ill-posed inverse problems that are at the core of many challenging applications in the natural sciences, medicine and life sciences, as well as in engineering and industrial applications. This survey paper aims to give an account of some of the main contributions in data-driven inverse problems.

/pdf/solving-inverse-problems-using-data-driven-models-3jeyo4a896.pdf

Solving inverse problems using data-driven models

Photoacoustic tomography (PAT) has become one of the fastest growing fields in biomedical optics. Unlike pure optical imaging, such as confocal microscopy and two-photon microscopy, PAT employs acoustic detection to image optical absorption contrast with high-resolution deep into scattering tissue. So far, PAT has been widely used for multiscale anatomical, functional, and molecular imaging of biological tissues. We focus on PAT’s basic principles, major implementations, imaging contrasts, and recent applications.

/pdf/tutorial-on-photoacoustic-tomography-39cd3dabln.pdf

Tutorial on photoacoustic tomography

Compared with visible light (380–700 nm), near-infrared light (700–1400 nm) undergoes weaker optical attenuation in biological tissue; thus, it can penetrate deeper. Herein, we demonstrate near-infrared optical-resolution photoacoustic microscopy (NIR-OR-PAM) with 1046 nm illumination. A penetration depth of 3.2 mm was achieved in chicken breast tissue ex vivo using optical fluence within the American National Standards Institute (ANSI) limit (100  mJ/cm^2). Beyond ∼0.6  mm deep in chicken breast tissue, NIR-OR-PAM has shown finer resolution than the visible counterpart with 570 nm illumination. The deep imaging capability of NIR-OR-PAM was validated in both a mouse ear and a mouse brain. NIR-OR-PAM of possible lipid contrast was explored as well.

/pdf/near-infrared-optical-resolution-photoacoustic-microscopy-24s6qdt5fi.pdf

Near-infrared Optical-resolution Photoacoustic Microscopy

We developed handheld photoacoustic microscopy (PAM) to detect melanoma and determine tumor depth in nude mice in vivo Compared to our previous PAM system for melanoma imaging, a new light delivery mechanism is introduced to improve light penetration We show that melanomas with 41 and 37 mm thicknesses can be successfully detected in phantom and in in vivo experiments, respectively With its deep melanoma imaging ability and handheld design, this system can be tested for clinical melanoma diagnosis, prognosis, and surgical planning for patients at the bedside

/pdf/handheld-photoacoustic-microscopy-to-detect-melanoma-depth-1mm2f5kdgz.pdf

Handheld photoacoustic microscopy to detect melanoma depth in vivo

Photoacoustic computed tomography (PACT) is a non-invasive imaging technique offering high contrast, high resolution, and deep penetration in biological tissues. We report a PACT system equipped with a high frequency linear transducer array for mapping the microvascular network of a whole mouse brain with the skull intact and studying its hemodynamic activities. The linear array was scanned in the coronal plane to collect data from different angles, and full-view images were synthesized from the limited-view images in which vessels were only partially revealed. We investigated spontaneous neural activities in the deep brain by monitoring the concentration of hemoglobin in the blood vessels and observed strong interhemispherical correlations between several chosen functional regions, both in the cortical layer and in the deep regions. We also studied neural activities during an epileptic seizure and observed the epileptic wave spreading around the injection site and the wave propagating in the opposite hemisphere.

/pdf/high-resolution-deep-functional-imaging-of-the-whole-mouse-21tvre4bi9.pdf

High-resolution deep functional imaging of the whole mouse brain by photoacoustic computed tomography in vivo

Photoacoustic 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 Gruneisen 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.

/pdf/absolute-photoacoustic-thermometry-in-deep-tissue-nrrb8ld4wi.pdf

Yong Zhou

Papers

Tutorial on photoacoustic tomography

Near-infrared Optical-resolution Photoacoustic Microscopy

Handheld photoacoustic microscopy to detect melanoma depth in vivo

High-resolution deep functional imaging of the whole mouse brain by photoacoustic computed tomography in vivo

Absolute photoacoustic thermometry in deep tissue.