Chromophore selective multi-wavelength photoacoustic remote sensing of unstained human tissues

Reza

2020

Opt. Lett.

Self Cite

Histological visualizations are critical to clinical disease management and are fundamental to biological understanding. However, current approaches that rely on bright-field microscopy require extensive tissue preparation prior to imaging. These processes are labor intensive and contribute to delays in clinical feedback that can extend to two to three weeks for standard paraffin-embedded tissue preparation and interpretation. Here, we present a label-free reflectionmode imaging modality that reveals cellular-scale morphology by detecting intrinsic endogenous contrast. We accomplish this with the novel photoacoustic remote sensing (PARS) detection system that permits non-contact optical absorption contrast to be extracted from thick and opaque biological targets with optical resolution. PARS was examined both as a rapid assessment tool that is capable of managing large samples (>1 cm 2) in under 10 minutes, and as a high contrast imaging modality capable of extracting specific biological contrast to simulate conventional histological stains such as hematoxylin and eosin (H&E). The capabilities of the proposed method are demonstrated in a variety of human tissue preparations including formalin-fixed paraffinembedded tissue blocks and unstained slides sectioned from these blocks, including normal and neoplastic human brain, and breast epithelium involved with breast cancer. Similarly, PARS images of human skin prepared by frozen section clearly demonstrated basal cell carcinoma and normal human skin tissue. Finally, we imaged unprocessed murine kidney and achieved histologically relevant subcellular morphology in fresh tissue. This represents a vital step towards an effective real-time clinical microscope that overcomes the limitations of standard histopathologic tissue preparations and enables real-time pathology assessment.

Section: Introductionmentioning

confidence: 99%

Non-contact reflection-mode optical absorption spectroscopy using photoacoustic remote sensing

Reza

2020

Opt. Lett.

Self Cite

“…To further improve the diagnostic utility of this device, development is focusing on the incorporation of faster repetition rate lasers and additional excitation wavelengths. These improvements will facilitate increased imaging speeds with larger imaging fields, while providing further selective contrast for biomolecules such as lipids and hemoglobin 18 . While the present results demonstrate the capabilities of PARS in the histological analysis of preserved brain tissues, this method will soon be applied to unprocessed freshly resected human brain tissue samples.…”

Section: Discussionmentioning

confidence: 99%

“…Recently our team, for the first time, utilized photoacoustic remote sensing (PARS) microscopy to demonstrate nuclear and cellular structure imaging in unstained human tissue preparations 17 , 18 . PARS operates by directing a nanosecond scale excitation pulse into the sample.…”

Section: Introductionmentioning

confidence: 99%

Improving maximal safe brain tumor resection with photoacoustic remote sensing microscopy

Ecclestone

Abbasi

et al. 2020

Sci Rep

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Malignant brain tumors are among the deadliest neoplasms with the lowest survival rates of any cancer type. In considering surgical tumor resection, suboptimal extent of resection is linked to poor clinical outcomes and lower overall survival rates. Currently available tools for intraoperative histopathological assessment require an average of 20 min processing and are of limited diagnostic quality for guiding surgeries. Consequently, there is an unaddressed need for a rapid imaging technique to guide maximal resection of brain tumors. Working towards this goal, presented here is an all optical non-contact label-free reflection mode photoacoustic remote sensing (PARS) microscope. By using a tunable excitation laser, PARS takes advantage of the endogenous optical absorption peaks of DNA and cytoplasm to achieve virtual contrast analogous to standard hematoxylin and eosin (H&E) staining. In conjunction, a fast 266 nm excitation is used to generate large grossing scans and rapidly assess small fields in real-time with hematoxylin-like contrast. Images obtained using this technique show comparable quality and contrast to the current standard for histopathological assessment of brain tissues. Using the proposed method, rapid, high-throughput, histological-like imaging was achieved in unstained brain tissues, indicating PARS’ utility for intraoperative guidance to improve extent of surgical resection.

“…To ensure negative surgical margins, the pathologist must examine several thin sections of resected tissue with sufficient resolution to distinguish cell nuclei. Previously, we reported a preliminary investigation into the visualization of cellular morphology in unstained human tissue and thick, formalin-fixed, embedded tissue blocks [14,15]. However, to visualize surgical margins in fresh tissue or in situ, it would be necessary to maintain subcellular resolution and recover cellular morphology in large field of views while operating in a reflection-mode configuration.…”

Section: Introductionmentioning

confidence: 99%

Rapid High-Resolution Mosaic Acquisition for Photoacoustic Remote Sensing

Abbasi

Reza

2020

Sensors

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Mechanical stages are routinely used to scan large expanses of biological specimens in photoacoustic imaging. This is primarily due to the limited field of view (FOV) provided by optical scanning. However, stage scanning becomes impractical at higher scanning speeds, or potentially unfeasible with heavier samples. Also, the slow scan-rate of the stages makes high resolution scanning a time-consuming process. Some clinical applications such as microsurgery require submicron resolution in a reflection-mode configuration necessitating a method that can acquire large field of views with a small raster scanning step size. In this study, we describe a method that combines mechanical stages with optical scanning for the rapid acquisition of high-resolution large FOVs. Optical scanning is used to acquire small frames in a two-dimensional grid formed by the mechanical stages. These frames are captured with specific overlap for effective image registration. Using a step size of 200 nm, we demonstrate mosaics of carbon fiber networks with FOVs of 0.8 × 0.8 mm2 captured in under 70 s with 1.2 µm image resolution. Larger mosaics yielding an imaging area of 3 × 3 mm2 are also shown. The method is validated by imaging a 1 × 1 mm2 section of unstained histopathological human tissue.