All-optical Reflection-mode Microscopic Histology of Unstained Human Tissues

Abstract

Surgical oncologists depend heavily on visual field acuity during cancer resection surgeries for in-situ margin assessment. Clinicians must wait up to two weeks for results from a pathology lab to confirm a post-operative diagnosis, potentially resulting in subsequent treatments. Currently, there are no clinical tools that can visualize diagnostically pertinent tissue information in-situ. Here, we present the first microscopy capable of non-contact label-free visualization of human cellular morphology in a reflection-mode apparatus. This is possible with the recently reported imaging modality called photoacoustic remote sensing microscopy which enables non-contact detection of optical absorption contrast. By taking advantage of the 266-nanometer optical absorption peak of DNA, photoacoustic remote sensing is efficacious in recovering qualitatively similar nuclear information in comparison to that provided by the hematoxylin stain in the gold-standard hematoxylin and eosin (H&E) prepared samples. A photoacoustic remote sensing system was employed utilizing a 266-nanometer pulsed excitation beam to induce photoacoustic pressures within the sample resulting in refractive index modulation of the optical absorber. A 1310-nanometer continuous-wave interrogation beam detects these perturbed regions as back reflected intensity variations due to the changes in the local optical properties. Using this technique, clinically useful histologic images of human tissue samples including breast cancer (invasive ductal carcinoma), tonsil, gastrointestinal, and pancreatic tissue images were formed. These were qualitatively comparable to standard H&E prepared samples.

Improving maximal safe brain tumor resection with photoacoustic remote sensing microscopy

“…While the current results use sectioned paraffin embedded brain tissues, the all-optical reflection mode architecture lends itself to imaging of thick tissue samples (> 1 mm). Previously this capability has been shown in thick formalin fixed paraffin embedded breast tissue blocks 17 . Moving forwards volumetric imaging will be explored in appropriate depth resolvable brain tissue samples, such as formalin fixed paraffin embedded tissue blocks, or freshly resected tissues.…”

“…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.…”

Spectroscopic and Deep Learning-Based Approaches to Identify and Quantify Cerebral Microhemorrhages

“…Histological sections remain the gold standard for assessing pathology from ex vivo tissue samples 14,32 . Clinical pathologists and researchers rely on data from these samples to guide patient management and gain mechanistic insights.…”

Biophotonic technologies for assessment of breast tumor surgical margins—A review

“…The authors proposed to solve the above issues by adopting microlens array and Gruneisen relaxation PAM [13]. More recently, Saad Abbasi et al developed a PA remote sensing (PARS) microscopy which could extract diagnostic quality histological information in a fast and contactless mode [34]. Herein, a 266 nm pulsed excitation beam induced photoacoustic pressure waves in the sample to modulate the refractive index of the light absorber while a cofocused 1310 nm CW superluminescent beam captured those modulations in the place of traditional ultrasonic transducer.…”