Clinical Validation of Stimulated Raman Histology for Rapid Intraoperative Diagnosis of Central Nervous System Tumors

Abstract

Stimulated Raman histology (SRH) is an ex vivo optical imaging method that enables microscopic examination of fresh tissue intraoperatively. The conventional intraoperative method uses frozen section analysis, which is labor and time intensive, introduces artifacts that limit diagnostic accuracy, and consumes tissue. SRH imaging allows rapid microscopic imaging of fresh tissue, avoids tissue loss, and enables remote telepathology review. This improves access to expert neuropathology consultation in both low- and high-resource practices. We clinically validated SRH by performing a blinded, retrospective two-arm telepathology study to clinically validate SRH for telepathology at our institution. Using surgical specimens from 47 subjects, we generated a data set composed of 47 SRH images and 47 matched whole slide images (WSIs) of formalin-fixed, paraffin-embedded tissue stained with hematoxylin and eosin, with associated intraoperative clinicoradiologic information and structured diagnostic questions. We compared diagnostic concordance between WSI and SRH-rendered diagnoses. Also, we compared the 1-year median turnaround time (TAT) of intraoperative conventional neuropathology frozen sections with prospectively rendered SRH-telepathology TAT. All SRH images were of sufficient quality for diagnostic review. A review of SRH images showed high accuracy in distinguishing glial from nonglial tumors (96.5% SRH vs 98% WSIs) and predicting final diagnosis (85.9% SRH vs 93.1% WSIs). SRH-based diagnosis and WSI-permanent section diagnosis had high concordance (κ = 0.76). The median TAT for prospectively SRH-rendered diagnosis was 3.7 minutes, approximately 10-fold shorter than the median frozen section TAT (31 minutes). The SRH-imaging procedure did not affect ancillary studies. SRH generates diagnostic virtual histologic images with accuracy comparable to conventional hematoxylin and eosin-based methods in a rapid manner. Our study represents the largest and most rigorous clinical validation of SRH to date. It supports the feasibility of implementing SRH as a rapid method for intraoperative diagnosis complementary to conventional pathology laboratory methods.

Keywords: artificial intelligence; brain tumors; frozen section; glioma; intraoperative diagnosis; stimulated Raman histology.

Fig. 1

Intraoperative diagnosis workflow using stimulated Raman histology (SRH)-imaging system versus conventional frozen section and smear cytology method.

Fig. 2

First arm with SRH-images with clinicoradiological histories specific to each case (A). E.g., Case #509 is a 20-year-old female with a 2.0 cm lobulated enhancing mass in the frontal horn of the left lateral ventricle. (B). Second arm with corresponding whole slide image (WSI)-digital images of permanent section hematoxylin & eosin staining.

Fig. 3

SRH images used in the first arm of the survey depicting histologic features of brain tumors. (A) Pilocytic astrocytoma, World Health Organization (WHO) central nervous system (CNS) grade 1, showing a mildly cellular lesion composed of long-fibrillary hair-like processes and (B) showing abundant black, cork-screw shaped Rosenthal fibers (black arrows). (C) Glioblastoma, IDH-wildtype, WHO grade 4, showing hypercellularity and infiltration by tumor cells through axons, which appear as white empty linear spaces (blue arrows); microvascular proliferation (green arrow), (D) necrosis (black star) and adjacent viable tumor cells (red star), and (E) a mitotic figure (black arrow). (F) Lymphoma (G) Meningioma, WHO grade 1, showing meningothelial whorls (green arrow), psammoma bodies (blue arrows), and (H) nuclear pseudo-inclusions (green arrow).

Fig. 4

SRH and frozen section images. Ependymoma, frozen section (A), and corresponding SRH-image (B). High-grade infiltrating glioma, frozen section (C), and corresponding SRH-image (D). Diffuse large B-cell lymphoma, frozen section (E), and corresponding SRH-image (F).