Chemically-selective imaging of brain structures with CARS microscopy

Abstract

We demonstrate the use of coherent anti-Stokes Raman scattering (CARS) microscopy to image brain structure and pathology ex vivo. Although non-invasive clinical brain imaging with CT, MRI and PET has transformed the diagnosis of neurologic disease, definitive pre-operative distinction of neoplastic and benign pathologies remains elusive. Definitive diagnosis still requires brain biopsy in a significant number of cases. CARS microscopy, a nonlinear, vibrationally-sensitive technique, is capable of high-sensitivity chemically-selective three-dimensional imaging without exogenous labeling agents. Like MRI, CARS can be tuned to provide a wide variety of possible tissue contrasts, but with sub-cellular spatial resolution and near real time temporal resolution. These attributes make CARS an ideal technique for fast, minimally invasive, non-destructive, molecularly specific intraoperative optical diagnosis of brain lesions. This promises significant clinical benefit to neurosurgical patients by providing definitive diagnosis of neoplasia prior to tissue biopsy or resection. CARS imaging can augment the diagnostic accuracy of traditional frozen section histopathology in needle biopsy and dynamically define the margins of tumor resection during brain surgery. This report illustrates the feasibility of in vivo CARS vibrational histology as a clinical tool for neuropathological diagnosis by demonstrating the use of CARS microscopy in identifying normal brain structures and primary glioma in fresh unfixed and unstained ex vivo brain tissue.

Raman spectroscopy: techniques and applications in the life sciences

“…CARS measurements of tissues rely predominantly on the backscattering of forward-generated CARS photons, as introduced in the previous section and seen in Figure 22(b), which is particularly important for endoscope-based CARS. Evans et al used CARS to image mouse brain tissue structures ex vivo [230]. Fu et al imaged nerve tissue, revealing calcium-dependent myelin degradation pathways [231].…”

From molecular structure to tissue architecture: collagen organization probed by SHG microscopy

“…the main component in lipids. Revealing the lipid distribution by CARS microscopy offers great potential for both ex vivo [44][45][46] and in vivo clinical diagnostics [47,48]. Aside from lipids other relevant molecules yield good CARS image contrast, e.g.…”

Molecular Spectroscopic Imaging Using a White-Light Laser Source

“…40 Moreover, the group of Enejder and others has investigated lipid storage in nematodes (Caenorhabditis elegans), models of multicellular organisms. 41 More recently, ex vivo visualization of brain tissue, 42 application to flow cytometry, 43 and visualization of catalysts 44 have been reported by CARS microscopy. As mentioned above, CARS microscopy has been developing and been applied to many fields.…”