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Validation of MRI microstructure measurements with Coherent Anti-Stokes Raman Scattering (CARS)

This paper is available in a repository.
This paper is available in a repository.

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Abstract

Purpose. Validation of MRI microstructure measurements, such as AxCaliber [1], is typically performed using optical [2,3] or electron microscopy[1,4]. These methods are limited in that only small portion of the tissue can be imaged (typical FOV on the order of 100 μm). Moreover, large-scale histology is time-consuming and susceptible to artifacts caused by fixation, staining, embedding, and cutting deformations. Coherent Anti-Stokes Raman Scattering (CARS) microscopy is a feasible alternative to conventional histology, which can be used to perform large-scale microscopy images of tissue with a high optical resolution (350nm) [5] (see Figure 1). Another advantage of CARS is that fresh tissue can be imaged without the need for staining because myelin can be used as an endogenous image contrast by setting the laser frequencies appropriately. The objective of this study was to perform a demonstration about the use of CARS imaging for validating MRI microstructure measurements. Methods. Acquisition. An ex vivo thoracic segment of rat spinal cord (perfusion and post-fixed fixed with paraformaldehyde 4%) was scanned on a 7T preclinical scanner (Agilent) equipped with 600 mT/m gradients. The tissue was inserted into a small glass tube filled with buffered water. A custom-made solenoid coil was used for transmission and signal reception (S 11 ~-30dB). A single shot EPI sequence was used: four axial slices, matrix 64x64, BW=24kHz, TR=1s, TE=70ms, δ=3/3/8/15ms, ∆ = 10/40/40/40 ms, Gmax = [0 .. 600] mT/m (200 increments). Resolution was 0.1x0.2x2 mm 3