A brief review of non-invasive brain imaging technologies and the near-infrared optical bioimaging

Abstract

Brain disorders seriously affect life quality. Therefore, non-invasive neuroimaging has received attention to monitoring and early diagnosing neural disorders to prevent their progress to a severe level. This short review briefly describes the current MRI and PET/CT techniques developed for non-invasive neuroimaging and the future direction of optical imaging techniques to achieve higher resolution and specificity using the second near-infrared (NIR-II) region of wavelength with organic molecules.

Keywords: CNS; Imaging techniques; NIR; Organic dyes.

Fig. 1

Modality of MRI/fMRI. a Axial MRI slice of a patient with a brain tumor. b BOLD dependent fMRI scans of verbal fluency task performed by healthy controls (left) and subjects with alzheimer’s disease (right). Adapted with permission from Crowe et al. (a) and from Preti et al. (b)

Fig. 2

MRI contrast agent. Infusion of the DaReNa, a dopamine sensor (BM3h) coated SPION complex, show the enhancement of contrast and relaxation near the injection site (striatum, Str) and along the corpus callosum (cc). Scale bar = 2 mm. Reprinted with permission from Hsieh et al. . Copyright 2017 American Chemical Society

Fig. 3

Modality of PET/CT. The standardized glucose uptake value ratios (SUVR) relative to the cerebellum from 18F-FDG PET scans of a healthy control (HC) and an Alzheimer’s disease patient. Adapted with permission from Kazemifar et al.

Fig. 4

Modality of MSOT imaging. a The chemical structure of CDnir7 and the experimental scheme. b MSOT signals in the cortex of both AD and control brains before (Prescan) and after the intravenous injection of CDnir7. SSS, superior sagittal sinus. Adapted with permission Park et al. ,

Fig. 5

Commonly used materials for fluorescence imaging. Diagrams of the spectral ranges of the major fluorescence materials and its tissue penetration capacity. SWNTs, single walled carbon nanotubes; RENPs, rare-earth doped nanoparticles; D-A-D, donor-acceptor-donor

Fig. 6

Modality of NIR-IIb fluorescent optical imaging. a In vivo mouse brain vessel imaging using a cerium-doped rare earth nanoparticle. b 3D reconstruction of cerebral blood vessels of the rhesus macaque based on ICG-mediated NIR-II fluorescence confocal microscopic in vivo imaging up to depth of 470 μm. Adapted with permission from Zhong et al. (a) and from Cai et al. (b)

Fig. 7

Examples of the chemical structures of NIR organic dyes. Sky colors represent adjustable structures of Cy7 derivatives, such as ICG, CDnir7, TiNIR, etc.; BBTD, benzobisthadiazoles