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Sacharz J, Perez-Guaita D, Kansiz M, Nazeer SS, Wesełucha-Birczyńska A, Petratos S, Wood BR, Heraud P. Empirical study on the effects of acquisition parameters for FTIR hyperspectral imaging of brain tissue. ANALYTICAL METHODS : ADVANCING METHODS AND APPLICATIONS 2020; 12:4334-4342. [PMID: 32844833 DOI: 10.1039/c9ay01200a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Fourier transform infrared (FTIR) spectroscopic imaging is a powerful technique for molecular imaging of pathologies associated with the nervous systems including multiple sclerosis research. However, there is no standard methodology or standardized protocol for FTIR imaging of tissue sections that maximize the ability to discriminate between the molecular, white and granular layers, which is essential in the investigation of the mechanism of demyelination process. Tissue sections are heterogeneous, complex and delicate, hence the parameters to generate high quality images in minimal time becomes essential in the modern clinical laboratory. This article presents an FTIR spectroscopic imaging study of post-mortem human brain tissue testing the effects of various measurement parameters and data analysis methods on image quality and acquisition time. Hyperspectral images acquired from the same region of a tissue using a range of the most common optical and collection parameters in different combinations were compared. These included magnification (4× and 15×), number of co-added scans (1, 4, 8, 16, 32, 64 and 128 scans) and spectral resolution (4, 8 and 16 cm-1). Images were compared in terms of acquisition time, signal-to-noise (S/N) ratio, and accuracy of the discrimination between three major tissue types in a section from the cerebellum (white matter, granular and molecular layers). In the latter case, unsupervised k-means cluster (KMC) analysis was employed to generate images from the hyperspectral images, which were compared to a reference image. The classification accuracy for tissue class discrimination was highest for the 4× magnifying objective, with 4 cm-1 spectral resolution and 128 co-added scans. The 15× magnifying objective gave the best accuracy for a spectral resolution of 4 cm-1 and 64 scans (96.3%), which was just above what was achieved using the 4× magnifying objective, with 4 cm-1 spectral resolution and 32 and 64 co-added scans (95.4 and 95.6%, respectively). These findings were correlated with a decrease in S/N ratio with increasing number of scans and was generally lower for the 15× objective. However, longer scan times were required using the 15× magnifying objective, which did not justify the very small improvement in the classification of tissue types.
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Affiliation(s)
- J Sacharz
- Centre for Biospectroscopy and School of Chemistry, Monash University, 3800, Victoria, Australia. and Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387, Kraków, Poland
| | - D Perez-Guaita
- Centre for Biospectroscopy and School of Chemistry, Monash University, 3800, Victoria, Australia. and FOCAS Research Institute, Technological University Dublin, City Campus, Dublin, Ireland
| | - Mustafa Kansiz
- Photothermal Spectroscopy Corp., 325 Chapala St, Santa Barbara, CA 93101, USA
| | - Shaiju S Nazeer
- Centre for Biospectroscopy and School of Chemistry, Monash University, 3800, Victoria, Australia.
| | | | - S Petratos
- Department of Neuroscience/Central Clinical School, Monash University, Alfred Centre, 99 Commercial Rd, Prahran, 3004, Victoria, Australia
| | - B R Wood
- Centre for Biospectroscopy and School of Chemistry, Monash University, 3800, Victoria, Australia.
| | - P Heraud
- Centre for Biospectroscopy and School of Chemistry, Monash University, 3800, Victoria, Australia. and Department of Microbiology and the Biomedical Discovery Institute, Faculty of Medicine, Nursing and Health Sciences, Monash University, 3800, Victoria, Australia
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Sacharz J, Wesełucha-Birczyńska A, Zięba-Palus J, Lewandowski MH, Kowalski R, Palus K, Chrobok Ł, Moskal P, Birczyńska M, Sozańska A. Epileptic rat brain tissue analyzed by 2D correlation Raman spectroscopy. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2018; 188:581-588. [PMID: 28772144 DOI: 10.1016/j.saa.2017.07.046] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Revised: 07/07/2017] [Accepted: 07/24/2017] [Indexed: 06/07/2023]
Abstract
Absence epilepsy is the neurological disorder characterized by the pathological spike-and wave discharges present in the electroencephalogram, accompanying a sudden loss of consciousness. Experiments were performed on brain slices obtained from young male WAG/Rij rats (2-3weeks old), so that they were sampled before the appearance of brain-damaging seizures symptoms. Two differing brain areas of the rats' brain tissue were studied: the somatosensory cortex (Sc) and the dorsal lateral geniculate nucleus of the thalamus (DLG). The Raman spectra of the fresh brain scraps, kept during measurements in artificial cerebrospinal fluid, were collected using as an excitation source 442nm, 514.5nm, 785nm and 1064nm laser line. The average spectra were analyzed by 2D correlation method regarding laser line as an external perturbation. In 2D synchronous spectra positive auto-peaks corresponding to the CC stretching and amide I band vibrations show maxima at 1660cm-1 and 1662cm-1 for Sc and DLG, respectively. The prominent auto-peak at 2937cm-1, originated from the CH3 mode in DLG brain area, seems to indicate the importance of methylation, considered to be significant in epileptogenesis. Synchronous and asynchronous correlations peaks, glutamic acid and gamma-aminobutyric acid (GABA), appear in Sc and DLG, respectively. In the 1730-1600cm-1 range occur cross-peaks which appearance might be triggered by glial fibrillary acidic protein (GFAP) activation.
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Affiliation(s)
- Julia Sacharz
- Faculty of Chemistry, Jagiellonian University, Kraków, Poland
| | | | | | - Marian H Lewandowski
- Department of Neurophysiology and Chronobiology, Institute of Zoology and Biomedical Research, Jagiellonian University, Kraków, Poland
| | | | - Katarzyna Palus
- Department of Neurophysiology and Chronobiology, Institute of Zoology and Biomedical Research, Jagiellonian University, Kraków, Poland
| | - Łukasz Chrobok
- Department of Neurophysiology and Chronobiology, Institute of Zoology and Biomedical Research, Jagiellonian University, Kraków, Poland
| | - Paulina Moskal
- Faculty of Chemistry, Jagiellonian University, Kraków, Poland
| | - Malwina Birczyńska
- The Department of Infectious Diseases, The University Hospital, Kraków, Poland
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