| Terahertz (THz) is referred as electromagnetic wave with frequencies in between0.1～10THz (1THz=1012Hz) and wavelength in between3～0.03mm, wave band of whichlocalized between microwave and infrared waves. Terahertz time-domain spectroscopy isone of the most developed THz detection techniques. It has been widely used in theexamination of biomacromolecules, oncological researches, dental caries examination anddetermination of the extent of burn injury, demonstrating the vast potential for futuredevelopment in biomedical field. As THz is highly sensitive to the interstitial water andcellular density and arrangements, it could be sensitive to pathological changes ofneurosurgical diseases.The current research focus on ischemic stroke and glioma in neurosurgery to find outthe preliminary evidences whether the THz-TDS technique could identify ischemic tissueand glioma practically.Section1THz-TDS research on brain tissue after rat middle cerebral arteryocclusionPurpose:To find out whether the THz-TDS technique could identify cerebral ischemia andextent practically.Methodology:72male Sprague-Daulry rats were randomly divided into ischemia3,6,12,24h fourgroups (N=18) and the model of middle cerebral artery occlusion (MACO) were established,using TTC staining, HE staining and detection of brain water content confirmed the modelsuccess and select terahertz detection site. Terahertz time-domain spectroscopy of the braintissue of occlusive lesions was measured by transmissive terahertz time-domainspectroscopy (THZ-TDS) system in each group. Then the Peaks-Valley absorption coefficient difference (Peak-Valley difference, PVD) in absorption coefficient curve wasanalyzed.Results:Terahertz absorption coefficient curve analysis showed ischemia3,6,12,24hocclusive lesions of brain tissue have significant differences, compared with normal braintissue; Analysis showed that ischemic brain tissue in1.4,1.5,1.6,1.7,1.8,1.9THzfrequencies were clearly appears PVD value decreased feature (P<0.05); Ischemia3,6and24h occlusive lesions of brain tissue have the most significant decrease PVD in1.7THz,while the most significant PVD decrease of12h lesions is in1.9THz. Cell density ofischemic brain tissue was significantly reduced and brain water content was significantlyhigher.Conclusions:Terahertz time-domain spectroscopy can detect ischemia within3hours of ischemicbrain tissue and determine the severity of ischemia; PVD value decrease degree in1.4,1.5,1.6,1.7,1.8,1.9THz is positively related to the severity of brain tissue ischemia; the abovespectral characteristics may be due to ischemia brain tissue water content and cell densitychanges.Section2THz-TDS examination of in vitro glioma specimenPurpose:To investigate the possibilities of THz-TDS to identify glioma tissue in specimens.Methodologies:1. Five cases of surgical resection specimens of glioma and refractory epilepsy.THz-TDS systems are utilized to examine the THz-TDS of each fresh tissue. Subsequentlythe samples are routinely fixed by paraffin wax and examined again by the THz-TDSsystem.2.30male C57mice22±2g were selected to establish the glioma implantation model;HE, immunohistochemical staining and7.0T MRI are applied to verify the successfulestablishments of the model and select the region that THz examines; THz-TDSexamination of in vitro glioma specimen. Results:1. Terahertz absorption coefficient of human glioma tissue are significant higher thannormal brain tissue and the coefficient and peak of absorption of different grades of gliomavaries; the absorption intensities of THz waves of glioma tissue are significant higher thannormal brain tissue while glioma with different grades have different absorption intensitiesand time delay.2. Refractive index, absorption coefficient, and dielectric constant of glioma tissue arehigher than normal brain tissue, especially in0.3,0.55and0.76THz where the mostsignificant differences in absorption coefficient locates.Conclusions:THz-TDS could identify the in vitro glioma tissue and their pathological grades whichis the most obvious at0.3,0.55and0.76THz. Mechanism of such contrast to identifyglioma tissue may relate to the water content, and the identical structures and componentsof glioma in contrast with normal brain tissue. |
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