Imaging brain tissue slices with terahertz near‐field microscopy

Abstract

Photoconductive antenna microprobe (PCAM)‐based terahertz (THz) near‐field imaging technique is promising for biomedical detection due to its excellent biocompatibility and high resolution; yet it is limited by its imaging speed and the difficulty in the control of the PCAM tip‐sample separation. In this work, we successfully realized imaging of mouse brain tissue slices using an improved home‐built PCAM‐based THz near‐field microscope. In this system, the imaging speed was enhanced by designing and applying a voice coil motor‐based delay‐line. The tip‐sample separation control was implemented by developing an image analysis‐based technique. Compared with conventional PCAM‐based THz near‐field systems, our improved system is 100 times faster in imaging speed and the tip‐sample separation can be controlled to a few micrometers (e.g., 3 μm), satisfying the requirements of THz near‐field imaging of biological samples. It took about ~30 min (not the tens of hours it took to acquire the same kind of image previously) to collect a THz near‐field image of brain tissue slices of BALb/c mice (500 μm × 500 μm) with pixel size of 20 μm × 20 μm. The results show that the mouse brain slices can be properly imaged and different regions in the slices (i.e., the corpus callosum region and the cerebrum region) can be identified unambiguously. Evidently, the work demonstrated here provides not only a convincing example but a useful technique for imaging biological samples with THz near‐field microscopy. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2741, 2019.

Single cell imaging with near‐field terahertz scanning microscopy

“…The dynamic range of the signal collected using this system can be better than ~60 dB for an integration time of 3 seconds (Section 3 in Supporting Information). For our previous near-field system, 19 it needs ~3 seconds to acquire a 90 ps long THz pulse waveform, and the signal dynamic range can only reach ~45 dB for an integration time of 3 seconds. As a whole, the performance of the new system is much better than our previous near-field system, particularly in the aspects of imaging speed and signal dynamic range.…”

“…To achieve high‐quality near‐field detection, the PCAM should be positioned as close as possible to the sample surface and the probe‐sample distance should be precisely controlled during the scanning in order to avoid the crash between the probe and sample. Recently, we have successfully imaged mouse brain tissue slices using a home‐built PCAM‐based near‐field THz‐TDS scanning microscope with a calibrated resolution of a few microns 19 . Unfortunately, imaging individual cells is highly demanded in the imaging speed, signal dynamic range and stability of a system other than the spatial resolution; hitherto, no work has been reported on imaging individual cells using a THz‐based imaging technique.…”

Synchrotron Radiation-Based FTIR Microspectroscopic Imaging of Traumatically Injured Mouse Brain Tissue Slices

“…All raw spectra in the 1000–3000 cm –1 were corrected for the Mie scattering using MATLAB R2018a (MathWorks Inc., Natick, MA, USA) according to the RMie-EMSC algorithm described by Paul Bassan et al PCA ,− and k -means clustering method were used to classify the data using MATLAB. , Score plots of PCA were prepared using Origin 8.5 software (OriginLab Co., Northampton, MA, USA).…”

W-Band Near-Field Microscope

“…The scattered radiation is detected with a quasi-optical Schottky diode (ACST, Germany). A conventional coaxial optical microscope is placed at the side of the tip to monitor the tipsample distance [26]. A 110 GHz beam is emitted from the horn antenna, and focused on the tip apex by a parabolic mirror (PM1).…”