Published online Dec 31, 2018.
https://doi.org/10.11637/kjpa.2018.31.4.133
3D Histology Using the Synchrotron Radiation Propagation Phase Contrast Cryo-microCT
Abstract
3D histology is a imaging system for the 3D structural information of cells or tissues. The synchrotron radiation propagation phase contrast micro-CT has been used in 3D imaging methods. However, the simple phase contrast micro-CT did not give sufficient micro-structural information when the specimen contains soft elements, as is the case with many biomedical tissue samples. The purpose of this study is to develop a new technique to enhance the phase contrast effect for soft tissue imaging. Experiments were performed at the imaging beam lines of Pohang Accelerator Laboratory (PAL). The biomedical tissue samples under frozen state was mounted on a computer-controlled precision stage and rotated in 0.18° increments through 180°. An X-ray shadow of a specimen was converted into a visual image on the surface of a CdWO4 scintillator that was magnified using a microscopic objective lens (X5 or X20) before being captured with a digital CCD camera. 3-dimensional volume images of the specimen were obtained by applying a filtered back-projection algorithm to the projection images using a software package OCTOPUS. Surface reconstruction and volume segmentation and rendering were performed were performed using Amira software. In this study, We found that synchrotron phase contrast imaging of frozen tissue samples has higher contrast power for soft tissue than that of non-frozen samples. In conclusion, synchrotron radiation propagation phase contrast cryo-microCT imaging offers a promising tool for non-destructive high resolution 3D histology.
Fig. 1
Schematic drawing of the experimental setup. Unmonochromatic beam arrived from the bending magnet device (B) was reduced to the beam size for matching the scintillator after passing the slit (S). The X-ray irradiated the object (O) positioned 34.8 m away from the source. Visible-light images on the surface of CdWO4 scintillator (St) placed at a distance of 10 cm from object were reflected at 90 degrees by a gold-coated mirror (M) and magnified by a microscope objective lens (X5–X20) (L). Finally, the images reached the CCD camera.
Fig. 2
Pictures of the cryo-tomogarphy devices. (a) The sample was directly exposed to liquid nitrogen stream. (b) The sample was embedded in OCT compound.
Fig. 3
Typical CT image (a) and three-dimensional micro-structural architecture (b) of the knee joint of collagen induced arthritis (CIA) mouse model. The typical findings of CIA, destructive changes in bones (*), and new bone formation (arrows), can be seen in detail. Scale bar=1 mm
Fig. 4
Phase contrast synchrotron micrographic images of mouse liver tissue, hydrated (a) and dried (b and c) samples. The edge enhancement effect was disturbed by water (a), but it was increased after drying tissue samples. Scale bar=500 µm.
Fig. 5
Comparison of X-ray phase contrast micro-CT images of the rat metatarsophalangeal joint of the 3rd toe according to the condition of micro-CT, (a) non-frozen agarose embedded sample (b) directly frozen sample (c) and frozen OCT embedded sample. The tomographic slices are on 3 sectional planes, horizontal plane (A and B), sagittal plane (C) and coronal plane(D) and the 3-dimensional volume-rendered images (E). Panel B shows the differences of the thickness of articular cartilage (*), the wideness of joint cavity (Jc) and the lining of synovial membrane (arrows) between each condition of microCT. Scale bar=1 mm.
Fig. 6
The tomographic slices of X-ray phase contrast cryo-microCT reconstruction images (A and C) and histologic images (B) of the metatarsophalangeal joints of the 3rd toe of normal control mouse (a) and collagen induced arthritis (CIA) mouse model. The typical findings of CIA, destructive change (arrows) in bone and pannus formation (*), can be seen in detail. Scale bar=1 mm.
Fig. 7
A tomographic slice of X-ray phase contrast cryo-microCT reconstruction image (a) and a 3-dimensional volume-rendered microCT image (b) of a mouse eyeball. Ci: ciliary body, Co: cornea, Ir: iris. Scale bar=1 mm.
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