In chapter 5, OCT and MPAM were performed on silicone-dye samples and mouse ears as a proof of concept. Different samples can be used. By imaging the skin in- vivo, the vascular network can be imaged with PAM and the structure with OCT. With sPA or MPAM different contrasts can be obtained and irregularities can be im- aged and tumours detected for instance. Performing OCT for guidance and sPA in- vivo on a mouse heart in both the right and the left ventricle could inform on their respective oxygen saturation and potentially help detecting some diseases. The mouse tail is an interesting sample since the OCT can show the different superficial layers of the tail, while IR MPAM could differentiate collagen from lipids. The brain contains a multitude of blood vessels for instance. For eye imaging, the cornea can be resolved by IR OCT, the retina imaged by NIR or visible OCT. Melanin and blood vessels can be imaged by MPAM. Histopathological samples containing tumours could be imaged by OCT and MPAM to separate affected tissue from healthy tissue. New ethical approvals were necessary to use histopathological sample and tis- sue delivery needed to be organised. Unfortunately, my period at the University of Kent was too short to organise such an agreement. To perform measurements
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FIGURE6.6: OCT B-scans, in-vivo, of (a) a fingertip, (b) and (c) of finger nails and skin. BV: blood vessel (↑), D: dermis, EP: epidermis (⋆), N: nail, SG: sweat glands
(↓). Scale bars: 500 µm.
on in-vivo mouse, the setup needed to be moved to a different facility. Even if the setup is portable, some additional developments were necessary to perform in-vivo imaging. To image the mouse heart, once anaesthesised then with the chest open, the heart keeps beating for less than 5-10 minutes. The alignment and the imag- ing need to be performed within that duration. To perform such experiment, an automatic switching of wavelengths with the VARIA, automatic saving of the PA signal amplitude for sPA and, quick alignment of the beams on the sample would be necessary. We did not have time to perform such a difficult experiment. Only in-vivo human fingers and in-vitro results of animal tissue are presented here.
OCT images were taken on only a few samples using the setup presented in sec- tion 5.1.3 of chapter 5 (1300 nm OCT). Figure 6.6a represents a B-scan of a fingertip and Fig. 6.6b and 6.6c of finger nails and skin. All measurements were performed on human fingers in-vivo. Sweat glands can be observed in the epidermis. Some superficial blood vessels can be observed in Fig. 6.6b.
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FIGURE 6.7: In-vitro OCT of a mouse heart with (a) en-face OCT selected from a depth of 0.6 mm (measured in air), position indicated in (b) by the arrow−→and, (b) B-scan taken at position indicated by the orange line in (a). Scale bars: 500 µm.
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FIGURE6.8: In-vitro OCT of a mouse tail with (a) summed voxel projection along the axial direction for 3 mm in air, (b) B-scan taken at position indicated by the orange line in (a) and, (c) 3D representation. D: dermis, EP: epidermis (⋆), H: hair
In-vitro mouse ear were imaged in section 5.3.2 (chapter 5) with OCT (and PAM). Different samples excised from the same mouse are imaged here with OCT. Figure 6.7 shows OCT images of part of the mouse heart. Unfortunately, we did not manage to observe the heart structure. The OCT imaging depth may be too short or we did not manage to place the heart in a way we could see the ventricles and atriums. The mouse heart has already been imaged with OCT where the ventricles and the atriums can be delineated [178, 179].
Figure 6.8 represents OCT images of a section of a mouse tail. The tail structure is observed with the epidermis, the dermis and hair. Similar results as in [180] are obtained.
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FIGURE6.9: In-vitro OCT of a mouse brain with (a) en-face OCT selected from a depth of 1.2 mm (measured in air), position indicated in (b) by the arrow−→, (b) B-scan taken at position indicated by the orange line in (a) and, (c) 3D representa-
Figure 6.9 presents part of the mouse brain imaged with OCT. The shape of the cerebrum is clearly observed in the en-face OCT in Fig. 6.9a. Several groups have imaged the brain with OCT [45, 181].
Figure 6.10 presents different views of an excised mouse eye. The total surface of the eye is scanned with the OCT. Scleral vessels are observed in Fig. 6.10a and 6.10c. The cornea is imaged as well as the ciliary body holding the eye lens. Eye imaging is the most common OCT application, therefore a large amount of publi- cations are covering the subject with much better quality imaging, in-vivo, but as well on human eye with the cornea and the retina [38, 39, 47, 50, 107, 182, 183].
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FIGURE6.10: In-vitro OCT of a mouse eye with (a) summed voxel projection along the axial direction for 3 mm in air, (b) B-scan taken at position indicated by the orange line in (a) and, (c) 3D representation. C: cornea (↓), CB: ciliary body (↑), S:
These different OCT images show the versatility of the OCT setup presented in section 5.1.3 (chaper 5) and show the potential for in-vivo mouse imaging. By com- bining sPA or MPAM with OCT, further information could be extracted from such samples. The blood oxygen saturation in the heart ventricles could be potentially measured with sPA, the lipids content of the mouse tale with MPAM in the IR, the blood oxygen saturation in the brain and in the retina with MPAM.