Evaluation of Mannitol Intervention Effects on Ischemic Cerebral Edema in Mice Using Swept Source Optical Coherence Tomography

Probe fusion all-optic OCT-PAM dual-mode imaging system for biomedical imaging

We proposed a non-contact photoacoustic (PA) detection method using spectral domain optical coherence tomography (SDOCT). Two interference spectrums (A-lines) were acquired before and after the PA excitation with SDOCT. PA signal propagated within the sample causing the vibration. The vibration inner the sample introduced phase change between the acquired two A-lines. Thus, the PA signal can be detected by evaluating the difference in phase between the two A-lines. Based on the method, an OCT-PAM dual-mode imaging system was constructed. In the system, SDOCT served as the detection unit for PAM. Thus, the combination of the two imaging modalities was simplified. Another advantage of the system is that it realizes non-contact all-optic detection, which is attractive for biomedical imaging. Using the system, we imaged phantoms of carbon fibers, asparagus leaves and human hairs. Furthermore, the cortical vasculature of rat was imaged in vivo and the flow status was evaluated quantitatively.

Multimodal OCT Control for Early Histological Signs of Vulvar Lichen Sclerosus Recurrence after Systemic PDT: Pilot Study

Photodynamic therapy (PDT) is a modern treatment for severe or treatment-resistant vulvar lichen sclerosus (VLS). The chronic and recurrent nature of VLS requires control of recurrences at an early stage. In this paper, a non-invasive multimodal optical coherence tomography (OCT) method was used to control for early histological signs of VLS recurrence after systemic PDT using Photodithazine®. To interpret the OCT data, a histological examination was performed before PDT and 3 months after PDT. Two groups of patients were identified: with early histological signs of VLS recurrence (Group I, n = 5) and without histological signs of VLS recurrence (Group II, n = 6). We use structural OCT, OCT angiography, and OCT lymphangiography throughout 6 months after PDT to visually assess the skin components and to quantitatively assess the dermis by calculating the depth-resolved attenuation coefficient and the density of blood and lymphatic vessels. The OCT data assessment showed a statistically significant difference between the patient groups 3 months after PDT. In Group II, all the studied OCT parameters reached maximum values by the 3rd month after PDT, which indicated recovery of the skin structure. At the same time, in Group I, the values of OCT parameters did not approach the values those in Group II even after 6 months. The obtained results of multimodal OCT can be used for non-invasive control of early histological recurrence of VLS after systemic PDT and for adjusting treatment tactics in advance, without waiting for new clinical manifestations of the disease.

Optical Coherence Tomography Angiography and Attenuation Imaging for Label-Free Observation of Functional Changes in the Intestine after Sympathectomy: A Pilot Study

We present in this study optical coherence tomography angiography (OCTA) and OCT attenuation imaging (OCTAI) for in vivo non-destructive visualization of intramural blood and lymphatic vessels of the intestine wall. Rabbit small intestine in the norm and after thoracolumbar sympathectomy served as the object of the intraoperative study. Compared to OCTA real-time imaging, OCTAI takes several minutes and can be termed as “nearly real time”. OCTAI signal processing was modified to take into account the signal-to-noise ratio and the final thickness of the intestine wall. The results showed that, after sympathectomy, changes in functioning of intramural blood and lymphatic vessels were observed with a high statistical significance. The occurrence of trauma-induced constriction of the blood and lymphatic vessels led to an especially pronounced decrease in the length of small-caliber (<30 µm) blood vessels (p < 10−5), as well as in the volumetric density of lymphatic vessels (on average by ~50%) compared to their initial state. Remarkably, OCTA/OCTAI modalities provide the unique ability for “nearly-instant detection” of changes in functional status of the tissues, long before they become visible on histology. The proposed approach can be used in further experiments to clarify the mechanisms of changes in intestinal blood and lymph flows in response to trauma of the nervous system. Furthermore, potentially it can be used intraoperatively in patients requiring express diagnosis of the state of intramural blood and lymph circulation.