Non-telecentric photoacoustic microscopy for multi-scale imaging.

Optical-resolution photoacoustic microscopy (OR-PAM) excels in precisely imaging a biological tissue based on absorption contrast. However, existing OR-PAMs are confined by fixed compromises between spatial resolution and field of view (FOV), preventing the integration of large FOV and local high-resolution within one system. Here, we present a non-telecentric OR-PAM (nTC-PAM) that empowers efficient adaptation of FOV and spatial resolution to match the multi-scale requirement of diverse biological imaging. Our method allows for a large-scale transformation in FOV and even surpassing the nominal FOV of the objective with minimal marginal degradation of the lateral resolution. We demonstrate the advantage of nTC-PAM through multi-scale imaging of the leaf phantom, mouse ear, and cortex. The results reveal that nTC-PAM can switch the FOV and spatial resolution to meet the requirements of different biological tissues, such as large-scale imaging of the whole cerebral cortex and high-resolution imaging of microvascular structures in local brain regions.

Speckle Variance Photoacoustic Microscopy for Microhemodynamic Imaging.

Relying on the strong optical absorption of hemoglobin to pulsed laser energy, photoacoustic microscopy provides morphological and functional information on microvasculature label-freely. Here, we propose speckle variance photoacoustic microscopy (SV-PAM), which harnesses intrinsic imaging contrast from temporal-varied photoacoustic signals of moving red blood cells in blood vessels, for recovering three-dimension hemodynamic images down to capillary-level resolution within the microcirculatory tissue beds in vivo. Calculating the speckle variance of consecutive photoacoustic B-scan frames acquired at the same lateral position enables accurate identification of blood perfusion and occlusion, which provides interpretations of dynamic blood flow in the microvasculature, in addition to the microvascular anatomic structures. We demonstrate high-resolution hemodynamic imaging of vascular occlusion and reperfusion in the microvasculature of mice ears in vivo. The results suggest that our SV-PAM is potentially invaluable for biomedical hemodynamic investigations, for example, imaging ischemic stroke and hemorrhagic stroke.

Improvement of spatial resolution in photoacoustic microscopy using transmissive adaptive optics with a low-frequency ultrasound transducer.

Maintaining a high spatial resolution in photoacoustic microscopy (PAM) of deep tissues is difficult due to large aberration in an objective lens with high numerical aperture and photoacoustic wave attenuation. To address the issue, we integrate transmission-type adaptive optics (AO) in high-resolution PAM with a low-frequency ultrasound transducer (UT), which increases the photoacoustic wave detection efficiency. AO improves lateral resolution and depth discrimination in PAM, even for low-frequency ultrasound waves by focusing a beam spot in deep tissues. Using the proposed PAM, we increased the lateral resolution and depth discrimination for blood vessels in mouse ears.

3D printing of self-standing and vascular supportive multimaterial hydrogel structures for organ engineering.

Three dimensional printable formulation of self-standing and vascular-supportive structures using multi-materials suitable for organ engineering is of great importance and highly challengeable, but, it could advance the 3D printing scenario from printable shape to functional unit of human body. In this study, the authors report a 3D printable formulation of such self-standing and vascular-supportive structures using an in-house formulated multi-material combination of albumen/alginate/gelatin-based hydrogel. The rheological properties and relaxation behavior of hydrogels were analyzed before the printing process. The suitability of the hydrogel in 3D printing of various customizable and self-standing structures, including a human ear model, was examined by extrusion-based 3D printing. The structural, mechanical, and physicochemical properties of the printed scaffolds were studied systematically. Results supported the 3D printability of the formulated hydrogel with self-standing structures, which are customizable to a specific need. In vitro cell experiment showed that the formulated hydrogel has excellent biocompatibility and vascular supportive behavior with the extent of endothelial sprout formation when tested with human umbilical vein endothelial cells. In conclusion, the present study demonstrated the suitability of the extrusion-based 3D printing technique for manufacturing complex shapes and structures using multi-materials with high fidelity, which have great potential in organ engineering.

Comparative study of optical coherence tomography angiography algorithms for rodent retinal imaging.

Optical coherence tomography angiography (OCTA) is a functional extension of optical coherence tomography for non-invasive in vivo three-dimensional imaging of the microvasculature of biological tissues. Several algorithms have been developed to construct OCTA images from the measured optical coherence tomography signals. In this study, we compared the performance of three OCTA algorithms that are based on the variance of phase, amplitude, and the complex representations of the optical coherence tomography signals for rodent retinal imaging, namely the phase variance, improved speckle contrast, and optical microangiography. The performance of the different algorithms was evaluated by comparing the quality of the OCTA images regarding how well the vasculature network can be resolved. Quantities that are widely used in ophthalmic studies including blood vessel density, vessel diameter index, vessel perimeter index, vessel complexity index were also compared. Results showed that both the improved speckle contrast and optical microangiography algorithms are more robust than phase variance, and they can reveal similar vasculature features while there are statistical differences in the calculated quantities.

Photoacoustic-fluorescence microendoscopy in vivo.

A miniature endoscope capable of imaging multiple tissue contrasts in high resolution is highly attractive, because it can provide complementary and detailed tissue information of internal organs. Here we present a photoacoustic (PA)-fluorescence (FL) endoscope for optical-resolution PA microscopy (PAM) and FL microscopy (FLM). The endoscope with a diameter of 2.8 mm achieves high lateral resolutions of 5.5 and 6.3 µm for PAM and FLM modes, respectively. In vivo imaging of zebrafish larvae and a mouse ear is conducted, and high-quality images are obtained. Additionally, in vivo endoscopic imaging of a rat rectum is demonstrated, showing the endoscopic imaging capability of our endoscope. By providing dual contrasts with high resolution, the endoscope may open up new opportunities for clinical endoscopic imaging applications.

Deep learning differentiates between healthy and diabetic mouse ears from optical coherence tomography angiography images.

We trained a deep learning algorithm to use skin optical coherence tomography (OCT) angiograms to differentiate between healthy and type 2 diabetic mice. OCT angiograms were acquired with a custom-built OCT system based on an akinetic swept laser at 1322 nm with a lateral resolution of ∼13 µm and using split-spectrum amplitude decorrelation. Our data set consisted of 24 stitched angiograms of the full ear, with a size of approximately 8.2 × 8.2 mm, evenly distributed between healthy and diabetic mice. The deep learning classification algorithm uses the ResNet v2 convolutional neural network architecture and was trained on small patches extracted from the full ear angiograms. For individual patches, we obtained a cross-validated accuracy of 0.925 and an area under the receiver operating characteristic curve (ROC AUC) of 0.974. Averaging over multiple patches extracted from each ear resulted in the correct classification of all 24 ears.

Posterior auricular artery free flap reconstruction of the retroauricular sulcus in microtia repair.

BACKGROUND: Autologous repair using costal cartilage grafts remains the most widely accepted method of microtia reconstruction. A major complication of current techniques is loss of ear shape caused by scarring, contracture and cartilage absorption. We present a new surgical technique utilizing the posterior auricular artery free flap in microsurgical reconstruction of the retroauricular sulcus in microtia. METHOD: Reconstruction is performed in two stages. In the first stage, a fabricated costal cartilage framework is inserted into a skin pocket as described by Nagata. In the second stage, the ear framework is elevated from the scalp and held by an additional cartilage wedge. Following indocyanine green angiography perforator mapping, a posterior auricular artery perforator flap is harvested from the contralateral (normal) ear and used to reconstruct the posterior auricular sulcus covering the cartilage framework and elevating wedge. RESULTS: The technique was applied to three patients aged 11-15 years with a follow-up time of 8 months to 3 years. The average flap artery diameter was 0.73 mm and the vein was 0.7 mm. Venous congestion occurred in one case and was resolved with a vein graft leading to complete flap recovery. Good ear shape, elevation, projection, skin color and texture were achieved in all the cases. CONCLUSION: Posterior auricular artery flap reconstruction of the retroauricular sulcus in microtia repair is a useful alternative to the current skin graft and tissue expander-based techniques. It provides the ideal skin color and texture match and may improve the overall results of microtia reconstruction by enhancing vascularity.

Effect of Nectaroscordum koelzi Methanolic Extract on Acute and Chronic Inflammation in Male Mice.

INTRODUCTION: The present study deals with the effect of Nectaroscordum koelzi fruit extract on acute and chronic inflammation. METHODS: A total of 84 NMRI mice were used in this study. The effect of the extract on acute inflammation was analyzed by increasing vascular permeability via acetic acid and xylene induced ear edema among mice. The extract was evaluated in terms of effects on chronic inflammation by means of the cotton pellet test among mice. For the assessment of inflammation degree, the mice paw edema volume was measured by the plethysmometric test. RESULTS: The findings showed that the extract was effective on acute inflammation induced by acetic acid in mice. In the xylene ear edema, N. koelzi extract indicated a significant activity in mice. In the cotton pellet method, the methanol extract produced a significant reduction in comparison with the control and dexamethasone. Mice paw edema volume decreased with the extract. CONCLUSION: In general, the data from the experiments indicated that the methanol extract of N. koelzi has an anti-inflammatory effect on acute and chronic inflammation. However, the exact contributing mechanisms have not been investigated for the pharmacological effects.

Cerebral angiography using transauricular access in a rabbit model: a new technique.

BACKGROUND: Cerebral angiography in a rabbit model is widely used in the field of interventional radiology. Conventionally, the femoral artery is used for cerebral angiography in radiology departments. However, angiographic studies require surgical cutdown of the femoral artery, which is technically difficult. PURPOSE: To evaluate a new cerebral angiography technique involving a transauricular approach in a rabbit model. MATERIAL AND METHODS: In each of 10 rabbits, central auricular arteries were punctured in the right or left ear with a 20-gauge i.v. catheter. A microcatheter (2.0 F) with a 0.016-inch guide wire was introduced through the i.v. catheter and advanced to the aortic arch. The microcatheter and guide wire were advanced selectively into cerebral arteries and angiography was performed. RESULTS: Central auricular arteries were successfully punctured with 20-gauge i.v. catheters. After approaching the aortic arch, microcatheter tips and guide wires were advanced manually to cerebral arteries on both sides. Difficulties in selecting the carotid arteries were resolved by using a looping technique within the cardiac chamber. Microcatheter loops within the cardiac chamber disappeared or remained during artery superselection. CONCLUSION: Transauricular cerebral angiography appears to be a feasible technique for brain or carotid intervention studies in rabbits. In addition, vertebral angiography using a transauricular approach is possible using the looping technique. Selection of carotid or vertebral arteries on each side was not difficult when the microcatheter and guide wire were looped within the cardiac chamber. The ear chosen for the initial puncture does not appear to be important.

The Many Faces of Persistent Stapedial Artery: CT Findings and Embryologic Explanations.

Persistent stapedial artery is a vascular anomaly with both clinical and surgical implications. Because of its scarcity, however, it remains underrecognized on imaging. Presented here is a series of 10 cases, demonstrating characteristic CT findings associated with this vascular anomaly and its most common pathognomonic imaging signs. The variable morphologic configurations and their corresponding embryologic underpinnings are described. Clinical and surgical implications of this rare anomaly are discussed.

Arterio-venous malformations of the ear: Description of distinct anatomical presentation and multidisciplinary management approach.

BACKGROUND: Arterio-venous malformations (AVMs) of the ear are a rare entity and their management should be decided in a dedicated multidisciplinary team (MDT) setting. The aim of this study is to describe the distinct anatomical patterns of the auricular AVMs in our unit and propose a combined interventional radiological and surgical approach. MATERIALS AND METHODS: All consecutive patients presenting with AVMs of the ear and reviewed by the Vascular Anomalies MDT between 2014 and 2019 were included in this study. Signs, symptoms, diagnostic investigations and operative findings were collected prospectively. RESULTS: After reviewing our nine patients, we identified four anatomical patterns of auricular AVMs: I: involves just a component of the ear and should undergo embolization followed by excision and reconstruction without significant loss of form; II: affects the superior two-thirds of the ear, sparing the lobule and part of the conchal bowl; these patients should undergo embolization, excision and monitoring before formal reconstruction of the ear is offered; III: involves the entire ear and should undergo embolization and pinnectomy; if there is no recurrence, the patients can be offered either a carved-rib cartilage reconstruction or a prosthesis, depending on the quality of the surrounding soft-tissues; IV: involves the ear and surrounding tissue, making surgical management and subsequent reconstruction extensive. CONCLUSION: The management of auricular AVMs is based on the extent of the ear involved. We feel that our combined interventional radiological and surgical approach will aid the management of these complex patients.

Intravital Imaging of Vascular Permeability by Two-Photon Microscopy.

The regulation of vascular permeability is critical in inflammation. It controls the distribution of water and plasma contents such as immunoglobulins in peripheral tissues. To regulate allergic diseases, it is important to study vascular biology especially in inflammation. Since the vascular permeability changes in minutes upon the exposure to proinflammatory mediators, intravital imaging system is a powerful technique to capture such dynamic responses. We here describe how to evaluate vascular permeability in vivo using multiphoton microscopy. We use various sizes of fluorescence-labeled dextran to visualize how leaky the blood vessels are in the steady state and in inflammation. Using this assay system, we can illustrate the dynamic kinetics of vascular permeability in vivo in real-time. This assay system provides a novel convenient way to study vascular biology that is beneficial in the assessment of various animal models of allergic disease.

Flow driven robotic navigation of microengineered endovascular probes.

Minimally invasive medical procedures, such as endovascular catheterization, have considerably reduced procedure time and associated complications. However, many regions inside the body, such as in the brain vasculature, still remain inaccessible due to the lack of appropriate guidance technologies. Here, experimentally and through numerical simulations, we show that tethered ultra-flexible endovascular microscopic probes can be transported through tortuous vascular networks with minimal external intervention by harnessing hydrokinetic energy. Dynamic steering at bifurcations is performed by deformation of the probe head using magnetic actuation. We developed an endovascular microrobotic toolkit with a cross-sectional area that is orders of magnitude smaller than the smallest catheter currently available. Our technology has the potential to improve state-of-the-art practices as it enhances the reachability, reduces the risk of iatrogenic damage, significantly increases the speed of robot-assisted interventions, and enables the deployment of multiple leads simultaneously through a standard needle injection and saline perfusion.

Effects of Botulinum Toxin Type A on Microvessels in Hypertrophic Scar Models on Rabbit Ears.

BACKGROUND: Although Botulinum Toxin Type A (BTXA) has been applied to scar prevention and treatment, the mechanisms still require further exploration. OBJECTIVE: To investigate the effects of BTXA on microvessels in the hypertrophic scar models on rabbit ears. METHODS: Eight big-eared New Zealand rabbits (males or females) were selected to establish scar models. One ear of each rabbit (4 models in each ear) was selected randomly to be injected with BTXA immediately after modeling and included in the treated group, while the opposite ear was untreated and included in the control group. The growth of scars in each group was observed and recorded, and 4 rabbits were sacrificed on days 30 and 45 after modeling. Then, scar height was measured by hematoxylin-eosin (HE) staining, vascular endothelial growth factor (VEGF) expression was detected by immunohistochemical (IHC) testing, and microvessel density (MVD) was calculated based on CD34 (human hematopoietic progenitor cell antigen). RESULTS: The wounds in each group were well healed and free from infection or necrosis. On days 30 and 45, the scar height, MVD value, and VEGF expression in the treated group were lower than those in the control group (P < 0.05). For the treated group, the above indicators on day 45 were lower than on day 30 (P > 0.05). Besides, there was a positive correlation between the MVD value and the VEGF expression in the treated group (P < 0.05). CONCLUSION: The injection of BTXA immediately after modeling inhibits VEGF expression and reduces angiogenesis, thereby inhibiting hypertrophic scar formation.

Transparent High-Frequency Ultrasonic Transducer for Photoacoustic Microscopy Application.

We report the development of an optically transparent high-frequency ultrasonic transducer using lithium niobate single-crystal and indium-tin-oxide electrodes with up to 90% optical transmission in the visible-to-near-infrared spectrum. The center frequency of the transducer was at 36.9 MHz with 33.9%, at -6 dB fractional bandwidth. The photoacoustic imaging capability of the fabricated transducer was also demonstrated by successfully imaging a resolution target and mouse-ear vasculatures in vivo, which were irradiated by a 532 nm pulse laser transmitted through the transducer.

Serum interleukin-16 significantly correlates with the Vasculitis Damage Index in antineutrophil cytoplasmic antibody-associated vasculitis.

BACKGROUND: Interleukin (IL)-16 is a T cell chemoattractant produced by peripheral mononuclear cells. We investigated whether IL-16 plays a pro- or an anti-inflammatory role in antineutrophil cytoplasmic antibody-associated vasculitis (AAV). Furthermore, we investigated whether the level of IL-16 could predict the activity and extent of organ damage in AAV based on AAV-specific indices. METHODS: Seventy-eight patients with AAV from a prospective observational cohort were included in this analysis. Blood sampling and clinical assessments, including the Birmingham Vasculitis Activity Score (BVAS), Five-Factor Score (FFS), Short Form 36-item Health Survey (SF-36), and Vasculitis Damage Index (VDI), were performed, and laboratory data were collected. Serum IL-16 was measured from stored sera. RESULTS: The median age was 62.0 years, and 27 patients were male. The median serum IL-16 concentration was 84.1 pg/dL, and the median BVAS, FFS, VDI, and SF-36 scores were 7.0, 1.0, 3.0, and 48.0, respectively. Among the AAV-related indices, the serum IL-16 concentration was correlated with VDI (R2 = 0.306, P = 0.006), but not with BVAS (R2 = 0.024, P = 0.834), FFS (R2 = - 0.069, P = 0.550), or SF-36 (R2 = - 0.015, P = 0.898). The serum IL-16 concentration also did not correlate with either the erythrocyte sedimentation rate or the C-reactive protein concentration. Per our analysis based on organ involvement, only patients with ear, nose, and throat manifestations had higher serum IL-16 concentrations relative to those with other conditions (P = 0.030). CONCLUSIONS: This was the first study to elucidate the clinical implication of serum IL-16 in patients with AAV. We found that the serum IL-16 level may reflect the cross-sectional VDI scores among AAV-specific indices. Future studies with larger numbers of patients and serial measurements could provide more reliable data on the clinical implications of serum IL-16 in AAV.

Pulse Pressure Variations and Plethysmographic Variability Index Measured at Ear Are Able to Predict Fluid Responsiveness in the Sitting Position for Neurosurgery.

BACKGROUND: Pulse pressure variation (PPV) and plethysmographic variability index (PVI), dynamic indicators of preload dependence based on heart-lung interactions, are used to predict fluid responsiveness in mechanically ventilated patients in the supine position. The sitting position for neurosurgery, by changing intrathoracic blood volume, could affect the capacity of PPV and PVI to predict fluid responsiveness. The aim of the study was to assess the ability of PPV and PVI to predict fluid responsiveness during general anesthesia in the sitting position. METHODS: In total, 31 patients were included after settling in the sitting position but before surgery began. PPV, PVI with a finger sensor (PVI finger), and PVI with an ear sensor (PVI ear) were recorded before and after a fluid challenge of hydroxylethylstarch 250 mL over 10 minute. Esophageal Doppler was used to record stroke volume. Patients were defined as fluid responders if stroke volume increased by more than 10% after the fluid challenge. RESULTS: In total, 13 (42%) patients were fluid responders. PPV and PVI ear were higher in responders than in nonresponders before the fluid challenge (12±5 vs. 7±3; P=0.0005 and 14±5 vs. 8±3; P=0.001, respectively). Areas under the receiver-operating curves to predict fluid responsiveness were 0.87 for PPV (P<0.0001), 0.87 for PVI ear (P<0.0001), and 0.64 for PVI finger (P=0.17). PPV ≥8% or PVI ear ≥11% predicted fluid responsiveness with sensitivities of 83% for both, and specificities of 83% and 91%, respectively. However PVI ear data were not available in 26% of patients. CONCLUSIONS: PPV can be used to predict fluid responsiveness in the sitting position for neurosurgery.

Development of a novel bio-inspired "cotton-like" collagen aggregate/chitin based biomaterial with a biomimetic 3D microstructure for efficient hemostasis and tissue repair.

Hemostatic materials based on collagen and chitin are commonly assessed with regard to their topical absorbability and bioactivity. However, their clinical application faces challenges such as relatively long hemostatic and wound healing times, single function, as well as wound bleeding in patients with blood diseases. Herein, a novel bio-inspired "cotton-like" collagen aggregate/chitin based biomaterial for rapid hemostatic and tissue repair (V-3D-Ag-col) was fabricated by a specific gradient-removal solvent approach. Significantly, for the first time, an advanced collagen aggregate (Ag-col) composed of typical D-periodic cross-striated collagen fibrils and thick collagen fiber bundles was used instead of traditional collagen molecules (Col) to construct a hemostatic material. The target material showed a biomimetic 3D microstructure and "cotton-like" appearance, as expected, which were conducive to platelet adhesion and aggregation. The fabricated V-3D-Ag-col exhibited superior thermo-stability, hemostatic activity and biodegradability. More importantly, V-3D-Ag-col could significantly promote cell growth and proliferation. Further, V-3D-Ag-col could accelerate the wound healing process better than the same material based on conventional collagen (V-3D-Col). In consequence, V-3D-Ag-col has the potential to become a new generation of collagen-absorbable functional hemostatic materials. Furthermore, Ag-col can replace the currently available conventional collagen materials as raw materials for the new generation of collagen-based biomedical materials.