High-Speed Integrated Endoscopic Photoacoustic and Ultrasound Imaging System.

Endoscopic integrated photoacoustic and ultrasound imaging has the potential for early detection of the cancer in the gastrointestinal tract. Currently, slow imaging speed is one of the limitations for clinical translation. Here, we developed a high speed integrated endoscopic PA and US imaging system, which is able to perform PA and US imaging simultaneously up to 50 frames per second. Using this system, the architectural morphology and vasculature of the rectum wall were visualized from a Sprague Dawley rat in-vivo.

Intra-operative point-of-procedure delineation of oral cancer margins using optical coherence tomography.

OBJECTIVES: Surgical margin status is a significant determinant of treatment outcome in oral cancer. Negative surgical margins can decrease the loco-regional recurrence by five-fold. The current standard of care of intraoperative clinical examination supplemented by histological frozen section, can result in a risk of positive margins from 5 to 17 percent. In this study, we attempted to assess the utility of intraoperative optical coherence tomography (OCT) imaging with automated diagnostic algorithm to improve on the current method of clinical evaluation of surgical margin in oral cancer. MATERIALS AND METHODS: We have used a modified handheld OCT device with automated algorithm based diagnostic platform for imaging. Intraoperatively, images of 125 sites were captured from multiple zones around the tumor of oral cancer patients (n = 14) and compared with the clinical and pathologic diagnosis. RESULTS: OCT showed sensitivity and specificity of 100%, equivalent to histological diagnosis (kappa, ĸ = 0.922), in detection of malignancy within tumor and tumor margin areas. In comparison, for dysplastic lesions, OCT-based detection showed a sensitivity of 92.5% and specificity of 68.8% and a moderate concordance with histopathology diagnosis (ĸ = 0.59). Additionally, the OCT scores could significantly differentiate squamous cell carcinoma (SCC) from dysplastic lesions (mild/moderate/severe; p ≤ 0.005) as well as the latter from the non-dysplastic lesions (p ≤ 0.05). CONCLUSION: The current challenges associated with clinical examination-based margin assessment could be improved with intra-operative OCT imaging. OCT is capable of identifying microscopic tumor at the surgical margins and demonstrated the feasibility of mapping of field cancerization around the tumor.

The effect of melanin on in vivo optical coherence tomography of the skin in a multiethnic cohort.

BACKGROUND: Noninvasive real-time assessment of living tissue is quickly becoming invaluable for bolstering histologic and dermatoscopic measures of cutaneous conditions. While many skin researchers have explored the utility of noninvasive imaging in inflammatory and malignant skin conditions, there is yet to be a definitive and direct assessment of the effects of melanin on the quality of optical coherence tomography (OCT) imaging and its accuracy in multiethnic patient populations. We conducted a study to evaluate the effects of melanin on the quality of in vivo OCT imaging. METHODS: Volunteers of all Fitzpatrick skin types were imaged once in five skin regions. Images were analyzed for quality, defined quantitatively as depreciation of light as it passes through the depth of skin, and qualitatively as depth and contrast ranked by blinded clinicians. RESULTS: Our analysis of sixteen subjects shows that there is a significant difference in quantitative OCT image quality between light (Fitzpatrick I-III) and dark (IV-VI) skin types for both epidermal (p 0.0328) and dermal levels (p 0.0021). However, there was no significant difference in qualitative blinded rater measures of image clarity (p 0.11) or perceived depth (p 0.13). CONCLUSION: Based on our definition of image quality, our study shows that OCT images taken from darker skin types have slightly lower quality than those taken from lighter skin. However, because blinded rater assessment showed no differences in clarity or perceived depth, we conclude that OCT may be used without hesitation for manual visualization of skin and its appendages in all Fitzpatrick skin types. Further studies are required to more extensively characterize the effects of melanin on OCT imaging. Lasers Surg. Med. 51:407-411, 2019. © 2019 Wiley Periodicals, Inc.

Deep imaging in highly scattering media by combining reflection matrix measurement with Bessel-like beam based optical coherence tomography.

Multiple scattering in biomedical tissue limits the imaging depth within a range of 1-2 mm for conventional optical imaging techniques. To extend the imaging depth into the scattering medium, a computational method based on the reflection matrix measurement has been developed to retrieve the singly back-scattered signal light from the dominant detrimental multiple-scattered background. After applying singular value decomposition on the measured matrix in the post-process, the target image underneath the turbid media is clearly recovered. To increase the depth of focus of the incident light by elongating the focal spot along the optical axis, a digital grating pattern is specially designed and displayed on a phase-only spatial light modulator to generate the Bessel-like beam for lateral point scanning. According to the results, the depth of focus is increased up to 2.4 mm which is much longer than the value of ∼50 µm obtained by using the conventional focused Gaussian beam, leading to a deeper penetration depth due to the self-healing feature of the Bessel-like beam. In addition, generation of the Bessel-like beam simplifies the axial scanning process by getting rid of the need to mechanically translate the focal zone along the optical axis of an objective with a high numerical aperture. By combining this method with an optical coherence tomography system with a low coherence light source, a depth-resolved optical image is obtained underneath a highly turbid medium.

Intravascular Optical Coherence Tomography for Characterization of Atherosclerosis with a 1.7 Micron Swept-Source Laser.

The main cause of acute coronary events, such as thrombosis, is the rupture of atherosclerotic plaques. Typical intravascular optical coherence tomography (IVOCT) imaging systems that utilize a 1.3 µm swept source laser are often used for identifying fibrous cap thickness of plaques, yet cannot provide adequate depth penetration to resolve the size of the lipid pool. Here, we present a novel  IVOCT system with a 1.7 µm center wavelength swept light source that can readily penetrate deeper into the tissue because of the longer wavelength and allows for better identification of plaques due to the lipid absorption spectrum at 1.7 µm. Using this system, we have imaged a human coronary artery to evaluate the performance of the novel OCT system and verified the results by hematoxylin and eosin (H&E) histology. The significantly improved imaging depth and better identification sensitivity suggest that the 1.7 µm OCT system holds great potential  that can be further translated for in-vivo applications of atherosclerosis characterization.

Evaluation of Contemporary Holmium Laser Fibers for Performance Characteristics.

INTRODUCTION: Several holmium:YAG laser fibers for urologic applications are currently commercially available. We compared contemporary holmium laser fibers with different core sizes for performance characteristics, including energy transmission, fiber failure, fiber flexibility, and core diameter. METHODS: Single-use fibers from Cook, Boston Scientific, and Storz were tested in small (200 and 272/273 µm), medium (365 µm), and large (550 and 940/1000 µm) core sizes. Fibers were tested in straight and deflected configurations. All fibers were evaluated for flexibility, true fiber diameter, energy transmission, and fiber failure. For energy transmission, fibers were tested at a pulse energy of 1 J and a frequency of 10 Hz for 30 seconds. All tests were performed on a 30 W holmium laser. RESULTS: For the small core fibers, Storz, Cook OptiLite, and Smart Sync had the smallest core diameter (p < 0.005). In the large core group, Cook OptiLite and Boston Scientific AccuMax showed the smallest diameter. Among the small core fibers, Storz and Cook Smart Sync showed a significant higher deflection, whereas in the 550 µm group, Boston Scientific AccuMax and Cook Smart Sync were the most flexible fibers. In the large and medium core groups, Boston Scientific AccuMax showed superior energy transmission (p = 0.007 and p = 0.001, respectively), whereas in the small core group, there was no significant difference between the fibers, except for 272/3 µm (Storz was inferior compared with the competitors [p < 0.0005]). For fiber failure, Storz, Cook OptiLite, and BS AccuTrac completed all testing without failing (200 µm, bending radius <0.5 cm). In the 365 µm group, Cook OptiLite showed superior results, whereas in the large core group, Boston Scientific AccuMax was superior. CONCLUSIONS: Performance characteristics differ significantly between different laser fiber diameters and manufacturers, and fiber choice should depend on specific surgical requirements. There is a trend for less fiber fracture at long pulse, high energy, and low frequency, but this finding will require further investigation.

Intrarenal and extrarenal autonomic nervous system redefined.

PURPOSE: The autonomic nervous supply to the kidneys is involved in the development of several diseases including hypertension. The neural distribution at the segmental vessels and intrarenal vasculature has not been well characterized. Thus, we evaluated the autonomic nerve distribution from the great vessels to the renal cortex in a cadaveric model. MATERIALS AND METHODS: We performed a detailed anatomical nerve dissection from the inferior mesenteric artery to the renal operculum in 2 human cadaveric torsos. Autonomic nerve fibers were verified by dissecting the greater splanchnic, sympathetic trunk and ganglia. We then systematically cross-sectioned the kidneys in 12, 1 mm slices across 3.6 cm, and stained the slices for histopathological analysis of neural tissue in relation to segmental arteries and other anatomical landmarks. Advanced reconstructive software was used to create a 3-dimensional computer image. RESULTS: Autonomic nerve fibers are located almost exclusively anteriorly on the main renal arteries and segmental arteries, and are absent from veins. Histopathology revealed that the intrarenal nerves continued to track exclusively with the arteries but were more circumferentially distributed. There is minimal nerve tissue around the veins. Many nerves were within a few millimeters of the renal collecting system. CONCLUSIONS: The autonomic nerves supplying the kidney maintain their distribution almost exclusively along the anterior surface of arteries as they pass from the aorta to the segmental arteries. Once inside the renal parenchyma, the nerves are circumferentially distributed around the renal arteries and are in close proximity to the renal collecting system.