This PDF file contains the front matter associated with SPIE Proceedings Volume 12355, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

Infrared lasers may provide an alternative to conventional radiofrequency and ultrasonic devices for hemostatic sealing of vascular tissues during surgery. This study explores UV light induced fluorescence from blood vessel walls as a potential non-destructive optical feedback method for indicating successful laser seals. A light emitting diode (LED) with center wavelength of 340 nm and 0.1 mW power was used with a Y-shaped fiber bundle, composed of seven 200-μm-core fibers. The central excitation fiber was split and connected to the LED, while the detection ring of six fibers was connected to a spectrometer. A long-pass filter with 360 nm cut-on wavelength rejected diffusely reflected excitation light. The 7-fiber bundle was aligned with porcine renal arteries compressed between optical windows to simulate placement between laparoscopic sealing device jaws. The fluorescence spectrum was acquired before and after sealing vessels (diameter = 3.0 ± 0.6 mm) with a 1470 nm diode laser for 5 s using incident powers of 30 W (sealing, n = 10) or 5 W (control, n = 10). The tissue fluorescence signal increase in 470-520 nm spectrum using 1s integration times was correlated with vessel seal strengths using industry standard destructive vessel burst pressure measurements. The integrated fluorescence signal increased 71 ± 25% at 30 W (sealing) versus 19 ± 14% at 5 W (control) (p < 0.05), corresponding to successful vessel seals averaging 639 ± 189 mmHg versus failed seals averaging 39 ± 41mmHg (control) (p < 0.05). The increase in tissue fluorescence signal during laser vessel sealing may provide a non-destructive optical method for indicating hemostatic seals. Future work will focus on performing real-time measurements and integrating the fiber optic bundle into the upper jaw of a laparoscopic device.

Atrial fibrillation (AF) is the most common arrhythmia worldwide. An increasingly common treatment option is catheter ablation. During this procedure, the electrophysiologist steers a catheter into the left atrium and ablates a lesion fence around common sources of ectopic signals. This blocks arrhythmogenic tissue from initiating an erroneous heartbeat. Technological advancements in this maturing procedure have made ablations more widespread and effective for patients, but there is still a need to improve long term efficacy of the procedure. The national rate of recurrent AF after an ablation is 20% to 40% and this is almost universally due to reconnection via poor lesion quality. With current catheter feedback available to clinicians, it is difficult to assess whether a lesion line will remain durable or heal to initiate recurrent AF. We have previously shown that polarization-sensitive optical coherence tomography (PSOCT) can monitor lesion formation in vivo during an ablation procedure. This feedback at the catheter tip may help clinicians assess lesion quality by measuring tissue changes. To further understand the technology’s utility and limitations, we are conducting experiments to characterize PSOCT detection of gaps between lesions. Lesion gaps are a common failure mode when AF recurrence is caused by reconnection. We ablate left atrial swine myocardium ex vivo and collect PSOCT images to compare with histology and identify the detection limits of small lesion gaps. Using PSOCT at the catheter tip to detect small gaps in lesion lines could help clinicians reduce recurrence by decreasing opportunities for reconnection.

Infrared (IR) lasers are being tested as an alternative to conventional radiofrequency and ultrasonic surgical devices for rapid hemostatic sealing of vascular tissues. During previous studies, a reciprocating, side-firing optical fiber delivered a linear laser beam across compressed vessels, simulating pressure from laparoscopic device jaws. However, technical challenges include limited field-of-view of vessel position within the jaws, and matching the fiber scan length to variable vessel diameters (2-7 mm). Use of transparent laparoscopic jaws may improve the surgeon’s visibility and enable customized treatment. Transparent quartz square tubing (with dimensions of 2.7 x 2.7 x 25 mm, compatible with a standard 5-mm-outer-diameter laparoscopic port) was sealed on its distal end with a black resin plug for absorbing residual forward directed light. Optical transmission studies were conducted using an infrared (IR) diode laser (1470 nm / 30 W). Razor blade scans and an IR beam profiler were used to acquire side-firing fiber (550-um-core / 0.22 NA) spatial beam profiles. Thermocouples (TC) and a thermal camera recorded peak temperatures and cooling times on the inside and outside surfaces of the quartz jaw, respectively. Side-firing fibers polished at a 50° angle delivered 94% of the light radially (90°) and 2.3% in the forward (0°) direction at powers ≤ 34 W. Total reflection losses for the two quartz-air interfaces measured 6% with 94% of side-firing light transmitted through the quartz tubing wall. Peak TC temperatures on the external surface of the jaw measured 85 ± 14 °C with 23 ± 8 s to cool to body temperature (37 °C). Optical and thermal measurements were conducted on a transparent laparoscopic device jaw for IR laser sealing of vascular tissues. Further development and improved visibility may enable customization of fiber scan length to match variable compressed vessel widths during placement within device jaws.

Photoplethysmography (PPG) is an optical technique to study light absorption variations by blood pulsation. We have developed a flexible thin-film photodiode array combined with flexible LED light sources, both integrated into a wearable form factor, to measure PPG signals at various wavelengths and at any location on the human body in reflection. The array contains 256 photodiodes over an area of approximately 4 cm², which can be read out at high frequencies up to 5.4 kHz. The large number of photodiodes operated at high speeds enables spatiotemporal PPG information with a high signal quality. Furthermore, applying independent component analysis to the data array allows for signal quality mapping and enhancement of the PPG signals over the full array. These wearable sensor arrays allow for new types of cardiovascular health related analysis, such as local biomarker mapping and in-situ probing of blood pulsation at different depths underneath the skin.

A non-contact, laser-based technology is deployed to monitor the detailed mechanical operations of the various chambers and valves of the heart. The high sensitivity, optical speckle-tolerant laser technology enables cardiac signature detection from the skin vascular network at all locations throughout the patient’s body surface, even in the presence of light-blocking surface coverage such as clothing and shoes. In experiments, observed signal features are identified with specific cardiac activity and corroborated with other modalities including electrocardiography. To demonstrate applicability, cardiac monitoring signals were obtained from patients with widely varying ethnical backgrounds. Abnormal signal from one patient exhibiting sinus arrhythmic symptoms was collected and analyzed, indicating the technology’s potential for medical diagnostics.

Laser Doppler vibrometer (LDV) sensors can measure skin vibrations originating from propagating superficial arterial pulse waves, which can be used to assess arterial stiffness and identify stenosis and heart failure. A key challenge is to get sufficient diffusely reflected power from bare skin in order to avoid the use of a retroreflective patch. Here we report a prototype, enabled by silicon photonics, that can directly measure the vibrations of bare human skin. We demonstrate a resolution better than 10 pm/sqrt(Hz) when the skin surface is placed at the focal plane of the sensing beams. This result holds great promise for the targeted cardiovascular applications.

Visualization of collagen fibers in cardiac tissues is essential for clinical diagnosis and pathological analysis of cardiac fibrosis. Selecting a proper imaging method is still challenging for researchers and clinicians who want to determine specific information about the collagen network in cardiac tissues. We examined fibrillar collagen network from mouse ventricular myocardium by commonly available light microscopy techniques using our home-built multimodal microscope. Myocardial slices were unstained or stained with either Picrosirius red or collagen type I antibody/dye conjugation, then imaged by polarized light, confocal fluorescence, second harmonic generation (SHG), two-photon excited fluorescence (TPEF), and stimulated emission depletion (STED) microscopy techniques. This study is intended to serve as a reference for basic research and clinical evaluation of fibrillar collage network in cardiac tissues.

Arrhythmia is the heartbeat losing its regularity or deviating from its average number. Among the types of arrhythmia is atrial fibrillation (AF) and atrial flutter (AFL), which are considered risk factors for development due to high morbidity and mortality. The early detection of AF/AFL is essential because their effects on the heart or complications appear after a considerable time. Electrocardiography (ECG) is a widely used screening method in primary care because of its low cost and convenience. ECG records the heart's electrical activity for a period of time via electrodes attached to the body. Owing to the development of computing power and interest in big data, attempts at deep learning (DL) have increased. The transformer was proposed by Google in 2017 and has achieved state-of-the-art performance in natural language processing. Various transformer-based models have been applied to various tasks beyond natural language processing and have shown promising prospects. However, there have been few cases of vision transformer (ViT) applications in ECG domain. It was difficult to determine whether ViT had sufficient influence in ECG domain. This study determined whether our extensive ECG dataset could make an AF/AFL diagnosis. We also confirmed whether the recently proposed ViT has AF/AFL diagnostic power.