This PDF file contains the front matter associated with SPIE Proceedings Volume 11936, including the Title Page, Copyright information, Table of Contents, and Conference Committee listings.

Infrared lasers may provide faster and more precise sealing of blood vessels and with lower jaw temperatures than ultrasonic and electrosurgical devices. This study explores an oscillating or reciprocating side-firing optical fiber method for transformation of a circular laser beam into a linear beam, necessary for integration into a standard 5-mm-diameter laparoscopic device, and for uniform irradiation perpendicular to the vessel length. A servo motor connected to a side-firing, 550-μm-core fiber, provided linear translation of a 2.0-mm-diameter circular beam over either 5 mm or 11 mm scan lengths for sealing small or large vessels, respectively. Laser seals were performed, ex vivo, on a total of 20 porcine renal arteries of 1-6 mm diameter (n = 10 samples for each scan length). Each vessel was compressed to a fixed 0.4-mm-thickness, matching the 1470-nm laser optical penetration depth. Vessels were irradiated with fluences ranging from 636 J/cm² to 716 J/cm². A standard burst pressure (BP) setup was used to evaluate vessel seal strength. The reciprocating fiber produced mean BP of 554 ± 142 and 524 ± 132 mmHg, respectively, and consistently sealing blood vessels, with all BP above hypertensive (180 mmHg) blood pressures. The reciprocating fiber provides a relatively uniform linear beam profile and aspect ratio, but will require integration of servo motor into a handpiece.

Percutaneous coronary intervention (PCI) for improving calcified coronary artery compliance remains a challenge and is associated with high rates of complications and adverse outcomes. In addition to traditional rotational atherectomy devices for improving coronary artery compliance, recently, electric discharge plasma mediated shockwave therapy has been introduced to cause calcium fracture and improve coronary compliance. However, this intervention has cardiac pacing limitations. Laser lithotripsy is commonly utilized to fracture kidney stones. High powered laser pulses are transmitted via small diameter optical fibers (200-400 μm core diameter) to the stone surface, where they induce fracture. We implemented a novel catheter device that utilizes indocyanine green (ICG) filled balloon to produce calcium fractures. At 2mg/mL, ICG has greater than 5x higher absorption coefficient (256cm^-1, 755nm) than water at 2.1 μm, a typical target of holmium lasers (~40cm^-1, 2.1μm) during lithotripsy. To demonstrate the feasibility of laser induced calcium fracture a balloon catheter device (2mm outer diameter un-inflated, 1 meter long) was constructed with a fiber port coupled to alexandrite lasers (755nm) and a balloon port to fill biocompatible ICG in front of the fiber. Different temporal pulse regimes (millisecond to sub-nanosecond) were explored inducing shockwaves pressure amplitudes higher than 50 atm sufficient to cause fracture in coronary artery phantoms made from Ultracal 30® material. This approach does not require cardiac pacing and can markedly improve arterial vessel compliance during stent deployment.

Coronary chronic total occlusions (CTOs) are atherosclerotic plaques comprised of lipid, fibrous and hard calcific material that originate in the vessel wall and extend into the lumen, restricting luminal cross-section by 100% resulting in complete stoppage of blood flow in the affected artery for at least three months. Due to their structure and calcific composition, CTOs are very difficult to treat with existing percutaneous coronary interventional (PCI) techniques. CTOs frequently have a hard fibro-calcific cap on the proximal side with a softer lipidic composition in the interior and distal side. We constructed a novel catheter system with a fiber coupled Ho:YAG laser (2.1um, Coherent Inc) for cutting and a biocompatible CO₂ cooling system delivered through a 200um conduit for intravascular cooling. Laser radiation delivered a maximum average power of 20W corresponding to a pulse energy of 300mJ, pulse duration of 200μs, and a pulse repetition rate of 10Hz. Light emitted from the fiber was directed onto ex vivo suspect-calcified CTO arteries (n=3). Successful CTO crossing was achieved in all ex vivo samples. Histological processing showed greater than 50% reduction in residual thermal damage in crossed CTO regions with CO₂ cooling compared to no cooling. The miniature device was also used to cross CTOs in an in vivo rabbit femoral CTO model (n=4) under Xray fluoroscopy guidance and subsequent contrast angiography confirmed restoration of blood flow.

High-power infrared (IR) diode lasers are capable of sealing blood vessels during surgery. This study characterizes an optical feedback system for real-time, nondestructive identification of vessel seals. A low power, red aiming beam (635 nm) was used for diagnostics, co-aligned with a therapeutic high-power IR beam (1470 nm). The IR laser delivered either 30 W for 5 s for successful seals or 5 W for 5 s for unsuccessful seals (control). All studies used a linear beam measuring 8.4 x 2.0 mm. Optical signals for successful and failed seals were correlated with vessel burst pressures (BP) using destructive testing via a standard BP setup. Light scattering increased significantly as vessels were coagulated. Successful seals correlated with a percent decrease in optical transmission signal of 59 ± 11 % and seal failures to a transmission decrease of 23 ± 8% (p < 0.01). With further development, the real-time optical feedback system may be integrated into a laparoscopic device to de-activate the laser upon successful vessel sealing.