Nondestructive optical feedback systems for use during infrared laser sealing of blood vessels

High-power infrared lasers are capable of sealing blood vessels during surgery. A real-time diagnostic feedback system utilizing diffuse optical transmission is characterized by nondestructive identification of vessel seals.

For real-time diffuse optical transmission experiments, two approaches were studied. First, a low-power (1.2 mW) visible aiming beam (635 nm) was used for diagnostics, co-aligned with the therapeutic high-power infrared beam (1470 nm). Second, the 1470 nm beam was used simultaneously for both therapy and diagnostics. For both studies, the 1470-nm laser delivered 5 W for 5 seconds for unsuccessful seals (control) versus 30 W for 5 seconds for successful seals, using a linear beam profile (8.4 × 2 mm). Diffuse optical transmission signals were correlated with vessel burst pressures measured using a standard burst pressure setup.

Diffuse optical transmission studies using the low-power, 635-nm aiming beam were promising. A decrease in the visible transmitted signal of 59 ± 11% was measured for successful seals versus 23 ± 8% for failed seals (p = 5.4E-8). The use of the high-power, 1470-nm infrared laser for simultaneous therapeutics and diagnostics proved inconsistent and unreliable, due in part to the dynamic and rapid changes in water content and absorption during the seal.

A low-power, visible aiming beam, integrated with the therapeutic high-power infrared diode laser, may be used as a real-time diagnostic system for indicating successful laser seals, based on significant changes in optical scattering and diffuse optical transmission between native and coagulated compressed vessels. With further development, this simple and inexpensive optical feedback system may be integrated into a laparoscopic device for laser de-activation upon successful vessel sealing.