Effects of 532 nm pulsed-KTP laser parameters on vessel ablation in the avian chorioallantoic membrane: implications for vocal fold mucosa.
OBJECTIVE
Selective vascular ablation (photoangiolysis) using pulsed lasers that target hemoglobin is an effective treatment strategy for many vocal fold lesions. However, vessel rupture with extravasation of blood reduces selectivity for vessels, which is frequently observed with the 0.45-ms, 585-nm pulsed dye laser. Previous studies have shown that vessel rupture is the result of vaporization of blood, an event that varies with laser pulse width and pulse fluence (energy per unit area). Clinical observations using a 532-nm wavelength pulsed potassium-titanyl-phosphate (KTP) laser revealed less laser-induced hemorrhage than the pulsed dye laser. This study investigated settings for the pulsed KTP laser to achieve selective vessel destruction without rupture using the avian chorioallantoic membrane under conditions similar to flexible laryngoscopic delivery of the laser in clinical practice.


METHODS
The chick chorioallantoic membrane offers convenient access to many small blood vessels similar in size to those targeted in human vocal fold. Using a 532-nm pulsed KTP laser, pulse width, pulse energy, and working distance from the optical delivery fiber were varied to assess influence on the ability to achieve vessel coagulation without vessel wall rupture.


METHODS
Third-order vessels (n = 135) were irradiated: Energy (471-550 mJ), pulse width (10, 15, 30 ms), and fiber-to-tissue distance (1 mm, 3 mm) were varied systematically.


RESULTS
Selective vessel destruction without vessel wall rupture was more often achieved by increasing pulse width, increasing the fiber-to-tissue distance, and decreasing energy. Vessel destruction without rupture was consistently achieved using 15- or 30-ms pulses with a fiber-to-tissue distance of 3 mm (pulse fluence of 13-16 J/cm).


CONCLUSIONS
This study substantiates our clinical observation that a 532-nm pulsed KTP laser was effective for ablating microcirculation while minimizing vessel wall rupture and hemorrhage.
Broadhurst
Matthew S
MS
Department of Surgery, Harvard Medical School, Center for Laryngeal Surgery and Voice Rehabilitation, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.
Akst
Lee M
LM
Burns
James A
JA
Kobler
James B
JB
Heaton
James T
JT
Anderson
R Rox
RR
Zeitels
Steven M
SM
D000818:Animals; D016063:Blood Loss, Surgical / Q000517:prevention & control; D002642:Chick Embryo; D049033:Chorioallantoic Membrane / Q000098:blood supply* / Q000601:surgery; D006801:Humans; D007431:Intraoperative Complications / Q000517:prevention & control; D007828:Laryngoscopy / Q000379:methods; D017075:Laser Coagulation / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*; D007834:Lasers; D008833:Microcirculation / Q000601:surgery; D018715:Microscopy, Video; D023421:Models, Animal; D010710:Phosphates; D012421:Rupture; D013997:Time Factors; D014025:Titanium; D014827:Vocal Cords / Q000098:blood supply / Q000601:surgery
D010710:Phosphates; C064806:potassium titanylphosphate; D014025:Titanium