Human prostatic tissue constituents respond differently to thermal injury induced by Nd-YAG laser ITT fiber applied ex-situ.

BACKGROUND AND OBJECTIVE: The human prostate is a glandular organ that has intervening fibromuscular elements. The objective of this study was to evaluate the thermocoagulative effect on the different components of the organ exposed to Nd-YAG laser irradiation using a new ITT optic fiber design (Interstitial Thermal Therapy). STUDY DESIGN/PATIENTS AND METHODS: Twelve fresh transvesical prostatectomy specimens were irradiated ex-situ at 4 to 6 sites using an ITT fiber with laser energies ranging from 900 to 4500 joules (J) applied at times ranging from 60 to 300 seconds corresponding to 10 to 15 watts. The specimens were serially sectioned to include the proximal, mid and distal regions of the centrally coagulated channel. An ocular grid was utilized to measure the radius (r) of thermal injury from the margin of the centrally coagulated channel to the furthermost detectable area of thermally induced changes. RESULTS: The maximal extent of thermal injury was seen at the mid-length of the irradiated channel at energy of 2700 J (15w/180 sec). The fibromuscular compartment of the prostate was more affected (r = 855 microm) and showed more interstitial vacuolization and charring than the adenomatous one (r = 495 microm). Utilization of higher energy doses did not significantly alter the depth of injury but did reduce the extent of interstitial vacuolization of both components. CONCLUSION: The study indicates that the extent of laser induced coagulative necrosis depends on the histologic architecture of the prostate and also varies in extent along the length of the channel surrounding the fiber.

Endometrial laser interstitial hyperthermy: a potential modality for endometrial ablation.

This study was undertaken to evaluate the efficacy and safety of an intrauterine device designed for endometrial ablation by Nd-YAG laser interstitial hyperthermy. Eight hysterectomy specimens were treated in vitro with an output power of 30 W for 5 minutes; tissue temperatures, recorded by thermocouples, were plotted to draw time-temperature and time-distance curves. As a preliminary series, ten patients were treated, with the first five subjected to local temperature monitoring; all ten were followed-up for 6-17 months. Immediate and delayed (6 weeks) histologic data were obtained. The intramural temperature at 6 mm from the fibers ranged from 55-60C). In vivo, the cooling effect of the arterial blood flow lowered the serosal temperatures under 41C. The histologic data and the hysterographic pictures suggest that endometrial ablation was effective. This new device does not require distending medium, hysteroscopic control, or high-powered Nd-YAG laser machines. Preliminary long-term results suggest that the device could be used for endometrial ablation.

A neodymium:YAG fiber delivery system for interstitial photothermal therapy.

We describe here a highly durable 600-mu optical fiber with a 20-mm frosted distal tip protected by a smooth transparent cover that is capable of remaining in contact with tissue for prolonged periods. When used with a neodymium:YAG (Nd:YAG) laser, the active fiber surface diffuses optical radiation in a radial pattern, delivering up to 40 W power, and thus providing consistent and uniform interstitial photothermal therapy. Preliminary animal studies have demonstrated the feasibility of using these fibers to treat a variety of soft-tissue tumors, including benign prostatic hyperplasia.