In vivo effects of transurethral balloon laser prostatectomy on the canine prostate

Theoretical analysis of transurethral laser-induced thermo-therapy for treatment of benign prostatic hyperplasia. Evaluation of a water-cooled applicator

A mathematical model for predicting the temperature rise in transurethral laser-induced thermo-therapy for benign prostatic hyperplasia was developed. In the model an optical line source emitting light from an Nd:YAG laser isotropically was placed in the urethra. Water cooling of the urethral epithelium was modelled using a two-tube system. The relationship between the difference in outlet and inlet water temperatures and the highest tissue temperature level reached was theoretically investigated. It was found that the water temperature difference was linearly dependent on the steady-state maximum tissue temperature. The theoretical calculations suggest that the water-cooled applicator can be used to measure the maximum tissue temperature. With temperature control, the prostatic tissue temperature can be prevented from exceeding the boiling point of water, excluding tissue carbonization. The model was also used to evaluate the influence of a number of different parameters on the damaged tissue volume. Increasing the urethral lumen radius by a factor of two by means of inserting different sized tubes was found to augment the tissue volume raised to therapeutic temperatures by up to 50%. The calculations showed that cooling of the urethral epithelium can result in an increase in the damaged volume by 80% as compared to not applying any cooling. The temperature of the cooling water was found to influence the tissue temperature only to a small extent.

Transurethral balloon laser thermotherapy: effects of a directionally shielded balloon in canine prostates

BACKGROUND

Transurethral balloon laser thermotherapy (TUBAL-T) improves objective, but not subjective, symptoms of benign prostatic hyperplasia (BPH). We studied whether or not an Nd:YAG laser beam with a shielded balloon could successfully irradiate the prostate during TUBAL-T in selective manner, to improve the subjective symptoms.

METHODS

TUBAL-T was performed on canine prostates using the balloon with a laser probe, which was shielded anteriorly at 90 degrees (from the center of the balloon) and posteriorly at 90 degrees.

RESULTS

At 20 watts laser power, the relative power density in the bilateral non-shielded areas was 17.4 and 17.8, and in the shielded area it was 1.0. Observation by thermography revealed that the temperature after laser radiation in a non-shielded area of a fish cake phantom was higher than in a shielded area. Following transurethral thermotherapy using a shielded balloon in dogs, a cavity was formed bilaterally around the urethra, and the tissues at the anteroposterior sides and the urethra were preserved.

CONCLUSIONS

TUBAL-T, which has been performed in clinical cases of benign prostatic hyperplasia, might be useful in selective irradiation of adenoma if a shielded balloon is used.

Transurethral balloon laser prostatectomy in the canine: medium-term, follow-up results

BACKGROUND AND OBJECTIVE

To demonstrate surgical complications in transurethral balloon laser prostatectomy by medium-term, follow-up observation.

STUDY DESIGN/MATERIALS AND METHODS

Three dogs were treated with transurethral laser irradiation using 15 watts for 20 minutes at 60 degrees C at a 5 mm depth of the prostate, one dog was for 5 minutes with same parameters, and one dog was with only laser balloon probe as a control. All animals were followed for 24 weeks.

RESULTS

A large cavity in the prostatic urethra was formed in laser-treated animals 4 weeks later, whereas the cavity in the balloon-treated animals was not shown. Cavity volume did not significantly change for 6 months, and there was no bladder neck stricture or urethral stenosis observed in any case. An increase in collagen fibers in the periurethral tissue was barely observed by Mallory staining.

CONCLUSION

The risk of bladder neck stricture and urethral stenosis was estimated to be low for transurethral balloon laser prostatectomy.