Temporal and spatial temperature profile of the bladder serosa in intravesical neodymium-YAG-laser irradiation. An investigation to determine the therapeutic range of a new process for the treatment of bladder tumors

Free-Beam and Contact Laser Coagulation

Laser coagulation of benign prostatic hyperplasia (BPH) encompasses a variety of techniques using different laser wavelengths, application systems, and surgical techniques to achieve contrasting tissue effects. During transurethral laser coagulation, known as visual laser ablation of the prostate (VLAP), the prostate is irradiated by free-beam Nd:YAG or diode laser energy. The coagulated and necrotic tissue sloughs off within weeks to months. In randomized studies comparing laser coagulation and transurethral resection of the prostate (TURP), symptoms and some voiding parameters improved significantly after laser coagulation, although not to the level obtained with TURP. However, the operative duration and the length of hospitalization have been shorter than for TURP, and major complications have not occurred. Follow-up clinical data and retreatment rates are available for up to 5 years with a remarkable variability. Although retreatment rates may be high, patients who are "responders" to the treatment after 2 to 3 years seem to have durable results after 4 to 5 years and even longer.

Neodymium-YAG laser treatment in localized prostatic cancer. High rate of local failure

Clinically localized prostatic cancer, T0-2,NX,M0, was treated with extended transurethral resection and subsequent neodymium-YAG laser irradiation of the prostatic cavity in 20 patients in 1987-1990. The patients' mean age was 71 (range 64-84) years. During 12-month follow-up only three patients had negative biopsies, whereas 16 had residual cancer and one had atypical, suspectedly malignant cells. Eight of the 16 with residual cancer underwent repetition of the combined resection and laser treatment, but this led to negative biopsies in only two cases. The treatment per se was well tolerated and side effects were few, but the poor outcome concerning local tumor control is contradictory to previous reports and raises doubts as to the advisability of offering such treatment as an alternative to radical prostatectomy.

Application of lasers in bladder cancer

The Nd:YAG laser enables endoscopic destruction of bladder tumors under excellent viewing conditions in a specific and calculable way for induction of homogeneous necroses with simultaneous occlusion of blood and lymphatic vessels. The low local relapse rate, in contrast to that with TUR, is remarkable. By Nd:YAG laser application in combination with or without pelvic lymphadenectomy we were able to reduce the cystectomy rate significantly in recent years.

Bladder perforation resulting from the use of the neodymium:YAG laser

Complications resulting from the use of the neodymium:YAG (Nd:YAG) laser to treat superficial bladder cancer are uncommon and are usually associated with abnormally high laser power outputs. We report a case of bladder perforation in a human attributed to the Nd:YAG laser used at a low power setting and comment on those factors that contributed to this complication.

Neodymium: YAG laser specifications for safe intravesical therapy

The depth of penetration of a laser beam is a critical factor in determining the therapeutic potential and risks of treatment. Variable parameters of laser energy were applied endoscopically in dog bladders. Although there was a clear trend toward greater depth of necrosis with increased energy, marked variability occurred within each set of energy specifications. Full thickness injuries with penetration depths up to five mm. were observed in some animals at all energy levels above 120 joules. A number of variables affect the penetration depth of a Nd:YAG laser, some of which are difficult to control with precision in an endoscopic setting.

Installation and use of a neodymium-YAG laser in a urology department

We report our experience in setting up a urological laser unit. An operating theatre was upgraded to include the required safety features and a neodymium-YAG laser was installed. A preliminary study using cadaver bladders was performed to establish the technique of cystoscopic laser application. We treated 55 bladder tumours in 12 patients by laser coagulation, with total destruction of 54 tumours and no serious complications; 6 patients developed recurrent tumours. Twenty-one patients underwent surgery with the contact laser scalpel. The instrument proved slow but effective, with excellent haemostasis and almost painless wounds. Healing was delayed in 2 cases but there were no wound infections. All wounds healed with good cosmetic scars. The neodymium-YAG laser is an effective means of destroying superficial non-invasive bladder tumours endoscopically and can also be used in conjunction with a laser scalpel for open surgery.

Laser induced shock wave lithotripsy--biologic effects of nanosecond pulses

Laser energy of a Nd-YAG laser (1064 nm. wave length, 8 nsec pulse duration) was directed against various tissue cultures and the urothelium of the ureter, bladder and kidney parenchyma in pigs. Single pulse energy was 50 to 120 mJ with a repetition rate of 20 Hz. Urothelium and kidney parenchyma were irradiated in seven pigs. Tissue samples were examined histologically and electron microscopically directly, two, four, eight and 12 days after irradiation. No macroscopic lesion could be found. Maximum energy caused a small 'rupture cone' of 40 micron. depth. No thermic effects or necrosis resulted, so that no harm is to be expected with unintentional irradiation during laser stone disintegration.

YAG laser treatment of early carcinoma of the prostate

We describe our initial experience of a method which develops the role of endoscopic surgery in the treatment of early prostatic carcinoma. An "extended" transurethral resection of the prostate (TURP) under ultrasound control reduces the prostatic tissue to a thin residual capsule suitable for subsequent transmural coagulation by endoscopic YAG laser. Twenty patients with early disease were entered into the pilot study. Three were excluded after staging (2 T0a and 1 with positive nodes on pelvioscopy-T2 N1 M0); 17 received a full course of treatment. Mean follow-up was 6 months (range 1-14). Two early patients with excessive residual tissue had initially positive biopsies and underwent second treatments with subsequently negative biopsies. Two patients continue to have positive biopsies and the rest are negative. No tumour has progressed and complications have been minimal. One patient experienced reduced frequency of erections and 1 required bladder neck incision for symptomatic bladder neck stenosis at routine follow-up endoscopy. There were no other effects on either potency or continence.

ND: YAG nomogram dosimetry scale for the bladder

Bowel perforation and damage to surrounding organs is probably the most significant risk with the use of Nd-YAG laser in the bladder. To prevent this unwanted damage, a nomogram dosimetry scale was developed by delivering different settings of laser energy via a cystoscope to 25 female pigs. One week following treatment, exploratory laparotomy and cystectomy were performed. Microscopic analysis of the depth of laser irradiation was accomplished. From this study it was learned that, although the greater the energy delivered, the deeper the tissue damage, this is not uniform. Pulsed energy produced a deeper effect than continuous energy. The use of 30 watts of either pulsed or continuous energy for no longer than 15 seconds (450 joules) or 10 watts of either form of energy for less than 30 seconds (300 joules) did not produce bowel perforation. Other different combinations of high number of watts or pulses translated into transmural necrosis of the bladder with or without perforation and with or without bowel injury. Other factors such as density, thickness, color and temperature of tissue, type and wave length of laser and optimal focusing played a significant role in the final outcome. Useful information for human clinical use may be extrapolated from this experimental model.

Treatment of invasive bladder cancer with a neodymium:YAG laser

In a controlled setting a neodymium:YAG laser is capable of producing a transmural coagulation of the bladder wall without perforation. A total of 21 patients with known muscle-invading bladder cancer underwent treatment with transurethral endoscopic application of neodymium:YAG laser energy. One patient suffered a sigmoid colon perforation that possibly was treatment-related but no other complications were observed. Four of 5 patients with clinical stage B1 and 3 of 6 with stage B2 lesions have had normal post-treatment biopsies. Local tumor control has been achieved in only 1 of 4 patients with a clinical stage C tumor and none of 6 with metastatic cancer, although palliative debulking was accomplished.

Laser ablation of human atherosclerotic plaque without adjacent tissue injury

Seventy samples of human cadaver atherosclerotic aorta were irradiated in vitro using a 308 nm xenon chloride excimer laser. Energy per pulse, pulse duration and frequency were varied. For comparison, 60 segments were also irradiated with an argon ion and an Nd:YAG (neodymium:yttrium aluminum garnet) laser operated in the continuous mode. Tissue was fixed in formalin, sectioned and examined microscopically. The Nd:YAG and argon ion-irradiated tissue exhibited a central crater with irregular edges and concentric zones of thermal and blast injury. In contrast, the excimer laser-irradiated tissue had narrow deep incisions with minimal or no thermal injury. These preliminary experiments indicate that the excimer laser vaporizes tissue in a manner different from that of the continuous wave Nd:YAG or argon ion laser. The sharp incision margins and minimal damage to adjacent normal tissue suggest that the excimer laser is more desirable for general surgical and intravascular uses than are the conventionally used medical lasers.

Transurethral laser coagulation for treatment of urinary bladder tumors

Owing to the biophysical properties involved, the Nd:YAG laser is most suited for coagulation of even inhomogeneous tissue. We determined the optimal laser parameters for therapy of urinary bladder tumors. Deep homogeneous necroses can be obtained without perforation risk of the bladder wall, and the procedure does not cause dangerous damage to the intestinal loops. We have studied animal experiments by close examination and systematic inquiry, and thus we were able to determine sufficient laser parameters in dependence on tissue thickness. Clinical studies verified these results for living human tissue. After some years of clinical use of the Nd:YAG laser we can make the first statistical statements.