GreenLight PVP Laser
PHOTOSELECTIVE VAPORIZATION OF THE PROSTATE
Photoselective Vaporization of the Prostate (PVP) is a minimally invasive surgical technique for treating
BPH. The PVP surgical system, called the GreenLight PV™ System, utilizes a specially designed high power KTP laser that emits an average power of 80 W at a wavelength of 532
nm. A side-firing optical fiber is used to deliver the laser light to the prostate. The laser system and fiber optic delivery device were developed by Laserscope in concert with researchers from the Mayo Clinic. Low power KTP lasers (40 W) have been used for prostate treatment since 1991. In 1996, principal investigator Reza Malek performed the first animal studies using a Laserscope KTP laser with an output power of 60
W. Subsequently, Dr. Malek developed the same procedure as a clinical routine in a selected group of patients at the Mayo
Clinic. Over the following years, the procedure was further improved by increasing the laser power to 80 W which facilitates fast tissue vaporization.
The optical fiber is guided to the prostate through a continuous flow laser
cystoscope. The laser light of the GreenLight PV System is delivered through the Laserscope Angled Delivery Device
(ADDStat™) optical fiber and applied to the tissue in a near-contact mode. The ADDStat fiber emits a divergent beam at an angle of 70° relative to the fiber axis. Laser light is directed towards the prostatic adenoma at both the lateral and median lobes. KTP laser energy is fully transmitted through the irrigation fluid present between fiber tip and urethral wall allowing an efficient energy deposition on the tissue.
The laser wavelength of 532 nm is selectively absorbed by the hemoglobin in the prostate tissue giving the PVP Procedure its name
(Photoselective Vaporization of the Prostate). The shallow optical penetration depth of 800 µm causes high volumetric power densities inside the tissue and creates very efficient tissue vaporization. In addition to the vaporization effect, the laser beam induces a thin coagulation zone in the remaining tissue. The extent of the coagulation zone is limited to 1-2 mm because of the shallow optical penetration depth of the KTP laser. The coagulation effect creates hemostasis and thus, gives the surgeon a virtually bloodless procedure.
The tissue effects of the PVP Procedure are far superior to the outcome of the VLAP procedure because the penetration depth of the KTP laser beam is one order of magnitude smaller then the penetration depth of the Nd:YAG laser beam. The KTP laser rapidly heats a superficial tissue layer to the boiling point and vaporizes it immediately. The vaporization progresses layer by layer as tissue is exposed to the laser beam for an extended time. In contrast, the Nd:YAG laser penetrates very deeply into the tissue
(10 mm optical penetration depth) and spreads out itís thermal energy over a larger volume then the KTP laser. A bulk of tissue is heated to the temperature where coagulation occurs but the boiling point is barely reached at the tissue surface. The Nd:YAG laser thus causes a low vaporization efficiency and a deep coagulation necrosis that results in excessive edema formation and delayed sloughing.
The GreenLight PV System quickly vaporizes and removes the prostatic obstruction completely, leaving an open cavity and bloodless urethral channel behind. The PVP Procedure is performed in an outpatient setting, typically a hospital or surgical center, with a typical operative time for an average size gland (50 g) of 30 minutes. Once the PVP Procedure is completed, patients exhibit immediate symptom relief and dramatic improvements in AUA symptom scores, flow rates, and post-void residual volumes.
The PVP Procedure combines the immediate symptom relief and dramatic flow rate improvements of the current "gold standard" procedure,
TURP, with minimal side effects, extremely fast operative and recovery times, and catheterization times that typically range from 0 to 24 hours.
The following tables display the long-term clinical results of KTP laser vaporization of the prostate as reported by Malek et al.14 at the Mayo Clinic. The dramatic improvement of patient performance has been shown to be durable over a
5-year follow-up period.
Post-operative side effects have been minimal and transient. Because the GreenLight PVP Procedure does not cause deep thermal damage or delayed necrosis and tissue is effectively removed to the level of the transverse fibers, there is little risk for retention and many patients are sent home without catheter insertion. Others are sent home with catheters that are typically removed within 24 hours after treatment.
Disadvantages: The GreenLight PVP Procedure can be performed in an outpatient setting with minimal anesthesia (prostate block with mild sedation). Unlike previous laser procedures
(VLAP, ILC), the GreenLight PVP Procedure does not produce delayed necrosis or sloughing of tissue. Therefore, there is no risk of chronic or long-term
dysuria. Moreover, patients do not experience urinary retention and are immediately relieved of the bladder outlet obstruction. In fact, 40% of patients do not require a foley catheter and patients are usually symptom free within a week. The GreenLight PVP Procedure produces
TURP-like effects without the significant morbidity and recovery time. Complications are rare but include retrograde ejaculation and mild transient
The only complications reported from the Mayo Clinic study12
- Mild dysuria in 6% of patients, which resolved within 2 weeks without
- Soft bladder neck contracture in 2% of patients at 3 months, which was
- Delayed hematuria in 3% of patients, due to strenuous exercise.
- Retrograde ejaculation in 28% of patients at 3 months.
The PVP Procedure, like no other BPH treatment option, has been clinically shown to provide dramatic and immediate symptom relief while concurrently providing significant uroflow results and minimal side effects. The PVP Procedure is a fast and easy to learn outpatient treatment that drastically improves both the subjective (symptom relief) and objective
(uroflowometry results) requirements of a successful BPH treatment. Other minimally invasive BPH treatment options require compromises to be made by the patient and/or the physician. With the GreenLight PVP Procedure, there are no compromises, patient's symptoms are drastically reduced and flow rates are significantly improved.