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Laser in urology

LASERS IN UROLOGY

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Laser in urology

  1. 1. LASERS IN UROLOGY Urology NIMS
  2. 2. INTRODUCTION LASER is an acronym for: • L : Light • A : Amplification (by) • S : Stimulated • E : Emission (of) • R : Radiation The world’s first laser was developed by Theodore Maiman in 1960 Term coined by Gordon Gould. Laser means to absorb energy in one form and to emit a new form of light energy which is more useful.
  3. 3. LASER CHARACTERISTICS
  4. 4. LASER Vs LIGHT  Stimulated emission Spontaneous emission.  Monochromatic. Polychromatic  Highly energized Poorly energized.  Parallelism Highly divergence  Coherence Not coherent  Can be sharply focussed. Can not be sharply Focused
  5. 5. LASER PHYSICS • Light as electromagnetic waves, emitting radiant energy in tiny package called ‘quanta’/photon. • Each photon has a characteristic frequency and its energy is proportional to its frequency.
  6. 6. THREE BASIC WAYS FOR PHOTON& ATOMS TO REACT  ABSORPTION  SPONTANEOUS EMISSION  STIMULATED EMISSION
  7. 7. • Stimulated emission leads to a chain reaction and laser emission • If a medium has many excited molecules, one photon can become many(Population inversion medium)
  8. 8. The biophysics of laser-tissue interactions  Factors affecting laser-tissue interactions:    Local tissue properties Local blood circulation Laser:    wavelength Energy mode
  9. 9. The biophysics of laser- tissue interactions • Molecules, proteins, and pigments may absorb light only in a specific range of wavelengths 
  10. 10. The biophysics of laser- tissue interactions  Surgeons currently using lasers seek 4 different effects—     Thermal Mechanical Photochemical tissue welding effects
  11. 11.  •The most common utilization is the thermal effect, whereby light energy is absorbed and transformed into heat •The wavelength of laser light can be proportional to the depth of penetration into specific tissues •The longer the wavelength, the deeper the expected penetration •The mechanical effect results, for example, when a very high power density is directed at a urinary calculus.This creates a plasma bubble that swiftly expands and acts like a sonic boom to disrupt the stone along stress lines
  12. 12. The photochemical effect refers to the selective activation of a specific drug or molecule, which may be administered systemically but is taken up in selected tissues
  13. 13. • Finally, the tissue-welding effect is derived by focusing light of a particular wavelength to induce collagen cross- linking 
  14. 14. CLASSIFICATION OF LASERS • Solid State Ruby Nd.Yag Erbium.YAG • Gas Argon Krypton He-Neon CO2 • Metal Vapour Cu Gold Dye Rhodamine Excimer Argon fluoride Krypton fluoride krypton chloride Diode Gallium-Alluminium Arsenide(GaAlAs)
  15. 15. Today, the types of lasers most commonly used in urology include: • KTP (potassium titanyl phosphate) • LBO (lithium triborate) • Diode laser. • Nd:YAG • Ho:YAG (holmium:YAG); • Thu:YAG (thulium:YAG); • CO2 (carbon dioxide);
  16. 16. • Gas as active medium: Nitrogen (N), carbon dioxide (CO2), helium (He) and neon (Ne). • Liquids as medium soon followed: the so-called ‘dye lasers’, because the lasing agent is an organic dye . Dye lasers have the advantage of being able to generate amplified light with a wider range of wavelengths. • Solid-state lasers utilized Nd:YAG (neodymium-doped yttrium aluminium garnet) as a medium.
  17. 17. Classification of laser output of particular practical importance in urology PULSED WAVE (PW) • PW operation on the other hand, delivers forceful bursts of laser energy, which is useful for stone fragmentation CONTINUOUS WAVE (CW). • CW operation the output of the laser is continuous and of constant amplitude. • The clinical effect is a more controlled interaction with the tissue.
  18. 18. • A basic understanding of the light-tissue interaction of lasers is required in order to fully appreciate important aspects such as penetration depth, thermal effects and reflection. • Absorption is the most important interaction of laser light with tissue. A chromophore is required in order to achieve absorption: body chromophores accessible for laser light include blood, water and melanin. • Absorbed laser light is converted to heat and depending on the amount of heat, the clinical effect will be tissue coagulation or vaporization. Absorption depth is dependent on the wavelength of the laser.
  19. 19. Characteristics of particular individual lasers Nd:YAG laser • was the most commonly used laser in the past . • It is characterized by more than 1 cm tissue penetration and by 1064 nm wavelength. • It causes deep coagulative necrosis and considerable thermal tissue injury. • Nd:YAG laser can be used for : -Non-contact ‘visual laser ablation of the prostate’ (VLAP), -Contact ablation or interstitial laser coagulation (ILC) of the prostate. • Oedema occurring after procedure frequently leads to irritative lower urinary tract syndrome (LUTS) and urinary retention, which often requires long-time catheterization.
  20. 20. Ho:YAG laser • is a pulsed type of laser that emits energy absorbed by the water. • It is characterized by wavelength of 2140 nm and pulse duration of 350 ms. • The depth of penetration in the prostate tissue is only 0.4 mm. The depth of necrosis and thermal damages is limited. • Ho-laser causes rapid coagulation of small and medium-sized vessels to the depth of about 2 mm. • Because this laser requires contact with the tissue, prostate can be precisely incised, dissected and enucleated. • Ho-laser is mainly used for procedures on the prostate, in lithotripsy, ablation of urothelial tumours and for upper and lower urinary tract strictures incision
  21. 21. KTP: YAG laser • KTP: YAG laser, also called green light laser, is derived from Nd: YAG laser. • Passing the invisible Nd:YAG beam via a KTP crystal, doubles the frequency and halves the wavelength from 1064 nm to 532 nm. • Its energy is selectively absorbed by haemoglobin, but not by water. • The penetration depth is about 0.8 mm. • It is characterized by a very good coagulation effect, which results in a good control of haemostasis. • Because energy of KTP laser is absorbed only by haemoglobin, it is possible to perform operations in noncontact use called photoselective vaporization of tissue. • Due to shallow absorption rate, necrosis of the tissue localized beneath the vaporized area is limited. An additional advantage is an almost bloodless course of the procedure.
  22. 22. Tm:YAG laser • The Tm:YAG laser produces continuous, 2000 nm wave. • Energy is absorbed only by water and slightly shorter wavelength of thulium laser decreases the depth of penetration to 0.25 mm. • The Tm-laser is used for transurethral vaporization, enucleation or resection of the prostate.
  23. 23. lithium triborate (LBO) laser • Dderived from KTP-laser. • The wavelength of both lasers is equal. • However, LBO-laser has an accelerated and a more efficient energy transfer and enhanced working distance (from 0.5 mm for KTP to 3 mm for LBO) • A significant disadvantage of this laser is a marked decrease in haemostatic ability in comparison to KTP laser
  24. 24. Diode lasers • Diode lasers emit a beam of wavelength between 940 to 1470 nm. • • Their energy is absorbed by both water and haemoglobin. • As a result, good haemostatic and vaporisative effects are obtained . • Some reports on a 980 nm diode laser demonstrate its better haemostatic effect during prostate vaporization in comparison to 120 W LBO laser • Higher incidence of complications, such as postoperative irritative symptoms and epididymitis, is noted.
  25. 25. ADVANTAGES OF LASER • Greater precision and accuracy • Less invasive • It seals blood vesselS so less bleeding,swelling and pain • Good alternative in patients with high comorbidities that are not suitable for open surgery • Operating and hospitalisation time short • Most of procedure can be done on outpatient baisis
  26. 26. DISADVANTAGES • Operator training and experience • Laser equipment are costly and not widely available • Strict safety precaution in operating room
  27. 27. Uses
  28. 28. Benign prostatic hyperplasia • The ability of the laser to ablate prostatic tissue with minimal hemorrhage has concentrated most of the interest in urologically applied lasers to benign prostatic hyperplasia (BPH) • The use of different lasers types allows the performance of BPH ablation, enucleation, coagulation and vaporization • laser treatments are performed in 0.9% NaCl environment, so transurethral resection syndrome, which occurs in 1.4% pts. after TURP, does not occur after laser techniques •
  29. 29. • One of the earliest techniques used for Nd:YAG laser treatment of BPH was called ‘visual laser ablation of the prostate’ (VLAP). • This involves lasing prostatic tissue in a noncontact fashion to create an area of heat-induced coagulative necrosis that extends about 10 mm into the tissue. The method is reasonably simple to learn and perform, is safe in anticoagulated patients and carries no risk of the TURP syndrome. However, edema and prolonged sloughing of the coagulated tissue leads to irritative lower urinary tract syndrome (LUTS) and urinary retention requiring catheterization, often for long periods (3 months), in up to 30% of cases
  30. 30. • Another approach in which the Nd:YAG laser can be used is the contact mode, which leads to real-time destruction of prostatic adenoma. • A ‘contact tip’ converts laser light to heat, which induces vaporization and immediate creation of a cavity. • As with VLAP, no tissue is available for histology, but this approach has the advantages of immediate relief of obstruction, early catheter removal and decreased postoperative LUTS and urinary retention. •
  31. 31. • Apart from VLAP and contact ablation, the Nd:YAG laser can also be used for performing interstitial laser coagulation (ILC) of the prostate. • The procedure is performed by placing laser-diffusing fibers directly into the prostatic adenoma, either via the transurethral cystoscopic approach, or the perineal approach. • Laser energy then produces coagulation necrosis within the adenoma, which subsequently undergoes atrophy • As is the case with VLAP, this method is safe in anticoagulated patients, but substantial tissue edema also usually necessitates prolonged (7–21 days) postoperative catheterization.
  32. 32. • KTP laser, green light laser, frequency-doubled Nd:YAG laser and photoselective vaporization of the prostate (PVP) all refer to the same modality. • It is used in a noncontact fashion, causes immediate vaporization of prostatic tissue and is a virtually bloodless procedure. • Due to the limited absorption depth, necrosis of the tissue underlying the vaporized area, with subsequent edema, is not a problem. • Some authors have reported discharging patients on the day of surgery without a catheter, even those with prostates sizes in excess of 100 g • They reveal that photoselective vaporization of the prostate (PVP) seems to be a safe and effective procedure and could play an important role in the surgical treatment of symptomatic BHP patients with larger prostate volumes • Today, ‘high-power’ KTP laser prostatectomy refers to a power output of 80 W.
  33. 33. • The 120 W lithium triborate (LBO) laser was the next step in the evolution of the 532 nm lasers. The aim with this system was to overcome the still relatively slow tissue ablation ability of the ‘high-power’ 80 W KTP, which leads to time-consuming procedures in patients with large prostate glands . • Not only is energy transfer and tissue ablation faster and more efficient, but the working distance is also increased (working distance for KTP is 0.5 mm, for LBO it is up to 3 mm), making the LBO laser technically simpler to use. • Unfortunately, a drawback of the higher power setting is a reduction in the hemostatic ability.
  34. 34. • The Ho:YAG laser to be the pinnacle of evolution of urological lasers: not only is it ideally suited for procedures on the prostate,but it is also extremely effective as an intracorporeal lithotriptor for most stones. • used in the setting of ablation of urothelial tumors and incision of strictures of the upper and lower urinary tract . • The following features of the holmium laser make it such a useful instrument in prostate surgery: a) Absorption depth in the prostate is only 0.4 mm, creating a high energy density sufficient for vaporization. b) Dissipating heat causes simultaneous coagulation of small blood vessels to a depth of about 2 mm. c) This enables precise, char-free and virtually bloodless incision in prostatic tissue.
  35. 35. • The Thu:YAG Vaporisation (ThuVAP), vaporesection (ThuVARP), vapoenucleation (ThuVEP) and enucleation of the prostate (ThuLEP) with thulium laser are also effective and promising techniques. • thulium lasers do not allow lithotripsy which limits their application and usefulness.
  36. 36. • The incidence of urinary incontinence after KTP PVP is 1.4%, 0.7% after LBO PVP, after diode PVP ranges from 0-10%, and after HoLEP is about 0% while after TURP is 3% • Retrograde ejaculation occurs at a similar level in laser and TURP groups and is observed in approximately 50% of cases. • Narrowing of the bladder neck was observed in 3.6% of patients after LBO PVP and in 7.4% of patients after TURP
  37. 37. Stones • use of the pulsed dye laser for stone fragmentation appeared in 1987 • This was a very promising new technology enabling endoscopic fragmentation of more than 80–95% of stones and urothelial injury being rare. • Drawbacks were very high initial costs and expensive disposables (coumarin dye), as well as trouble with fragmentation of notoriously ‘hard’ stones composed of calcium oxalate monohydrate (COM) and cysteine • It is also shown that laser lithotripsy is a superior method in cost-effectiveness analysis compering to SWL for renal stones <1.5 cm
  38. 38. • The FREDDY (frequency doubled double-pulse Nd:YAG) laser was the next step in laser lithotripsy, and • consists of a KTP crystal incorporated into a Nd:YAG laser. • This enables the laser to produce two pulses: a 20% green light component at 532 nm and an 80% infrared component at a wavelength of 1,064 nm. • This combination works in synergy to enable highly effective stone fragmentation, mainly via a mechanical shockwave with very little thermal effects. • Another major advantage is the extremely low risk of damage to the ureteral wall when using this laser . • Unfortunately the ‘hard’ types of calculi also present a challenge to this laser, as is the case with the pulsed dye lasers • Another problem is that the FREDDY laser is only able to effectively fragment dark or colored stones that absorb the green wavelength.
  39. 39. • The use of the Ho:YAG laser has also become the one most commonly used for lithotripsy . • Fragmentation occurs through a photothermal effect and requires direct contact of the laser tip with the stone • A major advantage is minimal retropulsion effects during stone fragmentation • • its ability to fragment all types of stones, including cysteine, brushite and COM . • The holmium laser can either reduce stones to tiny fragments that are easily cleared from the collecting system with outflow or irrigant, or larger stones can be broken up and fragments removed using baskets or grasping forceps
  40. 40. Use in bladder Carcinoma • Several reports suggest the superiority of the laser method over TURBT, because it seems that a recurrence of cancer after laser treatments is not more frequent than after TURBT and complication rates seem to be lower after modern laser procedures when compared to TURBT • Laser techniques allow laser vaporization (LV), en bloc resection of BC and BC ablation. LV is suitable as an outpatient procedure because it does not require general anaesthesia. • However, staging of BC is impossible after LV, therefore, LV is not recommended for the treatment of primary BC
  41. 41. Transitional cell carcinoma • The Ho:YAG and Nd:YAG lasers are the ones most frequently used for treating lesions located in the renal pelvis and ureter. • . The Nd:YAG laser coagulates tissue to a depth of several millimeters (5–10 mm) and is appropriate when dealing with large tumors. • Direct contact of the laser fiber with the tumor is unnecessary and should be prevented, as this causes charring at the tip of the fiber with a resulting decrease in the effectiveness of the laser. • The depth of penetration of the Ho:YAG laser is significantly less (0.4 mm), which makes this a much safer choice when dealing with small tumors in the ureter
  42. 42. • Photodynamic therapy (PDT) for superficial TCC of the bladder is a diagnostic and treatment modality where laser light can be used. The PDT mechanism relies on in situ generation of toxic agents by the activation of a light sensitive drug (also called the ‘photosensitizer’) • Diode lasers are popular here as they can be produced to match the desired wavelengths of most photosensitizer drugs (630–760 nm), but other light sources can also be used
  43. 43. Strictures of the upper and lower urinary tract • An argon laser for the treatment of urethral strictures • Using the laser instead of a cold knife, in the same way as was initially described by Sachse [1978], seemed to be effective, but further follow up revealed a high recurrence rate of up to 70.1% at a mean of 15.2 months . • Other lasers that have also been investigated include the Nd:YAG, KTP and Ho:YAG lasers. • More recently, the Thu:YAG laser was investigated in this setting. Its penetration depth of only 0.3 mm should cause very little injury to surrounding tissue, making it an ideal instrument for optical urethrotomy
  44. 44. Ureteropelvic junction (UPJ) obstruction • can also safely be managed with endopyelotomy using the Ho:YAG laser. Results seem to be more or less similar to those achieved with the ‘hot-wire balloon’ • The holmium laser is also effective in the minimally invasive treatment of ureterovesical anastomotic strictures after renal transplant as well as ureterointestinal anastomotic strictures after urinary diversion
  45. 45. Laser tissue soldering • Laser tissue soldering (LTS) has been used to obtain a watertight anastomosis in different tissues for more than 20 years. • A diode, CO2 or Nd:YAG laser can be used with albumin as a solder . • LTS relies on the photothermal properties of laser light. • When performing LTS, laser energy is applied to a solder in conjunction with laser wavelength-specific chromophores to facilitate laser light absorption. The resultant temperature increase denatures the solder, which then forms a coagulum that increases the strength at the repair site . • In urology it has been successfully utilized in anastomosis of skin (hypospadias repair), bladder, urethra, renal pelvis (UPJ repair), as well as for vasovasostomy. • In order to safely perform LTS, the laser power needs to be regulated: although higher power densities provide a stronger initial weld, there will be increased thermal damage to surrounding tissue which compromises tensile strength of the repair after a few days. Average soldering speed is around 1 minute per centimeter of incision length
  46. 46. Penis carcinoma • It is generally accepted that the risk of metastases is low for patients with penile squamous cell carcinoma exhibiting favorable histologic features (stages Tis Ta, T1, grades 1–2). • Laser ablation is one of the organ-preserving therapeutic strategies that may be considered in these cases . • The CO2 laser is often used in this setting. Some centers have combined it with the Nd:YAG laser to increase the depth of tissue necrosis in the tumor base
  47. 47. Prostate carcinoma • The possibility of focal laser ablation (another term for interstitial laser coagulation) of localized prostate cancer has recently been investigated. • The Nd:YAG laser or diode laser can be used.
  48. 48. Genital skin lesions • Condylomata accuminata can occur on the prepuce, glans, penile shaft and intra-urethrally. The CO2 laser has been used since the late 1970s to vaporize multifocal, small lesions. • For larger condylomata, coagulation with the Nd:YAG laser was later introduced. • Intra-urethral lesions can be treated using the Nd:YAG or KTP laser • Owing to the risk of dispersion of the oncogenic virus in the aerosol, laser vaporization of condylomata is not recommended in patients with HIV
  49. 49. • Current shortcomings of urological lasers include the high cost of the technology, relatively complex hardware and collateral injury to surrounding normal tissue . • New lasers are continuously being developed: one of the more recent ones introduced for possible use in urology is the erbium:YAG (Er:YAG) laser. It operates at a wavelength of 2940 nm and can be used in all of the applications where the Ho:YAG laser is used. In an aqueous solution, this laser has a penetration depth of only 3 µm. Early studies seem to indicate that the Er:YAG laser may be slightly more effective than the holmium laser at breaking up stones . Unfortunately there are still some unresolved issues: normal silica fibers cannot be used for this laser and the alternative materials are extremely expensive and potentially toxic. The hemostatic ability at this wavelength is also insufficient.
  50. 50. • Laser techniques are versatile tools in urology. Particularly significant is their use in patients with diseases of the prostate. • Promising therapeutic effects of laser procedures tend to demonstrate their usage in treatment of patients with other diseases.
  51. 51. • THANK YOU

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