Laser therapy in surgery

department ofsurgery,kathmandu medical college

1. LASER THERAPY IN SURGERY ERENA PRADHAN MS RESIDENT FIRST YEAR

2. Objectives: Introduction C omponents Principle of LASER and effects in tissue Some medical laser and its properties General applications Advantages/disadvantages

3. L -LIGHT A - AMPLIFICATION OF S -STIMULATED E -EMISSION OF R -RADIATION

4. LASER beam invented by MAIMAN in 1960 1962 , Leon Goldman Dr. Goldman’s experiment was the first use of lasers in the medical history  One of the most influential technological achievements

5. What is a LASER? device that transforms light of various frequency into a chromatic radiation in visible, infrared and ultraviolet regions with all the waves in the phase capable of mobilizing immense heat and power when focused at close range

6. Properties of LASER Monochromacity Directional Coherent

7. Monochromacity Light emitted from LASER is of one wavelength In contrast, ordinary white light- combination of many colors or wavelength

8. Directional LASER light is emitted in narrow beam in a specific direction

9. Coherent Wavelengths form LASER are in a phase in space and time Ordinary light can be mixture of many wavelength

10. Components of LASER ACTIVE MEDIUM: An optical cavity at the center of the laser device Core is composed of chemical elements, molecules or compounds LASER are generically named for the material of the active medium May be gas, crystals, semiconductors Gas-CO2, Argon , HE Solid state semiconductors: chromium, yttrium, scandium

11. EXCITATION MECHANISM : Pump energy into active medium by one of the three basic methods: optical, electrical or chemical OPTICAL RESONATOR : HR mirror(high reflectance): reflects 100% of laser light Partially transmissive mirror: reflects less than 100% light and transmits remainder

12. Lasing action Energy applied to active medium raising electrons to unstable energy level Atoms spontaneously decay to relatively long lived, lower energy, metastable stage. Population inversion achieved in metastable stage Lasing action occurs when electron spontaneously returns to the ground state and produces a photon If energy is of precise wavelength, it will stimulate production of another photon of same wavelength

13. HR mirror and partially reflective mirror directs the photon back in the medium along the long axis of the laser Partially reflective mirror allows transmission of small amount of coherent radiation

14. Effects of LASER in tissue Biological effects laser light is due to absorption phenomenon by chromophores. CHROMOPHORES- light absorbing substances in tissue(water, Hb , Melanin) Absorption – function of wavelength and chromophores If absorption is greater penetration is less and vice versa

15. Thermal effects Mechanical effects Photo ablative effects Photodynamic effects

16. Thermal effects Three distinct phenomena: Conversion of light to heat Transfer of heat Tissue reaction

17. Conversion of laser light to heat Tissue reflectivity is important in determining what proportion of beam will effectively penetrate the tissue. Wavelength if longer , reflectivity considerably lower, absorption is less, penetrance is higher Conversion of absorbed light to heat produces “Primary heat” Transfer of heat in tissue via Conduction of heat results in increase volume  “Secondary heat” Secondary heat  denaturation of tissue

18. Results of thermal effect Hyperthermia : moderate rise in temperature 41º to 44º resulting in cell death due to changes in enzymatic processes Coagulation : irreversible necrosis without immediate tissue destruction temperature reaches from 50º to 100º C for around a second produces desiccation, blanching, and a shrinking of the tissues by denaturation of proteins and collagen  

19. Volatilization : means a loss of material. various constituents of tissue disappear in smoke at above 100º C in a relatively short time of around one tenth of a second. At the edges of the volatilization zone  region of coagulation necrosis there is a gradual transition between the volatilization and healthy zones. hemostatic effect is due to this region of coagulation necrosis. If the volatilized zone has a large area in diameter, it is possible to destroy tumours bigger than those treated by a simple coagulation. If the volatilized region is narrow  a cutting effect obtained .

20. Example of thermal effects P ort-wine stains  presence from birth of abnormal blood vessels in the upper part of the dermis  reddish color in skin When a wavelength is used which is absorbed more by hemoglobin than by the epidermis or the non-blood components of the dermis  selectively heats the red corpuscles present in the abnormal vessels The heat will then be diffused from the corpuscles to the walls of the vessel ne crosed and permanently closed I mportant to select the exposure time so that the heating will not go beyond the vessel If exposure time prolonged  scarring effect due to involvement of epidermis and dermis

21. Tumors of trachea causing obstruction Nd:Yag Laser at 1065nm  coagulation of the mass of tumor  volatilization of the coagulated zone to remove the obstruction For a cancer, the volatilization effect of the laser temporary , but will allow the establishment of a slower, more long-term treatment such as radiotherapy

22. Mechanical effect creation of a plasma an explosive vaporization the phenomenon of cavitation E ach of which is associated with the production of a shock wave.

23. With nano or pico second pulsed Nd:YaG laser a very high intensity of luminous flux over a small area ionizes atom creates a plasma At the boundary of ionized region  high pressure gradient  propagation of shockwave  expansion of the shock wave causes destructive effect Principally used in ophthalmology to break the membranes developing after implanting artificial lens

24. When exposure time of laser is lower than characteristic time for thermal diffusion  produces a thermal containment  accumulation of heat without diffusion  explosive vaporization of the target Mechanism involved in selective photothermolysis Treatment of cutaneous angiomas. Capillaries of angiomas are not coagulated  but explode resulting in purpura(briefly)  reabsorbed through the skin

25. If mechanical containment added to thermal containment  gas bubble created which will implode when the laser beam is interrupted  creating a phenomenon of cavitation Mechanism used for fragmentation of urinary calculi.

26. Photoablative effect P ure ablation of material without thermal lesions at the margins, such as one would get with a scalpel occurs because of the P rinciple of dissociation With very short wavelengths (190 to 300 nm), the electric field associated with the light is higher than binding energy between molecules  Molecular bonds broken  the tissue components vaporized without generation of any heat at the edges E ffect obtained with lasers of very energetic wavelengths such as those emitting in the ultra-violet (excimer lasers emit at 193 nm ( ArF ), 248 nm ( KrF ) or 308 nm ( XeCl )). A ction is very superficial, only over several microns, because light at these wavelengths is very strongly absorbed by tissue.

27. N o practical advantage for making incisions or for ablating vascular tissues because they will bleed in the same way as with a scalpel C an only be used on tissues which will not bleed Lasers are suitable for this application because of the reproducibility of their effects which can be modelled, and because of the absence of mechanical contact with the tissue Excimer lasers have found an application in ophthalmology for photorefractive keratoplasty . L aser used is an argon-fluoride excimer laser laser beam at 193 nm,  immediately stopped by the superficial layers of the cornea  resulting in a photoablation of the surface.

28. Photodynamic effect I nvolves the relatively selective uptake of a photosensitizing drug and subsequent irradiation with light of a suitable wavelength In the presence of oxygen, singlet oxygen is produced with the induction of a cytotoxic action Illumination is required at a wavelength corresponding to the peak absorption of the drug

29. The illumination delivered at several hours to several days after the administration of the photosensitizer A wavelength is used which is absorbed well by the drug and which suits the depth of the desired effect in tissue Light in the green region of the spectrum is used for superficial effects and in the red for deeper effects A laser is used as the source of light because it is necessary to use a fiber optic for endoscopic treatments

30. SOME MEDICAL LASERS AND THEIR PROPERTIES

31. EXCIMER LASER “ Exc ited d imer ” Form of ultraviolet laser Are of Nobel gas halide types Photo ablative effect Wavelength depends on the molecules used

32. APPLICATIONS : The ultraviolet light from an excimer laser is well absorbed by biological matter and organic compounds . E xcimer lasers have the useful property  remove exceptionally fine layers of surface material with almost no heating or change to the remainder of the material which is left intact. W ell suited to precision delicate  surgeries such as eye surgery LASIK.

33. ARGON LASER Use of nobel gas argon as the active medium Tissue depth penetration of 1mm-superficial coagulation Precise cutting with minimal damage to surrounding tissue Applications: Retinal photocoagulation Arterial recanalization

34. DYE LASER Uses organic dye as a lasing medium Usually liquid solution(rhodamine, kitone red) Dye can be used for much wider range of wavelength Wide bandwidth makes it suitable for tunable laser or pulsed laser

35. Applications: Dermatology- to make skin tone even Wide range of wavelengths allows very close matching to the absorption lines of certain tissues, such as melanin or hemoglobin, while reducing the possibility of damage to the surrounding tissue. Port-wine stains and other blood vessel disorders scars and kidney stones   Tattoo removal

36. CO2 Laser Most effective laser scalpel The CO 2  laser produces a beam of  infrared light Cutting and vaporization instrument Seals lymphatics as it cuts through, thus decreasing spread of malignant cells Loss of tissue through evaporization

37. Application : Carbon dioxide lasers have become useful in surgical procedures because water (which makes up most biological tissue) absorbs this frequency of light very well  best suited for soft tissue  procedures Advantages : less bleeding, shorter surgery time, less risk of infection, and less post-op swelling gynecological,  dentistry, oral and maxillofacial surgery , Skin resurfacing

38. Nd : YAG LASER Most widely used in medical field High penetration capacity of >5mm Mechanism: P hotocoagulation Endoscopic LASER Application: To arrest bleeding GI varices Debulking GI and pulmonary tumors Coagulates bladder tumor used to remove skin  cancer used for laser prostate surgery

39. Ho: YAG LASER solid state laser, where YAG (Yttrium Aluminum Garnet) crystals are doped with rare-earth holmium ions Treats tissue in liquid filled environment( blood, saline) Endoscopic laser Application: Ablation of tissues, urology, prostatic surgery Orthopaedic laser used in arthroscopy

40. Er:YAG LASER Shallow penetration the output of an Er:YAG laser is strongly absorbed by water Extreme surgical precision Application:  laser resurfacing of human skin; acne scarring,   melasma the output of Er:YAG lasers also absorbed by  hydroxyapatite  makes it a good laser for cutting bone as well as soft tissue

41. DIODE LASER Semiconductor device that emits LASER light as electric current passes through them Tunable laser Fiberoptic delivery system Mechanism: photocoagulation Application : Hair removal

42. KTP LASER solid-state   laser  that uses a potassium titanyl phosphate ( KTP ) crystal as its frequencing doubling device Fiberoptic delivery system Application : Cholecystectomy

43. General applications VASCULAR MALFORMATIONS OF GIT Diffuse gastric antral vascular ectasia Colonic vascular malformation Argon & Nd:YAG lasers Photocoagulation therapy 80 % success rate in controlling recurrent blood loss & subsequent transfusions

44. UPPER GI CARCINOMA Early Gastric cancer Endoscopic laser therapy ( Nd : YAG ) can eliminate cancers completely 3 Requirements: Lesion <4cm with no lymph node metastasis , Follow-up, operator Advanced carcinoma : palliative procedure to relieve obstruction , dysphagia or bleeding Destroy neoplastic tissues & recanalise lumen Relief of dysphagia 92%,perforation 10% Outpatient basis

45. LIVER Fibrotic Liver Resection Controlled resection of liver without bloodloss possible Nd:YAG Laser with tissue contact tip Insitu ablation of Intrahepatic malignancies (metastases ) Palliation in HCC

46. BILE DUCT STONES Laser Lithotripsy Coumarin pulsed dye laser For Bileduct stones that can’t be extracted easily Break stones into small fragments which pass spontaneously Light energy to Acoustic energy

47. VASCULAR APPLICATIONS Laser Endarterectomy – Argon laser Combination of Helium laser for fluorescence excitation & Holmium laser for plaque ablation are tried Laser Angioplasty – Co2,Argon,Nd:YAG  

48. UROLOGY Renal stones - Laser lithotripsy Coumarin -based pulsed dye laser Light energy is delivered through Flexible quartz fibers, directed Endoscopically onto a calculus Mechanism of action occurs via plasma formation between the fiber tip and the calculus, which develops an acoustic shockwave that disrupts the stone along fracture lines Endoscopic extraction

49. BPH Photovaporisation - Tissue water is vaporized resulting in an instantaneous Debulking of prostatic tissue. KTP or Greenlight is commonly used for its vaporization effects on prostate tissue. Less bleeding and fluid absorption than standard TURP Demerit: Lack of tissue obtained for postoperative pathological analysis

50. Urothelial stricture Disease Nd:YAG , KTP, and Ho:YAG lasers used vaporize fibrous strictures Urothelial malignancies Transitional cell carcinoma of bladder, ureter, and renal pelvis

51. SKIN LESIONS CO2 Lasers - Condyloma acuminata , Haemangioma of external genetalia,early penile carcinoma .

52. Advantages Bloodless field Excellent Hemostasis Excellent Healing Allow precise Microsurgery Less postoperative pain & edema Lower infection rate Outpatient procedure

53. Disadvantages Atmospheric contamination: Laser Plume Mutagenic, Teratogenic or vector for viral infection. Interstitial pneumonia Bronchiolitis Reduced muco -ciliary clearance, inflammation

54. Misdirection of laser energy perforation of viscous or large blood vessels Eye damage Skin damage Fire and explosion Gas embolism: laparoscopic or Hysteroscopic laser surgery

55. THANK YOU