department ofsurgery,kathmandu medical college

1. ERENA PRADHAN
MS RESIDENT
FIRST YEAR

2.  Introduction
 Components
 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.  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.  Monochromacity
 Directional
 Coherent

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

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

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

10. 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

13.  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

14.  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

16.  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

17.  Thermal effects
 Mechanical effects
 Photo ablative effects
 Photodynamic effects

18. Three distinct phenomena:
 Conversion of light to heat
 Transfer of heat
 Tissue reaction

19. • 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

20.  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

21.  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.

22.  Port-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 necrosed and permanently closed
 Important 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

23.  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

24.  creation of a plasma
 an explosive vaporization
 the phenomenon of cavitation
Each of which is associated with the production of a shock wave.

25.  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

26.  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

27.  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.

28.  Pure ablation of material without thermal lesions at the margins, such as
one would get with a scalpel
 occurs because of the Principle 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
 Effect 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)).
 Action is very superficial, only over several microns, because light at
these wavelengths is very strongly absorbed by tissue.

29.  No practical advantage for making incisions or for ablating vascular
tissues because they will bleed in the same way as with a scalpel
 Can 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.
 Laser 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.

30.  Involves 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

31.  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

32. SOME MEDICAL LASERS AND THEIR PROPERTIES

34.  “Excited dimer”
 Form of ultraviolet laser
 Are of Nobel gas halide types
 Photo ablative effect
 Wavelength depends on the molecules used

35.  APPLICATIONS :
 The ultraviolet light from an excimer laser is well absorbed
by biological matter and organic compounds.
 Excimer 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.
 Well suited to precision delicate surgeries such as eye
surgery LASIK.

36.  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

37.  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

38. 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

39.  Most effective laser scalpel
 The CO2 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

40. 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

41.  Most widely used in medical field
 High penetration capacity of >5mm
 Mechanism: Photocoagulation
 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

42.  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

43.  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

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

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

46. 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

48. 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

49. 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

50. 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

51. 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

52. 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

53. 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

54. 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

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

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

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

58.  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

59. THANK YOU