MEDICAL APPLICATIONS OF LASERS

J.K. Chhabra Consultant IIIT Allahabad

Ex Scientist and Deputy Director, C.S.I.O. Chandigath

Chhabra_jk@yahoo.com

Medical Applications begin

1967

KUMAR PATEL C. Kumar N. Patel born in Baramati, 1938.

Bachelor's in Poona University at the age of 19 (1958)

MS (1959) and PHD (1961) Stanford University.

Hired by AT&T Bell Labs, Upon joining Bell Labs in 1961,

Discovered laser action in carbon dioxide (1963)

invented the nitrogen carbon dioxide (CO2) laser --- the first gas laser to produce high power radiation continuously (1964).

Among military applications, its most striking contribution has been to

the "Star Wars" system once promoted by Ronald Reagan and still being developed today. In fact, scientists find further uses for Patel's CO2 laser

all the time.

LASER in medicine Cosmetic treatments

Ophthalmology: inner eye surgery

Surgical Laser Scalpel

Dentistry

Cancer , Cytometry and fundamental Research,

laser versus ordinary lights:

The directionality of laser beam offers a great advantage over ordinary lights since it can be concentrate its energy onto a very small spot area. This is because the laser rays can be considered as almost parallel and confined to a well-defined circular spot on a distant object.

Sample problem: we compare the intensity of the light of a bulb of 10 W and that of a laser with output power of 1mW (10-3 W). For calculation, we consider an imagery sphere of radius R of 1m for the light spreading of the bulb, laser beams illuminate a spot of circular area with a radius r = 1mm.

2522 /108

)100(410

410 cmW

cmW

RW

API bulb

bulb−×====

ππ

222

3

2

3

/103)1.0(

1010 cmWcmW

rW

API laser

laser−

−−

×====ππ

400/108/103

25

22

≈××

= −

−

cmWcmW

II

bulb

laser

Mechanisms of laser interaction with human tissues

When a laser beam projected to tissue

•reflection, •transmission, •scattering, •re-emission, •absorption.

Five phenomena:

Laser light interacts with tissue and transfers energy of photons to tissue because absorption occurs.

Selective absorption of laser light by human tissues

Optical Properties of Tissue

Selective absorption

Selective absorption occurs when a given color of light is strongly absorbed by one type of tissue, while transmitted by another. Lasers’ pure color is responsible for selective absorption.

The main absorbing components of tissues are: • Oxyhemoglobin (in blood): the blood’s oxygen carrying

protein, absorption of UV and blue and green light, • Melanin (a pigment in skin, hair, moles, etc): absorption in

visible and near IR light (400nm – 1000nm), • Water (in tissues): transparent to visible light but strong

absorption of UV light below 300nm and IR over 1300nm

Penetration-depth (d=1/A) vs. wavelength

UV VISIBLE Near-IR Mid-IR

(0.2-0.4) (04.-0.7) (0.8- 2.1) (2.7-3.2) um

(0.05-0.5) mm (0.5-2.0)

(2.0-6.0)

(0.2-0.5) 0.05 mm

Water 3 absorption peaks: 1.45, 1.93, 2.94 um

Pain Relief Sports Injuries

Lasers in beauty therapy

Lasers application in beauty therapy are based on:

• selective absorption of absorbing components.

• photo-vaporization process for removal of the treated components.

• pulsed lasers are used.

Nd YAG Laser – superficial pigmented lesions

Nevi: biopsy if suspicious Q-switched Nd:YAG 532, 694, 755nm

lasers respond within 1-3 treatments

Melasma: Q-switched Nd:YAG laser hormonal control bleaching agents sun avoidance tend to recur

Rosacea: topicals (antibiotics, tretinoin) oral abx IPL KTP laser

Laser -- deep pigmented lesions • Deep lesions-deeper, therefore treated

better with longer wavelength (goes deeper): can use ruby, alexandrite, and

Nd:YAG – blue nevi:

• 1064 nm Nd:YAG laser – nevus of ota and ito: Q-switched

1064nm Nd:YAG laser • multiple treatments • recurrence is unusual

Laser removal of port-wine stain

Yellow laser is absorbed by the presence of hemoglobin in blood vessels.

Laser skin rejuvenation

IR lasers are used to remove extremely thin layer of skin (<0.1 mm). In the absence of pigment in general, they take advantage of the presence of water in the skin to provide an ability to remove skin and body tissue.

SKIN TIGHTENING

MEDICAL: Laser treatment may be the answer to skin cancer. Trials show that as well as removing cancer cells, laser treatment also

stimulates the immune system. …skin cancer has a tendency to form metastases that create new types

of cancer that are virtually incurable using existing forms of treatment…

SKIN CANCER CURE

Laser hair removal

1. dermis

2. epi-dermis

3. sebacecusglands

4. follicle

5. root

6. Papilla

7. Blood vessel

hair

(1)(2)

(3)(4)

(5)(6)

(7)

Skin-hair structure

Laser -- hair removal

Goal = ablation of hair unit Wavelengths between 600 and 1000 nm most

effective Generally want spot size larger than the depth of

the target being treated--5mm to 1 cm for hair Optimal situation is dark hair with light skin Thermal relaxation time is key: epidermis: 3- 10 ms, hair follicle : 80-100 ms. Use pulse duration < 10 millisecond targets hair

on white skin. May need longer for darker skinned individuals.

Laser hair removal

selective absorption : absorbing component being melanin pigment in hair and follicle, it is best worked with a red light ruby laser. White hair can not be treated with any laser due to the lack of absorbing component.

Home use hand-held LED

4- color LEDs :

IR (940 nm) Yellow (580 nm)

Red (660 nm) Blue (470 nm)

Hair growth

Laser-comb Red-LED (630-695 nm)

Dental lasers (1) Hard tissue (dentin, carries) a) Biolase “water-laser” (Er:YSGG at 2.78 um) b) Lin/ITRI, mid-IR diode laser (2.7-3.0 um) (2) Diode laser (soft tissue) at 808, 940, 980 nm (3) Teeth whitening Nd:YAG (1064) + dye (4) Velcope Blue-light (or LED) to detect cancer tissue

Dental LASER

. Designed for a wide range of endodontic, periodontic and dental surgery procedures,

Picasso allows for clean cutting and hemostasis in soft tissue procedures, cuts gum tissue with precision, helps sterilize canals in endodontics, treats periodontal disease, and aids in tooth whitening.

Laser applications in dentistry

Laser applications in dentistry

Alternative to mechanical drills and CW lasers

Reduced thermal stress

And micro cracks in enamel

AMD Dental LASER

Lasers in ophthalmology

For cornea and lens, UV light emitted by the excimer laser is strongly absorbed by water and proteins, so their energy can be absorbed by transparent cornea and lens, permitting laser surgery on these areas.

• Cataracts: a milky structure in the lens of the eye. Photo-vaporization by using UV laser to remove the obaque regions.

• Correction of myopia: over focusing of the lens. Excimer laser removal of surface of cornea to make it flatten.

Excimer Lasers

Noble gas:Halide. Emit (UV) light that triggers a photochemical reaction on the target tissue.

This very short wavelength is capable of high resolution and microscopic surgery-note the letters etched into the human hair at right.

The most common medical application is the Argon:Fluorine (Ar:F) laser at 193 nm, used for PRK and LASIK vision correction. The laser beam is delivered through an operating microscope integrated with the laser housing and operating table.

Excimer laser radiation shows great promise for cardiac revascularization and lithotripsy, but is currently limited by the lack of durable UV-capable fiberoptic delivery devices.

Focusing Elements in EYE

• Refractive indicies within the eye

Cornea 1.37

Aqueous Humour 1.33

Crystalline Lens 1.38 (outer layers) 1.41 (inner layers)

Vitreous Humour 1.33

Lasers in Ophthalmology For retina operation, visible laser can be used. Visible light is transparent to the cornea and crystalline lens, and can be focused with eye’s lens on the retina. The most popular visible laser is the green argon laser. • Treatment of glaucoma: Argon laser is focused

externally on iris to make incision, creating drainage holes for excess aqueous humors to release pressure,

• Retina tear: photocoagulation burn to repair retina tears due to trauma to the head.

• Diabetic retinopathy: inadequate blood supply to the retina due to diabetes. Small photocoagulation burn by green argon laser to repair the retina due to vessels leakage.

Laser-Assisted in situ Keratomileusis LASIK , Developed in 1995

LASIK Operation

ADVANTAGES FOR THE LASER AS A MEDICAL CUTTING TOOL

Lasers & Medicine

Reduces pain and trauma for the patient

Speeds healing — thereby shortening costly hospital stays

Improves the accuracy of certain surgical procedures

ADVANTAGES FOR THE LASER AS A MEDICAL CUTTING TOOL

Lasers & Medicine

Reduces pain and trauma for the patient

Speeds healing — thereby shortening costly hospital stays

Improves the accuracy of certain surgical procedures

Touch less Brain and Spine Surgery

Laser Brain Surgery

This image cannot currently be displayed.

Lasers & Medicine

• Greater accuracy of incisions • Lasers can be inserted inside the body with little risk or discomfort

• Incisions can be guided by computers • The laser is extremely precise, and can be tuned to work on a micro-level, barely visible to the human eye

DATA KNIFE

ANGIOPLASTY

Cleaning Arteries

ANGIOLOGY Laser Guided Angioplasty

ANGIOLOGY Laser Guided Angioplasty

Early Cancer Diagonosis

Computed Tomography Laser Mammography (CTLM): Imaging Diagnostic Systems (Ft.

Lauderdale, FL)

• No X ray • No Dye Injections • Checks Blood circulation

Breast Cancer CTLM (Computed Tomography Laser Mammography )

808nm laser diodes: At this wavelength, haemoglobin absorb

the light, with little absorbance from water and fat.

This technology works well with dense breast tissue, which is a challenge for mammography.

High sensitivity, because it detects blood flow. Angiogenesis extends around a tumor. For example, a 3.0mm tumor can have a 4-6cm area of angiogenesis.

Lung Cancer •

408nm laser-diode excitation• charge-coupled detector (CCD) that detects

autofluorescence

Diagnostic Application Fluorescence Spectroscopy

Goal: Noninvasive tissue characterization to replace or guide physical biopsy, e.g. early diagnosis of lung cancer.

Single optical fiber

Laser

Camera Filters

Imaging bundle

Wavelength Em

issi

on in

tens

ity

Normal mucosa

Image

Image 2

Early carcinoma

© Deb Newberry 2008

New Technology Could Combine Detection and Treatment

Immediate sensing as a tumor is removed! Sandia National Laboratories

Fundamental Research Cell Biology

CONFOCAL MICROSCOPY

Cytometry

Optical manipulation of plasmid-coated particles and insertion into the cell through a small pore punctured by a short-pulsed laser. Plasmids produce a green fluorescent

protein once inside the cell.

Drawing is not to scale. (Image courtesy of the Gwangju Institute of Science and Technology

Optical tweezers, ultrafast laser pair to gently insert DNA into living cells

Seeing inside a HeLa Cell

Warning Signs

Laser Safety

Lasers are no Toy Guns

Absorption of the eye

Personal Protective Equipment

Thank You

CAUTION: Do not look a laser with remaining eye!

Thank you for your attention !! and

Thank you for your PATIENCE !!

Chhabra_jk@yahoo.com

Mobile 91 9888410066