The Basics of Laser (4)

What is photochemical effect of laser?

The main concept of photochemistry concerns a certain molecule which functions as a photosensitizer. With the existence of photosensitizer in a particular cell (e.g. cancer cell), the cell becomes sensitive to the damage caused by the photon absorption from a certain wavelength. The effect is selective and does not damage normal cells.

What is selective photothermolysis effect?

It is the thermal lytic effect resulted by light pulse which is selectively absorbed by pigmented target such as melanin and hemoglobin. Recent research showed that this effect enables cancer therapy with combination of selective nanophotothermolysis using primary and secondary antibodies, and gold nanoparticles. Laser radiation will form bubbles on the cancer cells’ wall and cause selective damage to the cancer cells.

What are the safety issues to be concerned in the use of laser?

A laser surgeon has medical, legal, and ethical responsibilities. He/she has to acquire information regarding basic laser knowledge, how to operate laser equipments, the indications, and contraindication of laser (“If you don’t need a laser,don’t use one but if you need it use it properly”). It is important to follow instructions from the manufacturers and laser safety officer at laser-applied institutions. Always use goggles (laser safety eyewear), smoke evacuator, warning sign on operating room entries, and laser safety doorlock.

How should laser be properly used?

Mind the buttons and facilities provided in the laser machine (main switch, safety keyswitch, standby/ready switch, emergency off switch, power regulator, mode regulator, frequency/pulse regulator, time regulator, fluence calculator). Turn on the main switch, then the safety keyswitch. Set the necessary parameter, use adequate protections, change standby to ready, direct the handpiece to the target, step on the footswitch after the direction is set correctly. Keep laser in vertical position against tissue surface and keep the movement so that the speed is constant. Release the step on footswitch after it is done. Repeat necessary procedures. Afterwards, turn off all switches in reverse sequence.

The Basics of Laser (3)

What are the types of laser pulse?

Continues wave: continuous power output while the shutter is being opened (pedal) Pulsed wave: interrupted light output (msec)

Superpulsed wave: very short light outswitched put (msec)

Ultrapulsed: very short light output (nsec)

Q-laser: very short exposure time with extremely high energy

How can the laser interact with the tissues?

Absorption of photon by the tissues is basically the main effect resulted by laser. Reflection, refraction, and transmission will have no effect in the absence of photon absorption.

What are the biological effects on the tissues?

Cells’ growth stimulation, increased cell regeneration, increased tissues’ activities, anti-inflammatory effect, reduced swelling/edema, increased microcirculation, less fibrosis, stimulation of nerves’ function, pain attenuation due to increased production of local endorphins, and increased ATP production in mitochondria

What does photothermal effect of laser mean?

Photothermal effect of laser is thermal effect resulted by the photon which directly related to kinetic molecule excitation produced by total movement, rotation, and molecular action of the tissues. Photothermal effect may cause an increase in temperature, coagulation, protein denaturation, hemostasis, carbonization, and tissue evaporation.

The Basics of Laser (2)

What are the characteristics of laser?

• Monochromatic: has single wavelength depends on the media

• Collimated: the light travels with a synchronized direction with very minimum degree of deviation

• Coherent: electromagnetic wave has the same form and phase

• Brightness: laser seems bright due to the high energy emission in the optic cavity

What is the difference between conventional light source and laser?

Conventional light source has diffuse distribution and is originally white because it consists of many color spectra (multiple wavelengths). Meanwhile, laser has single direction and single color or monochromatic (single wavelength)

What is the benefit of monochromatic characteristic?

Laser energy will be absorbed by specific chromophor of the target organ

What are the basic radiometry terms that you must understand?

Power output = radiant power = W(Watts)= J(Joule)/second

Power density = irradiance = intensity =W/cm²

Light energy = Joules =J

Fluence = energy density = J/cm²

The Basics of Laser (1)

What is laser?

Laser is a light as the result of a technology called Light Amplification by Stimulated Emmission of Radiation. The acronym of this technology became what we acknowledge as laser.

What is the basic theory of laser?

The basic concept of laser was first established by Albert Einstein in The Quantum Theory of Radiation (1917). In a “ground state” condition, atomic energy or molecules are surrounded by electrons. If there is sufficient amount of energy absorbed by the atoms or molecules, then the electron will be positioned in a higher orbit. The electron will be back to the previous orbit while emitting a light spontaneously (spontaneous emission). The unit of this light energy is called photon. In 1960, Maiman successfully invented laser light from ruby crystal.

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How can a laser be produced?

Laser is produced by placing atoms in a cavity which then given an electrical energy. The atoms will convert in an excited state called population inversion. Photon emission is parallel with the same speed, direction, and frequency. On one side of the cavity there is a mirror with total reflection ability, while on the other side there is a partial mirror from which the laser comes out.

What are the active media to produce laser?

Active material (or active media) to produce laser can be in the form of gas (Helium-Neon, carbon dioxide, Argon), liquid (dye in organic solution), solid (alexandrite, neodymium, erbium, chromium), or semi-conductor (gallium arsenide, diode).

Technique of Debulking of Nasal, Paranasal, Oral and Nasopharyngeal Tumours With Nd:YAG/KTP 532 Lasers*

ABSTRACT

Nd:YAG/KTP 532 lasers were aplied in surgical resection of upper aerodigestive tract tumours i.e. intra oral, oropharyngeal, intranasal, paranasal, nasopharyngeal tumours. The lasers were used to assist in primary tumours resection with coagulation of tumour bed, ablation, and evaporation of tumour lesions. The lasers were delivered through direct or open surgery and/or by endoscopy. Controls were done through telescopic or microscopic monitor. The tumours were intranasal polyps, intranasal myxoma, intranasal, and paranasal fibromyxoma, olfactory neuroblastoma, nasopharyngeal carcinoma, palatal adenoid cystic carcinoma, and squamous cell carcinoma, tonsillar malignant lymphoma, nasopharyngeal angiofibroma, and rhabdomyosarcoma.

Video recording of laser ablation in a persistent nasopharyngeal carcinoma will be presented. In our opinion, Nd:YAG/KTP 532 lasers were useful adjunct in the control of primary tumours and for palliative debulking of tumours to maintain patient's quality of life.

Keywords: Nd:YAG/KTP 532 laser, upper aerodigestive tract tumours

* Paper presented at The Shanghai International Conference in Laser Medicine and Surgery, November 4-6, 1997, Shanghai, China

Copyright to L.S. Handikin, M.D., FASLMS, FIPA
(any kind of reproduction on this paper should strictly be done under the permission of the author)

A Brief Introduction to Laser

The word laser is an acronym for Light Amplification by Stimulated Emission of Radiation.

Laser is an absolutely outstanding inventions of the last century. It has become a valuable tool in various fields, including medicine. Laser is a light source, but different from the traditional light source, it is not used for illumination purposes.

Laser light is the result of a process called stimulated emission. Stimulated emission occurs when an incoming photon stimulates an excited atom so that it emits a photon identical to the incoming photon. The incoming photon has to have a wavelength (i.e. energy) which is identical to the energy which the atom will release when it falls from the excited level to a more stable one.

The use of laser in medicine is clearly evident. I have used laser for the purpose of surgical and non-surgical procedures, mostly in otorhinolaryngology head & neck surgeries. The results were significant, i.e. minimal bleeding in minimal invasive surgery.

From what I have experienced, I concluded that laser is the therapeutic modality which is beneficial in numerous medical conditions. Surely, it promotes better quality of life and affect humankind, especially through biostimulation and anti-inflammatory effects of low power laser.

To know more about lasers in medicine, keep yourself posted to this blog!