Laser” is an acronym for light amplification by stimulated emission of radiation. A laser is created when the electrons in atoms in special glasses, crystals, or gases absorb energy from an electrical current or another laser and become “excited.”Characteristics ,working ,types and application of lasers exclusively in medicine and biology.
Light Amplification by Stimulated Emission of Radiation. Its basic principle of working, features or characteristics, types, applications, hazards caused by LASER and future scopes.
Light Amplification by Stimulated Emission of Radiation. Its basic principle of working, features or characteristics, types, applications, hazards caused by LASER and future scopes.
Lasers in medicine, basic principles and applicationAugustine raj
Lasers are being used frequently in medical practice. every physician should know the mechanism of action and indications and different types of lasers used in medical practice. i have tried to simplify the entire presentation.
This belongs to Physical Chemistry portion and it contains most of
things about laser working and principles.
By Aaryan Tyagi's Group
M.Sc. Applied Chemistry (1 Sem)
Amity University, Noida
You can learn about Need for bio-amplifier, Frequency range used by animals, human beings and Mammals, BASIC ELECTRONIC RECORDING SYSTEM, Differential Amplifier, DIFFERENTIAL AMPLIFIER IN ECG RECORDING SYSTEM, EQUIVALENT CIRCUIT FOR THE INPUT OF AN ECG AMPLIFIER (OR) IMPEDANCE MATCHING CIRCUIT, Method to increase input impedance, Limitations of differential amplifier, Instrumentation Amplifier, Requirements of a Good Instrumentation Amplifier, Advantages of Three Op-amp Instrumentation Amplifier,RIGHT LEG DRIVEN ECG AMPLIFIER (OR) DRL (DRIVEN RIGHT LEG)
The common feature of spectroscopic measure-
ments is that they all measure some spectroscopic properties that are related to the composition and
structure of biochemical species in the sample of interest. There are several types of spectroscopic
measurements: absorption, scattering (elastic and inelastic), and emission. A typical spectroscopic
experiment that allows us to analyze complex biological systems is conceptually simple. Light at a
certain wavelength λ (or frequency ν = c/λ) is used to irradiate a sample of interest. This process is called excitation. Properties of the light that then emerges from the sample are measured and ana-
lyzed. Some properties deal with the fraction of the incident radiation absorbed by the sample: the
techniques involved are collectively called absorption spectroscopy (e.g., ultraviolet [UV], visible, and
infrared (IR) absorption techniques). Other properties are related to the incident radiation reflected
back from the samples (elastic scattering [ES] techniques). Alternatively, one can measure the light
emitted or scattered by the sample, involving processes that occur at wavelengths different from the
excitation wavelength; the techniques involved are fluorescence, phosphorescence, and inelastic scat-
tering (Raman scattering). Other specialized techniques can be used to detect specific properties of the
emitted light, such as its degree of polarization and decay times.
Lasers in medicine, basic principles and applicationAugustine raj
Lasers are being used frequently in medical practice. every physician should know the mechanism of action and indications and different types of lasers used in medical practice. i have tried to simplify the entire presentation.
This belongs to Physical Chemistry portion and it contains most of
things about laser working and principles.
By Aaryan Tyagi's Group
M.Sc. Applied Chemistry (1 Sem)
Amity University, Noida
You can learn about Need for bio-amplifier, Frequency range used by animals, human beings and Mammals, BASIC ELECTRONIC RECORDING SYSTEM, Differential Amplifier, DIFFERENTIAL AMPLIFIER IN ECG RECORDING SYSTEM, EQUIVALENT CIRCUIT FOR THE INPUT OF AN ECG AMPLIFIER (OR) IMPEDANCE MATCHING CIRCUIT, Method to increase input impedance, Limitations of differential amplifier, Instrumentation Amplifier, Requirements of a Good Instrumentation Amplifier, Advantages of Three Op-amp Instrumentation Amplifier,RIGHT LEG DRIVEN ECG AMPLIFIER (OR) DRL (DRIVEN RIGHT LEG)
The common feature of spectroscopic measure-
ments is that they all measure some spectroscopic properties that are related to the composition and
structure of biochemical species in the sample of interest. There are several types of spectroscopic
measurements: absorption, scattering (elastic and inelastic), and emission. A typical spectroscopic
experiment that allows us to analyze complex biological systems is conceptually simple. Light at a
certain wavelength λ (or frequency ν = c/λ) is used to irradiate a sample of interest. This process is called excitation. Properties of the light that then emerges from the sample are measured and ana-
lyzed. Some properties deal with the fraction of the incident radiation absorbed by the sample: the
techniques involved are collectively called absorption spectroscopy (e.g., ultraviolet [UV], visible, and
infrared (IR) absorption techniques). Other properties are related to the incident radiation reflected
back from the samples (elastic scattering [ES] techniques). Alternatively, one can measure the light
emitted or scattered by the sample, involving processes that occur at wavelengths different from the
excitation wavelength; the techniques involved are fluorescence, phosphorescence, and inelastic scat-
tering (Raman scattering). Other specialized techniques can be used to detect specific properties of the
emitted light, such as its degree of polarization and decay times.
In thermogravimetric analysis, the change in weight in
relation to a change in temperature in a controlled environment is measured. Heat is used in TGA to force
reactions and physical changes in materials. Thermogravimetric analysis (TGA) is a reliable method to determine
endotherms, exotherms, measure oxidation processes, thermal stability, decomposition points of explosives,
characteristics of polymers, solvent residues, the level of organic and inorganic components of a mixture,
degradation temperatures of a material, and the absorbed moisture content of materials. Materials analyzed by
thermogravimetric analysis include explosives, petroleum, chemicals, biological samples, polymers, composites,
plastics, adhesives, coatings, organic materials, and pharmaceuticals.The thermogravimetric analysis instrument usually consists of a high-precision balance and sample pan.
The pan holds the sample
material and is located in a
furnace or oven that is
heated or cooled during the
experiment. A thermocouple
is used to accurately control
and measure the
temperature within the oven.
The mass of the sample is
constantly monitored during
the analysis. An inert or
reactive gas may be used to
purge and control the
environment. The analysis is
performed by gradually
raising the temperature and plotting the
substances weight against temperature. A
computer is utilized to control the
instrument and to process the output
curves.
Spectroscopy is the measurement and interpretation of electromagnetic radiation absorbed or emitted when the molecules or atoms or ions of a sample move from one energy state to another energy state. UV spectroscopy is a type of absorption spectroscopy in which light of the ultra-violet region (200-400 nm) is absorbed by the molecule which results in the excitation of the electrons from the ground state to a higher energy state.Basically, spectroscopy is related to the interaction of light with matter.
As light is absorbed by matter, the result is an increase in the energy content of the atoms or molecules.
When ultraviolet radiations are absorbed, this results in the excitation of the electrons from the ground state towards a higher energy state.
Molecules containing π-electrons or nonbonding electrons (n-electrons) can absorb energy in the form of ultraviolet light to excite these electrons to higher anti-bonding molecular orbitals.
The more easily excited the electrons, the longer the wavelength of light they can absorb. There are four possible types of transitions (π–π*, n–π*, σ–σ*, and n–σ*), and they can be ordered as follows: σ–σ* > n–σ* > π–π* > n–π* The absorption of ultraviolet light by a chemical compound will produce a distinct spectrum that aids in the identification of the compound.
Medical devices are heavily regulated because of their
intended uses in human beings. Generally medical devices
are classified into different categories depending upon the
degree of potential risks and regulated accordingly.Many medical devices are involved with relative moving parts,
either in contact to the native tissues or within the biomaterials,
and often under loading. Important issues, such as friction and
wear of the moving parts, not only affect the functions of these
devices but also the potential adverse effects on the natural tissues.
Biotribology deals with the application of tribological principles,
such as friction, wear and lubrication between relatively motions
surfaces, to medical and biological systems. Biotribology plays an important role in a number of medical devices
Protein based nanostructures for biomedical applications karoline Enoch
Proteins are kind of natural molecules that show unique
functionalities and properties in biological materials and
manufacturing feld. Tere are numerous nanomaterials
which are derived from protein, albumin, and gelatin. Tese
nanoparticles have promising properties like biodegradability, nonantigenicity, metabolizable, surface modifer, greater
stability during in vivo during storage, and being relatively
easy to prepare and monitor the size of the particles.
These particles have the ability to attach covalently with
drug and ligand
A Schering Bridge is a bridge circuit used for measuring an unknown electrical capacitance and its dissipation factor. The dissipation factor of a capacitor is the the ratio of its resistance to its capacitive reactance. The Schering Bridge is basically a four-arm alternating-current (AC) bridge circuit whose measurement depends on balancing the loads on its arms .
A Maxwell bridge is a modification to a Wheatstone bridge used to measure an unknown inductance (usually of low Q value) in terms of calibrated resistance and inductance or resistance and capacitance. When the calibrated components are a parallel resistor and capacitor, the bridge is known as a Maxwell-Wien bridge. It is named for James C. Maxwell, who first described it in 1873.
It uses the principle that the positive phase angle of an inductive impedance can be compensated by the negative phase angle of a capacitive impedance when put in the opposite arm and the circuit is at resonance; i.e., no potential difference across the detector (an AC voltmeter or ammeter)) and hence no current flowing through it. The unknown inductance then becomes known in terms of this capacitance.
A Kelvin bridge, also called a Kelvin double bridge and in some countries a Thomson bridge, is a measuring instrument used to measure unknown electrical resistors below 1 ohm. It is specifically designed to measure resistors that are constructed as four terminal resistors.
Dc bridge types ,derivation and its applicationkaroline Enoch
The DC Bridge is used for measuring the unknown electrical resistance. This can be done by balancing the two legs of the bridge circuit. The value of one of the arm is known while the other of them is unknown
The bridge uses for measuring the value of unknown resistance, inductance and capacitance, is known as the AC Bridge. The AC bridges are very convenient and give the accurate result of the measurement.The construction of the bridges is very simple. The bridge has four arms, one AC supply source and the balance detector. It works on the principle that the balance ratio of the impedances will give the balance condition to the circuit which is determined by the null detector.
Photodynamic therapy (PDT) is a two-stage treatment that combines light energy with a drug (photosensitizer) designed to destroy cancerous and precancerous cells after light activation. Photosensitizers are activated by a specific wavelength of light energy, usually from a laser.
Preamplifier and impedance matching circuitskaroline Enoch
A preamplifier circuit with a very low noise characteristic can be built by simply combining a FET transistor with a bipolar one. The input impedance of the preamp circuit is almost the same as the gate impedance of the FET transistor (around 1MΩ) The output impedance at the other end is about 1KΩ.
Phototherapy is a type of medical treatment that involves exposure to fluorescent light bulbs or other sources of light like halogen lights, sunlight, and light emitting diodes (LEDs) to treat certain medical conditions
The word “laser” is an acronym for light amplification by stimulated emission of radiation. Most sources of visible light radiate energy at different wavelengths (ie, different colors) and at random time intervals (noncoherent). The unique properties of laser energy are monochromaticity (single wavelength), spatial coherence, and high density of electrons. These allow focusing of laser beams to extremely small spots with very high-energy densities.
A laser consists of a transparent crystal rod (solid-state laser), or a gas- or liquid-filled cavity (gas or fluid laser) constructed with a fully reflective mirror at one end and a partially reflective mirror at the other. Surrounding the rod or cavity is an optical or electrical source of energy that will raise the energy level of the atoms within the rod or cavity to a high and unstable level, a process known as population inversion. When the excited atoms spontaneously decay back to a lower-energy level, their excess energy is released in the form of light. This light can be emitted in any direction. In a laser cavity, however, light emitted along the long axis of the cavity can bounce back and forth between the mirrors, setting up a standing wave that stimulates the remaining excited atoms to release their energy into the standing wave, producing an intense beam of light that exits the cavity through the partially reflective mirror. All of the light produced has the same wavelength (monochromatic) and phase (coherent), with little tendency to spread out (low divergence). The laser light energy can be emitted continuously or in pulses, which may have pulse durations of nanoseconds or less.
he 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) [Anson et al. 1994]. Despite tremendous advances in the surgical and minimally invasive treatment of BPH, transurethral resection of the prostate (TURP) is still considered the ‘gold standard’. The risks of TURP are always mentioned when discussing the reasons for seeking alternative treatment modalities for BPH. Bleeding certainly remains a concern, especially in patients on some form of anticoagulation (heparin, coumarin related compounds, antiplatelet agents) or those with prostates in excess of 60–80 g. On the other hand, with the availability of transurethral resection in saline (TURiS), the TURP syndrome is nowadays considered by many to be a relatively rare complication
Lasers have been used successfully to treat a variety of vascular lesions including superficial vascular malformations (port-wine stains), facial telangiectases, haemangiomas, pyogenic granulomas, Kaposi sarcoma and poikiloderma of Civatte. Lasers that have been used to treat these conditions include argon, APTD, KTP, krypton, copper vapour, copper bromide, pulsed dye lasers and Nd:YAG. Argon (CW) causes a high degree of non-specific thermal injury and scarring and is now largely replaced by yellow-light quasi-CW and pulsed laser therapies.
The pulsed dye laser is considered the laser of choice for most vascular lesions because of its superior clinical efficacy and low-risk profile. It has a large spot size (5 to 10mm) allowing large lesions to be treated quickly. Side effects include postoperative bruising (purpura) that may last 1-2 weeks and transient pigmentary changes. Crusting, textural changes and scarring are rarely seen.
The term LASER is an acronym for ‘Light Amplification by the Stimulated Emission of Radiation’. As its first application in dentistry by Miaman, in 1960, the laser has seen various hard and soft tissue applications. In the last two decades, there has been an explosion of research studies in laser application. In hard tissue application, the laser is used for caries prevention, bleaching, restorative removal and curing, cavity preparation, dentinal hypersensitivity, growth modulation and for diagnostic purposes, whereas soft tissue application includes wound healing, removal of hyperplastic tissue to uncovering of impacted or partially erupted tooth, photodynamic therapy for malignancies, photostimulation of herpetic lesion. Use of the laser proved to be an effective tool to increase efficiency, specificity, ease, and cost and comfort of the dental treatment.
Photolithography, also called optical lithography or UV lithography, is a process used in microfabrication to pattern parts on a thin film or the bulk of a substrate (also called a wafer). It uses light to transfer a geometric pattern from a photomask (also called an optical mask) to a photosensitive (that is, light-sensitive) chemical photoresist on the substrate. A series of chemical treatments then either etches the exposure pattern into the material or enables deposition of a new material in the desired pattern upon the material underneath the photoresist. In complex integrated circuits, a CMOS wafer may go through the photolithographic cycle as many as 50 times.
Photolithography shares some fundamental principles with photography in that the pattern in the photoresist etching is created by exposing it to light, either directly (without using a mask) or with a projected image using a photomask. This procedure is comparable to a high precision version of the method used to make printed circuit boards. Subsequent stages in the process have more in common with etching than with lithographic printing. This method can create extremely small patterns, down to a few tens of nanometers in size. It provides precise control of the shape and size of the objects it creates and can create patterns over an entire surface cost-effectively. Its main disadvantages are that it requires a flat substrate to start with, it is not very effective at creating shapes that are not flat, and it can require extremely clean operating conditions. Photolithography is the standard method of printed circuit board (PCB) and microprocessor fabrication. Directed self-assembly is being evaluated as an alternative to photolithography
The Piezoelectric transducer is an electroacoustic transducer use for conversion of pressure or mechanical stress into an alternating electrical force. It is used for measuring the physical quantity like force, pressure, stress, etc., which is directly not possible to measure.The piezo transducer converts the physical quantity into an electrical voltage which is easily measured by analogue and digital meter.
The piezoelectric transducer uses the piezoelectric material which has a special property, i.e. the material induces voltage when the pressure or stress applied to it. The material which shows such property is known as the electro-resistive element
Photoelectric transducers and its classificationkaroline Enoch
The photoelectric transducer converts the light energy into electrical energy. It is made of semiconductor material. The photoelectric transducer uses a photosensitive element, which ejects the electrons when the beam of light absorbs through it.
Piezoresistive pressure sensors are one of the very-first products of MEMS technology. Those products are widely used in biomedical applications, automotive industry and household appliances.
The sensing material in a piezoresistive pressure sensor is a diaphragm formed on a silicon substrate, which bends with applied pressure. A deformation occurs in the crystal lattice of the diaphragm because of that bending. This deformation causes a change in the band structure of the piezoresistors that are placed on the diaphragm, leading to a change in the resistivity of the material. This change can be an increase or a decrease according to the orientation of the resistors.
Palestine last event orientationfvgnh .pptxRaedMohamed3
An EFL lesson about the current events in Palestine. It is intended to be for intermediate students who wish to increase their listening skills through a short lesson in power point.
Francesca Gottschalk - How can education support child empowerment.pptxEduSkills OECD
Francesca Gottschalk from the OECD’s Centre for Educational Research and Innovation presents at the Ask an Expert Webinar: How can education support child empowerment?
Introduction to AI for Nonprofits with Tapp NetworkTechSoup
Dive into the world of AI! Experts Jon Hill and Tareq Monaur will guide you through AI's role in enhancing nonprofit websites and basic marketing strategies, making it easy to understand and apply.
Biological screening of herbal drugs: Introduction and Need for
Phyto-Pharmacological Screening, New Strategies for evaluating
Natural Products, In vitro evaluation techniques for Antioxidants, Antimicrobial and Anticancer drugs. In vivo evaluation techniques
for Anti-inflammatory, Antiulcer, Anticancer, Wound healing, Antidiabetic, Hepatoprotective, Cardio protective, Diuretics and
Antifertility, Toxicity studies as per OECD guidelines
Model Attribute Check Company Auto PropertyCeline George
In Odoo, the multi-company feature allows you to manage multiple companies within a single Odoo database instance. Each company can have its own configurations while still sharing common resources such as products, customers, and suppliers.
The French Revolution, which began in 1789, was a period of radical social and political upheaval in France. It marked the decline of absolute monarchies, the rise of secular and democratic republics, and the eventual rise of Napoleon Bonaparte. This revolutionary period is crucial in understanding the transition from feudalism to modernity in Europe.
For more information, visit-www.vavaclasses.com
A Strategic Approach: GenAI in EducationPeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
Overview on Edible Vaccine: Pros & Cons with Mechanism
Laser characteristics as applied to medicine and biology
1. LASER CHARACTERISTICS AS
APPLIED TO MEDICINE AND
BIOLOGY
Karolinekersin E
Assistant professor
School of Engineering
Avinashilingam institute of home science and higher
Education for women
3. Laser
• Laser, a device that stimulates atoms or molecules to
emit light at particular wavelengths and amplifies that
light, typically producing a very narrow beam
of radiation.
• The emission generally covers an extremely limited
range of visible, infrared, or ultraviolet wavelengths
5. History of laser
• 1917-Albert Einstein lays the foundations for laser
technology when he predicts the phenomenon of
“Stimulated Emission,” which is fundamental to the
operation of all lasers.
• 1939-Valentin Fabrikant theorizes the use of stimulated
emission to amplify radiation.
• 1950-Charles Townes, Nikolay Basov, and Alexander
Prokhorov develop the quantum theory of stimulated
emission and demonstrate stimulated emission of
microwaves.
6. Contd…
• 1959-Columbia University graduate student Gordon
Gould proposes that stimulated emission can be used to
amplify light.
• 1960-Theodore Maiman builds the first working
prototype of a laser at Hughes Research Laboratories in
Malibu, California.
• This laser uses synthetic ruby as the active medium and
emits a deep red beam of light with a wavelength of
694.3 nm.
7. Contd…
• The first application for the ruby laser was for military
range finders and is still used commercially for drilling
holes in diamond because of its high peak power
• 1963-The Carbon Dioxide (CO2) laser is developed by
Kumar Patel at AT&T Bell Labs. The CO2 laser has much
lower cost and higher efficiency than the ruby laser.
8. Einstein theory for lasers
• Atom composed of a nucleus and electron cloud
• If an incident photon is energetic enough, it may be
absorbed by an atom, raising the latter to an excited state.
• An excited atom can be revert to a lowest state via two
distinctive mechanisms
Spontaneous Emission
Stimulated Emission
9. Basic components of laser
• Lasing material (crystal, gas, semiconductor, dye, etc...)
• Pump source (adds energy to the lasing material , e.g.
flash lamp, electrical current to cause electron collisions,
radiation from a laser, etc.)
• Optical cavity consisting of reflectors to act as the
feedback mechanism for light amplification
10. Working
• Electrons in the atoms of the lasing material normally reside
in a steady-state lower energy level.
• When light energy from the flashlamp is added to the atoms of
the lasing material, the majority of the electrons are excited to
a higher energy level -- a phenomenon known as population
inversion. This is an unstable condition for these electrons.
• They will stay in this state for a short time and then decay
back to their original energy state. This decay occurs in two
ways:
spontaneous decay
stimulated decay
.
11. • Spontaneous decay - the electrons simply fall to their ground
state while emitting randomly directed photons;
• stimulated decay -- the photons from spontaneous decaying
electrons strike other excited electrons which causes them to
fall to their ground state
• This stimulated transition will release energy in the form of
photons of light that travel in phase at the same wavelength
and in the same direction as the incident photon.
12. • If the direction is parallel to the
optical axis, the emitted photons
travel back and forth in the optical
cavity through the lasing material
between the totally reflecting
mirror and the partially reflecting
mirror.
• The light energy is amplified in
this manner until sufficient energy
is built up for a burst of laser light
to be transmitted through the
partially reflecting mirror..
13. Classification of lasers
Lasing medium
• Solid state lasers
• Liquid lasers
• Dye lasers
• Gas lasers
Wavelength
• UV lasers,
• visible lasers
• IR lasers
14. Solid state lasers
• Solid state lasers have lasing material distributed in a
solid matrix.
• e.g., the ruby or neodymium-YAG (yttrium aluminum
garnet) lasers.
• The neodymium-YAG laser emits infrared light at 1.064
micrometers.
15. Gas lasers
• Gas lasers (helium and helium-neon, HeNe, are the
most common gas lasers) have a primary output of a
visible red light.
• CO2 lasers emit energy in the far-infrared, 10.6
micrometers, and are used for cutting hard materials.
16. Excimer lasers
• Excimer lasers (the name is derived from the
terms excited and dimers) use reactive gases such as chlorine
and fluorine mixed with inert gases such as argon, krypton, or
xenon.
• When electrically stimulated, a pseudomolecule or dimer is
produced and when lased, produces light in the ultraviolet
range.
17. Dye lasers
• Dye lasers use complex organic dyes like rhodamine 6G in liquid
solution or suspension as lasing media.
• They are tunable over broad range of wavelengths.
18. Semiconductor lasers
• Semiconductor lasers, sometimes called diode lasers, are
not solid-state lasers. These electronic devices are generally
very small and use low power.
• They may be built into larger arrays, e.g., the writing source in
some laser printers or compact disk players.
19. Interaction of lasers
The physical processes involved in the interaction of a
laser beam and a material are divided into three parts
(1) absorption of some of the laser beam energy.
(2) transformation of this energy into chemical energy
and/or into heat, and diffusion of heat away from the
irradiated zone.
(3) eventually, chemical reaction and/or phase
transformation .
21. Absorption and reflection
• When a laser beam hits the surface of any material, one part,
R, of its energy is reflected, while the rest penetrates into the
material and is absorbed and/or transmitted.
• It is the absorbed energy that determines the behaviour of the
irradiated material.
• The value of R is given by the nature of the irradiated matter.
It depends on the wavelength, λ, of the incoming light.
• For transparent media, given the refractive indexes of the
incoming (n0) and irradiated media (n1), the reflectivity of the
interface at normal incidence is given by the well known
formula
22. contd..
• In medical applications, only the absorbed light is useful. The
light is absorbed either by water in the tissue or by some other
absorber, called a chromophore.
• The chromophore is generally either haemoglobin or melanin.
• When a light beam of intensity I0 hits a medium of thickness
d, the intensity I at the output of the medium is give
where α is the absorption coefficient
and
α−1 is the absorption length.
23. Contd..
• The absorption length is a measure of the thickness
where the light energy is transferred to the irradiated
medium.
• The smaller is the absorption length, the smaller the
transformed zone. So, well localized treatments are
possible when the absorption length is very short.
24. Diffusion of heat
• In general, light absorption takes place via electronic
excitation. The excited electrons are unstable.
• They decay by giving their energy to the lattice. This results in
the heating of the irradiated material.
• The transformation from light to thermal energy is very rapid .
• Hence the laser-heated zone corresponds exactly with the
irradiated one.
25. • Now, the heat diffuses in the material at a rate
determined by the nature of the irradiated material.
• When heat diffusion is the major mechanism, the
characteristic heat diffusion length, LD, is given by
where D is the heat diffusivity (in cm2 s−1) and t is the diffusion time
26. Thermal effects
• When the light energy is absorbed, various effects take place,
depending on the wavelength, the laser fluence and the nature
of the irradiated material.
• The most used effect is thermal heating of the irradiated
material.
• In this case, when heat diffusion is negligible, the absorbed
energy is the sum of the thermal energy necessary to heat the
irradiated volume to the transformation temperature plus the
latent heat of transformation
27. Electromagnetic effects
• When the laser fluence is very high, the electric field may attain the
order of magnitude of the electric field present within the molecules.
This electric field is in the range 107 to 1012 V m−1 .
• In this case breaking of chemical bonds and ionization take place,
leading to the well known electric breakdown of the medium.
• This breakdown results in various effects. One of them is the
creation of a shock wave.
• This is the origin of the sound emitted during air or gas breakdown.
28. contd..
• In biological (and other) materials, the plasma (ionized
gas) expands rapidly, giving rise to an electroacoustic
shock wave. This is able to destroy solid grains
• The electric field ε associated with a laser beam of power
P
where r is the radius of the laser beam,
µ0is the vacuum permeability
c is the velocity of light
29. Laser diagnostics and treatment
• Treatment cover everything from the ablation of tissue
using high power lasers to photochemical reaction
obtained with a weak laser.
• Diagnostics cover the recording of fluorescence after
excitation at a suitable wavelength and measuring
optical parameters
30. Biological effects of lasers
• Laser light waves penetrate theskin with no heating
effect, no damage to skin & no side effects.
• Laser light directs bio stimulative light energy to the
body’s cells which convert into chemical energy to
promote natural healing & pain relief.
• Stimulation of wound healing
– Promotes faster wound healing/clotformation
–Helps generate new & healthy cells & tissue
31. • Increase collagen production
–Develops collagen & muscle tissue
• Increase macrophage activity
– Stimulates immune system
• Alter nerve conduction velocity
– Stimulates nerve function
33. contd..
• Direct effect
occurs from absorption of photons
• Indirect effect
produced by chemical events caused by
interaction of photons emitted from laser and the tissues
34. Lasers in surgery
Laser surgery is a type of surgery that uses special light beams
instead of instruments for surgical procedures. Laser light can be
delivered either continuously or intermittently and can be used
with fiber optics to treat areas of the body that are often difficult
to access.
• To remove tumors
• To help prevent blood loss by sealing small blood vessels
• To seal lymph vessels to help decrease swelling and decrease the
spread of tumor cells
• To treat some skin conditions, including to remove or improve
warts, moles, tattoos, birthmarks, scars, and wrinkles
35. Carbon dioxide (CO2) lasers
• Carbon dioxide (CO2) lasers can remove a very thin layer
of tissue from the surface of the skin without removing
deeper layers.
• The CO2 laser may be used to remove skin cancers and
some precancerous cells.
36. Neodymium:yttrium-aluminum-garnet
(Nd:YAG) lasers
• Neodymium:yttrium-aluminum-garnet (Nd:YAG) lasers can
penetrate deeper into tissue and can cause blood to clot
quickly.
• The laser light can be carried through optical fibers to reach
less accessible internal parts of the body.
• For example, the Nd:YAG laser can be used to treat throat
cancer.
37. Laser-induced interstitial thermotherapy
(LITT)
• Laser-induced interstitial thermotherapy (LITT) uses lasers to
heat certain areas of the body.
• The lasers are directed to areas between organs (interstitial
areas) that are near a tumor.
• The heat from the laser increases the temperature of the
tumor, thereby shrinking, damaging, or destroying the cancer
cells.
38. Argon lasers
• Argon lasers pass only through superficial layers of tissue
such as skin.
• Photodynamic therapy (PDT) uses argon laser light to
activate chemicals in the cancer cells.
39. Medical lasers-Low power diode lasers
BioScan – 670 nm/70 mW for superficial applications
• The energy of a red light-emitting laser is absorbed in
superficial layers of skin and tissue (penetrating to less than
1 cm).
• A 70 mW output provides a sufficient power reserve to
achieve biostimulating effects.
Most suitable for:
• Corrective dermatology,
• Cosmetology,
• Aesthetics,
• Plastic surgery and surgery
41. BioScan – 830 nm/450 mW for deep-seated
applications
• An infra-red laser is an ideal tool for the irradiation of deep-
seated tissue structures.
• A high power output makes even the most demanding
pathologies treatable in a relatively short time.
• A simultaneously irradiated red-laser pilot beam provides
exact control over the treated area.
Most suitable for:
• Physiotherapy,
• Rehabilitation,
• Rheumatology,
• Sports medicine, and
• Orthopaedics.
43. High-power 980 nm surgical laser system
Quanta – Polysurge
• A high-power 980 nm surgical laser system which can deliver optical
power up to 200 W at an output of 600 μm fibre.
• The emission mode can be pulsed or continuous. The 980 nm
wavelength has a particular characteristic: it can be absorbed in a
similar way by water and haemoglobin.
• Because tissues contain a high percentage of water, it is important
for a surgical laser to be absorbed by water to ablate tissues
properly.
• The light absorption of the same wavelength by haemoglobin is also
important for coagulation and successful haemostasis.
44. contd..
Due to the low absorption of melanin, this wavelength can
also be used for dermatological transcutaneous treatments.
Other possible application areas are removal of bladder tumors,
ureterostenosis,
• ENT
• Proctology
• Urology
• Pneumology
• Gastroenterology,
• Gynecology,
• Percutaneous laser disc decompression (PLDD),
45. contd..
• Phlebology
• General surgery
• Dermatology
• Transcutaneous treatments, etc.
• Wavelength can be 808 nm, 940 nm, or 1064 nm (Nd:YAG).
46. Medical applications of VECSEL – visible optically
pumped semiconductor lasers (OPSLs)
• In the field of dermatology, semiconductor diode lasers are
widely adopted in the areas of tattoo removal and hair
removal.
• More recently, system builders have begun to use visible
optically pumped semiconductor lasers (OPSLs) in the
treatment of pigmentation, blood vessels or wrinkles because
of the better absorption of yellow wavelengths in melanin
compared with the legacy green laser solutions.
• OPSLs have recently also been used for photocoagulation in
ophthalmology.
47. contd..
• Lasers generate up to 8 W at 532 nm, and also use a unique
yellow wavelength of 577 nm up to 5 W.
• This new yellow wavelength is exactly matched to the main
absorption peak of oxygenated haemoglobin.
• It provides a higher degree of tissue selectivity than any
previous laser wavelength.
• This delivers superior results with reduced patient discomfort
48. contd..
• Semiconductor lasers are also used in medical and
biomedical diagnostics.
• An example is the application of super luminescent
diodes in optical coherence tomography and also
in confocal microscopy
49. Laser Regulation
Lasers are classified according to the hazard
•Class 1 and 1M (magnifier) lasers are
considered safe
• Class 2 and 2M (magnifier)
emit visible light at higher levels than Class 1,
eye protection is provided
•can be hazardous if the beam is
viewed directly with optical instruments
50. • Class 3R (Restricted) Laser
Produce visible and invisible light that are
hazardous under direct viewing conditions;
• Class 3B lasers
Produce visible or invisible light that is hazardous under
direct viewing conditions
They are powerful enough to cause eye damage in a time
shorter
Laser products with power output near the upper
range of Class 3B may also cause skin burns;
51. Class 4 lasers
• High power devices capable of causing both
eye and skin burns,
• Their diffuse reflections may also be hazardous
• The beam may constitute a fire hazard