15 Radiation & Lasers Flashcards
Electromagnetic Radiation (EMR)
Refers to the waves or their photons (particles) from an electromagnetic field
- Radio waves
- Microwaves
- Infrared light
- Visible light
- UV light
- X rays
- Gamma rays
Electromagnetic Field
Force field that consists both electric and magnetic components resulting from the motion an electric charge and containing a definite amount electromagnetic energy
Inductance
Electrons flow around wire induce magnetic field around the wire
Wire coiled repeatedly around an iron core
Electromagnetic
Expresses dual nature electricity and magnetism
Electric current + magnetic waves
Changing magnetic waves = electric current
Wavelength λ
Trough to trough
Peak to peak
Frequency
Number oscillations
Shorter wavelength = higher frequency & stronger energy
Reflected
Reflects directly back to source
Refracted
Reflects indirectly
Diffracted
Reflects indirectly at lower frequency
Absorbed
Light not reflected
Radiation
Energy emission
Non-ionizing (visible, UV or infrared light, radio waves, microwaves)
Ionizing (beta, gamma, or X-rays)
Average Natural Radiation
300mrem
Beta Particle Radiation
Neutrons are excessive → convert to proton and electron
Electron ejected at high speed
Travels only few meters in air before being absorbed
Shielding w/ radiation-absorbing material necessary
Alpha Particle Radiation
2 protons & 2 neutron are ejected as 1 particle
Heavy & slow
Travel only few cm in air before energy expended
Gamma Radiation
Nucleus in excited state emits “energy packet” known as photon
Number protons & neutrons are not altered but instead the nucleus moves from higher to lower energy state
Travel long distances & shielding best achieved w/ lead
X-ray Radiation
Less energy than gamma rays & less penetrating
Require less shielding
Ionizing Radiation
Radiation w/ enough energy to remove tightly bound electrons from atom orbit
Causes atom to become charged or ionized
Alpha, beta, gamma, & X-rays (UV)
Radiation Units
Absorbed dose - amount energy deposited per unit mass (grays Gy or milligray mGy)
Equivalent dose - absorbed dose multiplied by converting factors based on biological radiation effects (sieverts Sv or millisieverts mSv)
Amount ionizing radiation required to produce the same biological effect as one RAD high-penetration X-rays
RAD radiation absorbed dose
Milliroentgen mrem
C-arms
Portable X-ray machine that are used in ORs & ICUs
X-ray beam directed toward the patient and tube
Stand at least 6ft away to minimize exposure
X-ray Safety
Distance from source
Barriers (shielding)
Exposure time
Radiation intensity INVERSELY proportional to _____
Distance from the source
Intensity = 1/d^2
6ft away = 0.5mm lead shielding
LASER
Light Amplification Stimulated Emission Radiation
Light emitted when electrons jump from more distant orbitals to orbitals closer to the nucleus
LASER Physics
Monochromatic
Coherent
Collimated - light has minimal dispersion yielding narrow light band
- Generate intense light beams
- Send beams efficiently & accurately through lenses
- Deliver intense energy to small target site
Photochemical
UV <400nm & visible wavelengths <500nm
Photo absorption excites molecules & react to form unwanted chemical products cause erythema & vesiculation
Thermal
Occurs at all wavelengths
Tissue heated via laser energy absorption
Thermal effects depend on energy rate & absorption to dissipation
Continuous Wave
Output expressed in power terms (energy rate)
Watts
Produces beams that are constant & power delivered to tissue does not vary
Pulsed Lasers
Output expressed in energy terms per pulse
Joules
Produces beams in small bursts controlled by the user
Power levels are more intense than maximum power levels generated by continuous wave lasers
Q-Switched Mode Lasers
Both continuous & pulsed wave mode
Clinical Laser Uses
Coagulation
Cutting
Vaporization
Laser Safety
Airway fire risk Bleeding Pneumothorax Tissue damage & edema ETT cuff failure Laser injury Surgical smoke inhlalation
Maximum Permissible Exposure
MPE
Determines level eye/skin protection needed
Eye protection important d/t lens multiplies power density at the retina
Retina - photoreceptors location (neurons sensitive to light)
Optimal Density
OD indicates inverse amount light transmitted through material
Wear eye protection whenever operational conditions have potential eye hazards
Eyewear labeled w/ rated wavelength & OD
Ensure sufficient OD at correct laser wavelength
OD = 5
10^-5 or 0.001%
Laser Classifications
Class 1 - no beam hazard
Class 2 - no realistic hazard
Class 3a - CAUTION label normally no eye hazard w/in 0.25sec
DANGER label potentially exceed MPE in 0.25sec remains low hazard
Class 3b - hazardous to view directly or specular reflection normally no diffuse reflection or skin hazard
Class 4 - hazard to view beam or specular or diffuse reflection also skin & fire hazard
*Most healthcare laser systems are class 4
Reflections
Specular (mirror-like) more hazardous than diffuse reflections
Keep shiny surfaces away from field to prevent specular reflections
Utilize blackened, anodized, or matte finish to minimize specular reflections
