Non-Ionizing Radiation Flashcards
What are the four types of lasers?
- Solid state (e.g., ruby)
- Gas (e.g., He, Ar, CO2)
- Dye (e.g., tunable dye)
- Semiconductor (e.g., gallium arsenide)
What is the wavelength for an ultraviolet laser?
0.18 µm – 0.40 µm
What is the wavelength for UV-C?
0.10 µm – 0.28 µm
What is the wavelength for UV-B?
0.28 µm – 0.315 µm
What is the wavelength for UV-A?
0.315 µm – 0.40 µm
What is the wavelength for a visible laser?
0.40 µm – 0.78 µm
What is the wavelength for a near infrared laser?
0.78 µm – 1.40 µm
What is the wavelength for a far infrared laser?
1.40 µm – 30.00 µm
Laser Hazards
0.40 µm – 1.40 µm (visible and near-IR)
Class II – IV
- A focusing effect through the lens increases the effective power by a factor of 100,000.
- Retina damage
- Skin burns
Laser Hazards
- 315 µm – 0.40 µm (UV-A)
- 40 µm – 3.00 µm (mid-IR)
Class II – IV
- Acute exposure ⇒ “Welder’s flash” or “snow blindness”
- Chronic exposure ⇒ Heat absorption at the lens causes cataracts.
- Skin burns
- UV is carcinogenic
Laser Hazards
- 10 µm – 0.315 µm (UV-C/B)
- 00 µm – 10.00 µm (far IR)
Class II – IV
- Temporary cornea “flash blindness” lasts for a few days.
- Skin burns
- UV is carcinogenic
What are all of the classes of lasers from least to most dangerous?
I Least dangerous
IIA
II
IIIA
IIIB
IV Most dangerous
What class of laser is a fire hazard?
IV
What classes of laser have direct ocular hazards?
IIA Only after 1,000 seconds
II Only after 0.25 seconds
IIIA
IIIB
IV
What are some beam hazards associated with lasers?
- Thermal damage (burn) ⇒ Tissues are heated to the point where denaturation of protein occurs.
- Photochemical ⇒ Light triggers chemical reactions in tissue.
- Explosions ⇒ Rapid rise in temperature in tissue can cause rapid boiling and subsequent shockwaves to surrounding tissue.
Laser Hazards
(non-Beam Viewing)
What different categories are there for these laser hazards?
- Combustion
- Ignition
- Electrical
- Vaporization
Laser Hazards
(non-Beam Viewing)
Combustion
- Description
- Safety Precautions
- Anesthetic and endotracheal tube fires caused by penetration by a direct or stray laser beam.
- Moistened cotton around the tubes or reflective tape.
Laser Hazards
(non-Beam Viewing)
Ignition
- Description
- Safety Precautions
- Inadvertent laser beam exposure to paper drapes, gauze sponges, wooden tongue bales.
- Positive footswitch activation, aiming guides, and moist drapings
Laser Hazards
(non-Beam Viewing)
Electrical
- Description
- Safety Precautions
- High voltages of the equipment
- No wearing of metallic objects, know resuscitation procedures, don’t work with wet equipment.
Laser Hazards
(non-Beam Viewing)
Vaporization
- Description
- Safety Precautions
- Lasers create large quantities of smoke that can be noxious or contain tumor cells.
- Air evacuation / suction systems can be installed to adapt to current ventilation systems.
Radiant Energy
- Define
- Symbol
- Units
Radiant Energy
- Define ⇒ The energy of electromagnetic and gravitational radiation. It is calculated by integrating radiant flux (or power) with respect to time.
- Symbol ⇒ Q
- Units ⇒ Joule (J)
Radiant Flux (Power)
- Define
- Symbol
- Units
- Define ⇒ The radiant energy emitted, reflected, transmitted, or received, per unit time.
- Symbol ⇒ Φ
- Units ⇒ Watt (W)
Irradiance
- Define
- Symbol
- Units
Irradiance
- Define ⇒ The radiant flux (power) received by a surface, per unit area.
- Symbol ⇒ E
- Units ⇒ Watt cm-2
Radiant Fluence (Exposure)
- Define
- Symbol
- Units
Radiant Fluence (Exposure)
- Define ⇒ Energy (in Joules) received by a surface, per unit area.
- Symbol ⇒ H
- Units ⇒ Joule cm-2
Radiance
- Define
- Symbol
- Units
Radiance
- Define ⇒ The radiant flux (in watts) emitted, reflected, transmitted, or received by a given surface, per unit area, per unit solid angle.
- Symbol ⇒ L
- Units ⇒ Watt cm-2 sr-1
Integrated Radiance
- Define
- Symbol
- Units
- Define ⇒ The radiance integrated over time of exposure.
- Symbol ⇒ Lp
- Units ⇒ Joule cm-2 sr-1
What is the pathological effect would you have from the following laser?
UV-B (0.28 - 0.315 µm) and UV-C (0.10 - 0.28 µm)
Photokeratitis (inflammation of the cornea, equivalent to sunburn)
What is the pathological effect from a laser in the UV-A wavelength range?
Photochemical cataract (clouding of the eye lens)
What is the pathological effect from a laser in the visible wavelength range?
Photochemical damage to the retina, retinal burn
What is the pathological effect from a laser in the near-IR wavelength range?
Cataract, retinal burn
What is the pathological effect from a laser in the IR wavelength range?
Cataract, corneal burn, aqueous flare (dispersion of light)
What are the two ranges of gain (G) for energy distribution in a microwave antenna?
G = 1 ⇒ “Unity gain,” Isotropic radiator (omnidirectional)
G > 1 ⇒ Energy is focused in a direction
What are visible symptoms among personnel chronically exposed to microwaves?
- Increased fatigue
- Periodic or constant headaches
- Extreme irritability
- Sleepiness during work
- Decrease in olfactory sensitivity
What are clinical signs among personnel chronically exposed to microwaves?
- Bradycardia
- Hypotension
- Hyperthyroid
- Increase in blood histamine levels
Microwave Hazards (by Frequency)
< 150 MHz
- Site of Major Tissue Effect
- Major Biological Effects
- None
- Body absorbs energy in the region from 30 – 100 MHz
Microwave Hazards (by Frequency)
150 MHz – 1,200 MHz
- Site of Major Tissue Effect
- Major Biological Effects
- Lens of the eye
- Critical wavelength band for eye cataracts
Microwave Hazards (by Frequency)
1,000 MHz – 10,000 MHz
- Site of Major Tissue Effect
- Major Biological Effects
- Lens of the eye
- Critical wavelength band for eye cataracts
Microwave Hazards (by Frequency)
3,000 MHz – 10,000 MHz
- Site of Major Tissue Effect
- Major Biological Effects
- Top layers of skin, lens of eye
- Lens of eye particularly susceptible
Microwave Hazards (by Frequency)
10,000 MHz
- Site of Major Tissue Effect
- Major Biological Effects
- Skin
- Skin heating with sensation of warmth
Microwave Hazards (by Frequency)
> 10,000 MHz
- Site of Major Tissue Effect
- Major Biological Effects
- Skin
- Skin surface acts as reflector or absorber with heating effects
Exposure to Static Magnetic Fields
Occupational Guideline
Whole working day
- 200 mT
- 2,000 G
Exposure to Static Magnetic Fields
Occupational Guideline
Ceiling limit
- 2 T
- 20,000 G
Exposure to Static Magnetic Fields
Occupational Guideline
Extremities
- 5 T
- 50,000 G
Exposure to Static Magnetic Fields
General Public Guideline
24 Hours per Day
- 40 mT
- 400 G
What tissues have significant energy absorption for the following wavelength laser?
(0.78 - 1.40 μm)
Skin, retina, cornea, and lens
What tissues have significant energy absorption for the following wavelength laser?
Far infrared laser (1.40 - 30.00 μm)
Skin and cornea
What tissues have significant energy absorption for the following wavelength laser?
UV-B (0.28 - 0.315 μm)
Skin and cornea
What tissues have significant energy absorption for the following wavelength laser?
Visible laser (0.40 - 0.78 µm)
skin and retina
What tissues have significant energy absorption for the following wavelength laser?
UV-C (0.315 - 0.40 μm)
skin and lens
Identify and justify the anatomical structure of the eye that is most sensitive to damage for the following laser.
Far infrared, carbon dioxide laser (10.6 μm)
- Cornea
- This wavelength is strongly absorbed by most organic molecules, including those in corneal tissue, located in outer eye structure
Identify and justify the anatomical structure of the eye that is most sensitive to damage for the following laser.
Visible, gold vapor laser (0.628 μm)
- Retina
- This wavelength is transmitted to the retina and largely absorbed in the pigmented retinal epithelium, thereby causing thermal effects and damage
Identify and justify the anatomical structure of the eye that is most sensitive to damage for the following laser.
UV-A, nitrogen laser (0.337 μm)
- Lens
- UV-A radiation has a long wavelength and will be absorbed in the lens, producing photochemical effects, leading to possible cataracts.
Identify and justify the anatomical structure of the eye that is most sensitive to damage for the following laser.
UV-C, krypton fluoride excimer laser (0.248 μm)
- Cornea
- Shorter wavelength UV-C radiation is strongly absorbed superficially in corneal tissues, thereby producing effects such as conjunctivitis and possible corneal clouding
Why does MPE vary so drastically across a short spectrum of wavelengths?
MPEs vary significantly between wavelengths of 0.647 μm (red) and 0.530 μm (green) because retinal tissue is the major tissue at risk.
The first pathology occurs in the pigmented retinal epithelium (PRE)
The damage to the retinal tissue varies with wavelength because
- The percentage of light transmitted to the retina and PRE varies with wavelength
- The energies of photons and consequent thermal energy produced by absorption vary inversely with wavelength
- The efficiency of absorption of photons by melanin the PRE varies somewhat with wavelength
What are the effects to the skin of UV-A, UV-B, and UV-C?
UV-A
- Reflected to a significant extent
- Unless the individual is extremely (unusually) photosensitive, significant skin effects should not occur
UV-B and UV-C
- At significant exposures, both can be expected to produce erythema, skin tanning, premature skin aging, and possible skin cancer
- Melanoma is strongly associated with UV-B exposure
Generic FDA Laser Class Characteristics
Class I
Class II
Class III
Class IV
Class I ⇒ Not an ocular hazard
Class II ⇒ 0.25 second exposure threshold
Class III ⇒ Momentary intrabeam viewing is hazardous
Class VI ⇒ Can damage skin or eye from diffuse reflection
- Iris
- Pupil
- Cornea
- Lens
- Retina
- Sclera
- Optic nerve
Provide an example of ELF electromagnetic radiation
50 – 60 Hz radiation resulting from the generation, propagation, and use of common household, commercial, and industrial alternating current
Sketch a spatial graph of a plane, sinusoidal electromagnetic wave.
List two sources of electromagnetic radiation in video display terminals.
Describe the radiation and normal operating values.
Examples
- Flyback transformer
- Electron deflection coils
The electromagnetic fields from these components are pulsed and produce a wide range of harmonic frequencies.
- Electric field strengths at operator locations are typically about 50 V m-1
- Magnetic field strengths at operator locations are typically about 0.50 A m-1
What biological effect of RF electromagnetic radiation is the primary basis for establishing RF electromagnetic radiation exposure criteria?
(NCRP 86)
Thermal effect
What is the ANSI recommendation for microwave exposure?
10 mW cm-2 averaged over 6 minutes
