Lasers and radiation Flashcards
Who discovered X ray
- Wilhelm Roentgen
Radiation From motion of atoms; combine electricity and magnetism
- Electromagnetic
Radiation that Only travels through substances
Mechanical
Radiation that is Unstable atom nuclei
Nuclear (neutron)
Radiation that is electrons only such as sun rays that travels almost the speed of light
Cosmic (beta)
Non ionizing radition
Can’t knock electrons off atoms but is stable.
Doesn’t break molecular bonds
Harmful only due to heat energy (radio wave or microwaves)
ionizing radiation
When electrons are knocked off atoms they create ions
What does Ion electrical charges cause what intracellular chemical reactions
Break DNA chains…cell apoptosis
Mutate DNA chains…cancer
Mutated sperm or egg cell… birth defects
can be additive
What is the similarity between x rays and light rays (2)
Both are electromagnetic energy
Carried by particles called photons
Term fo difference in energy level
wavelength
Radio wave length compared to visible light
longer wavelength/lower energyradio waves
X ray wave length compared to visible light
shorter wavelength/higher energy X-ray waves
How light is emitted
Caused by the movement of electrons in atoms
How are small atoms affected by radiation
Electron orbitals are separated by low jumps in energy because their orbits aren’t as far apart and don’t need as much energy to jump from orbit to the next. As they go back to the OG orbit = putting out less energy.
Less likely to absorb xray photons
ie. Soft tissue
How to large atoms affect radiation
Greater energy differences between orbitals because their orbits are further apart = require more energy to jump to a new orbit and fall back releasing more energy/ photons = brighter light
More likely to absorb photons
ie. Bones
How does that cathode on an xray machine work?
Is a Filament in center of machine that heats.
Current heats filament (like a fluorescent lamp)
Heat causes electrons to fly off of filament and go onto another orbital level
How does the anode of a x ray machine work?
Positively charged and attracts the electrons. After the electrons fly off with the cathode the anode attracts the electron to move down the tube and release the photons
Made of tungsten
Attracts electrons across the tube
Terms for electrode pairs in the x ray machine
A cathode and an anode
How do the photons reach the machine?
Thick shield surrounds entire machine
Window in shield allows a narrow beam of photons to escape
What does the camera on the x ray machine do?
Camera on opposite side records the pattern of x-ray photons
Chemical reaction on film
Ambient light can darken or lighten
Intensity changes to beam (over/under exposure) alter appearance
Radiation dose times a weighting factor
Rem
Measured as millirem (mrem) or 1/1000 of a Rem
Annual allowable radiation doses/ year
5,000 mrem whole body
50,000 mrem extremities
15,000 mrem lens of eye
500 mrem for pregnancy
When are we okay with pregnancy radiation exposure
in the 2nd and 3rd trimester after oganogenosis
Direct sources of radiation from cxray, coronary angiogram, angioplasty, and CT
CXR: 5-10 mrem
Coronary angiogram: 1,500 mrem
Angioplasty: 5,700 mrem
CT: 5,000 mrem
Indirect sources of radiation
Scattered radiation
Reflected off tables, patients, other surfaces
Kinds of ways that affect scatter and how much you get
Collimation, object thickness, air gap
affects of body habitus with scatter
Skinny ppl will have less scatter, and heavier ppl will have more scatter because the broader habitus would allow the photons to shoot off at greater angles.
Fetal dose of radiation and age of the effects
Fetal doses < 10,000 mrem unlikely to cause effects
After 20 weeks
Transient erythema was seen at what dose of radiation?
200,000 mrem
ALARA stands for
Radiation protection
As Low As Reasonably Achievable
ALARA factors to consider
Time
Distance
Distance from beam related to radiation exposure
if you double the distance from the beam, you ¼ the exposure rate
moving from 2 ft to 4 ft might change exposure from 20mrem/min to 5 mrem/min
Distance to be from patient undergoing radiation
attempt to be > 6ft from patient
dosimeters
1- outside the apron on the collar
2- inside the apron on the waist
MRI is based on the interactions between______
Static magnetic field in the machine and the Individual atom nuclei
How does MRI affect the cells
The Magnetic field in the machine is used to orient nuclei of hydrogen molecules in each at and causes them to north-south pole orient
Radio waves of the MRI pulses change orientation from North south of specific atoms which radiates energy. As the enrgy radiates off then we create image of white gray or black.
Creates image
MRI contrast between tissues is generated by _____
Contrast is generated by the energy that’s occurring and the time till tissue relaxation when Radio Frequency waves being turned off and on
Different tissues have different energies/ different hydrogens in their nuclei and they have different chemical and physical properties, and when those waves are turned on and turned off then we see a picture/ brightness/ darkness differentieated in our pictures.
T1 view of MRI
Magnetic vector relaxes
Fat appears bright; water dark….provides good grey-white matter contrast…anatomy
T2 MRI view
Axial spin relaxes
Fat is darker than water…identifies tissue edema easily…pathology
Most common contrast material
Gadolinium
How does Gadolinium work?
Alters the magnetic properties of nearby water molecules which enhances the quality of MR images.
Side effects of Gadolinium
Mild side effects: itching, rash, abnormal skin sensation
Rare severe reactions
Clears with normal GFR in 24 hours
What kinds of objects are attracted to the magnetic field?
Ferro (iron) magnetic objects experience
Attractive force…pulled towards center of magnet
Torque…an attempt to line up with the field
Risks in MRI (4)
Projectile risk
Radiofrequency energy cause tissue/device heating
Electromagnetic interference causes artifacts… interpretation of ECG
Acoustic noise ? 125 dB (as loud as a chainsaw)…. Hearing protectors for CRNA and patient
What does Laser stand for
Light Amplification by Stimulated Emission of Radiation
Characteristics of Laser (3)
A specific wavelength
Focused narrow beam
High-intensity
How do we produce the radiation from lasters
If the electrons get energy/ excited/ heated then them move to the next higher orbit and then get rid of the energy/ heat dissipates and the go back to the orbit and then photons are produced
Monochromatic
All the photons in the laser beam are the same wavelength
Coherence
Travel of photons is synchronized in time and space
Don’t move randomly
Collimation
The laser beam photons are nearly parallel
Allows beam to be focused on small area
Argon Laser
Modest tissue penetration (0.05-2mm)
Used in derm
Carbon dioxide laser
Scatter is minimal
Surrounding tissue damage is negligible…absorbed by water/disperses little heat
Great for vocal cords, oropharynx
Nd:YAG Laser
Most Powerful
Deeper tissue penetration (2-6mm)
Used for tumor debulking
Hazards of Laser (5)
- Atmospheric contamination
- Perforation of a vessel or structure
- Embolism
- Inappropriate energy transfer
- Airway fire
Laser Plume and side effects
Fine particulates produced d/t vaporization of tissue
HA, nausea after inhalation
Could cause interstitial pneumonia, bronchiolitis, emphysema
Could be carcinogenic
Fire triad
Ignition source
Fuel
Oxidizer
Generic laser safety
Laser glasses for provider
Laser glasses for patient with eyes taped
Windows covered
Laser plume masks for vaporized viruses
Appropriate suction
Water/saline irrigation on back table
Don’t tent drapes/have pockets of oxygen
Two major sources of OR fires
ESU
Laser
Preoperative evaluation of airway with laser
Stridor,
flow volume loops,
CT,
fiberoptic eval/ brochoscopy
consider how narrow their airway is
Mutual planning with surgeon
Intermittent apneic oxygenation, jet ventilation
Oxygen level and med to avoid for laser in the airway
O2 < 30%, avoid nitrous
