Exam 1: Radiology/ Laser Safety Flashcards
Who/when discovered X-ray therapy and how?
- Wilhelm Roentgen (1895)
- While experimenting with currents in a glass tube noticed that a fluorescent screen in the lab began to glow.
- Placed objects between the screen and the tube –> called “x” ray = something unknown
S3
What are the four types of radiation?
- Electromagnetic = from motion of atoms (combined with electricity and magnetism)
- Mechanical = travel through substances (not much travel through air)
- Nuclear (neutron) = unstable atom nuclei
- Cosmic (beta) = electrons only; travels at almost speed of light (ex: sunlight)
S4
What is non-ionizing radiation?
- Radiation that cannot knock electrons off atoms and doesn’t break molecular bonds
- Only harmful from heat energy (ex: radiowaves or microwaves)
This is the stable form of radiation because it doens’t kick off electrons
S5
What is ionizing radiation?
- These types of radiation knock off electrons which create ions
- Ion electrical charge causes intracellular chemical changes
- Risk can be additive (can add up)
S5
What are the negative effects of ionizing radiation?
- Break DNA chains = cell apoptosis
- Mutate DNA chain = cancer
- Mutated sperm or egg cell = birth defects
Berry Pops Miniature Candy Each Day
S5
What are the similarities of x-rays to visible light rays?
What is the difference?
Similar:
- Both are electromagnetic energy
- Carried by particles called photons
Difference in energy levels (wavelengths): higher energy = higher frequency
S6
X-rays have _______ wavelengths and _________ energy.
Radio waves have _______ wavelengths and ________ energy.
- X-rays have shorter wavelengths and higher energy (high frequency).
- Radio waves have longer wavelengths and lower energy (low frequency).
S6
How is light emitted?
- Caused by the movement of electrons in an atom
1. Moving particles excite atoms (when heated)
2. Electron “jumps” to a higher energy level (orbit)
3. To fall back to the original orbit, it must release energy (photon or light)
S7
How do smaller atoms affect the amount of photons released?
- Electron orbitals are seperated by low jumps in energy
- Less likely to absorb X-ray photons
- This will show up as a greyish color on the X-ray image
Ex: soft tissue
S8
How do larger atoms affect the amount of photons released?
- Greater energy difference between orbitals d/t orbits being further apart
- More likely to absorb photons
- This will show up as a whiter or brighter color on the X-ray image
ex: bones
S8
What makes up an electrode pair of an X-ray machine?
- Cathode
- Anode
S10
What is a cathode?
- A filament (in the center) shape that is heated up as machine charges.
- The heat filament current causes electrons to fly off of filament
- Negative charged side of the x-ray tube
S10
What is an anode?
- A positively charged metal disc of tungsten that will attract electrons across the tube from the cathode
- This absorbes the photos to caputre the xray
S10
Components of the x-ray machine (3)
- Thick shield surrounds the entire machine
- The window in the shield allows a narrow beam of photons to escape
- A camera is on the opposite side of the tube that records the patterns of the X-ray photons
S11
What does the camera of the x-ray machine do?
- Produces a chemical reaction on the film
- Ambient light can darken or lighten - so take the picture in a dark room
- Intensity changes to photon beam (over/under exposure) alter appearance
S11
What do we use medical x-rays for?
Diagnostics
Radiography
- bone fractures, tube placement, foreign objects
Mammography
Computed Tomography (CT)
- 3D image generated when x-ray combines with computer processing
Fluoroscopy
- real-time image (with/without contrast)
S12
Can x-rays be used theraputically?
- YES, as radiation therapy
- At higher doses, radiation can damage the cancer cell’s DNA
S13
What is the most common side effect of radiation therapy?
Fatigue
S14
How is radiation measured?
- REM = radiation dose x weighting factor
- nearly equilivalent to a Rad
- measured as milirem (mrem) or 1/1000 of a Rem
S15
Annual allowable radiation dose:
- Whole body in 1 year
- Extremities
- Eye lens
- Pregnancy
Whole body in 1 year = 5,000 mrem
Extremities = 50,000 mrem
Eye lens = 15,000 mrem
Pregnancy (after 2nd/3rd) Trimester = 500 mrem
S15
What is known as the direct sources of radiation?
- Primary X-ray beam
- Leaking from other sites within the equipment
S16
How much Rem exposure comes from the following sources:
CXR
Coronary angiogram
CT
Angioplasty
- CXR: 5-10 mrem
- Coronary angiogram: 1,500 mrem (b/c it uses fluro)
- CT: 5,000 mrem
- Angioplasty: 5,700 mrem
How do we minimize direct radiation?
- stay 6 feet away to minimize scatter
- use lead or protective equipment
S16
What are indirect sources of radiation?
- Scattered radiation: This is radiation that reflect off tables, patients, and other surfaces
S17
What are three factors that affect scatter radiation?
- Collimation (width of the beam; wider collimation has more radiation scatter)
- Object thickness (thicker patients - obese - will result in more radiation scatter)
- Air Gap (distance between patient and cassette; the greater the distance, the more radiation scatter)
COG
S17
How much rem will cause transient erythema?
- 200,000 mrem
studies looked as pts with high amounts of radiation from hospital settings and they only saw transient erythema with high doses - so minimal symptomes with xrays
* Fetal doses <10,000 mrem after 20 weeks are unlikely to have effects
S18
What is ALARA?
- As Low As Reasonably Achievable
- Radiation protection
S19
What are the 3 things to reduce radiation?
- Limit time spent near beam entry
- Distance
- direct source: double distance from beam = 1/4 the exposure rate
- indirect source: scatter = > 6 ft from patient
3 . Shielding
- lead aprons, portable shields, thyroid, lead glasses
DTS: Down To….Shit?? haha
S19
What is a dosimeter?
A badge that measures the cumulative radiation over time (usually per year)
Lecture and slide 20
How do you wear the dosimeters?
Two badges:
1. Outside the apron on the collar
2. Inside the apron on the waist
S20
What are the 3 “Don’ts” to dosimeters?
- Don’t mix up (outside or inside badge)
- Don’t share dosimeter with others
- Don’t leave in the car on the dashboard/seat
S20
41 residents were involved in a monitoring project for 3 months with occupational radiation exposure
- 82% had “high” or “very high” exposure = concerning
- <10% had recommended whole body exposure exceeding
- <4% had recommended eye exposure exceeding
lecture and S21
The principles of MRI are based on interactions between what two things?
- Based on the interaction between the static magnetic field and individual atom nuclei.
S24
The magnetic field of the MRI is used to orient the nuclei of ____ molecules to north-south poles.
- Hydrogen
S24
How does the MRI create an image?
- Radio wave pulses change the orientation of specific atoms, which radiates energy to create an image.
S24
How is contrast between tissues generated?
- Contrast is generated by time til tissue relaxation when the radio frequency is turned off.
- When the radio frequency is turned off, protons realign with the magnetic field releasing electromagnetic energy.
S25
What factors affect the tissue contrast generated?
- Various densities of hydrogen nuclei in tissues
- Different chemical and physical properties of the tissues
S25
What are the two contrast images for MRI?
- T1 contrast/ view
- T2 contrast/ view
S25
Describe a T1 contrast/view.
- Relaxation of the magnetic vector
- Radio frequency is off and not trying to move the orientation of the atom
- Provides a good grey-white matter contrast
- Good for viewing anatomy
S25
How do fat and water appear on a T1 weighted image?
Fat appears bright
Water appears dark
S25
Describe a T2 contrast/view.
- Axial spin relaxes
- Radio frequency turned on
- Great for identifying tissue edema
- Good for viewing pathology
S25
How do fat and water appear on a T2 weighted image?
Fat is darker
Water is lighter
S25
What is the most common contrast material used for MRI?
- Gadolinium
S26
How does Gadolinium enhance the equality of MRI images?
- Gadolinium dye alters the magnetic properties of nearby water molecules, enhancing the quality of MR images.
S26
What are the side effects of Gadolinium?
How is it cleared from the body and how quickly?
- Mild side effects: itching, rash, abnormal skin sensation
- Cleared with normal GFR in 24 hours. (Kidney clearance)
S26
25mg benadryl should take care of itching
In the MRI room, what do ferro magnetic objects experience?
- Attractive force - they are pulled toward the center of the magnet
- Torque - an attempt to line up with the magnetic field
S27
Is the magnetic field always on?
YES
S27
Examples of ferro magnetic objects
- O2/Nitrous tanks
- Anesthesia machine
- Monitors
- Infusion pumps
- Stretchers
- Crash carts
S27
Risks in MRI?
- Projectile risk
- Radiofrequency energy causes tissue/device heating (not that common though)
- Electromagnetic interference causes artifacts such as the interpretation of ECG artifact
- Acoustic noise up to 125 dB == wear hearing protectors (CRNA and patient) - this dB level is a loud as a chainsaw
REAP the risks of MRI
S28
Anesthesia plan for MRI
- We are usually called to MRI for claustrophobia (they usually just need sedation) - they must hold still for each imaging sequence up to 10 min each sequence
- Sedation or GETA: PO or TIVA, sevo is the MRI-safe vaporizer
S29
What are the AANA Standards of Care for MRI?
- EKG, pulse ox, BP, capnography q 15 minutes when providing anesthetics
- Airway (cannula, mask, ETT vs. LMA)
- Suction
- Spontaneous ventilation vs. ventilator
- Minimize movement (versed comes in handy)
- Complications (ex. airway access)
- MRI-compatible infusion pumps…. vs long, long, IV tubing
- Laryngoscope handles, blades…induction may occur in a separate room
S30
Things to know about patient positioning for MRI?
- Head and neck scans will result in an inaccessible airway.
- Abdominal scans will have the patient’s arms over their head. This can lead to brachial plexus injuries.
As always, minimize extreme positions
S31
What objects could be in the patient that can be effected or affect the MRI scan?
- Pacemakers
- AICDs
- Implanted insulin pumps
- New generations of these devices are MRI-compatible
S32
When the provider does this, it can cause dizziness, HA, light flashes and nausea
rapid movement towards the magnetic field (>1m/sec)
S32
What objects are considered MRI-compatible?
- Heart valves are safe
- Endovascular and biliary stents are usually embedded after eight weeks
- Coronary stents OK immediately
- Vascular ports and IVC filters are safe
- Any Orthopedic implants…titanium, safe; screws are made of lead and securely in bone.
S32
What does L.A.S.E.R. stand for?
- Light Amplification by Stimulated Emission of Radiation
S35
What is ordinary light vs laser light?
- Ordinary light contains many wavelengths that spread out in many directs
- Laser has a specific wavelength with a focused narrow beam and high intensity
S35
The unexcited state electrons orbit the nucleus at the ____ energy.
- lowest
S37
In the unexcited state, electrons occupy orbits ____ to the nucleus.
- closest
S37
How is radiation produced?
- As the electrons absorb energy from a source, they become excited and move to a higher orbit
- Upon return from an excited state to ground state, they spontaneously emit photons of energy (electromagnetic radiation)
S37
Properties of Laser Radiation?
- Monochromatic: All photons in the laser beam are the same wavelength
- Coherence: Travel of photons is synchronized in time and space (not random movement)
- Collimation: Laser beam photons are parallel (allow the beam to focus on a small area)
S38
Advantages of LASERs
- Precision
- Good hemostasis (bovi a vessel and colguate)
- Rapid healing
- Less Scar formation
- Less postop edema and pain
- Lower infection rates
S39
What gives a type of laser its name?
- The Lasing Medium
S40
What are the 3 lasing mediums?
- Argon
- Carbon dioxide
- Nd:YAG
S40
What should be known about Argon lasers?
- Used in dermatology
- Modest tissue penetration (0.05-2 mm)
S40
What should be known about CO₂ lasers?
- Used in vocal cords, oropharynx
- Scatter is minimal
- Surrounding tissue damage is negligible and absorbed by water/disperse little heat
S40
What should be known about Nd:YAG lasers?
- Most powerful laser
- Used for tumor debulking (prostate, bladder tumors)
- Deeper tissue penetration (2-6 mm)
S40
What are the 5 hazards of laser?
What are the two hazards CRNAs are most concerned with for lasers?
- Atmospheric contamination (most concern) - particulate masks
- Airway fire (most concern)
- Perforation of a vessel or structure
- Embolism
- Inappropriate energy transfer
S41
Atmospheric Contamination
What is a Laser Plume?
- Fine particulates produced d/t vaporization of tissue
- Laser Plume can result in HA, nausea after inhalation
- Laser Plumes could cause interstitial pneumonia, bronchiolitis, emphysema
- Laser Plumes could be carcinogenic
Definitely use a particulate mask
S42
LASER safety
- laser glasses for provider
- laser glasses with gauze tape for pt
- windows covered
- laser plume masks for vaporized viruses
- appropriate suction
- water/saline irrigation on the back table (to put out a fire if there is one)
- dont tent drapes/have pockets of oxygen (this decreases fire ignitors)
S43
What makes up the fire triad?
- Ignition source (aka Laser)
- Fuel (drapes, ET Tube, nasal cannula)
- Oxidizer (oxygen)
S44
What are the two major sources for OR fires?
- ESU (Electrosurgical units aka “Bovie”)
- Laser
S44
What are some scenarios for endotracheal fire discussed in the lecture?
- Surgeon is lasering airway through the ETT and burns through PVC tube…
- Surgeon is completing tonsillectomy in a pediatric patient with an uncuffed tube…
- Surgeon uses bovie to “cut” through trachea for a tracheotomy…
For all of these scenerios, decrease the O2 concentration to 21% if the pt can tolerate it to decrease the oxidizer close to the ignitor
S45
How to prevent Airway fire?
- Laser-resistant ETTs
- Low-inspired (21% if possible) O2
- Wet pledgets around the ETT (tape strings to face to prevent loss)
- Methylene blue in the ETT cuff (visual)
- Use scissors to cut into trachea instead of bouvie (for emergent airway or planned trachostomy)
- Remove ETT during laser procedure and reinsert ETT prn sats
S46
Anesthesia Plan for the patient undergoing Laser therapy.
- Preoperative evaluation of airway (stridor, flow volume loops, CT, fiberoptic eval)
- Mutual planning with surgeon) Intermittent apneic oxygenation, jet ventilation)
- Total IV anesthesia (Propofol, remifentanil, Xylocaine spray) - TIVA because apnic ventilation will affect your gas - duh
S47
Anesthesia plan to prevent airway fire:
- Methylene blue in cuff
- Saline gauze protection of airway/face
- Short, repeated pulses of laser instead of long continuous mode
- Keep O2 < 30%, avoid nitrous
- Communicate and monitor video camera for signs of airway fire
S48
