84 terms

Rad test 1

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Know how x-rays are generated
When circuit is activated, exposure switch is closed
Filament transformer sends electricity to cathode.
Cathode temp rises and e boil off, creating e cloud (thermionic emission)
E cloud focused onto focal spot of + anode
Anode converts e to x-rays which are directed towards the patient
Properties of X-rays
Only travels in a straight line
Short wavelength (more energy abd penetrability)
As x-rays pass through tissues they are absorbed
Some substances (rate earth phosphors) will fluoresce
X-rays can cause biological change in living tissue
Heel effect
X-rays are closer together at cathode end (x-rays more intense at sides of cathode)
Cathode has more energy
Angle of anode target yields uneven X-ray photon distribution
Use as advantage- head and chest are thickest part of patient, so place these facing the cathode
Upper limits of exposure a person is allowed
50 mSv a year
10 mSv x age cumulative
Measured with personal dosimeter
Scatter radiation def
Primary beam hits objects and x-rays scatter in straight lines in all directions
How to reduce scatter radiation
Collimate
Avoid retakes
Increase distance from self to beam
Don't lean over table
Use chemical restraint if possible
Wear protective gear
Personal Protective Equipment
Lead apron/thyroid shield/gloves/goggles
Leaded drapes/gonadal shield
Personal dosimeter
mA
Provide energy to filament to heat it and cause it to release e
quantity of electrons
Increase mA increase e cloud size
The more mA, the higher the strength/intensity of x-ray
KVp
Energy applied between cathode and anode that accelerate the e towards the anode
Quality of penetration
Higher KVp means higher penetration
Object density
Lowest to highest is
Gas
Fat
Water
Bone
Metal
Film density
Lowest to highest
Metal
Bone
Water
Fat
Gas
Function of grid
Absorb scatter radiation
Where is the grid placed?
between the patient and the film to improve quality of image
Can be built into cassette, placed on top of cassette, or be build into x-ray table
How does a grid work?
Made of alternating pieces of lead strips and low density strips
Only beans going straight (mainly primary beams) are able to pass through the grid and reach the film
Align focal point of grid on focal spot of X-ray tube so primary beams are not cut off
Grid factor
Grids absorb primary beams too
2-3 x more rays must be generated when grids are used compared to when they're not
Add KVp
ALARA
As Low As Reasonably Achievable
Ensure sensible decision making, rules about exposure of personnel, and equipment care and attention to protective gear
X-ray label
Name of patient
Owner name
Date of exposure
Hospital name
Cassette
Lightproof case that holds film
Lightproof to avoid unwanted exposure
Designed to contain intensifying screen and film
Intensifying screen
convert x-rays to photons after they have penetrated the patient
Reduce need for rad exposure for rad
Blue film/screen system
Emit blue light
Screens require blue receiving film
Various speeds of conversion efficiency
Green film/screen systems
Emit green or blue green light
Require green receiving film
Single speed of conversion efficiency
More commonly used
Speeds of intensifying screens
Depends on crystal size
Larger crystals mean faster screen, but detail is decreased
Large screens have less latitude
Small screens are better for detail
Medium screens are most commonly used
Latitude
Amount you can over or under expose your film and still get an acceptable image
Developer solution
Runs latent image into visual image
Exposed silver halide crystals to metallic silver
Developer does not affect unexposed crystals in the film (unexposed are white)
Rinse (first)
Stops developer
Removes remaining developer chemicals
Fixer solution
Remove unexposed silver halide crystals
Harden gelatin coating
Wash (second)
Rinse off all of the chemicals and residue of silver halide still on film
Steps in chemical processing
Develop
Rinse
Fix
Wash
When to use table top vs under the table for taking rad
10 cm or below, use tabletop
11 or above go under the table
The unit of absorbed ionizing radiation dose is
Gray (Gy)
Constant factors in making a technique chart
SID
Film processing
Type of grid
Amount of beam filtration
How to make a technique chart
Use a series of trial exposures using an average sized dog
14x17 cassette
Medium film speed
Use 200 mA for medium screen
Use sante's rule for KVp
Sante's rule
KVp = (2 x tissue thickness) + FFD + grid factor
FFD = 40 inches
Grid factor for 8:1 grid = 10 KVp
Rules for finishing technique chart after Sante's rule
Subtract 2 KVp from original KVp for every cm less than that of original

Add 2 KVp from original KVp for every cm over that of original

If KVp is between 80-100 increase KVp by 3 instead of 2

If KVp is over 100 m, increase KVp by 4 instead of 2
Latent image
Image that is formed but is invisible until processed
New arrangement of halide particles is lattice network
Formed within emulsion of x-Ray film when x-rays and light activate silver particles in the emulsion.
Benefits of collimation
Decrease scatter rad
increase safety to tech
Increase safety to patient
BIPS
Barium Impregnated Polyethylene Spheres
Comes in 2 different sizes
Mainly to evaluate motility
Also for obstruction but difficult if obstruction isn't complete
What does overpenetration mean? How do you fix it?
Means too bright
Underexposed
Increase KVp
Signs that good x-ray was taken for OFA
Straight spine
Parallel femurs
Patellas centered on distan femoral condyles
Obtorator foramen symmetrical
How to correct motion artifact
Sedation
Positioning aid
Increase mA, decrease time
Measure and center of beam for lateral thorax
Caudal border of scapula for both
Measure and center of beam for VD thorax
Caudal border of scapula for both
Measure and center of beam for lateral abdomen
Caudal aspect of 13th rib for both for dogs
Cats measure caudal aspect of 13th rib and center beam 2-3 fingers caudal to this
Measure and center of beam for VD abdomen
Dogs caudal aspect of 13 rib for both
Cats measure caudal aspect 13 rib and center beam 2-3 fingers below
Measure and center of beam for lateral pelvis
greater trochanter of femur for both
When positioning, leg on the table goes anterior to the other leg
Measure and center of beam for VD pelvis extended
Measure at thickest part of pelvis
Center beam at caudal ishia
Measure and center of beam for VD pelvis frog leg
Measure at thickest part of pelvis
Center at pubis
What does it mean when film is silver halide color?
Not processed
Can be exposed or unexposed
What does it mean when film is clear
Film is unexposed and processed
What does it mean when film is black?
Film is exposed and processed
When can artifacts occur?
Transport
Chemical
Handling
Transport artifacts
Created when film is in processor

Examples include plus/minus density, scratch, pick off, chatter, pi lines, hesitation, wet entrance, and guide shoe
Chemical artifacts
Created by chemicals during processing

Examples include dichotic fog, underreplenishment, temp too cool/warm, fixer not replenishing, fixer overconcentrated/exhausted/empty, incorrect mixing, wash water empty or not circulating
Handling artifacts
Examples include foreign object, dust on feed tray, double exposure, film fog, extrafocal radiation, static, sweaty fingerprints, film creases, incorrect darkroom conditions
Dichotic film artifact
Film has oily pattern of color in reflected light
Caused by fixer leaking into developer
Blur artifact
Usually due to motion or double exposure
Static electricity artifact
Causes black tree branch like pattern
Can be caused by dragging film along a surface
Crease artifact
Black crescent
Expose silver halide/turn in black
What can happen if cassette and primary beam aren't lined up
Artifacts
Get part of radiograph exposed
OFA
Looks for degenerative changes
Does dog have dysplasia at this time
Needs one view
Rate excellent to severe
Penn hips
Will pet get hip dysplasia
Do joints look loose on distracted view
Needs 3 views
Penn hip vs OFA
OFA has 1 view, penn has 3
OFA- p is 2 yo, penn p is 16 wo
OFA- anyone can take film
Penn- certified personnel take films
Positive contrast agents
Radiopaque- shows up white
Made of elements of high atomic number and absorb more x-rays
Ex is barium or iodine
Negative contrast agents
Radiolucent- show up black
Gases (CO2, oxygen, air)
Why administer contrast agent?
Tell you shape, position, size, lining of membrane, function

Function is to tell density difference
Side effects of ionic preparations
Anaphylaxis
Acute renal failure
Transitory pulmonary edema
Vomiting
Barium contrast
Given orally
Ideal for GI studies (insoluble, Not absorbed by body)
Prepare as oral paste, liquid, or powder
Can cause granulomas w/ perforation (escapes bowel) or cause aspiration if given too quickly
Side effects of negative contrast studies
Gas embolism
Usually occurs with room air (CO2 is better)
Double contrast studies
Combination of positive and negative contrasts
Ex is intravenous urography or excretory urography for urethra it intravenous pyelography for kidney/ureter/bladder
myelography
Spinal cord
Only use nonionic preparations
Blown disc push on cord and change in shape
Angiography
Visualize circulation
Iodine
Venous portography shoes portal venous system to evaluate for shunts
Scintigraphy
Noninvasive
Radioactive material used and goes into area that is highly metabolic
Nuclear medicine use
Provides physiologic info about function of specific organs
No info on anatomic detail
Uses technetium 99
Steps to critiquing a film
1) what view is it
2) too light/too dark
3) position/center of beam
4) colimation
5) artifacts
6) ID/positional markers
7) inspiration/expiration
Which alternative imaging techniques don't use radiation
MRI
Ultrasound
How does nuclear scintigraphy work?
Gamma scintillation camera detects emissions from radionuclide and forms black and white image
Radionuclide excreted in urine/feces
What are hot spots?
Areas that show up on a bone scan that indicate increased blood flow or bone remodeling
How does CT scan work
Uses x-rays and computer to produce images and show anatomy in cross section
X-ray tube moves around patient
Good for hard tissue, CNS, PNS, axillary region
MRI
Similar to CT but w/o ionizing radiation
Uses magnet to disturb H molecules
Best for soft tissue
Better resolution than CT but not good for hard tissue
Ultrasound
Uses high frequency sound waves
Transducer frequencies can vary (higher megahertz means better picture but poorer penetration- use high mega for small patient)
Transducer has piezoelectric crystals
Transducer emits sound wave. If wave hits an echogenic surface it returns some of wave back to transducer
Different display modes exist (A, B, M)
Echogenicity
Indicate liquid or solid composition of the tissue
Anechoic
Reflect few, if any, echos
Ex bladder/fluid is black
Hypoechoic
Reflect few echos
Soft tissue is grey
Hyperechoic
Reflect many echoes
Bright white
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