Test #2 Flashcards
What is a technique chart?
a way of knowing what to set the exposure to
Purpose of technique chart?
to provide consistent way of exposure for a diagnostic radiograph
Caliper
device used to measure the patient for radiograph
always use centimeters
Where to measure when doing elbow
distal humerus
where to measure when doing radius/ulna
distal humerus
where to measure when doing stifle
distal femur
where to measure when doing tibia/fibula
distal femur
How to start a technique chart
mesure a medium sized dog/cat for abdominal
Set machine to 2.5mAs & 65 kvp
set shortest exposure time to achieve 2.5 mAs
adjust technique as needed
Always log the techniques!
Suggest kVp ranges for extremities
55-65kVp
Suggest kVp ranges for abdomen
65-85kVp
Suggest kVp ranges for thorax
75-95kVp
Suggest kVp ranges for pelvis
55-75kVp
Factors to consider when developing a technique chart
tissue thickness
screen type
grid factor
Primary beam
a group of rays that make up beam
Central ray
most central ray
part of primary beam
Primary rays
the rays on either side of central ray
part of primary beam
Secondary rays
outer edges of beam and do not have enough energy to pass through the patient
part of primary beam
Cone
beam limiting device that slides on the end of the tube under the filter to limit the size of the beam
Collimator
beam limiting device
LEAD SHUTTER BEAM LIMITING DEVICE
adjusts down to decrease the size of the primary beam
Advantages of limiting the beam
decrease the amount of radiation to the patient and you
better detail
Backscatter
rays that become scattered by bouncing off object
grids are used to decrease this
A grid is a device that either sits
*between patient and film
on top of cassette
built into cassette
Grid composition
alternating strips of lead and spacer material
Grid ratio
height of lead strips in relation to the material between
example 8:1
Linear grid pattern
lead strips are parallel to each other and horizontal to the surface
Crossed grid pattern
2 linear grids that are at right angles to each other
Parallel/Unfocused grid
not the most effective
lead strips are parallel to each other and upright to the surface
Focused/Angled grid
lead strips in the center are parallel but the strips on the edges are angled
too effective, low quality
Pseudo-focused grid
combo of parallel and focused grids
prevents the absorption of primary beam at the edges
best quality
Inventor of the grid & year
Dr. Gustov Bucky
1913
Inventors of moving grid
1920
Hollis Potter & Dr. Bucky
“Potter-Bucky diaphragm”
Radiographic quality is dependent on
density
quality contrast
factors affecting detail
Radiographic density
the amount of black or darkness on the radiograph
5 main radiographic densities: most dense to least dense
Air Fat Tissues of H2O density Bone Enamel/Metal
4 factors affecting radiographic density
milliamperage
kilovoltage
object density
tissue thickness
4 ways to increase radiographic density
increase mA
increase kVp
increase developing time
increase temperature of developing
Radiographic contract
varying sades of gray on radiograph
the density difference between 2 adjacent areas
5 things that influence contrast
Subject contrast kVp Scatter radiation Film type Film fog
Short scale contrast
more measurable difference between two adjacent areas on radiograph
black and white
Long scale contrast
less measurable difference between 2 adjacent areas on radiograph
more shades of gray
Radiographic Detail
sharpness and clarity of rad
Geometric unsharpness & causes
type of decrease in radiographic detail fog (fuzziness) on a particular area of the radiograph poor screen/film contrast focal spot size focal film distance motion
Geometric distortion and magnification
type of geometric unsharpness
“flashlight effect”
elongation- object appears longer than actual size
foreshortening- object smaller than actual size
does not effect quality, only size
Radiographic noise
type of geometric unsharpness
variations in density not associated with normal tissue/bone densities
2 types of radiographic noise
Mottle- grainy due to wrong film type, dirty chemicals in processor
Artifacts- fogged film
Black crescents or lines - causes
static electricity
finger prints
roller marks
Black areas - causes
exposure to white light
White areas - causes
grid lines
overlapping body parts
too much difference in body measurement
Film too dark
overexposed
decrease technique
Film too light
underexposed
increase technique
Doubly dark
can barely distinguish the object
all black film
1/2 Doubly dark
able to distinguish object from the rest of primary beam but dark around the edges
not very good detail
1/4 Doubly dark
able to distinguish object, but just slightly dark
cant see small details
Doubly light
can barely distinguish the object almost all grayish-white
1/2 Doubly light
able to distinguish object, but hard to recognize most detail
1/4 Doubly light
able to distinguish object, can see detail, but not small details
Doubly dark & Doubly light adjustment values
kVp- 15%
mAs- 50%
1/2 Doubly dark & Doubly light adjustment values
kVp 10%
mAs 30%
1/4 Doubly dark & Doubly light adjustment values
kVp by 2-3
Purpose of film
provide a permanent record that contains vital dx info
X-ray film base
transparent polyester that provides flexible support
X-ray film emulsion
gelatin suspension of silver halide crystals that coat the film evenly
Silver Halide
compound made up of silver and either bromine, chlorine, or iodine
silver bromide crystals are the most common type
What happens when X-rays hit the film
converts silver halide into black metallic silver
how much is converted depends on films sensitivity
Film sensitivity
how sensitive the film is to the xrays
can be sensitive to either blue or green spectrum of light
more sensitive= faster speed
Fast speed film
larger silver halide crystals
requires less exposure from xrays
poor image detail
good for body cavities
Slow speed film
smaller crystals
decreased sensitivity
increased detail
Medium film (par)
most commonly used
fairly good detail without too much radiation
Film storage and handling
store in vertical position
temp. should be kept 50-60 degrees with low humidity
film is least sensitive to red light and most sensitive to white light
2 types of film holders
cassettes
cardboard (dental rads)
Intensifying screens
> 95% of the exposure recorded is from the light coming from screens
sheets of luminescent phosphor crystals bound together and mounted in cassette
when the crystals are struck by xrays, they fluoresce and convert the xrays into visible light
4 parts of intensifying screen
- Base layer/support
- Reflective- reflects light toward film
- PC layer- blue or green fluoresce
- Protective coat
Calcium tungstate screen
Old version
invented in 1896 by Thomas Edison
emissions of blue light
doesn’t convert light very well
Rare Earth Phosphor screen
much greater xray to light conversion
4x the ability to convert
emission fo light can be green or blue
decreases radiation dose
Fast screen speed
decreased exposure time
larger crystals
decreased detail
more efficient light conversion
Slow screen speed
Increased exposure time
smaller crystals
increased detail
less efficient light conversion
Medium screen speed
most common
medium screen with medium film
Screen care
cleaning solution recommended by manufacturer
70% alcohol solution
Kim wipes- never ever use paper towels!!!
Layers of cassette
- cassette top
- top padding
- intensifying screen
- film
- intensifying screen
- bottom padding
- cassette bottom
5 steps to processing any film
- developing
- rinsing/stop bath
- fixing
- washing
- drying
Developer
alkaline chemical that converts latent image into visible image
Rinse bath
stops the developing process
rinses developer off the film
prevents contamination fo the fixer
Fixer
an acidic solution that removes the unexposed crystals and hardens the gelatin coating to prevent damaging from drying
Washing
removes the chemicals from the film
in manual processing, the film should be washed for 30 min.
Manual developing
68 degrees for 3 min.
for each degree lower than 68 degrees increase time by 30 seconds
for each degree higher than 68, decrease time by 30 seconds
never develop for longer than 5 min or shorter than 2 min.
Fixing
twice the developing time
Clearing time
the minimum amount of time film needs to be in the fixer
20 seconds
2 types of water baths
stationary
circulating
rinse 20-30 min.
hang to dry
Automatic processing
involves some routine except operates at a much higher temp. and special chemicals to speed up processing (90-94 degrees)
Care for manual equipment
buy dilute chemicals
concentrated chemicals
needs to be kept clean and changed regularly
Care for automatic equipment
service tech will come service the machine every 3-4 months
Silver recovery
any old film must be sent to silver recovery
Film identification
all radiographs must contain a permanent label
Film ID must include
name and address of hospital
date
patient and owners name
age, sex, breed, DOB
3 methods of labeling
lead markers (old version)
lead impregnated tape (equine)
embosser
Split plates
when more than one view can be placed on a piece of film
light area must be closed only to specific area to be radiographed
cover un-used parts with lead
Thoracic Radiographs most common visible structures
Heart, lung fields, trachea, rings, aorta, cranial and caudal vena cava
D/V best for
heart evaluation
V/D best for
lungs
never do V/D for dyspnic patient
Lateral
right side down
Dyspnic patient postions
standing or sternally recumbent
lateral decubitus
Most common visible structures on abdominal xray
Liver Stomach Kidneys- left= lower Urinary bladder \+/- intestines \+/- spleen
Why take abdominal radiograph?
Foreign bodies
tumors
uroliths (stones)
confirm pregnancy
Confirming pregnancy in dogs and cats
can be anywhere from 45-50 days of age
Zippers
Dystocia (find where fetus is)
Why take pelvic rads?
dx hip dysplasia arthritis degree see fractures tell where fluxation is legg-clave-perthes syndrome= small breed dogs: jumping destroys cartilage
common pelvic views
V/D & Lateral
OFA stands for
Orthopedic Foundation for Animals
OFA established
1966 to assist breeders in addressing hip dysplasia
OFA also has a database for
Elbow deformities Patellar deformities Thyroid dz. Congenital heart dz. DNA- VonWillebrands dz.
Objectives of OFA
to gather and distribute info
to advice, encourage, and establish control problems
to encourage and finance research
to receive funds and make grants
How old must an animal be to be OFA eligible
2 years
Top 2 breeds for hip dysplasia
Bulldogs & Pugs
X-rays for OFA
Only 1 needs to be sent, but take 2 and keep one for backup
2 pieces of film in one cassette
OFA Embossing card
dogs registered name or # DOB Vet case or X-ray # Date Dr. name or hospital name
OFA radiograph is reviewed by
3 randomly selected, board certified radiologists
breed, age, and sex of animal are taken into consideration
7 categories for OFA registration
Passing:
Excellent hip joint conformation
Good hip joint conformation
Fair hip joint conformation
Failing:
Borderline hip conformation
Mild hip dysplasia
Moderate hip dysplasia
Severe hip dysplasiaPenn Hip official name
Pennsylvania Hip Improvement Program
PennHip established in ___ by ___
1983
Dr. Gail Smith
PennHip asses
the quality of K9 hip joint and quantitatively measures hip joint laxity
PennHip is accurate in puppies as young as
16 weeks old
PennHip has been on the market since
1994
3 factors that compose PennHip
diagnostic radiographic technique
network of trained vets
medical database for scientific analysis
3 views required for PennHip
Extended
Compression (frog leg)
Distraction (hind legs placed in position perpendicular to the table top)
