Diagnostic Imaging (Radiology) Exam 2 (MSU VMT)

technique chart

-chart with predetermined exposure factors based on tissue thickness

-provides a fast, easy, and consistent way to determine the radiograph machine settings to produce a diagnostic film

-if other factors are in place, eliminates retakes

-helps with ALARA

-designed for species and area of interest

suggested charts

-abdomen with grid

-thorax with grid

-pelvis and spine with grid

-extremity and skull with no grid

-avian and exotics with no grid

creating a technique chart

-need a sample patient

-position sample patient

-set sid to 40 inches

-set the mas and kvp for test radiograph

-select film

-take test radiograph

-process radiograph

-evaluate radiograph

-make adjustments if needed

-plot rest of chart

ideal sample patient

-cooperative adult dog with average body condition

-roughly 50 lbs.

the biggest

what size cassette should be used when creating a technique chart?

decrease mAs and kvp

what adjustment should be made if the radiograph is too dark?

increase mAs and kvp

what adjustments should be made if radiograph is too light?

2(TT)+40+gf=kvp

what is sante's rule?

mAs

ma x s=?

decrease seconds

what does an increase in ma do?

2 kvp

for every 1 cm increase or decrease in tissue thickness up to 80 cm add or subtract _________ _________ respectively

3 kvp

for every 1 cm increase in tissue thickness between 80-100 cm add _________ __________

4 kvp

for every 1 cm increase in tissue thickness for kvp above 100 cm add ________ ________

special considerations for birds

-do not worry about inspiratory and expiratory films

-avoid taping over keel

-turn down lights and reduce noise as much as possible

-keep head covered when not imaging to reduce stress between images

-block off any potential exits

-when available, perform radiographs under anesthesia

-remove tape in the direction of growth of feathers

Lateral (usually right), VD

What are the standard studies for the body cavity of birds? (2)

mediolateral, caudocranial (crashing bird)

What are the standard studies for the wings of birds?

positioning bird

-place in dorsal recumbency

-extend wings laterally at 90 degree angle to the body

-extend limbs caudally

-tape over the neck, humerus and carpus and tape over the tarsometatarsal joint to maintain wings and hind limbs parallel to the image receptor

collimating birds

-include entire birds

-larger birds: caudal cervical vertebrae to cranial coccygeal vertebrae and include the proximal humerus and femur

crashing bird view

-positioning: grasp the hind limbs and lift the dorsal aspect off the table top, place cranial aspect of the wing against the tabletop, extend the wing laterally at a 90 degree angle

lateral, DV

What are the standard studies from small mammals?

lateral, VD

What are the standard views for large mammals?

positioning small mammals for lateral view

-place animal in left or right lateral recumbency

-extend forelimbs cranially and the hind limbs caudally

-tape head and neck at base of skull

-tape over the forelimbs and hindlimbs to secure them in place

-tape over the tail

lateral w/ horizontal beam, DV

What are the standard studies for lizards?

lateral and DV

what are the standard studies for snakes?

chemical side

-film processing

-film drying

-chemical tanks

dry side

-loading and unloading

-film storage

-storage of cassettes

-labeling films

film storage

-light-tight bin protected from light and radiation

-store upright to prevent damage to the emulsion

-store in dark room

cassette storage

-store upright

-load with appropriate unexposed film

-store away from radiation

-store in dark room

prevent sticking

Why should film be stored upright?

prevent damage

Why should cassettes be stored upright

why dark room door is left open

-only when not processing film

-improves ventilation and reduces humidity which can damage the film emulsions and make surfaces sticky

-paint walls with a high gloss white or cream colored paint to maximize illumination of safe light

-only light should be from safelight

maximize illumination

Why are the dark room walls painted white?

light leaks

-most likely to occur around doorways

-damage the films in a process known as film fogging

around door ways

where are light leaks most likely to occur?

film fogging

What do light leaks cause?

monitoring light leaks

-enter and allow eyes to adjust for 5-8 minuets

-perform safe light test

preventing light leaks

-place towels or weather strips around the door jambs

-use rotating or double doors for entry and exit

-turn on in use warning light outside the darkroom when working with film

safelight test

-test for film fogging

-set piece of unexposed film on work bench

-cover about 1/4 of film and expose film for 30 seconds, move lead and expose another 1/4 for 30 seconds, then repeat again

-go straight to processor and process it

safelights

-light that is used inside the darkroom to see but which will not cause harm to unprocessed film

-reds are most versatile because they're safe to use with either type of light sensitive film

-filter eliminates every visible color except for red

-install at least 4 feet away from any work area

-bulb must be 15 watts or less

blue and green

what colors are films usually sensitive to?

direct safelights

lighting directly over the work area

indirect safelight

-lighting directly toward the ceiling and reflected over the entire room

-preferred

4 ft.

How many feet away from work area should safelight be installed?

15 watts or less

how strong should the safe light bulb be?

film fogging from safelight

-positioned to close to work area

-bulb is too bright or intense

-incorrect filter is used for the film youre working with

-film is left exposed to safelight for an extended period of time

exposed

is exposed or unexposed film more susceptible to fogging?

image receptor

-the cassette

-the intensifying screen

-film

-mini dark room

cassette

-light proof

-holds film during imaging

-film is placed in between intensifying screens

-protects the film before processing

-provides direct film screen contact during imaging

-back is lined with lead

intensifying screen

-converts x-ray energy into visible light

-base

-reflective layer

-phosphor layer

-protective layer

-x-rays penetrate cassette and strike sceen

-phosphor crystals glow and emit visible light when struck by x ray

-reflective layer bounces light back

screen lag

-if screen continues to emit light after x ray has stopped

-image fogs and details and clarity is lost

bone above and below

What should be included in a radiograph of a joint?

joint above and below

What should be included in a radiograph of a bone?

positioning forelimb

extend hindlimbs caudally and parallel to table with stifles parallel and rotated medially slightly

collimating for forelimb

-caudal to last rib

-caudal to stifle

frog leg view

-suspect trauma cases

-positioning: place animal in dorsal recumbency, extend the forelimbs cranially and allow the hind limbs to assume a natural position

-measuring: ischiatic tuberosities

-collimation: cranial to wind of ilium and mid diaphysis of the femur

pelvic landmarks

-all of dorsal vertebrae

-part of tail

-ischiatic tuberosity

-stifle

-greater trochanters

lateral view of pelvis positioning

-place animal in lateral recumbency on either the right or left side

-extend the forelimbs cranially

-extend the limb on the tabletop cranially and extend the opposite limb caudally "running man"

greater trochanters

What should be used when measuring and centering for a lateral view of the pelvis?

collimating for for lateral view of pelvis

-cranial to wind of illium and caudal to ischiatic tuberosity

-include entire dorsal aspect and atleast 1/3 of femurs

-place marker

study for signs of hip dysplasia

What are PennHIP and OFA?

hip dysplasia

abnormal development of the hip

signs of hip dysplasia

-shallow acetabulum

-flattened femoral head

-secondary degenerative joint changes such as thickening or remodeling of femoral neck, sclerosis of the acetabulum

-luxation or subluxation of femoral head

-increase in joint space

larger crystals

-faster screen speed

-less radiation required

-poorer image detail

-image created faster

smaller crystal

-slow screen speed

-used for abdomen

-more time needed

-more detail

film

-purpose is to permanently capture diagnostic image and provide permanent record for present and future

-composed of base, adhesive layer, emulsion, and supercoat

emulsion layer

-has photosensitive silver halide crystals

-where image forms

silver halide crystal

Which crystals absorb visible light?

darker

the more silver halide crystals the ___________ the image will be

phosphor crystals

Which crystals emit visible light?

how film works

-silver halide crystals in the emulsion layer absorb the visible light emitted by the intensifying screens

-exposed crystals undergo a molecular shift

-chemicals in processing completes this change

-altered silver halide crystals are converted to metalic silver during processing

invisible

The captured on the film before processing will be?

photoimprinting

-each film becomes part of the patient's medical record and must be labeled

-be consistent with location of label

-label before processing using x radiation

-write with metallic ink

included on label

-veterinarian

-clinic name and address

-date

-owner and patient name

-signalment

-type of study

processing

-development

-rinsing

-fixing

-washing

-drying

developing

-invisible image becomes visible

-no permanent image

-exposed silver halide crystals are converted to black metallic silver

-if the temperature is too high or if the film stays in the developer too long, film fog will occur

-lasts about 30-60 seconds

rinsing

-excess chemicals from developing tank are removed

-prevents contamination of fixing chemical

fixing

-image becomes permanent

-unexposed halide crystals are removed and super coat shrinks

-image can safely be taken out of dark room

-crystals turn black or white

-if not done correctly the film looks milky or pink

washing

-all remaining chemical residues are removed

-inadequate of this leaves the film stained and difficult to read

-requires fresh flowing water to prevent buildup of chemicals

unexposed halide crystals

-can darken film and cause fogging if exposed to light

drying

-film is completely dried before being hung on view box

-films will be sticky if done improperly

-emulsion will crack if temperature is too high

black

If you expose a film to x-rays, what will the film look like after processing?

transparent

What will an unexposed piece of film look like after processing?

viewers left

Where will the patient's head be pointed toward for lateral views?

top of view box

Where will the patient's dorsal aspect be placed for a lateral view?

patient's head

What will be pointed towards the top of the view box for VD/DV views

lateral views

When will the marker be placed dorsal or ventral to the anatomy indicating side closest to the image receptor?

VD/DV

When will the marker be placed on either side of the patient?

proximal aspect of limb towards top of view box, patient's left on viewer's right

How should a limb be positioned for a craniocaudal/caduocranial/dorsopalmar etc. view?