Lesson 4: Positioning And Small Animal Radiography

Which is the preferred position for mediolateral projection of the femur?

Femoral head toward cathode end of X-ray tube

You should always try to ensure that the part being radiographed is as ______ to the cassette as possible to decrease ______ and increase ______.

close

distortion

detail

All radiographs should be taken on ______ to decrease movement. With the exception of xraying the thorax which should be taking on ______

Expiration

Full inspiration

What is positioning?

refers to the way the animal looks when lying on the table ready to have the radiograph exposure made. This includes what side the animal is lying on, what if any limbs are pulled, and where any positioning aids are used.

The term landmarks refers to what?

parts of the animal that you can use to determine whether or not you're including the entire body part of interest in the radiograph.

Name two landmarks for each body part or body cavity

one caudal and one cranial, one distal and one proximal, or even one cranial and one central. There must be two landmarks to adequately delineate where the radiograph will be taken.

A minimum of how many radiographic views is/are recommended to be able to get a 3D picture of an area?

Two views minimally

When an animal is placed in "lateral" it's lying on its _______.

side

In radiographic nomenclature, VD stands for _______.

ventrodorsal

In the VD position the patient is lying on its _______.

spine

When taking a radiograph of the right knee, make sure that the pet's _______ knee is closer to the cassette.

right

Please list three types of positional aids.

Tape, gauze, sandbags, foam wedges, v-troughs, beanbags, rope

When xraying the thorax and the abdomen, the kVp should be lower and higher for which body parts?

Lower for thorax

Higher for abdomen to create better contrast in the radiograph

Why are full body xrays not recommended

There is no way for the technique to be adequate for all body parts seen on the film.

How to ensure the liver or cranial portion of abdomen is included in the xray?

find the caudal tip of the sternum and then move two inches cranially to it. This spot is your cranial abdominal landmark.

If an animal cannot breath or vomits in a VD position, what should you do?

Quickly place animal in sternal (ventral) recumbency

For an animal to be truly lateral, the spine and the sternum need to be the same ________ off the table.

distance

What are positioning sponges and how are they used

-help get the animal in true lateral form.

the sponge locations for the thorax are under the elbows and under the ventral abdomen. The sponge locations for the lateral abdomen positioning are under the mid-sternum area and under the stifles

Positioning sponges should never:

Be placed under the animal in the area being radiographed as this can cause an artifact in the film.

For a lateral thoracic and abdominal view, explain what the film would like like if the pet is in a true lateral position.

thoracic: ribs over the heart. If the animal is truly lateral, the right and left ribs over the heart will be superimposed and look as one

abdominal: e lateral process on the right side of the vertebra should superimpose over the lateral process on the left side

When determining whether or not an animal is truly ventrodorsal on a thoracic radiograph, look to the _______ and ________

Sternum and spine

In a true ventrodorsal position, the sternum and the spine should be ________ over each other

superimposed

. At what point during expiration and inspiration should an abdominal radiograph be taken?

Full expiration

What are the most common views taken of the thorax and abdomen?

Lateral and ventrodorsal

What area of the ribs should be superimposed when looking at the lateral chest?

Over the heart

When looking at symmetry for the abdominal cavity, you need to look at the _______.

processes of the vertebra

What is the most common error when taking an abdominal radiograph?

The liver isn't fully included in the view

What is the term for the position of front extremities/body parts when an animal is on its back

craniocaudual

What is the term for the position of front extremities/body parts when an animal is on its sternum

caudocranial

What is hip dysplasia?

an inherited disease occurring in dogs and cats in which the hip joint is malformed, leading to a lax joint, weak rump muscles, and often lameness. The condition occurs most often in purebred animals because of the small breeding populations—and thus, limited genetic variance—characteristic of most pure breeds.

What does hip dysplasia cause?

a lax joint, weak rump muscles, and often lameness

What documentation is necessary to know which animals are good candidates for breeding to eliminated displasia?

detailed family histories of the parent animals, as well as information on sibling health

What organizations keep information regarding good breeding candidates?

Orthopedic Foundation for Animals (OFA) and the University of Pennsylvania Hip Improvement Program (PennHIP).

Waht is the OFA

a voluntary dysplasia control registry to provide information, establish control programs, and finance research in orthopedic and genetic disease in animals. This registry includes the world's largest data bank of radiographic evaluations of hip status in dogs.

What are the 7 classifications used by the OFA when evaluating radiographs sent by breeders>

1. Excellent 2. Good 3. Fair 4. Borderline 5. Mild canine hip dysplasia (CHD) 6. Moderate CHD 7. Severe CHD

What hip grades given by the OFA are considered within normal limits?

The hip grades of excellent, good, and fair are within normal limits and are given OFA numbers.

What age are animals evaluated for breeding in the OFA?

Animals normally are evaluated at two years of age. However, breeders often want to evaluate a puppy earlier to determine which puppies in a litter are suitable for use as show or breeding dogs and which are more suited to be sold as pets

The OFA accepts radiographs on puppies as young as ______ months of age for evaluation of the hip. They won't certify an animal as normal until the hip is reexamined at ____ years of age

4

2

Film labeling for OFA certification includes:

-The registration number and/or patient's complete registered name

-The date that the radiograph is taken

-The date of birth, breed, and sex of the patient

-The name of the owner

-Identification of the veterinarian or hospital

-Left or right positioning labels

*bare minimal includes the p's name, registration # and the date.

Where was the hip improvement program (PennHIP) developed?

By researches at the University of Pennsylvania's School of Veterinary Medicine in the 1980s.

-It is now an Antech Diagnostics and no longer apart of the university.

Explain the PennHIP process.

dogs as young as 16 weeks of age can be evaluated for susceptibility to developing hip dysplasia. Radiographs are evaluated for the following:

-Distraction index (DI)

-Arthritis

-Breed laxity profile ranking

What is Distraction Index (DI)?

is a measure of hip laxity—the distance the ball can be distracted (displaced) from the hip socket, using a score scale of 0-1. A DI of 0 means the dog has very tight hips and no indication of hip dysplasia. A DI of 1 means the dog has very loose hips and significant hip dysplasia is suspected. A measurement of less than 0.3 means there's very little chance of hip dysplasia occurring in the dog's lifetime.

What is Breed laxity profile ranking?

Looks at the rank of a particular dog within its breed based on the dog's DI. This is used to help breeders select better breeding candidates—dogs in the tighter hip population are the ones recommended for breeding.

Explain the DI (distraction index) measurements:

DI of 0 means the dog has very tight hips and no indication of hip dysplasia. A DI of 1 means the dog has very loose hips and significant hip dysplasia is suspected.

PennHIP requires what 3 specific radiographs for submission?

1. Hip-extended radiograph—the hind limbs are placed in extension.

2. Compression radiograph—the hind limbs are placed in a neutral, weight-bearing orientation with the femoral heads seated into the acetabula.

3. Distraction radiograph—this is the same position as the compression radiograph with a special device used to show joint laxity.

When taking xrays for hip confirmation, what view should be taken? (PennHIP)

the ventrodorsal extended hip projection is the view you should take. This view is specially designed to help evaluate the hips and requires special positioning and in some instances tranquilization.

If a fracture is suspected while taking PenHIP xrays, what view should be avoided and what view should be taken?

the extended view isn't recommended. The frogleg projection, with the legs bent, may be best. The extended view requires that you fully extend the rear legs caudally. If this is done, and there are fractures present, the jagged fracture pieces can move and possibly do damage, even puncturing the bladder or colon. It's advised not to pull on rear legs until you have a better idea of the status of the pelvis.

Explain the bone rule: (PennHIP)

states that the beam should be centered over the mid-section of the bone, and it should include the joints at each end of the bone. If the joints at each end are included in the radiograph, then you're sure to get all of the bone in between.

Explain the Joint Rule: (PennHIP)

states that all joint radiographs should be centered directly over the joint and should include approximately one inch of each of the bones that join to make the joint. The full bone isn't necessary to include in the joint radiograph. One inch of each bone is sufficient.

Hind limbs are generally divided into the following: (PennHIP)

-Femur (including the hip joint, femur, and knee joint)

-Stifle (including the distal portion of the femur, the knee joint, and the proximal portion of the tibia)

-Tibia/fibula (including the distal portion of the femur, the knee joint, and the tarsus)

-Tarsus (including the distal portion of the tibia, the tarsal joint, and the proximal metatarsals)

-Metatarsus (including the distal portion of the tarsus to the end of the phalanges)

When taking hind limb xrays, what positioning is typically used? (PennHIP)

lateral projection and a caudocranial projection

What does OFA stand for?

Orthopedic Foundation for Animals

What does CHD stand for?

Canine hip dysplasia

What do the PennHIP radiographs evaluate?

Distraction index, arthritis, and breed laxity profile ranking

In the PennHIP radiograph, what does a DI of < 0.3 mean?

Very minimal chance of hip dysplasia

Rear limb radiographs are generally taken with the cassette located _______.

on the tabletop

Xraying front limbs: At the distal end of the leg, the second view of the foot is a __________.

dorsopalmar.

Xraying front limbs: The middle section of the leg from carpus to elbow is a _________.

craniocaudal

Xraying front limbs: The upper section of the leg from the humerus to the scapula is a ________.

caudocranial

Xraying front limbs: The shoulder area can also be referred to as the ________ ____________.

thoracic girdle

The thoracic girdle includes:

the scapulae and clavicle.

How are the front limbs usually divided for xrays?

-Humerus (including the shoulder joint, humerus, and elbow joint)

-Elbow (including the distal portion of the humerus, the elbow joint, and the proximal portion of the radius)

-Radius/ulna (including the distal portion of the humerus, the elbow joint, and the carpus)

-Carpus (including the distal portion of the radius, the carpal joint, and the proximal metacarpals)

-Metacarpus (including the distal portion of the carpus to the end of the phalanges)

Which area is evaluated for dysplasia in the front limb?

Elbow joint

Imaging of the thoracic girdle uses a technique similar to that for the _______.

abdomen

What is a common mistake when it comes to radiographing the elbow?

People assume if the paw is flat the elbow should be straight, but it isn't—the elbow being straight means the paw is not flat on the table surface

. The two views taken to highlight the humerus to the scapula are the _______.

lateral and caudocranial

Besides the lateral, what other view is used to look at the foot?

Dorsopalmar

What is the preferred method for evaluating the skull?

CT scan

A true lateral skull xray shows:

structures on the right-hand side of the animal superimposed directly over the structures of the left-hand side of the animal so that they look as one.

The key to getting true lateral skull rads:

look at the natural lines of the skull and line them up in the proper direction

What is a scout film?

a lateral film that's done with no pulling and centering on the area that may be damaged. By doing this film first, you can avoid causing further damage to the animal's spine by pulling on its limbs during routine positioning for radiographs

Landmarks used to find the joints between the different types of vertebrae:

-Base of the skull

-Shoulder

-Origin of the last rib

-Greater trochanter

The cervical vertebrae view includes the base of the skull and the _________. The thoracic vertebrae view includes the shoulder and the origin of the __________. The lumbar vertebrae view includes the origin of the last rib and the greater _______

shoulder

last rib

trochanter

True or false? When a dog comes into the veterinary hospital after being hit by a car, you radiograph its spine and limbs using the usual positioning.

False

When radiographing the spine of an animal, there are four "points" that we use for landmarks. What are these four points?

Base of the skull; shoulder; where the last rib meets the spine; the greater trochanter of the femur

What projections (besides lateral and DV or VD) are used to look at the sinuses?

Rostrocaudal closed mouth, rostrocaudal foramen magnum, VD rostrocaudal open mouth

A lateral oblique view of the skull looks at what two structures?

Tympanic bullae and temporomandibular joint

A flexed lateral cervical spine radiograph looks at which vertebrae and spaces?

C4-C5 vertebrae and space

Dental radiology machines are available as:

portable, stationary, handheld

dental radiology info

dental radiograph machine is much like the regular radiograph machine: It uses the same settings, milliampere (mA), kilovoltage (kVp) and time(s), and each unit has an x-ray tube head, a control panel, and an adjustable arm

Major differences in dental units:

the ease with which you can adjust the angle of the x-ray tube head. They produce less radiation.

Dental image receptors can be:

regular film, digital sensors, phosphor plates.

What is a dental image receptor?

Device used to take the dental xray.

What are phosphor plates in dental radiology?

basically a cross between digital sensors and traditional film.

Name the two positioning techniques used in dental radiography:

parallel technique and bisecting angle technique

Describe parallel technique for dental rads

similar to taking a lateral radiograph of a body part and is used to image mandibular fourth premolars and molars.

Describe the bisecting angle technique for dental rads

used to image the rest of the teeth by using the plane of the root of the tooth and the plane of the sensor. The bisecting angle is then the line between the two planes

When should dental radiographs be taken?

Before and after any extraction is performed and after a cleaning is performed

In what position should an animal be for dental radiographs?

Lateral, sternal, or dorsal recumbency

What are two common errors that occur in dental radiography?

Elongation and foreshortening

What are the two techniques used to obtain dental radiographs?

Parallel and bisecting angle techniques

True or false? Dental radiographs generally require less radiation than traditional radiographs.

True

For small species, ______ _______ radiographs are often performed.

Whole body

Special equipment used when xraying small species:

positioning boards for feathered patients, special medications used for tranquilizing, and even special film or cassettes for finer detail

_______ and _______ patients seem to react to stress more severely.

Avian and exotic

When xraying exotic species:

A tabletop technique is generally used with no grid and the focal film distance is usually ___ inches.

40

When xraying exotic species:

The settings on the machine should use a _____ mA and ______ kVp than is usually used with dogs and cats

higher mA and lower kVp

What is the typical focal-film distance for taking radiographs of exotic small animal species?

40 inches

What type of views are typically taken of birds?

Lateral and ventrodorsal views of the whole body

Name a few of the positioning aids used in exotic small animal radiography

Avian restraint boards, acrylic snake tubes, rodent restraint boxes, brown paper bags, towels, empty paper towel rolls, tape, gauze, Plexiglas, Velcro