radiology AI-generated flashcards
Large Animal Imaging
Views
Coffin bone: lateral
Coffin bone: 45 degree dorsopalmar
Navicular: lateral
Navicular: skyline (palmar proximal)
Pastern: lateral
Pastern: dorsopalmar (dp)
Fetlock: flexed lateral
Fetlock: dorsopalmar
Metacarpal: lateral
Carpus: flexed lateral
Carpus: extended lateral
Carpus: dorsopalmar
Tarsus: lateral
Tarsus: dorsoplantar
Tarsus: DLPM oblique - dorsal lateral plantar medial oblique
General principles
MRI, CT, and nuclear scintigraphy have replaced standard x-ray imaging of large animals in most areas
Principles of radiology and radiation safety that apply to small animals also apply to large animals
Special considerations
Patient preparation and restraint
Equipment
Safety
Positioning devices
Horses generally require a minimum of four views for most positions, and six for many joints
The primary beam is always centered on the bone or joint in question and the measurement taken at that point
Always place the image receptor as close to the body part as possible and parallel to the body part to avoid distortion or magnification as a result of altered object-film distance
Equipment / safety
Portable x-ray machines
Safety concerns
Machines can be aimed in any direction
Must use longer exposure times to produce diagnostic images
Use cassette holders
Stand back as far from the primary beam as possible
Use tripods
Patient preparation
Minimize sudden movements and loud noises
Use sedation if possible
Bovine patients are usually restrained in stocks without sedation
Brush haircoat to remove dirt or other debris and dry thoroughly
For the equine foot
Remove the shoe and trim back any overgrown portions of the foot
Pick and thoroughly clean the sole and clefts
Pack the sulci adjacent to and in the center of the frog
Substances: play-doh, methylcellulose, or softened soap
Eliminates gas shadows caused by the grooves of the frog
Positioning aids
Foot block
Cassette tunnel
Navicular block
Directional requirements: limb views
Coffin bone
Lateral
45-degree dorsopalmar
DMPL oblique
DLPM oblique
Navicular
Lateral
Skyline (palmar proximal)
65 degree dorsopalmar
Pastern
Lateral
Dorsopalmar
DMPL oblique
DLPM oblique
Fetlock
Flexed lateral
Extended lateral
Dorsopalmar
DMPL oblique
DLPM oblique
Phalanges
Lateral
Laminitis
Metacarpals and metatarsals
Lateral
Dorsopalmar
DMPL oblique
DLPM oblique
Carpus
Flexed lateral
Extended lateral
Dorsopalmar
DMPL oblique
DLPM oblique
Tarsus
Lateral
Dorsoplantar
DLPM oblique
PLDM oblique
Flexed lateral
Summary
The majority of x-rays obtained in large animal medicine use portable x-ray machines
Use of portable x-ray machines in large animal facilities can be particularly dangerous with regards to radiation exposure
Horses are not anesthetized for most radiology studies and procedures are usually performed with the animal standing and weight breaking
Movement artifacts, poor positioning of the patient or the x-ray beam, and inadequate exposure factors are the most common reasons that radiographs must be repeated
Prepare the animal by brushing the hair coat; be sure the haircoat is cleared of dirt or other debris and thoroughly dried
Small animal pelvic girdle and hindlimbs
Forelimb
Scapula
Shoulder
Humerus
Elbow
Radius / ulna
Carpus
Metacarpus / phalanges
When, why, where
Most frequently done secondary to injury or trauma to limb
Need 2 views, lateral / A-P
Measurement should be done over the thickest portion of limb
Image quality
Need to have joints above and below area of interest in view
May be required to take comparison views of opposite side
Want an image with high contrast
Hindlimb views
Mediolateral projection of the femur
CrCd projection of the femur
Mediolateral projection of the stifle
CdCr projection of the stifle
Mediolateral projection of the tibia
CdCr projection of the tibia and fibula
Mediolateral projection of the tarsus
DPI projection of the tarsus
Oblique projections of the tarsus
Extended lateral projection of the tarsus
Flexed lateral projection of the tarsus
DPI projection of the metatarsus
Mediolateral projection of the metatarsus
DPa projection of the digits
Lateral projection of the digits
Used to detect fractura and evaluate the condition of the joints
Usually taken with the x-ray cassette on the tabletop since the measurement for dog and cat limbs tend to be fairly small
Keep the limb as close to the cassette as possible and parallel to the cassette to avoid magnification and distortion of the image
For long bones, the joints proximal and distal to the bone are included
Images of the joints include about ⅓ of the bone proximal and distal to the joint
Oblique views may sometimes be needed
Flexed and extended views of some areas may also be warranted
Hindlimb
Pelvis
Femur
Stifle joint
Tibia / fibula
Tarsus
Metatarsus / phalanges
Femur lateral images should have the leg close to the cassette pulled cranial while the up leg is pulled caudal
OFA / PennHip
Used to evaluate hip dysplasia
Sedation is a MUST
Patella’s centered on femur
Femur equal coverage of ischium
Obturator foramen equal in size
Hip evaluation
Sedation is necessary for appropriate positioning of radiographs
Extended limb VD standard view (used by OFA)
This view assesses degree of laxity, degree of abnormal conformation, and degree of secondary osteoarthritis
OFA will not certify hips until the patient is 2 years of age
Limbs extended and parallel with patellas, superimposed on midline of distal femurs
Femurs should cross the ischiatic tuberosity equally
Wings of the ilium and obturator foramen should be equally symmetric
Include entire pelvis and both stifles (patellas)
Pelvic views
Lateral projection of the pelvis
VD extended hip projection
VD frogleg projection
Used to evaluate the bones and joints of the hip
Hip dysplasia is a genetic abnormality that results in malformation of the hip joint that can cause severe pain and debilitation
Also referred to as osteoarthritis and degenerative joint disease
Orthopedic foundation for animals (OFA) provides evaluation services for dogs to certify that they do not have hip dysplasia
The PennHIP technique evaluates both the quality of the hip joints and the degree of hip joint laxity
Uses precise measurements of hip laxity
Nordberg angle
This measurement is made from the extended limb VD standard view of the pelvis
The angle represents a numerical measurement of joint laxity
The nordberg angle is defined by a line connecting the centers of the femoral heads and secondary lines from the centers of the femoral heads to the cranial acetabular rims
Nordberg angle scores
Normal: ≥105 degrees
Abnormal: ≤90 degrees
Borderline: 90 to 105 degrees
Excellent: superior conformation present with a very tight joint space and almost complete coverage of the ball by the socket
Good: most of the socket covers the ball and there is a congruent joint space
Fair: slightly incongruent (subluxated) space with the persistence of good ball coverage by the socket or there is a congruent joint space but the socket’s weight bearing surface is deviated inward
Borderline: there is no clear cut consensus between the radiologists to place the hip into a given category of normal or dysplastic, it is generally recommended to repeat the radiographs at a later date for comparison
Mildly dysplastic: the joint is obviously incongruent or sublaxated, usually there is a shallow socket only partially coverint the ball
Moderately dysplastic: there is significant sublaxation present with the femoral head barely seated in the shallow acetabulum, secondary osteoarthritis is usually present
Severely dysplastic: the shallow acetabulum only partially covers the femoral head, there are pronounced osteoarthritic changes
Osteosarcoma
The most common primary bone tumor
75% of osteosarcoma is in the appendicular skeleton; generally a monostotic aggressive lesion originating in the metaphysis of the long bones
Common sites: distal radius and proximal humerus (away from the elbow), distal femur and proximal tibia (toward the stifle), distal tibia, proximal femur (rare)
Front legs are affected twice as often as rear limbs
Although only 10-15% of dogs have radiographically detectable lung or bone metastasis at presentation, 90% of dogs will die with metastasis within one year when treated with amputation alone
3-4 month without treatment
11 month with treatment
Increase in ALP
Away from the elbow towards the knee
Check for mets
Fracture types
Incomplete - fracture through only one cortex
Complete - transverse/simple, oblique, spiral
Segmenta / comminuated - multiple fractures that do not meet at a single point
Closed or open - open fractures have a skin defect, emphysema, or foreign debris deep within the surrounding tissues
Compression - often appeared as increased bony opacity with no distinct radiolucent line
Pathologic - a fracture of bone that has been weakened by an underlying process that may be developmental (incomplete ossification of humeral condyle in spaniels) or acquired (neoplasia, hyperparathyroidism)
Stress - a fracture that occurs when repetivice stress causes bone fatigue
Summary
Diagnostic images of the pelvis are used to evaluate the bones and joints of the hip
The orthopedic foundation for animals (OFA) provides evaluation services for dogs to certify that they do not have hip dysplasia
The PennHIP technique is an additional procedure used for evaluation of dogs for hip dysplasia and requires specialized training
Commonly performed pelvic views are the lateral, VD extended hip, and VD frogleg projections
Diagnostic images of the hindlimbs are used to detect fracture and evaluate the condition of the joints
Hindlimb images are usually taken with the x-ray cassette on the tabletop since the measurement for dog and cat limbs tend to be fairly small
When the area of interest is a long bone, the joints proximal and distal to the bone are included
Images of the joints include about ⅓ of the bone proximal and distal to the joint
Flexed and extended views of the joints may also be warranted
Images in chapter 13 pelvis hindlimbs powerpoint
Quiz
The distal collimation point for a metatarsal film is distal to the digits
When positioning for a lateral projection of the tarsus, the affected limb is closest to the tabletop; pull the upper limb laterally out of the way
A patient must be in dorsal position for a dorsoplantar view of the tarsus
For a mediolateral projection of the right stifle, the animal is positioned in right lateral
The cranial collimation border when taking an image of the femur is located at the wing of the ilium
If the dog being submitted for OFA hip film evaluation is an AKC registered dog, the information is recorded on the film
An OFA is centered at the midline level of ischial tuberosities
When setting up for a VD hip film or OFA evaluation, the patella would be centered over the stifle joint
The thickest part of the pelvis is usually located at the level of the greater trochanter
The PennHIP technique looks for hip dysplasia
Genetics are believed to cause hip dysplasia
Small animal thoracic girdle and forelimbs
Thoracic girdle and forelimbs views
Mediolateral projection of the shoulder
CdCr projection of the shoulder
Lateral projection of the scapula
CdCr projection of the scapula
Lateral projection of the humerus
CdCr projection of the humerus
CrCd projection of the humerus
Mediolateral projection of the elbow
CrCd projection of the elbow
Flexed mediolateral projection of the elbow
Mediolateral projection of the radius and ulna
CrCd projection of the radius and ulna
Mediolateral projection of the carpus
DPa projection of the carpus
Flexed mediolateral projection of the carpus
Oblique projections of the carpus
DPa projection of the metacarpus
Mediolateral projection of the metacarpus
DPa projection of the phalanges
Mediolateral projection of the phalanges
Thoracic girdle
Consists of the paired scapulae and clavicles
Imaging is used to detect fractures
Maintain the bones as close as possible to the cassette to minimize distortion and magnification
Restricted the beam to the area just lateral to the area of interest
Reduced the effects of scatter radiation
Use settings similar to those used for abdominal imaging
Forelimbs
Used to detect fracture and evaluate the condition of the joints
Orthopedic foundation for animals (OFA) provides evaluation services for dogs to certify that they do not have elbow dysplasia
Usually taken with the x-ray cassette on the tabletop since the measurement for dog and cat limbs tends to be fairly small
Keep the limb as close to the cassette as possible and parallel to the cassette to avoid magnification and distortion of the image
For long bones, the joints proximal and distal to the bone are included
Images of the joints include about ⅓ of the bone proximal and distal to the joint
Oblique views may sometimes be needed
Flexed and extended views of some areas may also be warranted
Summary
Diagnostic images of the thoracic girdle are usually performed to detect fractures of the paired scapulae and clavicles
Techniques for imaging the thoracic girdle are similar to the settings used for the abdomen
Diagnostic images of the forelimbs are used to detect fracture and evaluate the condition of the joints
The orthopedic foundation for animals (OFA) provides evaluation services for dogs to certify that they do not have elbow dysplasia
Forelimb images are usually taken with the x-ray cassette on the tabletop since the measurement for dog and cat limbs tends to be fairly small
When the area of interest is a long bone, the joints proximal and distal to the bone are included. Images of the joints include about ⅓ of the bone proximal and distal to the joint
Oblique views of the forelimbs may sometimes be needed and flexed and extended views of some areas may also be warranted
Digital Imaging
Key terms
Computed radiography
Detective quantum efficiency
Dose creep
Grayscale bit depth
Image noise
Photostimulable storage phosphor imaging plate
Pixel
Voxel
Digital radiography steadily replaced traditional film-based radiographs
Increased safety
Minimal repeat exposures
Software programs capable of correcting most exposure problems
Safety increased do to removal of chemicals needed for processing of film
CR/DR
Two types of digital systems
Computerized or computed radiology (CR)
Digital radiology (DR)
Digital radiology is sometimes referred to as direct digital imaging (DDI)
Systems differ in regard to equipment and procedures
Both utilize standard x-ray machines to generate the x-rays
Primary difference in how the latent image is produced and processed for viewing
Quality of digital images based on factors
Resolution
Image noise
Pixels size and number
Field of view
Digital image recorded as a combination of rows and columns
Matrix
Smallest component of the matrix is the pixel (picture element)
Location of pixel corresponds to a three-dimensional volume of tissue referred to as voxel
Digital images
Each pixel can represent a wide variety of different shades of grey
Number of shades of grey is determined by the grayscale bit depth
Range from 8-32 bits
Grayscale bit depth of 12 produces 4096 shades of gray (2n bits)
Resolution is related to the size of the pixels that make up the image
Larger matrix size = greater number of smaller pixels
Smaller, more numerous pixels create sharper images
Image noise
Image noise is unwanted random variations in shades of gray
Image noise inversely related to image contrast
Increased noise decreases image contrast
Electronic noise produced by
Image processing units
Monitors
Quantum noise
Random distribution of electrons striking the image receptor
Higher mAs or kVp can minimize this type of noise
Increasing exposure factors comes at the expense of the safety of patients and personnel
Dose creep is the term used to describe increases in exposure factors made in an attempt to reduce the amount of image noise
Computed radiology (CR)
CR systems similar to standard film-based systems
Require a cassette with an intensifying screen
Difference is screen composed of photostimuable phosphors
Referred to as photostimuable storage phosphor imaging plate (PSP)
Imaging plate (IP)
Plate is located in the cassette and the cassette placed either in the bucky tray or on the tabletop, depending on the size of the body part being radiographed
Imaging plates have several layers on top of supporting layer
Protective layer shields the plate from handling damage
Phosphor layer contains the stimuable phosphors
Conductor layer aids in minimizing electrostatic interference with image formation
Light-shielding layer to protect the plate from light damage
Formation of image
Electrons on IP get excited when interact with x-rays
Some electrons are evaluated into a high energy state
Leaves gaps in the phosphor layer
Gaps produce the latent image
Reminder of the excited electrons emit light and fall back to their stable state
Imaging plate processed by loading the cassette into the image reader
Image reader uses a red focused laser beam to release the high-energy electrons
Causes additional release of light in proportion to the amount of radiation to which the electrons were exposed
Released light is directed to a photodetecttor which converts that visible light into an electronic signal
Converted to a digital signal
Plate is exposed to bright flash white light
Returns all the electrons to their stable state
Fully erasing the image
Makes IP ready to reuse
Imaging plates are sensitive to scatter
Ip is also prone to wear and “ghosting”
Issue where the prior image cannot be fully erased
The plate may have to be replaced when this occurs
Digital radiography (DR)
Digital radiography image receptor is built into the x-ray table
Cassettes and separate image processing units are not required
Image receptor interfaces with the processing system
Converts and displays the image
Constant changes in the technology used for digital radiology
Two types of DR systems
Direct detector systems
Thin-film-transistor (TFT) device to detect and display the image
Indirect detector systems
Charged couple device (CDC)
Both systems use a scintillator
Material that flouresces when exposed to the x-ray beam
Light emitted detected by the TFT or CCD
TFT and CCD convert that light energy to electrical energy which is processed by the computer to display the digital image
Differ in the mechanism of producing the image
Detective quantum efficiency (DQE) describes the sensitivity and accuracy of the system
Expressed as a percentage of the x-ray energy that strikes the detector
Ultimately converted to the final image
Most digital systems have a DQE of about 80%
20% of the image that is not a direct result of the x-ray beam interaction with the detector is filled in by the computer software programs
Image processing
All systems have software applications that translate that signal to the viewable radiograph
Software performs a number of operations
Convert the signal
Optimize the image
Minimizing artifacts
Software contains a number of algorithms that can correct some exposure errors
System generates a histogram from the image data
Histogram is a graphical representation of the signal intensity of each of the pixel
System analyzes the histogram data
Compares the pixel values to an internal standard that is specific for the body part being studied
System optimizes the intensity of the pixels
If exposure factors differ from the comparison standards, the software can rescale the image to correct
System uses internal standard referred to
Look-up table to adjust the contrast to the most desirable contrast for the body part being imaged
Two additional operations are performed
Windowing - controls the range of densities displayed
Leveling - controls the brightness of the image
Best viewed with a medical grade monochrome LCD monitor
Consumer type LCD monitors are commonly used and newer models have acceptable resolution for most routine applications
PACS
Picture activating and communication system (PACS)
Processes, procedures, and technology required
Create, distribute, archive digital images
Medical images use a universal format known as DICOM
DICOM: digital imaging and communications in medicine
Easily incorporated into the patient’s electronic medical record and would contain all the identifying information already attached to the file
Artifacts
Artifacts result from
Damage to imaging plates
Software problems
Ghost images
Incomplete IP erasure
May require several erasure cycles if IP is subjected to extreme overexposure
Light spots
Dust on IP
May be able to be cleaned
Fogging
Background and scatter radiation
Digital imaging plates are more sensitive to radiation than film
Reduced resolution in all or part of an image
Dust accumulations on imaging unit
Usually accompanied by reduced contrast
Linear white lines on the final image
Foreign materials on the light collection guide in a CR reader
Clean the reader and intake rollers
Summary
Digital systems are classified as either computerized or computed radiography (CR) or digital radiology (DR) systems
DR and CR systems have led to improved safety since the number of repeat exposures is minimized and there are no potentially hazardous chemicals to handle
The quality of digital images is related to resolution, image noise, pixel size and number, and field of view
Image noise refers to unwanted random variations in shades of gray produced on a digital radiograph and is inversely related to image contrast
CR systems require a cassette with a photostimuable storage phosphor imaging plate
There are two types of DR systems: direct detector systems and indirect detector systems that types differ in the mechanism of producing the image
Picture archiving and communication system (PACS) refers to the processes, procedures, and technology required for creating, distributing, and archiving digital images
Medical images use a universal format known as DICOM
Contrast Studies
Commonly used adjunctive tests
Used to help make a diagnosis when there is insufficient contrast to adequately visualize specific body parts with standard radiography
Three types of contrast studies commonly performed
Gastrointestinal (GI)
Urogenital
Spinal cord
Type of contrast agent used depends on
Test being performed
Level of comfort of clinician
Agent availability
Agent types
Four types of contrast agents
Soluble ionic radiopaque mediums: iothalamate, diatrizoate
Soluble nonionic radiopaque mediums: iohexol, iopamidol
Insoluble inert radiopaque mediums: barium sulfate
Radiolucent gases: air, nitrous oxide, carbon dioxide
The type of study being performed will determine which of the agents could be used in the patient
Soluble ionic agent
Iothalamate
Diatrizoate
Negatively charged benzoic acid derivatives
Contain three iodine molecules, combined with sodium or meglumine form a positive soluble salt
Route given
Oral administration for GI studies
Intravenously (IV) for excretory urography
Intraarticular studies
Draining wound
Fistulography
Sodium ionic agents
May cause increase in intravascular fluid volume when given intravenously
Care should be taken in dehydrated patients or with a sensitivity to iodine
Oral administration of these agents may result in diarrhea
Do not use in myelography or respiratory studies
Direct contact with neural tissue can leade to muscle spasms, seizures, cerebral edema, hypotension, coma, and death
Soluble nonionic agents
Spinal cord or respiratory tract tests use nonionic radiopaque agents
Iohexol
Iopamidol
Do not dissociate into positive and negative ions
Ideal contrast agent for myelography and respiratory studies
Lower incidence of adverse effects on patients, and a lower osmolality
Insoluble agents
Insoluble inert positive contrast agents
Barium sulfate
Barium impregnated polyethylene spheres (BIPS)
Barium has a high atomic number, and absorbs a large volume of radiation
Calcium has an atomic number of 20 compared to iodine which is 53
Barium is a more dense solution than the surrounding tissue
Results in more absorption of the x-rays
Whiter image on the finished radiograph
Increase in radiographic opacity, allows evaluation surrounding structures more easily
Barium works well to coat and soothe the GI tract better than ionic mediums as it is not absorbed into the surrounding tissue
Barium suspensions
Two systems used to measure the barium ulfate suspension
Weight to volume (w/v)
Adding a certain weight of barium added to water to reach a predetermined total volume
25% w/v suspension is completed by adding 25 grams of barium sulfate to enough water to equal 100 ml total
Weight to weight (w/w)
Adding a certain weight of barium added to water to reach a predetermined weight
25% w/w suspension is completed by using 35 grams of barium sulfate and adding 75 grams of water to reach a total weight of 100 grams
Barium sulfate also comes prepared in a paste form which is commonly used for esophagography studies as it is easier to administer, less likely to cause aspiration and adheres to the mucosa better than liquid barium
Negative drawbacks
Constipation
Risk of upper or lower perforation of the GI tract
Aspiration when administered orally
Barium should be administered via orogastric tube unless evaluation of esophagus is warranted
Multiple forms
Liquid
Paste
Powder
Risk of over dilution with water resulting in a solution that is too thin and does not coat the system well enough to provide diagnostic information
Liquid and paste tend to outline upper and lower GI system better than compared to reconstituted powder
Barium impregnated polyethylene spheres (BIPS)
Determine if a motility issues are present
BIPS are an inert structure
Maintains same weight as ingested food
Each animal receives the same volume of BIPS to evaluate for motility
BIPS are in capsule form and can be administered with or without food for evaluation
Larger capsule contains 10 (5mm diameter) spheres
Smaller capsule contains 30 (1.5mm diameter) spheres
BIPS
Small BIPS similar to passage of food
Evaluation of motility or lack of motility
Larger BIPS are used to determine if there is a potential obstruction in the GI tract
BIPS offer better evaluation of gastric emptying time
Negative contrast
Negative contrast media/radiolucent gases
Gases absorb fewer x-rays than surrounding soft tissue
More radiolucent effect on the radiograph
Include
Air
Oxygen
Carbon dioxide
Nitrous oxide
Used in combination with the positive contrast agents
Referred to as a double contrast study where both a positive and a negative agent are used
Negative contrast agents provide less mucosal detail than positive agents
Care should be taken to prevent over expansion of hollow organs
Urinary bladder
Over inflation can result in a rupture of the organ
Carbon dioxide or nitrous oxide
Agents of choice when performing negative contrast studies
Room air can produce an air embolisms that could result in cardiac arrest
Esophagography
Assess the status of the esophagus, potential motility issues and surrounding tissue
Fluoroscopy is best for performing an esophagography study
Standing imaging is the next best option
Allows patient to ingest contrast/food, decreased risk of aspiration
Lateral and dorsal-ventral positioning are the least effective
Most commonly used in general practice
Indications
Abnormal swallowing, foreign body of obstruction, dysphagia, megaesophagus, regurgitation of undigested food, and head/neck trauma
Media and dose
Barium sulfate liquid or paste, commonly mixed with canned food
Oral aqueous iodine if perforation of the esophagus or GI tract is of concern
Dose between 5-20 ml of contrast agent
Supplies
Syringe, canned dog/cat food
Patient preparation
Remove coller, leashes, or halters
Fasting is recommended
Sedation may be necessary
Be selective in drugs chosen due to potential central nervous depression resulting in slower motility
Positioning
Standard right lateral positioning
Full length of esophagus from the base of the skull to T12
Ventrodorsal is optional but not commonly used
Procedure
Survey lateral and VD base of skull to T12
Position animal in lateral recumbency with cassette and machine settings ready
Administer barium into the buccal pouch or provide barium soaked food being cautious not to cause aspiration of barium
Allow animal to swallow barium or food. Perform a series of exposures to the patient approximately 2-5 images while in lateral
Repeat steps 3 and 4 by adding more barium or increasing the frequency of exposures if non-diagnostic
Precautions
Increased risk of aspiration
If aspiration and asphyxiation is of concern, it is best to avoid the use of barium, use organic iodine instead
Double-contrast study
Similar to performing the standard esophography
Survey images
Administer barium or organic iodine 3-5 ml (cats/small dogs) or 8-10 ml (large dogs)
After contrast agent is administered, follow with 20-40 ml of air
Obtain a radiograph with the patient still in lateral recumbency
Upper gastrointestinal
Goal is to evaluate the morphology of the stomach and small intestines as well as visualization of extramural, mural, and intramural lesions of the GI tract
Gastric emptying and pyloric function can also be evaluated with a UGI
Motility testing should be performed with BIPS
Morphology evaluations should be completed using a barium agent
Sedation and/or anesthesia could alter motility
Indications
Recurrent vomiting, hematemesis, anorexia, melena, chronic weight loss, suspected foreign body or obstruction
Survey radiographs are non-conclusive as to the underlying problem
If it is suspected that the patient has a perforation within the GI tract, barium should not be used and iodinated contrast should be used in its place
Media / dose
Barium sulfate suspension: based on a 60% w/w
5-13 ml/kg of body weight
Iodinated contrast agents
2-4 ml/kg of body weight added to water to equal 13 ml/kg
Supplies
Oral speculum, gastric tube, 60 ml syringes, towels
Patient prep
Fasted for 12-24 hours prior to the study
Enema should be done the night before and the day of the procedure to remove any fecal material from the colon
Enema should be done at least 2-4 hours prior to the study to decrease the aount of gas in the lower Gi tract
Positioning
Measurement over thickest part of the abdomen
Cranially from thoracic vertebra T7 to the acetabulum
Procedure
Start with a survey radiograph to ensure proper settings and positioning
Calculated volume of contrast agent should be administered preferably via orogastric or via the buccal pouch
Image the patient in lateral and VD immediately following administration; this will be 0 time film
Depending on the clinician or what areas are being evaluated the following times should be used
Dogs: lateral/VD views 0, 15, 30, 60 minutes, then hourly until contrast agent reaches the distal small intestine
Cats: lateral/VD views 0, 15, 30, 45, 60 minutes, then 30-60 minutes until the contrast agent has reached the distal small intestine
Iodinated agents transit times will be faster so the times will need to be adjusted accordingly
Precautions
Aspiration of barium, due to vomiting or over distention of the stomach is of concern
Increase risk of aspiration when using buccal administration
Potential perforation of the GI tract and the alternate contrast agents available in this case
Double contrast study
Double contrast study will not help in identifying motility or gastric emptying times
Perform the surgery and standard contrast study
Administer 100-300 ml of air into the stomach or until the stomach is distended
Rotate the patient to coat the gastric mucosa and procees with a four view series (right/left lateral, VD, DV)
BIPS
Assist in the diagnostics
GI obstructions
Motility issues
Gastric emptying disorders
BIPS move through the GI tract in a similar fashion to food as compared to a liquid barium agent
Possible to count the spheres the clinician will be able to calculate the gut emptying and transition time
Method of administration of the BIPS
GI obstruction is the concern
Capsules are not given with food
Gastric emptying disoeder
Soft food is generally administered in addition to the capsules
Standard abdominal protocol is used
Obtain survery radiographs
Document time images were taken
BIPS packaging gives more detailed description of normal transit times
Lower gastrointestinal (LGI)
Purpose
Evaluate the cecum, colon, and rectum
Retrograde administration of a positive contrast agent
Identify and evaluate extramural masses, mucosal lesions, disease of the ileocolic valves and overall morphology of ascending and transverse colon
Remove feces prior to performing a LGI
Sedation and/or anesthesia may be requires
Motility is less with LGI than UGI in comparison
Indications
Abnormal defecation, excessive mucus, strictures, tenesmus, obstructions, rectal neoplasia, colitis
Differentiate between large intestines and gas filled loops of small intestine
Media / dose
Barium sulfate 20% warmed to room temperature. This dose is empirical in that less or more may be needed depending on the patient
Cats: 10-20 ml
Dogs: 30-60 ml
Double contrast study
½ of the barium dose is used
50-150 ml of air is added to the colon for dogs and 25-50 ml of air for cats
Iodinated contrast agents should be used in place of barium sulfate if perforation is suspected
Supplies
Foley urinary catheter
Enema set-up / material
Three-way stopcock valve
Lubricant
Syringes
Patient prep
Remove all fecal material removed prior to starting the study
No food should be allowed for 24-36 hours
Enema should be performed at least 12 hours prior to starting the study
Cold water and soap should be avoided as this may cause spasm of the colon
Positioning
Survey lateral and VD imaging should be completed prior to starting the study
Caudal abdomen is the area of interest with LGI studies
Procedure
Sedated/anesthetized prior to administration of contrast agents
Survey radiographs are taken to ensure proper settings and positioning
Balloon-tipped foley catheter is inserted rectally and the balloon inflated
Contrast agent is infused
Over a 5-7 minute period
Obtain lateral/VD images
Assess images for more contrast agent administration
Contrast agent can now be removed and the colon infused with air to perform a double contrast study
Precautions
Avoid trauma to the patient as possible perforation of the colon could occur
Avoid over-distention of colon, serious complications in the presence of a weakened tissue wall due to disease
Perforation is present, barium that leaks into the peritoneal cavity may incite severe granulomatous reactions
Pneumocolon
Utilizing air as the contrast agent
Morphology of the large intestine may be identified with this study
Assist with determining the position of the colon compared to the small intestine
Media / dose
Room air no true data is available on volume
Approximately 6-12 ml/kg
Supply
Syringe
Balloon foley catheter
Lubrication
Patient prep
Little to no prep is needed for this study
Positioning
Standard abdominal imaging for lateral and VD images
Procedure
Survey radiographs are taken to ensure proper settings and positioning
Sedation is generally not required for this procedure
A balloon-tipped foley catheter is inserted rectally and the balloon inflated
Infuse calculated volume of air into the rectum
Obtain lateral and VD images of the abdomen
If more air is needed administer more and retake images as needed
Precautions
Caution should be taken to not over dilate the colon
Excretory urography
Evaluate the kidneys, urinary bladder, ureters, prostate and urethra
Contrast agents assist in visualization of size, shape, function, and opacity of the renal system
Information on transit time from the kidney to ureters, and finally to the urinary bladder
Ultrasound, MRI, and CT has become more common in studying the urinary system
Media / dose
Water-soluble iodide: 850 mg/kg
Ionic iodide: diatrizoate (sodium hypaque)
Nonionic: iohexol (omnipaque)
Supply
Intravenous catheter
Urethral catheter
Time markers
Patient prep
Enema should be performed 4 hours prior
Food withheld for 24 hours prior to the study
Removal of urine from the urinary bladder is required to prevent
Collect urine samples at this time
Procedure
Patient should be sedated or anesthetized prior to administration of contrast agents
Survey radiographs are taken to ensure proper settings and positioning
Place the urinary catheter, remove urine, record the volume of urine removed
VD recumbency inject warmed solution within 2 minutes
Flush the IV catheter with saline
Obtain the following sequence of images
VD: within 10 seconds of administration of contrast agent
Lateral / VD: 5 minutes
Apply compression bandage to urinary bladder
Lateral / VD: 20 minutes
Remove compression bandage
Lateral / VD: 30-40 minutes
Positive or double contrast retrograde studies can be completed following the excretory contrast study
Nephrogram / pyelogram
Two stage study
Nephrogram
First stage of the test
Immediately following administration
Determining blood flow to the kidney
Pyelogram
Renal pelvis and ureters are evaluated
Compression bandage slows the draining from the kidneys
Identify anatomical issues associated with the renal pelvis and ureters
Excretory urography
Precautions
Caution with azotemic and non-azotemic patients
Assess the dehydration status of the patient
If dehydrated
Study should be postponed until the hydration status of the patient is corrected
Reactions can occur within 1-5 minutes of administration of the agent
Reactions can be minimal to fatal
Proper monitoring is important
Signs associated with reaction
Vomiting, diarrhea, urticaria, tachycardia, and hypotension
If signs develop stop study immediately and stabilixation procedures performed as necessary
Retrograde cystography
Evaluate the urinary bladder of the patient with either positive, negative, or a double contrast study
Patient history, clinical signs, ability to pass urinary catheter assist in determining the type of contrast agent that will be used
Media / dose
Positive-contrast: water soluble organic iodide 3-12 ml/kg
Negative contrast: CO2, N2O, room air 3-12 ml/kg
Double-contrast: cat: 0.5-1 ml positive agent plus negative agent (3-12 ml/kg)
Dogs less than 10 kg: 1-3 ml positive agent plus negative agent (3-12 ml/kg)
Dogs greater than 10 kg: 3-6 ml positive agent plus negative agent (3-12 ml/kg)
Supply
Sterile urinary cathete
Sterile lubricant
20-60 ml syringe
Three way valve
2-5 ml 2% lidocaine without epinephrine
Patient prep
Food withheld for 24 hours prior to procedure
Enema performed 4 hours prior to procedure
Aseptic technique should be used when placing the urinary catheter
Positioning
The standard lateral / VD imaging of the abdomen is used for this study
Procedure
Negative contrast study (pneumocystogram)
Positive contrast study (cystography) is the same with the exception of the contrast agent used
The patient should be sedated or anesthetized prior to administration of contrast agents
Survey radiographs are taken to ensure proper settings and positioning
Place foley urinary catheter, remove all urine, record the volume of urine removed
3 way stopcock, inject 3-5 ml of 2% lidocaine without epinephrine
Infuse contrast agent (positive/negative)
Monitor the bladder for distention to prevent over filling the urinary bladder
Close the 3 way stopcock once the correct volume and distention is reached
Right and left lateral / VD images
If male, oblique views on VD may be needed to prevent overlapping of the prepuce
Urethrography
Evaluate the urethra for strictures or masses that prevent or alter the flow of urine
Performed either by retrograde administration of positive, negative, or double contrast studies or by compression of the urinary bladder following positive contrast administration
Media / dose
Positive contrast organic ionic or nonionic agent. It is best to dilute the agent to 150-200 mg of iodine/ml
Dosing regimen
Dogs: 10-15 ml total volume
Cats: 5-10 ml total volume
Supplies
Sterile urinary catheter
Lubricant
20-60 ml syringe
Three way valve
2-5 ml 2% lidocaine without epinephrine
Patient prep
Food withheld for 24 hours prior to procedure
Enema performed 4 hours prior to procedure
Aseptic technique should be used when placing the urinary catheter
Positioning
The standard lateral / VD imaging of the abdomen is used for this study
Procedure
The patient should be sedated or anesthetized prior to administration of contrast agents
Survey radiographs are taken to ensure proper settings and positioning
Place foley catheter approximately 1-3 cm into the urethra orfice
Slowly inject the contrast agent until pressure is felt back onto the syringe
With the legs pulled cranially obtain lateral imaging of the urethra
Remove urinary catheter after diagnostic quality radiographs have been obtained
Antegrade / voiding urethrogram
Gentle pressure is applied to urinary bladder filled with positive contrast media
Place a towel under the patient to collect the urine/contrast medium to prevent artifact formation
Obtain a lateral radiograph when urine is noted at the urethral orfice
Precautions
Avoid inadvertent trauma to the urethra
Injection of air into a torn urethra may result in an air embolism resulting in death
Due to difficulty of urinary catheterixation in femal dogs and cats a voiding urethrogram may be better suited for these cases
Myelography
MRI and CT more common in evaluation of the spinal cord
Noninvasive nature
Speed with which they can be performed
Myelography
Injection of radiopaque contrast into the subarachnoid space
C1-C2 or lumbar region of L6-L7 to assist in evaluation of the spinal cord
Media / dose
Organic nonionic positive contrast iodine
Iopamidol (isovue)
Iohexol (omnipaque)
Supplies
Clippers
Scrub solution
Sterile drape
Sterile gloves
(2) 12 ml syringes for dogs
(2) 6 ml syringes for cats
Dogs: 20 gauge spinal needle with flat bevel, 2-4 inches
Cats: 22 gauge spinal needle with flat bevel
Collection tubes for CSF, usually EDTA tubes
Patient prep
General anesthesia being careful to avoid using phenohiazine based drugs
Shave hair and aseptically prep the area to be evaluated
Caudal skull (cisternal)
Lumbar spine (lumbar)
Positioning
Lateral / VD imaging prior to collection of CSF
Area of concern
Cervical
Thoracic
Thoracolumbar
Lumbar vertebra
Procedure
Obtain survey images to ensure quality of contrast / density and positioning of patient
Cervical myelography
Maximal flexion to aid in location of atlantoocipital space
Lumbar myelography
Flex the hind legs cranially, insertion location for a lumbar myelography is L5-L6 space
Place the needle into subarachnoid space
Withdraw an equal volume of CSF to the volume of contrast agent to be injected
Cervical injections should be done over a 3-5 minute time frame
Lumbar injections should be done over a 5 minute time frame
After the spinal needle has been removed, gently rotate the patient to ensure equal contact of the contrat agent and CSF
Cervical images
Elevate the head following injection to allow the contrast agent to move caudally
Obtain lateral / VD images song the vertebra until the site of concern is reached by the contrast agent
Oblique images may be necessary to visualize the mass or lesion
Lumbar images
Cap the needle and leave in place to prevent leaking of contrast agent into the epidural space
Obtain lateral images until the site of concern is reached
Site located, remove the needle and obtain a VD image of the area
Precautions
Must be anesthetized prior to performing the procedure
Collected CSF should be evaluated for systemic or local infections
Incorrect placement of the spinal needle or infusion of agent can have detrimental effects on the patient
Evaluate patient hydration status prior to the study
Cervical study
Keep the patient anesthetized for 45 min to 1 hour following the procedure to minimize the risk of seizures during recovery
Keep the patients head elevated will also help minimize this risk on recovery
Other contrast studies
Angiography
Identify cardiac abnormalities, vessel occlusions, lesions, and tumor locations
Water soluble organic iodide is used
Injected into the cephalic or jugular vein
Fluoroscopy is the best method for evaluation
Arthrography
Identify ruptured joint capsule, cartilaginous flaps, and meniscus tears
Water soluble organic iodide is used
Injected into the synovial fluid at the site of concern
Calligraphy
Identify abdominal cavity
Assist in determining a diaphragmatic hernia
Water soluble organic iodide is used
Injected into the abdominal cavity at the site of the umbilicus
Fistulography
Identifying the fistulous tracts, potential foreign bodies in the skin, muscle, soft tissue regions of the body
Summary
Contrast studies are commonly used adjunctive tests in vet radiology, primarily for evaluation of the GI system, urogential system, and spinal cord
The four types of contrast agents commonly used in vet radiology include soluble ionic radiopaque mediums, soluble nonionic radiopaque mediums, insoluble inert radiopaque mediums, and radiolucent gases
Studies involving the spinal cord or respiratory tract commonly use positive contrast agent nonionic radiopaque agents
The insoluble inert group of positive contrast agents includes barium sulfate and barium impregnated polyethylene spheres
Radiolucent gases include air, oxygen, carbon dioxide, and nitrous oxide and are used commonly in double contrast studies
Exotic Companion Animal Imaging
Diagnostic imaging
Machine should be capable of
Short exposure time: 1/60 or faster
High mA-capactity (>300): better detail
KvP range: 40-100
Bone is less radiopaque than mammals
2 KvP incremental charge
Exotic companion animal imaging views
Avian
Lateral whole body view
Ventrodorsal whole body view
Reptile
Lateral whole body view
Dorsoventral whole body view
Small mammal
Lateral whole body view
Ventrodorsal whole body view
Lateral view of the abdomen
Ventrodorsal view of the abdomen
Lateral view of the thorax
Ventrodorsal view of the thorax
Lateral view of the skull
Dorsoventral view of the skull
General guidelines
Minimize patient stress
Low light
Minimal noise
Escape routes blocked
Use sedation or anesthesia when possible
Can use non-screen film or dental film
Tabletop technique
Focal-film distance: 40 inches
May increase to provide additional magnification in very small patients
Patient positioning
Manual restraint when possible
Positioning aids
Restraint boards
Acrylic tubes
Paper bags
Perch (horizontal beam)
Reptiles: vasovagal response
Avian: lateral whole body view
Right lateral recumbency with neck extended
Foam wedge to maintain head in alignment with body
Wings extended dorsally: legs extended caudally
Measure at mid-sternum at thickest portion of chest
Collimate to include entire body within collimated area
Avian: ventrodorsal whole body view
Dorsal recumbency with neck extended and aligned with body
Foam wedge to maintain alignment of sternum and spinal column
Wings extended laterally; legs extended caudally
Measure at mid-sternum at thickest portion of chest
Center on mid-sternum at thickest portion of chest
Collimate to include entire body within collimated area
Reptile positioning
Chelonians
Dorsoventral
Tortoise in sternal position
Measure the thickest point between carapace and plastron
Plastron: flat part of the shell structure of a turtle, that one would call the belly
Carapace: dorsal, convex part of the shell structure, consisting of primarily the animal’s broad ribcage. The spine and ribs are fused to bony plated beneath the skin which interlock to form a hard shell
Lateral
Horizontal beam
Place tortoise on sponge
Cassette in vertical position
Vertical beam
Faten tortoise to cassette and position animal in vertical position
Craniocaudal
Horizontal beam
Tortoise on sponge
Cassette placed vertically and behind tortoise
Vertical beam
Fasten tortoise to cassette
Snake radiographs
Greatly underutilized
Restrained manually, place snake in tube or anesthetized
VD/LAT views needed
VD difficult to read, Lat is more diagnostic
Lizard radiographs
Need at minimum of a VD, lateral images can be difficult unless tube head can rotate
Difficult because of difference in anatomy between species of lizards
Imaging still needs to be performed
Reptile: lateral whole body view
Right lateral recumbency
Forelimbs extend cranially and hind limbs extend caudally
Secure limbs and body with tape
Foam wedges to maintain lateral position
Can also be completed with the horizontal beam with the animal placed on a translucent stand
Measure the thickest point of the body
Center at mid body
Entire body should be visible within collimated area
Reptile: dorsoventral whole body view
Ventral recumbency with limbs lateral to the body
Measure the thickest point of the body
Center at mid body
Entire body should be visible within collimated area
Hamster / gerbil radiographs
Focal film distance
40 inches for extremities
38 inches for whole body views
mA: 6.4 and kVp of 54 for skull
mA: 7.5 and kVp of 52 for whole body
Dental units provide best quality radiographs
Small mammal: lateral whole body view
Right lateral recumbency
Forelimbs extended cranially and hind limbs extended caudally and secured with tape
Foam wedges to maintain sternum parallel to cassette
Measure at last rib
Center between the last rib and the xyphoid process
Entire body should be visible within collimated area
Small mammal: ventrodorsal whole body view
Dorsal recumbency
Forelimbs extended cranially and the hind limbs extended caudally and secured with tape
Foam wedges to maintain alignment of sternum parallel to cassette
Measure at last rib
Center between the last rib and the xyphoid process
Entire body should be visible within collimated area
Small mammal: lateral view of the abdomen
Right lateral recumbency
Forelimbs extend cranially and hind limbs extend caudally and secured with tape
Foam wedges to maintain sternum parallel to cassette
Measure at last rib
Center between at the last rib
Collimate cranial to the xyphoid and caudal to the pubis
Small mammal: ventrodorsal view of the abdomen
Dorsal recumbency
Thorax secured with sandbags
Foam wedges to maintain alignment of spine and sternum
Hind limbs extended and secured
Measure at last rib
Center at last rib
Collimate cranial to the xyphoid and caudal to the pubis
Small mammal: lateral view of the thorax
Right lateral recumbency
Foam wedges to mantain alignment of sternum parallel to cassette
Fore limbs extended cranially; hindlimbs extended caudally and secured with tape
Measure at last rib
Center at xyphoid process
Collimate cranial to thoracic inlet and caudal to last rib
Small mammal: ventrodorsal view of the thorax
Dorsal recumbency
Foam wedges to maintain alignment of sternum and spine
Fore limbs extended cranially; hindlimbs extended caudally and secured with tape
Measure at last rib
Center at xyphoid process
Collimate cranial to thoracic inlet and caudal to last rib
Rodent / rabbit radiographs
Teeth
Tympanic bullae
Respiratory tract - reduced size
GI tract - prominent cecum
Urogential system
Skeleton
Need VD/LAT radiographs of bodies
Evaluation is same as in other mammals
Trichobezors (hair balls) commonly seen with anoretic rabbits and soft tissue mass in the stomach
Can be used for skull and dental
Rostrocaudal, dorsoventral, and lateral
Things to remember
Need to know normal anatomy
Thorax of rodents not clearly visualized because of small size
Abdomen of guinea pigs obscured due to gaseous cecal dilation
Look for basic changes in size, shape, location, opacity, and numbers
Small mammal: lateral view of the skull
Lateral recumbency
Foam wedges under neck to maintain skull parallel to cassette
If oblique views are desired, use foam wedges to obtain a 45-degree angle to the cassette
Deflect ears as needed to ensure they do not overlap the skull
Measure at the thickest portion (midpoint) of skull
Center at midpoint of skull
Collimate cranial to the nose and caudal to the base of the skull
Small mammal: dorsoventral view of the skull
Dorsal recumbency
Foam wedges to maintain skull parallel to cassette
Deflect ears as needed to ensure they do not overlap the skull
Measure at thickest portion of skull (midpoint)
Center at midpoint of skull
Collimate cranial to the nose and caudal to the base of the skull
Summary
Most companion exotic animals will require sedation or anesthesia to minimize handling stress and injury
Manual restraint is appropriate for most species of reptiles and some small mammals unless the animals are fractious, aggressive, or if manual restraint is prohibited by the laws of the jurisdiction
Positioning aids for small exotic species include avian restraint boards, acrylic snake tubes, and rodent restraint boxed
Whole body images are commonly performed in avian, reptile, and many small mammal species
In very small animals, object-film distance may be increased to provide magnification of structures
Small Animal Skull and Vertebrae
Views
Lateral projection of the skull
DV projection of the skull
VD projection of the skull
RCd sinuses closed mouth projection
RCd foramen mangum projection
VD RCd open mouth projection
Lateral oblique tympanic bullae projection
Lateral oblique temporomandibular joint projection
DV temporomandibular joint projection
VD cervical spine projection
Lateral cervical spine projection
Lateral cervical spine extended projection
Lateral cervical spine flexed projection
VD thoracic spine projection
Lateral thoracolumbar spine projection
VD lumbar spine projection
Lateral lumbar spine projection
VD lumbosacral projection
Lateral lumbosacral projection
VD coccygyeal spine projection
Lateral coccygeal spine projection
Skull views
Used for diagnosing disorders of the nasal sinuses, tympanic bullae, and foramen magnum and identify lesions of the skull bones
Nearly all canine and feline patients will require anesthesia or sedation to maintain proper positioning
Endotracheal tubes usually have to be removed prior to completing the exposure
Precise positioning is necessary to obtain radiographs that represent the symmetry of the two sides of the skull
Vertebrae
Imaging can identify fractures, bony lesions, and evaluate intervertebral disc space
The vertebral column must be placed as close to the cassette as possible and parallel to the cassette or tabletop
Tight collimation of the x-ray beam enhances the detail of the radiograph
Radiographs are usually performed on individual regions of the spinal column, ensure that any identification labels and directional markers remain within the collimated area but do not overlap the bone
General anesthesia is often required, especially with painful animals
Pain may manifest as muscle spasm, which can alter interverbral spacing
Summary
Imaging studies involving the skull are performed to diagnose disorders of the nasal sinuses, tympanic bullae, and foramen magnum as well as to identify lesions of the skull bones
Nearly all canine and feline patients will require anesthesia or sedation to maintain proper positioning
Precise positioning is necessary to obtain radiographs that represent the symmetry of the two sides of the skull
V-troughs and foam wedges are usually needed to maintain the alignment of the vertebral columb
Foam wedges are used to maintain the skull in a parallel plane