VCA 252 Principles of
Diagnostic Imaging
Dr. LeeAnn Pack
566-0841, 566-0920
Lpack@upei.ca
The Discovery of X rays
• Wilhelm Conrad Roentgen
• November 8 1895
• While working in his lab - saw the glow
coming from a phosphorescent screen
• Imaged his wife’s hand
• 1901 Nobel Prize for Physics
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Radiology/Radiologist
The History
• ARRS  RSNA
• Individuals who looked at plates and
compared them to the sx and autopsy
findings
• ACR - Radiologist – now with multiple areas
of specialty
• ACVR – the veterinary college
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THE Journal
• Journal which
highlights veterinary
diagnostic imaging
www.upei.ca/~vetrad
Forms of Diagnostic Imaging
• Diagnostic Radiology/Radiography
– X-rays used to produce image, transmitted
through patient
– Static images
– Dynamic images  fluoroscopy
– Contrast agents used
• Barium, Iodine  examples of studies
www.upei.ca/~vetrad
Forms of Diagnostic Imaging
• Ultrasonography
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Uses sound waves to produce image, transmitted
Sending out and listening for echoes
Internal architecture
Dynamic, US can not penetrate air or bone
Operator dependent
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Forms of Diagnostic Imaging
• Computed Tomography
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Uses X-rays to produce an image, transmitted
Cross sectional imaging
No superimposition of structures
Requires computer manipulation of images
www.upei.ca/~vetrad
Forms of Diagnostic Imaging
• Nuclear Scintigraphy
– Uses gamma rays to produce an image, emitted
from the patient
– Radioactive nuclide given IV, per os, per rectum
etc.
– Abnormal function, metabolic activity, abnormal
amount of uptake
– Poor for anatomical information
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Forms of Diagnostic Imaging
• Magnetic Resonance Imaging
– Uses a strong magnetic field and radiofrequency
waves to image structures
– No ionizing radiation
– Hydrogen protons – water
– Cross sectional imaging
– Great for soft tissue
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Forms of Diagnostic Imaging
• Radiation Therapy
– Uses radiation to treat and palliate neoplastic and
some benign diseases
– Cobalt
– Linear Accelerators
– Must have special training
www.upei.ca/~vetrad
What is an X ray?
Production of X rays
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Form of EM radiation
All forms move at the speed of light
Vary in energy and wavelength
They penetrate matter
Can cause fluorescence of some atoms
Can expose film
Can cause biological damage
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The X ray Tube
• Cathode – is the electron source
• Tungsten filament
• Negatively charged concave cup around
filament
• Focal spot
• Thermonic emission – current applied wire
heats up and electrons escape
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The X ray Tube
• Anode – is the target which electrons strike
• Tungsten target
• Stationary
– Anode in large block of copper – lots of heat
– Used in portable units
• Rotating
– Disc rotates which spreads electrons around the
target thus less heat build up
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The X ray Tube
Note the various
components and
remember what they
do.
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Anode Heel Effect
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The surface of the anode is angled
Allows for better cooling and maintains detail
X rays on cathode side more intense
How would this be used in practice?
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The Rest
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Exit window
Housing
Filtration – radiation safety
Collimation
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mAs
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Milliampere-second
Milliampere -> current applied to the filament
Seconds -> time current was applied
mAs determines Quantity of X rays
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kVp
• Kilovoltage peak
• Determines the speed of electrons as they hit
the target
• Higher speed -> more power
• Higher speed -> increases number of x rays
• kVp determines Quality of X rays
www.upei.ca/~vetrad