VCA 252 Principles of Diagnostic Imaging

Dr. LeeAnn Pack566-0841, 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

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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

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Forms of Diagnostic Imaging

• Ultrasonography– 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– Uses X-rays to produce an image, transmitted– Cross sectional imaging– No superimposition of structures– Requires computer manipulation of images

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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

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What is an X ray?Production of X rays

• 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

• 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

• Exit window• Housing• Filtration – radiation safety• Collimation

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mAs

• 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

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