sicp radiation principles
TRANSCRIPT
Basic Principles of Radiation
By the end of the presentation, the individual will be able to:
• Define ionizing radiation
• Correlate wavelength, frequency, and energy
• Differentiate mA and kVp
• Describe how x-rays are generated
• Identify parts of an x-ray tube and Image Intensifier
• Describe Line Focus Principle
• Discuss three reactions of photons when entering a material (patient)
Discovery of X-Ray
First Medical RadiographWilhelm Roentgen
Radiation?
• Electromagnetic Energy
Wavelength
• The shorter the wavelength, the higher the frequency, and therefore the higher the energy
Ionizing Radiation
• When electromagnetic radiation, as it passes through matter, produces ions it is called ionizing radiation
Ionizing and Non-Ionizing Radiation
The Electromagnetic Spectrum
How are x-rays generated?
• Acceleration Collision
X-Ray Tube• Produced, Accelerated, Stopped
Protective housing
• Steel lined with lead
• Window
• Function
• Contain
• Inhibit
• Isolation
• Cooling
X-Ray Imaging
• X-ray tube
• Generator
• High voltage circuit
X-RAY Generator• Power source
• Low voltage High Voltage
• Rectified
X-ray Tube
Negative(-)
Positive(+)
X-ray production
• Focal spot
• Collision + X-ray + Heat
• Smaller spot = better picture, more heat
Line Focus Principle
• Angle anode surface
• X ray beam
X-Ray Beam Production
• Anode + electrons = X ray
• Photons of different energies = primary radiation
Remnant Beam
Primary beam
Remnant
beam
Photons
• Penetrate
• Absorb
• Scatter
Differential absorption
• Density and Thickness
• Picture contrast
• Produce the gray scale in the radiograph
IMAGING EQUIPMENT
• X-Ray tube
• Image intensifier
• C-arm
• Cine camera
• TV monitor
Image Intensifier
Image Intensifier
• X ray Visible light
• Input phosphor –Cesium Iodide
• Converts x-rays to visible light
• Photocathode
• Attached to input phosphor
• Receives light and releases as electrons that travel through the glass envelope
• This is photoemission
Image Intensifier
• Electrostatic lenses
• Positively charged
• Help accelerate the electrons toward the anode
• Output phosphor
• Brightness gain occurs
• Increase in brightness from the input to output phosphor
• Fluorescent image is created much brighter than input phosphor
Magnification of Image
• Input screens of image intensifiers have various diameters
• During magnification the kVp and mAs are automatically increased
mAs = Quantity
• X-ray quantity is directly proportional to the mAs.
mAs - milli-Ampere-seconds
• mAs directly effects
• Radiographic density (blackness of film)
• Patient dose / patient exposure
• mAs does not effect
• Quality of the x-ray beam (penetrating ability)
• Radiographic contrast
• Geometric properties of the beam
kVp - Quality
• The penetrating power of an x-ray beam.
• Higher energy beams can penetrate farther than low energy beams
kV - Kilovoltage
• Higher kV settings provide more electron to x-ray conversion
• Higher kV settings produce shorter wavelength X-rays providing more penetrating ability
• kVp= low contrast (more gray tones)
• kVp= high contrast (more black and white tones)
Radiographic Contrast
• The differences in densities between two adjacent parts of a radiograph
• High contrast – black and white
• Low contrast – mostly grays
• The ideal image contains sufficient information to render a diagnosis, and sufficient contrast to demonstrate structure
Radiographic Contrast
Low contrastHigh contrast
Improvement of Radiographic Quality
• Patient Positioning
• Area of interest as close to film as possible
• Patient instructed to restrain from movement
• Understand anatomy
• Imaging devices
• Collimation, soft shutters, grids
• Selection of technique
Reduction of Scatter Radiation
• Use collimation
• Grids
• Aluminum filters
RADIATION
Hardening of the X-ray beam
• Aluminum filters remove low energy X-rays from beam
• Reduces scatter and patient/staff exposure
By the end of the presentation, the individual will be able to:
• Define ionizing radiation
• Correlate wavelength, frequency, and energy
• Differentiate mA and kVp
• Describe how x-rays are generated
• Identify parts of an x-ray tube and Image Intensifier
• Describe Line Focus Principle
• Discuss three reactions of photons when entering a material (patient)
Bye Bye