What are 3 forms of Non-Ionizing waves?
- Radiowaves
- Microwaves
- Visible Light
What are 3 forms of Ionizing waves?
- UV Light
- X-Rays
- Gamma Rays
These forms of EM (Electromagnetic Spectrum) have sufficient energy to ionize energy.
What is filtration?
Aluminum filtration removes low energy x-rays that do not contribute to the image. Also increases the mean energy of the x-ray beam.
What is kVp?
Kilovolt peak - An increase in kVp will increases mean energy and maximal energy
kVp controls the QUALITY of the exposure
What are benefits of increasing kVp?
- Increased Penetration
- Shortening of wavelength
- Decreased dose to skin
What are 3 consequences of increasing kVp?
- Increased anode heat production
- Decreased Contrast
- Increased dose to deep tissues
What is Tube current (mA)?
- mA controls the # of electrons
- When you increased ma you increase density (darkness)
- mA controls quantity of the exposure
- Can cause “Blooming” saturation effect
- Increased dose to the patient
A smaller effective focal spot produces…
Sharper x-rays
Focal spot is in the anode
Which part of the x-ray unit produces electrons?
Cathode
Which part of the x-ray unit produces x-rays? (focal spot)
Anode
What is attenuation?
- The removal of x-ray photons
- The reduction in x-ray beam intensity
- Affected by the density of the tissue
- As a result of tissue absorption and scatter from the x-ray beam as it penetrates through matter
What 3 things does scatter result in?
- Energy deposited in the patient
- Contributes to image degradation
- Loss of image contrast
What is Absorption?
Contributes to image contrast but will increase the dose to the patient
What is CMOS?
Complimentary Metal Oxide Semidconductor
What does CMOS do?
- Each pixel isolated and directly connected to a transistor
- Char is transferred to transistor as small voltage
- Voltage in each transistor is read by a frame grabber then stored and displayed as a gray value
What is CCD?
Charge Coupled Device
Describe 3 aspects of a CCD -
- Each pixel acts as a well for which a certain number of charged electrons are stored after the CCD has been exposed to x-rays
- Voltages in each pixel are sampled and assigned a numerical value (gray level)
- Image is read by transferring each row of pixel charges from one pixel to the next in a bucket brigade fashion.
What is PSP?
Photostimuable Phosphor Plate
Describe the PSP system…
- Computed Radiography (CR) for mammography
- PSP plate is exposed
- Latent image forms
- Latent image fluoresces when scanned with laser
- Fluorescent signal is read with photodiode which transmits the image data to computer
What 7 things effect image quality?
- Spatial Resolution
- Noise
- Density
- Contrast Resolution
- Magnification
- Distortion
- Quality Control
What is resolution?
Is the ability of a system to discriminate between two structures
What is spatial resolution?
The more line pairs that can be represented per mm, the greater the resolution capacity. Examples include: calcification in soft tissue, trabecular bone pattern
What is noise?
- Appearance of uneven density in uniformly exposed image
- Localized variations in density or “speckles” or grainy image
What is density?
- Density refers to darkness/blackness
- Too dark means excessive density
- Too light means insufficient density
