Mammography Equipment Flashcards
Name the five known interactions between x-rays and matter at the atomic level.
Compton effect, photoelectric effect, coherent or classical scattering, pair production, photodistintegration
What type of radiation is produced when a projectile electron striking the target of the x-ray tube interacts with an inner shell electron?
Characteristic or photoelectric radiation.
What is the name given to the negative electrode of the x-ray tube?
Cathode
When compared to stationary anodes, why are rotating anodes necessary?
To avoid the constant bombardment of electron in one spot. This can lead to pitting of the target due to heat buildup in one spot
What are the two common tube-target materials used in analog mammography tubes?
Molybdenum and rhodium
What effect will the decreasing target angle have on the focal spot sizes?
Decrease target angle will decrease effective focal spot.
In mammography, what type of imaging uses very small focal spot sizes?
Magnification
To minimize the anode heel effect, the cathode is positioned at which area of the breast?
The cathode is positioned to the chest wall.
Why is the material of the exit port window of mammography tube so important?
The tube window will filter the emerging beam. It is important that the tube not filter out the low-energy x-ray needed for mammography imaging.
Which target material is best for imaging fatty breast tissue, especially in analog imaging?
Molybdenum
At what exposures does the reciprocity law fail?
Very long and very short exposures especially in analog imaging
What is the maximum and minimum force o compression allowed in mammography imaging?
25-45lb (111-200 N) on automatic; 45lb (200 Newtons) maximum on manual
How will placing the AEC detector under the fatty portions o fa breast mixed with fatty and glandular tissue affect the final radiograph in analog imaging?
The dense areas of the final radiograph will be underexposed if the AEC is placed under the fatty breast tissue in a breast with both fatty and dense tissues. The AEC detector selector should be positioned under the dense areal of the breast.
How will grid use affect contrast and exposure in analog imaging?
Grid use will increase contrast however typically needed increase in technical factors and therefore radiation dose to the patient.
Why is close collimation not used in mammography imaging?
Extraneous light will compromise the perception of fine details.
Generally what is the average SID used in mammography imaging?
The range is 50-80 cm with an average of 60 cm.
Identify the single biggest advantage of using the single-emulsion system in analog mammography.
Improve recorded detail
Why is the toe of the characteristic curve never zero?
Blue dye added to the base, plus chemical fog will always result in a density reading.
In relation to a film with a higher speed, where will the slower speed film be located on a characteristic curve?
A curve with a slower speed will be positioned to the right of the curve with faster speed.
Name two factors affecting resolution and sharpness in analog imaging.
Motion, poor screen-film contact, increase focal spot size, increase OID, decrease SID, characteristic of the screen, relationship between OID and SID
What is the best method of controlling voluntary motion?
Clear communication of instructions to patients.
What is the main controlling factor of image brightness in digital imaging?
Image brightness can be controlled by the processing software, which is a predetermined digital processing algorithim. In any digital image, the user can alter the contrast after exposure.
What is the main controlling factor of image contrast in digital imaging?
Image contrast is controlled by the processing software, which is a predetermined digital processing algorithm. In any digital image, the user can alter the contrast after exposure.
Give two possible post processing options available with digital imaging.
Postprocessing options include:
* Windowing to adjust image contrast and brightness on the monitor. The window width will control the contrast and the window level controls the brightness. * Smoothing the image by bringing the brightness value of adjacent pixels closer together. * Magnifying or zooming all or parts of image * Edge enhancement to increase the brightness along the edges of the structures to increase the visibility of the edges. * Subtraction to remove background anatomy * Image reversal where the dark and light pixel values of an image are reversed (e.g. from negative to positive) * Annotating the image with text or numbers
Added filtration in mammography imaging is:
Generally the same element as the mammography tube target.
By having the same element as the mammography tube target, added filtration is designed to allow the K-characteristic of x-rays of the specific target to be emitted while absorbing the higher and lower energy bremsstrahlung x-rays
Which of the following does NOT describe mammography filtration?
Aluminum is not used in analog imaging, as this would absorb the low energies needed for breast imaging.
Inherent filtration in mammography imaging implies filtration by:
*Exit port window of the mammography tube
*Collimator light assemble
*Compression device
All of these structures are in the part of the beam as it leaves the anode. There they will have impact on the energy of the beam.
Components parts of mammography tube that differentiates it from a regular x-ray tube include:
*Size of the focal spot
*Type of added filtration
*Material of the exit port window
Mammography imaging used smaller focal spot sizes than general x-ray imaging. Also the material of the exit port window and the filtration used all are designed to minimally absorb the low energy photons needed for breast imaging.
Which of the following statements are NOT true of magnification mammography?
In general, magnification can be used to image the entire breast with one exposure.
Magnification mammography is used to magnify one area of the breast to image calcification, lesions or specimens. In general, magnification will not image the entire breast. The radiation dose to the patient, particularly to the patient’s skin is higher in magnification mammography because the breast is very close to the radiation source.
In analog imaging, AEC failure, resulting in an underexposed film, can be caused by
Improper placement of the AEC detector.
The placement of the AEC device is critical in analog imaging. If the device is placed under fatty breast tissue that is a mixture of fatty and dense, the dense areas will be underexposed.
The material of the exit port is necessary to
Allow the passage of low energy photons
The exit port is made of borosilicate glass or beryllium because regular glass would harden the emerging beam by eliminating the low-energy photons needed for breast imaging.
How does the material selected for the anode affect the beam quality?
The anode selection filters the beam by allowing only the necessary low energy photons to emerge from the tube.
The anode material produces characteristic x-ray in energies that will easily penetrate both fatty and dense breast tissue structures. After leaving the target, the beam is further filtered to remove low-or high-energy photons that are not needed in image production.
Which of the following factors will directly control the image contrast in digital imaging?
Image contrast is controlled by the processing software, which is a predetermined digital processing algorithm. In any digital image, the user can alter the contrast after exposure.
In digital imaging, a post process option that will change the image brightness is called:
Windowing:
Windowing can adjust image contrast and brightness on the monitor. The window width will control the contrast and the window level controls the brightness. Smoothing involves bringing the brightness value of adjacent pixels closer together. Edge enhancement will increase the brightness along the edges of the structures to increase the visibility of the edges. Subtraction is used to remove background anatomy.
Mammography uses ____frequency generators
High
X-Ray tube for mammo
Specially designed to allow for low Kv for tissue density and composition
K-she’ll creates
Photoelectric absorption
Kv used in mammography?
20-40 Kv, adjustable in 1-Kv increments
Target material for conventional x-Ray tube
Tungsten
Tube target for mammography?
Molybdenum
Tube target for denser breast?
Rhodium
Actual focal spot
The actual area of the target struck by electrons
Effective focal spot
Focal spot area as projected toward the patient and image receptor
Mammography grids
Improves contrast and reduces scatter 3:1. -5:1 ratio 30-50 lines /cm Linear Lead strips Interspace material - carbon fiber and fine wood
Regarding magnification: increased object to image distance results in:
A loss of resolution due to geometric blur.
Use a small focal spot to compensate
Film size for analog
18x24 and 24x30cm
Single emulsion- high contrast, high resolution
Emulsion facing toward screen away from tube
View box should provide an illumination level of:
50 lux or less
Bit depth
Refers to the number of shades of gray within a given pixel
PACS
Stores, retrieved, transmits and displays images on any system that use DICOM
Decreases Kvp results in
Reduces penetration which increased mAs
Darkroom lighting
White light and *safelight- used to safely process images Mounted 3-4 feet from feed tray Filter must be 4 ft above work station Bulb must be filtered 15 watt bulb for overhead 7.5 for closer fixtures
