Mammography Equipment

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1

Name the five known interactions between x-rays and matter at the atomic level.

Compton’s effect, photoelectric effect, coherent or classical scattering, pair production, photodisintegration

2

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

3

What is the name given to the negative electrode of the x-ray tube?

Cathode

4

What is the purpose of the line voltage compensator?

Line voltage from a wall outlet enters the x-ray circuit and is adjusted with a line voltage compensator. The line compensator measures the incoming voltage and adjusts that voltage to precisely 220 V. Incoming voltage can vary by as much as 5%, so the line voltage compensator ensures that the voltage going to the x-ray tube is always constant, with no variations or fluctuations.

5

What are common tube-target materials used in mammography tubes?

Molybdenum and rhodium

6

What effect will the decreasing target angle have on the focal spot size?

Decreasing target angle will decrease effective focal spot.

7

In mammography, what type of imaging uses very small focal spot sizes?

Magnification

8

To minimize the anode heel effect, the cathode is positioned at which area of the breast?

The cathode is positioned to the chest wall.

9

Why is the material of the exit port window of the 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.

10

Which target material is often used when imaging fatty breast tissue?

Molybdenum

11

At what exposures does the reciprocity law fail?

Very long and very short exposures, especially in analog imaging

12

What are the maximum and minimum forces of compression allowed by the initial automatic compression in mammography imaging?

25–45 lb (111–200 N) are the minimum and maximum forces on initial power drive of the automatic compression.

13

What is the purpose of the filament circuit?

The filament circuit is used to supply the lower voltage and higher current needed for the tube filament to heat the filament. The filament circuit therefore provides the electrons for interaction with the target. Adjusting the current being applied to the filament results in variations in the radiation intensity. When the tube current is varied, the number of electrons being supplied to the anode (target) varies. Increase mA will increase electron emission.

14

What type of transformer is used in the filament circuit?

The filament circuit is used to create thermionic emission at the cathode. The filament is located at the cathode end of the x-ray tube, and it is a coil of wire approximately 2 cm in diameter and 1 to 2 cm long. Connections from the autotransformer provide voltage for the filament circuit. However, this is a high voltage. A filament step-down transformer ensures that the voltage to the filament is low and the current is correspondingly high. The step-down transformer converts high voltage/low current to low voltage/high current. This high current causes the filament to glow and to emit heat and electrons. The cloud of electrons will remain in the vicinity of the filament before being accelerated to the anode when the high voltage is applied to the tube.

15

Why is close collimation not used in mammography imaging?

Extraneous light will compromise the perception of fine details.

16

Generally, what is the average SID used in mammography imaging?

The range is 50–80 cm with an average of 60 cm.

17

What principle is used to rotate the anode in the x-ray tube?

The anode rotates through the principle of electromagnetic induction. An induction motor consists of two parts separated from each other. The part outside the tube is called the stator, which is a series of electromagnets. The part inside is the rotor. Current in the stator winding induces a magnetic field that surrounds the rotor. The stator winding is energized sequentially so that the induced magnetic field rotates on the axis of the stator. The field interacts with the ferromagnetic of the rotor, causing it to rotate synchronously with the activated stator winding.

18

What is the photoelectron?

If a projectile electron strikes the target of the x-ray tube, it can interact with an inner shell electron, knocking the electron out of its orbit. The ejection of an inner shell or K-shell photoelectron results in a vacancy in the K shell, which is then filled by an outer shell electron. The movement of the electron from the outer shell to the inner shell results in the emission of an x-ray. The x-ray emitted, called characteristic radiation, has energy equal to the difference in the binding energies of the orbital electrons involved. A photoelectric interaction cannot occur if the energy of the incident electron is lower than the binding energy of the electron of the target. The higher the atomic number of the target, the higher the binding energy. This means that the characteristic radiation produced by each element will be different, depending on the atomic number of the element, and is not affected by the kVp.

19

What is bremsstrahlung radiation?

A projectile electron striking the target of the x-ray tube can lose its kinetic energy as it interacts with the nuclear field of the target atom. Because the electron has a negative charge and the nucleus is positive, the electron is attracted to the nucleus. It is slowed and will change course as it loses energy. The loss of kinetic energy reappears as an x-ray photon. This type of x-ray production is called bremsstrahlung x-ray. Unlike characteristic radiation with specific energies, the energy of bremsstrahlung radiation can vary tremendously because the incident electron can lose some, all, or very little energy. The only certainty is that the final energy cannot exceed the initial energy.

20

List some items responsible for inherent filtration.

Inherent filtration is represented by anything that the x-ray beam passes through before it enters the breast. The material used for the exit port or window in mammography tube is borosilicate glass or beryllium because a regular glass window would harden the emerging beam by eliminating the soft characteristic radiation. The oil in the x-ray tube, the mirror assemble of the collimation design, and the composition of the compression plate are all designed to attenuate very little of the x-ray beam.

21

What is the best method of controlling voluntary motion?

Clear communication of instructions to patients.

22

What is main controlling factor of image brightness in digital imaging?

Image brightness can be controlled by the processing software, which is a predetermined digital processing algorithm. In any digital image, the user can alter the brightness of the digital image after exposure.

23

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.

24

Give two possible postprocessing options available with digital imaging.

Postprocessing options include:

• 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 structures to increase the visibility of the edges

• Subtraction to remove background anatomy

• Image reversal, whereby the dark and light pixel values of an image are reversed (e.g., from negative to positive)

• Annotating the image with text or numbers

25

Added filtration in mammography imaging is:

(A) Generally the same element as the mammography tube target

(B) Of a higher filtration value than the filtration used in general imaging

(C) Sometimes not recommended

(D) Often replaced by the inherent filtration

(A) Generally the same element as the mammography tube target

26

Which of the following does not describe mammography filtration?

(A) It shapes the emerging beam by absorbing low-energy x-rays that would only be absorbed by the superficial tissue and contribute to patient dose.

(B) It will affect the HVL of the emerging x-ray beam.

(C) Filtration makes the emerging beam compatible with the breast characteristics.

(D) The filtration used in mammography imaging is usually aluminum.

(D) The filtration used in mammography imaging is usually aluminum.

27

Inherent filtration in mammography imaging implies filtration by:

(1) Exit port window of the mammography tube

(2) Collimator light assemble

(3) Compression device

(A) 1 and 2 only

(B) 2 and 3 only

(C) 1 and 3 only

(D) 1, 2, and 3

(D) 1, 2, and 3

28

Component parts of a mammography tube that differentiate it from a regular x-ray tube include:

(1) Size of the focal spots

(2) Type of added filtration

(3) Material of the exit port window

(A) 1 and 2 only

(B) 2 and 3 only

(C) 1 and 3 only

(D) 1, 2, and 3

(D) 1, 2, and 3

29

Which of the following statements are not true of magnification mammography?

(A) With magnification, patient dose increases.

(B) Magnification does not use a grid.

(C) Magnification can be used to assess suspicious lesions.

(D) In general, magnification can be used to image the entire breast with one exposure.

(D) In general, magnification can be used to image the entire breast with one exposure

30

What is the recommended resolution of the RWS?

(A) 2 megapixels

(B) 3 megapixels

(C) 4 megapixels

(D) 5 megapixels

(D) 5 megapixels

31

The material of the exit port is necessary to:

(A) Harden the emerging beam

(B) Attenuate low-energy photons

(C) Allow the passage of low-energy photons

(D) Increase the level of high-energy photons emerging

(C) Allow the passage of low-energy photons

32

How does the material selected for the anode affect the beam quality?

(A) The anode selection shapes the beam by produce characteristic radiation in an acceptable range.

(B) The anode selection filters the beam by allowing only the necessary low-energy photons to emerge from the tube.

(C) The anode selection shapes the beam by filtering out the high-energy photons.

(D) The anode selection shapes the beam by filtering out the low-energy photons.

(A) The anode selection shapes the beam by produce characteristic radiation in an acceptable range.

33

Which of the following factors will directly control the image contrast in digital imaging?

(A) mAs

(B) kV

(C) Processing software

(D) Exposure time

(C) Processing software

34

In digital imaging, a postprocessing option that will change the image brightness is called:

(A) Edge enhancement

(B) Windowing

(C) Annotating

(D) Subtraction

(B) Windowing