Sage-Tips

Why molybdenum filter is used in mammography?

When the molybdenum filter is selected as shown here it attenuates and blocks much of the bremsstrahlung spectrum above the energy of 20 keV. This results in the spectrum that is most often used in mammography, produced with the “moly/moly” anode/filter combination.

Why low kV is used in mammography?

Lower kV values are used to enhance contrast but do not provide sufficient penetration through thick or dense breast tissue where the higher kV values are required. When the kV is reduced in a specific examination, the mAs (in the units of mAs) must be increased to produce the necessary receptor exposure.

What material is used for the tube window in a mammography unit?

The material used for the exit port is also important in ‘hardening’ the beam in general X-ray equipment; however, in mammography a beryllium (Be) window permits the softer radiation to pass through and enhance the subject contrast.

What is a standard mammogram called?

A 3D mammogram (breast tomosynthesis) is an imaging test that combines multiple breast X-rays to create a three-dimensional picture of the breast. A 3D mammogram is used to look for breast cancer in people who have no signs or symptoms.

What is K edge in mammography?

The K-absorption edge (K-edge) refers to the abrupt increase in the photoelectric absorption of x-ray photons observed at an energy level just beyond the binding energy of the k-shell electrons of the absorbing atom.

What is AEC in mammography?

An automatic exposure control (AEC) is proposed for a scanning full field digital mammography system. It uses information from the leading part of the detector to vary the scan velocity dynamically, thus creating a nonuniform x-ray field in the scan direction.

Why high frequency generators are used in mammography?

All current mammographic imagers are high-frequency x-ray generators (see Chapter 7) that are smaller in size and less expensive than earlier single and three-phase mammographic units. High-frequency x-ray generators also provide exceptional exposure reproducibility, which is essential for consistent image quality.

What is MG screening?

Screening mammography is used to look for breast changes in women without signs of breast cancer. Typically, screening mammography involves two views (craniocaudal and mediolateral oblique views) of each breast.

What is CC and MLO views mammography?

So, ‘Cranial-Caudal’ (CC) is a view from above. while an oblique or angled view ‘mediolateral-oblique’, or (MLO). The ‘medio-lateral view’, (ML) is a view from the center of the chest outward, whilst the ‘latero-medial’ view (or LM) is a view from the outer side of the breast, towards the middle of the chest.

What is AK edge filter?

What is target composition in mammography?

Target. Need material that produces characteristic x-rays with energies of 17-20 keV (20-30 keV for larger breasts) to produce the best contrast. The commonly used material is Molybdenum (characteristic x-rays at 17.5 and 19.6 keV).

Why single emulsion film is used in mammography?

The single screen is used as a back screen for mammography because x-ray absorption (and emission of screen light) is highest on the side of the screen where the x-rays enter.

Which X-ray spectrophotometer is best for mammography?

Mo/Mo, Mo/Rh, and Rh/Rh all provide X-ray spectra suitable for mammography with mean energies around 20 keV; the combinations with Rh as filter have higher average energy because the spectra are cut off at higher energy by the K-edge of Rh.

Which elements are suitable for added beam filtration for mammography?

Mo, Rh, and Ag are typical elements with suitable K-edge energies for providing added beam filtration for mammography ( Figure 4.3 ). The added filter heavily absorbs both low-energy photons (<15 keV), due to high photoelectric absorption, and high energy ones (above the K-edge), due to dramatically increased absorption beyond the K-edge.

Can Mo be used as a filter material in X-ray?

If Mo is used as the target material, both Mo and Rh can be used as the filter materials. If Rh is used as the target material, then Rh itself is an acceptable filter material, but Mo would not be a good candidate because its K-edge is lower than the energies of characteristic X-rays produced by an Rh target.

What is the difference between the grids for mammography?

Compared to grids for general x-ray imaging, grids for mammography have a lower ratio and the material between the strips is selected for low x-ray absorption. The grid is contained in a Bucky device that moves it during the x-ray exposure to blur and reduce the visibility of the grid lines.