Physics Flashcards by Emily Mott

Low dose = ___ contrast

High

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Image contrast produced by an object depends on:

Beam attenuation

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Difference in density between two adjacent areas on an image

Contrast

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3 target materials used in mammo equipment

Molybdenum, Rhodium, Tungsten

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T/F: The system will choose the target that is best for tissue type and thickness

True

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Filter material is inserted into the x-ray beam to enhance:

Contrast

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Most common filter materials

Molybdenum, Rhodium, Aluminum, Silver

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_____ filtration: composed of parts of the x-ray tube

Inherent

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Material of the exit window of the tube housing

Beryllium

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Thin sheets of metal inserted into the x-ray beam

Added filtration

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Two roles of added filtration:

Removes soft energy photons (decreases dose)

Slows down higher energy photons (increases contrast)

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Molybdenum/Molybdenum target/filter combo best for:

Average breasts

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Molybdenum/Rhodium target/filter combo best for:

Thicker breasts

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Rhodium/Rhodium target/filter combo best for:

Very thick and dense breasts

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Tungsten/Aluminum target/filter combo best for:

Average breasts

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Tungsten/Rhodium target/filter combo best for:

thicker breasts

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Tungsten/Silver target/filter combo best for:

very thick and dense breasts

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Grids absorb ____% of scatter

75-85

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Grid ratio:

Height of leads strips to distance between the lead strips

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The higher the grid ratio, the ___ the image contrast

Better

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Grid ratios used in mammo

3:1 to 5:1

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Grid frequency: _____ lines per cm

30-50

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2 types of grids used in mammo

Linear/focused and Honeycomb/HTC

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T/F: Grids are used in magnification imaging

False

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Grids are often used in _______ imaging; only sometimes in _____ imaging

FFD (2D); 3D

Interspace material for honeycomb/HTC grids

Air

Interspacing material for linear/focused grids

Carbon

Lack of compression can cause _____ artifact

Summation

The compression paddle should not extend beyond the chest wall edge of the image receptor by more than ___% when compressed on the average breast

The shadow of the ___ edge of the compression paddle should not be visible on the image

vertical

Light field will come to the chest wall but must not exceed any edge by more than:

Light field brightness should provide and average illumination of no less than ____ lux at ____ cm, or the maximum SID, whichever is less

160; 100

The radiation shield must have the equivalent attenuation of at least ____ mm lead at ___ kVp

0.08; 35

Radiation barrier limits the operator's exposure to below ___ per week

1 mSv

Area of the anode bombarded by electrons

Actual focal spot

Downward projection of the actual focal spot; dependent on the steepness of the anode angle

Effective focal spot

The steeper the angle of the anode the _____ the effective focal spot and the _____ the detail

smaller; better

Large focal spot measurement

0.3mm

Large focal spot used for:

Standard imaging

Small focal spot measurement

0.1mm

Small focal spot used for:

Non-standard imaging (magnfication)

The mammo spots are generally ____ than other modalities

Smaller

When electrons hit a section of target that is very steep, a _____ x-ray field is created

Narrow

When electrons hit a section of target that is less steep, a _____ x-ray field is created

Wider

The anode acts as a filter; this is referred to as:

Self filtration

The x-rays at the ___ end of the tube have more intensity

Cathode

In mammo, the tube is moved ____ in the tube head

Anteriorly

Average kVp range in mammo

25-35

mA stations are [fixed/variable] in mammo

fixed

Typical mS selection for mammo

20-100 mA

Typical exposure time:

0.4 to over 1 second

Maximum backup time for grid techniques

600 mAs

Maximum backup time for non-grid work

300 mAs

The emerging x-ray beam is determined by 3 factos:

kVp, target material, filter material

Created by kVp; most common type of radiation produced

Bremsstrahlung

Determined by the anode material; x-rays produced are confined to 2 energy spikes.

Characteristic

This radiation is most important for determining x-ray beam penetration and giving us optimal contrast

Characteristic

X-rays produced with multiple energies (keV) starting low and ending high

Bremsstrahlung

The boundary between photon energies that are not attenuated and the photons energies that will be attenuated

k-edge

The k-edge is determined by the:

Atomic number of the filter material

Molybdenum's K-edge

20 keV

Rhodium's K-edge

23.22 keV

Aluminum's k-edge

16 keV

Silver's k-edge

26 keV

Filters used for thicker/denser breasts where higher energies are needed

Rhodium/silver

Filters used for average breasts to decrease contrast

Molybdenum/Aluminum

Moly anodes produce characteristic radiation spikes of:

17.6 keV and 19.7 keV

Rhodium produces characteristic radiation spikes of:

20.3 and 22.7 keV

Tungsten produces a characteristic radiation spike of:

59 keV and 68 keV

The MQSA requirement regarding compression force is _____pounds to _____ pounds of initial force applied.

25 / 45

The U.S. Congress directed the _____ to develop and implement MQSA (Mammography Quality Standards Act) regulations to ensure that all women have access to quality mammography for the detection of breast cancer in its earliest, most treatable stages.

FDA

The mammography technologist must perform _____ mammographic examinations over a _____ period in order to fulfill MQSA Continuing Experience requirements.

200 / 24-month

MQSA requires that the mammography technologist obtain _____ continuing education units (CEU) in a _____ period.

15 / 36-month

The _____ is a QC test performed by the medical physicist to ensure that the hardware is performing properly so as not to degrade the resolution of the image.

MTF

_____ artifact is unique to FFDM and results when a woman’s breast compresses to less than 2 cm in thickness demonstrating the edges of the compression paddle at the corners of the image.

Thin breast

_____ artifact is common to certain manufacturers and is more commonly seen in women with thick breasts.

“Breast-within-a-breast”

In the digital detector, _____ are similar to a collection of bins that store an electrical charge depending upon the number of x-rays that fall into that area.

Pixels

_____is NOT a choice of Automatic Optimization of Parameters (AOP) on a mammography unit.

Window – system selects the best window material, glass or Beryllium, for the breast density

Contrast on a mammogram results from the varying density differences between _____.

glandular and adipose tissues

The exposure increases or decreases _____ with each increment in the density setting.

10% to 20%

If magnification mammography were performed without the use of a small focal spot, the resulting image would be magnified and _____.

Blurred

Physics Flashcards

(81 cards)