Bushong Chapter 11. Scatter
Radiation
Image-forming x-rays include those which have been _. - Transmitted without
interaction, and Scattered through Compton interaction
Which kVp selection would result in the most scattered x-rays in the image forming
beam? - 90 kvp or whatever is the highest
Approximately _% of the x-ray beam incident on the patient is transmitted through the
patient without interaction to become part of the image-forming beam. - 0-9%
The x-ray interaction that contributes to the clear parts of the image is_. - photoelectric
interaction
Compton Scatter contributes to _. - image noise
The three primary factors influencing the intensity of scatter in the image-forming beam
are_. - kvp, field size, and patient thickness.
Decreasing the kvp will increase_. - patient dose
Photoelectric interactions increase when _ is decreased. - Kvp
Scatter radiation increases as _ increases - Field size
The x-rays that are transmitted through the patient without interaction contribute to _. -
useful information
Contrast resolution is improved by _. - tight collimation, lowering kvp, patient
compression
A fixed aperture diaphragm should leave a _ cm unexposed border on the film. - 1
The most commonly used beam restricting device is the _. - variable collimator
The use of a compression device will increase - contrast
lowering kvp _patient dose and _ image contrast. - increases, increases
The use of _ improves contrast and reduces patient dose. - collimation
, The positive beam limiting device assures that the x-ray beam is collimated to_ - 1cm
outside image receptor size
Federal regulations passed in_ required that positive beam limiting devices be on all
manufactured x-ray collimators - 1974
Beam restriction with a(n) _ is only accurate at a fixed SID. - aperture diaphragm
How can you improve image contrast with a heavy patient without increasing patient
dose? - Use tight collimation
Photons that change direction do what? - make scatter radiation
What are 3 ways to reduce the production of scatter - Optimal KVP
Beam restrictors
Compression devices
The larger the x-ray field size the_ - more scatter is produced
The thicker the patient and more dense the body tissues the_ - the greater the amount
of scatter radiation produced
The use of grids is recommended for imaging a body part of_? - 10 cm or greater
What does a grid do? - a grid allows only those x-rays emitted in a straight line from the
source to the image receptor
# of Grid strips per inch is called - called grid frequency
Name some grid problems and results - Off level - grid cutoff across image,
underexposed, light image
Off Center - grid cutoff across image, underexposed, light image
Off focus - Grid cutoff toward edge of image
Upside down - Severe grid cutoff toward edge of image
Off Center, Off focus - Grid cutoff on one side of image.
What is the air gap technique - Increase MAS 10% for every centimeter of air gap.
Equivalent to intermediate grid patient dose.
What is the bucky factor - Measure the penetration of both the primary and scatter
radiation through the grid
Higher the grid ratio, the higher the grid factor
Bucky factor increases with increasing kVp
Radiation
Image-forming x-rays include those which have been _. - Transmitted without
interaction, and Scattered through Compton interaction
Which kVp selection would result in the most scattered x-rays in the image forming
beam? - 90 kvp or whatever is the highest
Approximately _% of the x-ray beam incident on the patient is transmitted through the
patient without interaction to become part of the image-forming beam. - 0-9%
The x-ray interaction that contributes to the clear parts of the image is_. - photoelectric
interaction
Compton Scatter contributes to _. - image noise
The three primary factors influencing the intensity of scatter in the image-forming beam
are_. - kvp, field size, and patient thickness.
Decreasing the kvp will increase_. - patient dose
Photoelectric interactions increase when _ is decreased. - Kvp
Scatter radiation increases as _ increases - Field size
The x-rays that are transmitted through the patient without interaction contribute to _. -
useful information
Contrast resolution is improved by _. - tight collimation, lowering kvp, patient
compression
A fixed aperture diaphragm should leave a _ cm unexposed border on the film. - 1
The most commonly used beam restricting device is the _. - variable collimator
The use of a compression device will increase - contrast
lowering kvp _patient dose and _ image contrast. - increases, increases
The use of _ improves contrast and reduces patient dose. - collimation
, The positive beam limiting device assures that the x-ray beam is collimated to_ - 1cm
outside image receptor size
Federal regulations passed in_ required that positive beam limiting devices be on all
manufactured x-ray collimators - 1974
Beam restriction with a(n) _ is only accurate at a fixed SID. - aperture diaphragm
How can you improve image contrast with a heavy patient without increasing patient
dose? - Use tight collimation
Photons that change direction do what? - make scatter radiation
What are 3 ways to reduce the production of scatter - Optimal KVP
Beam restrictors
Compression devices
The larger the x-ray field size the_ - more scatter is produced
The thicker the patient and more dense the body tissues the_ - the greater the amount
of scatter radiation produced
The use of grids is recommended for imaging a body part of_? - 10 cm or greater
What does a grid do? - a grid allows only those x-rays emitted in a straight line from the
source to the image receptor
# of Grid strips per inch is called - called grid frequency
Name some grid problems and results - Off level - grid cutoff across image,
underexposed, light image
Off Center - grid cutoff across image, underexposed, light image
Off focus - Grid cutoff toward edge of image
Upside down - Severe grid cutoff toward edge of image
Off Center, Off focus - Grid cutoff on one side of image.
What is the air gap technique - Increase MAS 10% for every centimeter of air gap.
Equivalent to intermediate grid patient dose.
What is the bucky factor - Measure the penetration of both the primary and scatter
radiation through the grid
Higher the grid ratio, the higher the grid factor
Bucky factor increases with increasing kVp
