Chapter 9: Scatter Radiation and is Control

Unwanted exposure on an image is called:

Fog

The number of lead strips per inch is called:

Grid frequency.

The principle method for reducing scatter radiation fog is the use of a radiographic:

Grid

The primary source of scatter radiation is:

The patient

Grids with lead strips aligned in the direction of the diverging primary x-ray beam are called:

Focused grid

The process of an incoming x-ray photon interacting with an outer orbital electron, removing it from it from the atom is called:

Compton effect

The range of SID in which a focused grid is designed to be used in is called:

Focal range

A device placed between the patient and the IR to absorb scatter radiation

Grid

Scatter radiation that travels back towards the x-ray tube is termed:

Backscatter

Is similar to that which forms characteristic radiation in the x-ray tube. The incoming energy is an x-ray photon rather than an electron

Photoelectric effect

When the grid produces an image of itself on a radiograph, the image of the grid is called:

Grid lines

Radiation produced by the photoelectric effect is correctly referred to as:

Secondary radiation

Excessive absorption of useful radiation by the grid is called:

Grid cut-off

A grid with strips that are parallel to each other, rather than focused:

Parallel grid

This type of interaction occurs at energy levels throughout the diagnostic x-ray range of 40-125 kVp:

Compton effect

A special cassette with a grid built into the front side is a:

Grid cassette

Interaction in which an incoming x-ray photon interacts with the inner shell of an atom and knocks it out of orbit

Photoelectric effect

Device that should be used when the body part becomes greater than 10-12 cm in thickness or the kVp settings are greater than 60:

Grid

Is also known as Thompson scatter:

Coherent scatter

A moving grid is called a:

Bucky

The relationship between the height of the lead strips and the width of the spaces between them defines:

Grid ratio

A composite of two grids with the lead strips are right angles to each other:

Crosshatch grid

A high frequency grid that does not move during an exposure is called a:

Stationary grid

This type of interaction takes place at very low energy levels; less than 10 kEv:

Coherent scatter

Scatter radiation that travels in all directions:

Compton scatter

The interactions that produce scatter radiation occur primarily in the:

Patient

Compton scatter occurs when an x-ray photon interacts with which part of the atom in the patient’s body?

Outer orbital electron

A scattered photon has ________ energy than the incoming primary beam photon

less

At what kVp levels do Compton interactions occur?

45-125 kVp, the entire diagnostic range

The photoelectric effect occurs when an incoming photon from the primary beam interacts with which part of the atom in a patient’s body?

Inner shell electron

Scatter radiation affects radiographic appearance by causing:

Decreased contrast

Which of the following factors affects the quantity of scatter radiation fog on a radiograph?

1. Field size

2. Focal spot size

3. kVp

1 and 3 only

If the size of the x-ray field increases, what happens to scatter radiation fog?

In increases

If the volume of tissue increases, the amount of scatter radiation fog will

Increase

How does scatter radiation fog reduce the visibility of detail in a radiographic image?

By decreasing contrast

What is the principal source of scatter radiation in radiography?

Patient

The most effective and practical way to reduce scatter radiation fog on a radiograph is to:

Use a grid

The device that is placed between the patient and the IR to absorb scatter radiation is called a:

Grid

Compton scatter that is directed from the patient back toward the x-ray tube is called:

Backscatter

The number of lead strips per inch is called:

Grid frequency

The radiographic appearance of decreased density on the lateral margins of the image is most likely caused by grid:

Cutoff

As a general rule, a grid should be employed when the part thickness is greater than:

10 cm

Grids with lead strips that are aligned to coincide with the primary beam angle are called _____________ grids

focuse

If a grid is misaligned with the central ray, it can cause a light area on the side of the image called:

Grid cut-off

Which of the following reduces the amount of scatter radiation fog on a radiograph?

1. Decrease in kVp

2. Decrease in field size

3. Decrease in grid ratio

1 and 2 only

As kVp is increased, Compton interactions will:

Increase

As kVp is increased, photoelectric effect interactions will:

Decrease

Scatter radiation fog will:

1. Increase density.

2. Decrease contrast.

3. Reduce the visibility of spatial resolution.

All 3

How will the density, or atomic number, of the absorbing matter affect scatter?

It will decrease

Grid cutoff will occur when the

1. Tube is off-center.

2. Tube is tilted.

3. SID is too great.

All 3

When performing the collimator test, the four sides of the collimator must each be within ____% of the SID to be in control

2

When performing the beam alignment test, the x-ray tube must be within ____ degree(s) of perpendicular to be in control or ______%

1

A grid should be used when the kVp used is greater than:

60

Grid frequency can be as high as _______lines/inch

200