Midterm

Question 1

An image-processing technique commonly used to identify the edges of an image and assess the raw data prior to image display

Answer 1

Histogram Analysis

Question 2

Includes all the pixel values that represent the image before edge detection and rescaling

Answer 2

Data set

Question 3

Scatter radiation is primarily the result of (1) in which an incoming xr photon (2) and (3)

Answer 3

1. compton interactions
2. loses energy
3. changes direction

Question 4

Two major factors affect the amount and energy of the scatter radiation exiting the patient

Answer 4

1. Kilovoltage peak (kVp)
2. Volume of irradiated tissue

Question 5

Beam restriction serves 2 purposes:

Answer 5

1. Limiting pt exposure
2. Reducing amount of scatter radiation produced within the pt

Question 6

Limiting the xr beam field size is accomplished with a beam-restricting device. Located (1), the beam-restricting changes the size and shape of the (2)

Answer 6

1. just below the XRT housing
2. primary beam

Question 7

Beam restriction and pt dose relationship

Answer 7

Indirect

Question 8

Collimation and scatter radiation relationship

Answer 8

Indirect

Question 9

Most sophisticated, useful, and accepted type of beam-restricting device for radiography

Answer 9

Collimators

Question 10

Automatically limits the size and shape of the primary beam to the size and shape of the IR

Answer 10

Automatic collimators

Question 11

Automatic collimators aka

Answer 11

Positive beam-limiting device

Question 12

Makes it difficult for the radiographer to increase the size of primary beam to a field size larger than that of the IR, which would result in increasing pt’s radiation exposure

Answer 12

Automatic collimation

Question 13

Device consisting of very thin lead strips with radiolucent interspaces intended to absorb scatter radiation emitted from the pt

Answer 13

Radiographic grid

Question 14

Radiographic grids are approx. (1) thick and ranging from (2) to (3)

Answer 14

1. 1/4 in
2. 8x10 inches (20x25 cm)
3. 17x17 in (43x43 cm)

Question 15

Grid vs filter

Answer 15

Grid
- b/n pt and IR
- absorbs scatter rad’n = improved image quality

Filter
- b/n xrt and pt
- absorbs low energy xrs and allows high-energy to pass through = improved image contrast

Question 16

Grids contain thin lead strips or lines that have a precise (1), (2), (3)

Answer 16

1. height
2. thickness
3. space between them

Question 17

Grid construction

• (1) materials separates the lead lines
• Interspace material is typically made of (2)
• Lead lines and interspace material of the grid are covered by a/n (3) front and back

Answer 17

1. Radiolucent interspace
2. aluminum
3. aluminum

Question 18

Determines the efficiency of absorption mechanism of grids

Answer 18

Grid ratio

Question 19

Grid ratio formula

Answer 19

height/ distance

Question 20

Linear pattern of the lead lines of a grid

Answer 20

Grid pattern

Question 21

Two types of grid pattern

Answer 21

1. Linear
2. Cross or cross-hatched

Question 22

Orientation of the lead lines relative to one another

Answer 22

Grid Focus

Question 23

2 types of grid focus

Answer 23

1. Parallel
2. Focused

Question 24

Decrease in the number of transmitted photons that reach the IR because of some misalignment of the grid

Answer 24

Grid Cut-off

Question 25

Grid Cut-off Errors

Answer 25

1. Upside-Down Focused
2. Off-Level
3. Off-Center
4. Off-Focus

Question 26

Placing a focused grid upside down on the IR

Significant underexposure to the lateral edges of the IR

Answer 26

Upside-Down Focused

Question 27

Angling the x-ray tube across the grid lines or angling the grid itself during exposure

Decrease in radiation exposure to the IR

Answer 27

Off-Level