Image Quality

Question 1

What are the 3 constituent part of image quality/

Answer 1

Contrast

Resolution

Noise

Question 2

What things affect the contrast of an x-ray image?

Answer 2

Physical characteristics

• thickness
• density
• composition/ atomic number

Technique Factors

• beam quality
• beam quantity

Question 3

What are ‘characteristic curves’ in radiology?

Answer 3

The response of a given receptor/ detecter to different levels of exposure.

Question 4

What is Quantum mottle?

Answer 4

The random fluctuations in the number of photons that hit any specific area

Question 5

What technique factors decrease noise?

Answer 5

increasing mAs
increasing kVp
Increasing absorption efficiency
image/ frame averaging in flouroscopy

Question 6

What is the ‘focal spot size’ in radiology?

Answer 6

the size of the anode area that releases x-rays for the image

Question 7

What effect does a larger focal spot size have on image quality?

Answer 7

increases blurring

Question 8

What is the name for increase blurring from an increased focal spot size?

Answer 8

penumbra

OR

Edge gradient

Question 9

How does a larger focal spot size cause blurring?

Answer 9

x-rays from different edges of the focal spot will/ will not hit the edge of objects from different angles and will/ will not make it through to the receptor at certain angles

Question 10

Sources of Blur in X-ray generation?

Answer 10

finite focal spot

patient motion

shape of absorber (e.g. penumbra/ absorption blur)

in CR: scattering of laser light

in DR: aperture of detector element
geometric blurr

Question 11

What is SID in radiology?

Answer 11

source to image distance

Question 12

What are the positives/ negatives of changing Source to Image Distance?

Answer 12

Increasing SID with meant that items that are further will be less distorted but more radiation/ mAs is required

Question 13

What is OID in radiology?

Answer 13

Object to image distance

Question 14

What is ‘Source to Image Distance’?

Answer 14

The distance between the x-ray source and the image receptor

Question 15

What is ‘Object to Image Distance’?

Answer 15

the distance between an object and the image receptor

Question 16

What are the positives/ negatives of changing object to Image Distance?

Answer 16

Decreasing OID decreases distortion/ blurring (the bit closer to the source isn’t as magnified, and there’s less of a penumbra).

Question 17

What should you do with SID and OID to reduce blurring

Answer 17

maximise SID

minimise OID

Question 18

What are the ways to measure blur/ spatial resolution (mathematical concepts)

Answer 18

point spread function
line spread function
edge spread function
Modulation Transfer function

Question 19

PSF acronym in radiology

Answer 19

Point Spread Function

Question 20

LSF acronym in radiology

Answer 20

Line Spread Function

Question 21

ESF acronym in radiology

Answer 21

Edge spread function

Question 22

MTF acronym in radiology

Answer 22

Modulation Transfer Function

Question 23

What is Point Spread function

Answer 23

describes the lateral spread of information coming out of a single point. How blurred a point is

Question 24

What is Line Spread function

Answer 24

describes the lateral spread of information coming out of a single line. How blurred a line is

Question 25

What is Edge Spread function

Answer 25

How blurred a clearly define line appears on x-ray

Question 26

What is Modulation Transfer Function

Answer 26

Fourier transformation of the line spread function.