132 Unit 6

Image quality

The visibility and the accuracy of the anatomic structures

Sharpness

Spatial resolution

Distortion

Visibility

Brightness

Contrast

Brightness

The visibility factor of image quality

The amount of luminance

Monitor Quality

With digital imaging, how will brightness appear if the image was slightly over-exposed

The image will have appropriate brightness after processing

Why is EI important

True representation of the receptor exposure

Quantum noise is a result of

Too few x-ray photons reaching the IR

Quantum noise is also known as

Quantum Mottle

Quantum mottle appears as a

Blotchy or grainy appearance

What is the best method for reducing quantum mottle on a radiographic image?

Increasing the mAs of an x-ray beam

Noise is another word for

Quantum noise

Saturation is

Over exposure

Oversaturation is

8-10 times the exposure needed

What type of relationship exists between mAs and receptor exposure

Directly proportional

What formula is used to calculate mAs

mA X s = mAs

Convert milliseconds to seconds

move the decimal point 3 to the left

mAs can be doubled or halved by

Doubling or halving mA or time

Maintain mAs

Double mA and Halving time

Halve mA and Double time

Reciprocity Law

We can change the mA and change the exposure time by the same amount and still have the same mAs

Rule of thumb for mAs

Double or halving doubles or halves receptor exposure

Any kVp change is in

15% percent intervals

a 15% increase in kVp effect on receptor exposure

doubles

If you wanted to maintain receptor exposure and you increase kVp by 15%, how would the mAs need to be adjusted?

Halve mAs

IF you use 6 mAs with 50kVp and then change to 50 kVp what mAs will you need to maintain the original exposure

3

Generator output & technique/ receptor exposure

Decrease mAs by half

Increasing generator

decrease mAs by half

focal spot and receptor exposuer

Anodes with larger angles will

contribute to anode heel effect

decrease collimation and larger SIS

larger anode heel effect

What SID would produce the highest receptor exposure

40

Double SID

¼ of receptor exposure

Direct exposure formula

Exposure maintenance formula

Exposure maintenance formula

mAs1/ mAs2= (SID1)2/(SID2)2

Which of the following would result in the least amount of receptor exposure

4in OID

Which of the following filtration amounts would result in the least receptor exposure

3mm AL

Which of the following field sizes would result in the least receptor exposure

8×10

Beam Restriction Technique Adjustment

-Large anatomic structure/ body parts

-High kVp

-Low efficency/ no grid

Increased patient thickness will cause receptor exposure to

decrease

Which of the following field sizes would result in the most receptor exposure

14 × 17

Which will result in the least amount of receptor exposure

16 cm patient thickness

Using barium would result in

Decreased receptor exposure

Emphysema would result in

Increased receptor exposure

Casting material would result in

Decreased receptor exposure due to increased thickness

Grids remove

Scatter, and low energy photons

When we add a grid we need to

Increase our mAs

Going from CR (Computed Radiography) to DR (Digital Radiography)

Half the mAs

Image contrast is the

difference between adjacent IR exposure levels.

Subtle differences between the shades of grey next to eachother

Low contrast

Less discernable shades of grey

High contrast

Range/ scale of the shades or colors that we see on an image

Grayscale

High contrast has a

Short grey scale

Long grayscale has a

Low contrast

Radiographic/ image contrast

Allows visibility of anatomic structures

A radiograph that has brightness levels very similar to each other

Has low contrast and has a long grayscale

The proper ____ is important for the desired ____ through the patient for a given examination. This causes signal differences to the digital detector

kVp, Differential attenuation

Subject contrast is the

range of differences in the intensity of the x-ray beam after it has been attenuated by the subject.

Subject contrast is effected by

kVp, The amount, and type of irradiated material

Subject contrast is the

Remnant beam intensity

When there are significant tissue variations

There will be high subject contrast

the greater difference between the absorption of the tissue

The greater the contrast

A abdomen with similar tissue makes up will have

Low subject contrast

Barium in an abdomen x-ray will ____ subject contrast

Increase

Increased patient thickness will

Decrease subject contrast, and less differential absorption

Different ____ Will also effect subject contrast

pathologies

A high contrast image is with a _____ kVp

Low

A low contrast image is taken with a _____ kVp

High

High contrast images have

Less transmission and more differential absorption

Low contrast images have

More transmission and less differential absorption

What does an increased kVp have on scatter production

Increased kVp results in more scatter