Prime Factors (Ch 12)

Question 1

What are the three principle factors that affect x-ray quality and quantity?

Answer 1

1. Milliamperage per second (mAs)
2. kilovoltage (kVp)
3. Distance.

Question 2

The three principle factors are under the __________ ____________ of the radiographer.

Answer 2

Direct control

Question 3

What is “quantity” the measure of?

Answer 3

Measure of the number of x-ray photons of the useful beam. A.k.a. the output, intensity, or exposure.

Question 4

What is the unit of measure for quantity?

Answer 4

Roentgen (R)

Question 5

What is the prime controller of quantity?

Answer 5

mAs

Question 6

Quantity is also affected by _______, _________, & _____________.

Answer 6

kVp, distance and filtration

Question 7

What does quality measure?

Answer 7

Measure of the penetrating ability of the x-ray beam or distance it travels in matter.

Question 8

Quality is numerically represented by ________________.

Answer 8

Half value layer (HVL)

Question 9

The greater the HVL the _____________ the quality.

Answer 9

Greater

Question 10

What is the prime controller of quality?

Answer 10

kVp

Question 11

Quality is also directly affected by _____________.

Answer 11

Filtration

Question 12

Milliamperage (mAs) per second is the measure of x-ray tube ______________.

Answer 12

Current

Question 13

mA and time are both ________ proportional with the number of electrons crossing tube.

Answer 13

Directly

Question 14

As mA increases, so does the number of _____________.

Answer 14

Electrons

Question 15

As time increases so does the ___________.

Answer 15

Number of electrons

Question 16

Exposure index (EI)

Answer 16

Numeric exposure value of IR exposure assessed

Question 17

True or false

exposure index does not indicate patient dose

Answer 17

True

Question 18

True or false

Index range and values vary from vendor to vendor

Answer 18

True

Question 19

What is the prime controller of image receptor exposure?

Answer 19

mAs

Question 20

As long as mAs is constant, any combo of _____ and ______ will create the same exposure.

Answer 20

mA & time

Question 21

Increasing kVp will cause an _____________ in the speed and ___________ of electrons applied across the tube.

Answer 21

Increase and energy

Question 22

What is the 15% rule?

Answer 22

15% increase in kVp is equal to double the number of photons
15% decrease in kVp is equal to half the number of photons

Question 23

Doubling the kVp

Answer 23

The number of photons increase about four times

Question 24

Doubling the kVp

Answer 24

The number of photons increase about four times

Question 25

As kVp increases, so does the energy of each ___________.

Answer 25

Electron (quality)

Question 26

Greater photon energy=

Answer 26

More penetrability

Question 27

kVp affects both _____________ and _______________ of the x-ray beam

Answer 27

Quality, quantity

Question 28

An increase in kVp causes a(n) ____________ in penetrability and a ____________ in image contrast.

Answer 28

Increase, decrease

Question 29

Define contrast (IR)

Answer 29

Visibility of detail or differences between an IR exposure level; it is a characteristic of image quality

Question 30

Define Contrast

Answer 30

The ability to distinguish the differences in adjacent tissues or structures

Question 31

A primary beam with __________________ kV results in overall ___________ in penetration through all tissues, therefore resulting in a _____________ contrast radiograph or ___________ scale of contrast

Answer 31

Greater, rise, lower, longer

Question 32

High kVp= __________ contrast= __________ scale

Answer 32

Low, long

Question 33

Low kVp= _____________ contrast= __________ scale

Answer 33

High, short

Question 34

True or false

kVp should be used to control IR exposure

Answer 34

False. kVp is usually preset by vendor to yield optimal contrast

Question 35

At lower kVp, ___________ radiation is absorbed by the patient

Answer 35

More

Question 36

In general, higher kVp and ____________ mAs will reduce patient dose, but at the expense of contrast

Answer 36

Lower

Question 37

Inverse square law

Answer 37

Doubling of distance increases the area four times which decreasing the intensity by 1/4

Quantity remains unchanged; but distribution decreases within a given area (involves distance)

Question 38

Increasing distance causes a ______________ of exposure

Answer 38

Decrease

Question 39

Why do we use the direct square law?

Answer 39

To compensate for IR exposure changes when distance changes must be made

Question 40

Direct square law

Answer 40