HomeStretch CRACK Physics X-Ray Production

Question 1

Equation for maximum number of electrons a shell can hold

Answer 1

2n²

Question 2

for an EM wave, if you increase frequency what happens to wavelength?

Answer 2

high frequency = short wavelength (i.e. smaller)

Question 3

How much energy does it take to remove an electron from an atom?

Answer 3

15 eV = ionizing

Question 4

What are rays that originate from the nuclei of an atom called?

How about those that originate interactions between fast-moving electrons and atoms?

Answer 4

Gamma rays

X-rays

Question 5

alpha particles are what?

Answer 5

same as a helium nucleus (2 protons and 2 neutrons)

Question 6

what is a beta particle?

Answer 6

electron emitted from the nucleus

Question 7

Isotopes

Answer 7

same number of protons “Z” but a different number of neutrons and therefore different atomic mass “A”.

Question 8

Whats the purpose of the envelope?

Answer 8

maintain a vacuum

Question 9

electrons in from the filament are created on the cathode or anode side?

Answer 9

cathode is the place in the device where the elecrtons enter

Question 10

What is mA?

Answer 10

milliampere - unit of measurement to describe current

QUANTITY of electrons moving from the cathode to anode

Question 11

Focal spot sizes for :

Mammo

General X-rays

Answer 11

• Mammo = 0.1 mm and 0.3 mm
• General X-rays = 0.6 mm and 1.2 mm

Question 12

how to keep your actual focal spot and narrow you effective focal spon - small angle = _______ effective focal spot.

What about the cut-offs for this?

Answer 12

small angle = small effective focal spot (and better spatial resolution)

cut-offs = steeper (smaller) angle = greater Heel effect

also if the target angle is made too small the x-ray beam might not be large enough to expose a standard image receptor.

Question 13

Heel effect - the strongest x-rays are on what side?

how is it set up in mammo?

how about CXR and AP thoracic spine x-ray?

and how about in general?

Answer 13

Heel effect the CATHODE side has the stronger x-rays and therefore CHEST onto CATHODE side. (Chest wall Closer to Cathode)

CXR/Tspine = orientation is vertical with Cathode Down

In general = “thicker” tissue = cathode

Question 14

increasing focus to film distance (FFD) does what to the Heel effect?

Answer 14

Larger FFD = decreased Heel effect

Question 15

Smaller film does what to Heel effect?

Question 16

Heel effect worsens (increases) with?

Answer 16

Smaller anode angle

smaller FFD

larger film size (FOV)

Question 17

Heel effect improves (decreases) with?

Answer 17

Larger anode angle

Increased FFD

smaller film size (FOV)

Question 18

Filter vocab

Inherent filter

Added filter

Total Filtration

Minimum filtration of aluminum required for an x-ray tube operative over 70kVp?

Answer 18

Inherent = normal components of the tube that block soft xrays

Added = any piece of metal added

Total = inherent + added

2.5 mm of aluminum

Question 19

What does the focusing cup do?

Answer 19

reduces spatial spreading

Question 20

What are the three kinds of interactions at the anode?

Answer 20

Excitation (heat) = wiggling but not moving

radiative lauses (bremsstrahlung) = general xays (80% of the x-rays produced)

ionization = characteristic x-rays

Question 21

is keV the same thing as kVp?

Question 22

highest energy x-ray in the tube depends on what? what about the lowest energy x-ray?

Answer 22

kVp

filtration

Question 23

higher Z does what to “braking”

Answer 23

increases it! (proportionally) . . .

b emitters like Yttrium? block it with low z like plastic. .

Question 24

What is the K-Shell binding energy of the republic of Tungston?

how much energy to get some characteristic x-rays from Tungston?

Answer 24

69.5 keV

need more than that. . . ie 69 keV wouldn’t get you any

Question 25

kVp and characteristic x-ray production from tungsten

below 69.5 kVp

between 80-150

between 150 and 300

above 300 kVp

Answer 25

• below 69.5 kVp = 0
• between 80-150 = 10-25 % K-shell characteristic contribution
• between 150 and 300 = progressive decrease in contribution
• above 300 kVp = negligible contribution

Question 26

What is “beam intensity”? What are the units?

Answer 26

number of x-rays multiplied by the energy

Roentgens / min (R/min)

-this is not the same as the “total number of xrays”

Question 27

High Yield Recap of Bremmies

Answer 27

Most (80%) of the x-rays produced

bombarding electron interacts with the entire atom

radiation release due to diversion/slowing down

radiation released spans a large range of energies

x-ray energy depends on tube voltage.

Question 28

High Yield recap of characteristic radiation

Answer 28

only small % of x-rays produced (10-25% at 80-150kVp)

bombarding e- interact with inner shell e-

radiation released due to higher shell e- moving down into a lower state

radiation released is a specific energy

x-ray energy depends on element of target atom (not tube voltage).

Question 29

Quality versus quantity

Answer 29

quality = overall average energy of the beam / ability to penetrate an object

quantity = total number of x-rays under the curve in a spectrum diagram

Question 30

How does target material (Z) influence quantity and quality?

Answer 30

Large Z = more overall X-rays via Brem = change in quantity

Large Z = different characteristic energy peaks = change in quality

Question 31

How does kVp influence quantity and quality?

Answer 31

max x-ray energy will go up to match the kVp and the average x-ray energy will go up = change in quality

total number of x-rays will go up (more energy was available in those Bremmy x-rays) = change in quantity (beam intensity will increase as a square of kVp)

Question 32

equation:

Beam intensity =

Answer 32

proportional to (kVp)²

Question 33

How does mAs influence quantity and quality?

Answer 33

changes in mAs change quantity but not quality

Question 34

What is the 15% rule?!

Answer 34

if you increase kVp by 15% and decrease the mA by 1/2 you will maintain the same x-ray density on the radiograph.

Question 35

effect of single and triple phase generators on quantity and quality?

Answer 35

Single phase = more ripple = less quality and less quantity

Triple phase = the opposite

Question 36

what is half-value layer?

what is 10th HVL?

Answer 36

The ammount of material requeired to attenuate an x-ray to 1/2 the original output.

10 HVL = thickness of material that can attenuate an x-ray to 90%

Question 37

More filtration = less/more HVL

Answer 37

higher HVL

Question 38

What does filtration do to quantity and quality?

Answer 38

increased filtration = decreased quantity and INCREASED QUALITY

Question 39

the average Brems energy is equal to what percent of the kVp selected?

Answer 39

1/3

Question 40

recap

increasing the kV increases what?

Answer 40

increases max energy, average energy (quality) and increases quantity

Question 41

recap

increasing the ma does what?

Answer 41

increases quantity of x-rays

no change in characteristic energy, average energy (quality) or max energy

Question 42

recap spectrum diagrams

adding filtration does what?

Answer 42

increases the average energy of e- (quality)

decreases total quantity of electrons

Question 43

recap spectrum diagrams

rectifying the current does what?

Answer 43

increases average energy and total quality of xrays

no change in max energy

Question 44

recap spectrum diagrams

increased atomic number (Z) of the target

Answer 44

increased total quantity of x-rays

change in characteristic energy peaks (which will be higher with a higher Z)