Physics of Diagnostic Radiology Week 3

What is contained in a nucleon?

Protons and Neutrons

What is the term for The amount of energy required to remove an electron from an atom, molecule, or ion?

Electron binding energy

Which electron shell has the highest binding energy?

K-Shells

Which electron shell is closest to the nucleus?

K-Shell

T or F: kVe decreases as you get closer to the nucleus

False (decreases as you get further away)

What part of the x-ray produces electrons?

Cathode

What are the two types of x-rays produced?

Characteristic (15%)

Bremsstahlung (85%)

What type of x-rays are ionizing?

Characteristic

What is the term for an x-ray created when a projectile electron is slowed by the electric field of a target atom nucleus and then changes direction?

Bremsstrahlung x-ray

T or F: Bremsstrahlung x-rays produce a discreet spectrum of energy

False (continuous)

What is the term for. an x-ray created when an inner electron of the target atom is ejected, and an outer one drops down to stabilize the atom?

Characteristic x-ray

What energy is required to ionize tungsten?

69 kV

T or F: Characteristic x-rays produce a discreet spectrum of energy

True

What is the best element for imaging human tissue?

Tungsten (because of the characteristic energy, not the bremsstrahlung)

T or F: "Characteristic" is named so because energy emitted is dependent on anode material, and not on the tube voltage

True

What is the term for Flow of charged particles moving through a conductor or space?

Electric current

What wave form is used by x-rays?

Sine wave

What is the term for the Distance from one crest to another?

Wavelength

What is the term for One half the range from crest to valley?

Amplitude

What is the term for the Number of wavelengths that pass a point of observation per second?

Frequency

What type of current is used by general outlets?

Alternating current

What type of current has electric charge moving in one direction?

Direct current

What is the term for the Process of converting alternating current to direct current?

Rectification

What is required to ensure that the electrons flow from the cathode to the anode only?

Direct current

What type of current has a constant flow of electric charge?

DC

T or F: X-ray machines use both AC and DC current

False (only DC)

What is the term for when Inverse voltage is removed from the supply to the x-ray tube by rectification?

Half-wave rectification

T or F: Half-wave rectification wastes half the supply of power and has longer exposure time

True

What is the term for rectifying an entire wave form?

Full-wave rectification

What are the 3 types of X-ray generators?

Single phase

Three phase

High frequency

What are the types of single phase generators?

½ wave rectified

Full wave rectified

What are the types of three phase generators?

Six pulse

Twelve pulse

Which generator produces almost constant potential voltage?

High frequency

What is the term for variation in voltage?

Voltage ripple

T or F: Less voltage ripple increases radiation quantity and quality

True

What is the term for the fact that anodes have two focus spots (the x-ray source)?

Line focus principle

What size are small focal spots?

0.6 mm

What size are large focal spots?

1.2 mm

T or F: By angling the anode disc, a larger focal spot is created, but a smaller effective focal spot

True

What effect does a smaller anode angle have?

smaller effective focal spot

What ar the effects of a small disc angle?

More heat

More detail

What ar the effects of a large disc angle?

Less heat

Less detail

What is small disc angle used with?

Used with small filament

Used with small body part imaging

What is large disc angle used with?

Used with large filaments

Used with large body part imaging

T or F: you should match the cathode side with thicker anatomy and the anode side with thinner anatomy

True

Why should the anode be cephalic for upright imaging?

The upper anatomy is thinner (more air density)

What is the term for Radiation intensity on the cathode side being greater than on the anode side?

Anode heel effect

What is the term for reduction in energy as an electron or photon passes through matter?

Attenuation

What factors affect the anode heel effect?

Anode disc angle

Tube distance

Field of view

T or F: Smaller disc angles have less heel effect

False (more heel effect)

T or F: Shorter tube distances have more heel effect

True

What is the AKA of the penumbra effect?

Edge effect

What does the penumbra effect cause?

geometric unsharpness

T or F: Wider penumbra = less sharp image periphery

True

What influences the penumbra effect?

Focal spot size

Tube distance

Object-receptor distance

T or F: A more distance x-ray source has a smaller penumbra size

True

T or F: A smaller disc angle will have less penumbra and more detail

True

What are the two factors for x-rays?

kVp and mAs

Which chart is better to use, fixed kVp or variable kVp?

Fixed

What factor determines X-ray quality?

kVp

What is the term for the penetrating power of the x-rays?

kVp

What factor is inversely related to kVp?

contrast of the beam

What is kVp determined by?

the sequence of structures the x-rays must pass through

T or F: the optimum kVp for a certain view changes depending on the size of the patient

False (will not change from patient to patient)

What results from a high contrast image?

Stark whites and blacks

Short gray scale

Low kVp

What results from a low contrast image?

Why would you choose a low kVp?

good contrast

Why would you choose a high kVp?

Low patient dose

What is most spinal kVp taken at?

~80

What states that Small changes in kVp result in large changes of Contrast and density?

15% rule (kVp)

T or F: High kVp = lower contrast

True

What is the term for X-ray quantity?

Milliamperage time (MAS)

What determines what MAS you use for an x-ray?

the thickness of the part being x-rayed

What is directly related to the MAS of the x-ray?

optical density (OD)

T or F: MAS changes depending on the thickness of a patient

True

Why should you always choose the highest mA for the lowest time?

reduce motion artifacts

What is the degree of blackening of an x-ray?

Optical density

What primarily influences OD?

mAs

What should you do if a film is too light (under-exposed)?

Double mAs

What should you do if a film is too dark (over-exposed)?

Halve mAs

What % change of mAs is required to obtain a visible difference in OD?

30%

T or F: on the tube rating chart, for any given mA, any combination of kVp and time that lies above the mA curve is safe

False (below the curve)

What is the AKA of the tube rating chart?

radiographic rating chart

What does the anode cooling chart determine?

The maximum heat capacity of the anode

The time required for complete cooling after any level of what input

What type of vapor is produced by heat damage to the anode?

Tungsten vapor

What does tungsten vapor coat in the x-ray machine?

Glass envelope

What is the most common cause of tube failure?

tungsten vapor coating the glass envelope

How can you avoid heat damage to the anode?

Warm up tube if anode is cold

What will change both the quantity and quality of x-rays?

Voltage (kVp)

What will cause a decrease in quantity and increase in quality of x-ray?

Added filtration

What will decrease quantity and quality of x-rays?

Voltage ripple