Mock Registry Review #2

A comprehensive set of vocabulary flashcards based on the Mock Registry Review lecture covering tube construction, x-ray production, image intensification, radiation biology, and digital imaging.

When is the anode heel effect more pronounced (IR size, SID, collimation)?

Shorter IR size, greater SID, open collimation.

What material is typically used for the focusing cup?

Nickel (sometimes molybdenum).

How can you avoid being space-charge limited?

Operate the machine at $40kVp$ or higher.

What is the approximate speed of anode rotation?

$3000$ or $10000 \\text{ rpms}$.

What are common tube target materials?

Tungsten, molybdenum, rhenium, and graphite.

What components of the EM spectrum were mentioned in the lecture?

X-rays, gamma rays, visible light, UV light, and radiowaves.

What are the components of the cathode?

Filament, focusing cup, and associated wiring.

What are the primary functions of the cathode?

1. Produces thermionic cloud. 2. Conducts high voltage between cathode and anode. 3. Focuses electron stream.

What is the typical material for the filament?

Thoriated tungsten (rhenium and molybdenum are also suitable).

What is the relationship between filament wire dimensions and resistance?

A thinner and longer filament wire has greater resistance.

What is the effect of increased kVp on electrons?

Electrons become more penetrating (quality) and more interactions occur at the target (quantity).

What term is associated with intensity?

Quantity.

What is thermionic emission?

The process of electrons boiling off the tube filament.

What factors focus the electrons in the tube?

Low negative potential and the geometry of the focusing cup.

What are the primary functions of the anode?

1. Serves as a target surface and source of x-ray photons. 2. Conducts high voltage back into the generator. 3. Serves as the primary thermal conductor.

What are the reasons for using tungsten rhenium alloy?

High atomic number ($74$), high melting point, and heat-conducting ability.

What is x-ray quality?

The measurement of the penetrating ability of the x-ray beam.

What factors affect x-ray quality?

$\\text{kVp}$ and filtration (direct relationship).

What is x-ray quantity?

A measure of the number of x-ray photons in the useful beam.

What factors affect x-ray quantity?

$\\text{mAs}$, $\\text{kVp}$, distance, and filtration.

What is the kinetic energy conversion in x-ray production?

Over $99.8\\%$ of the kinetic energy of incident electrons is converted to heat (thermal energy).

What interactions are associated with an 'incident electron'?

1. Bremsstrahlung. 2. Characteristic.

What interactions are associated with an 'incident x-ray photon'?

1. Photoelectric absorption. 2. Compton scatter.

How likely are Compton interactions to occur in bone versus soft tissue?

They are just as likely to occur in bone as they are in soft tissue.

What is a Bremsstrahlung interaction?

An electron approaches a positive nuclear charge, changes direction (deflected), and loses energy.

How predictable is the energy of Bremsstrahlung?

Unpredictable.

What is the effect of increasing kVp on characteristic kEv?

Increasing $\\text{kVp}$ does not affect the $\\text{keV}$ of the characteristic interaction.

What is the result of increasing kVp from 70 to 80 on characteristic quality?

There is no effect; increasing $\\text{kVp}$ does not change the quality/energy of the characteristic beam.

What is the result of increasing kVp from 60 to 68 on Bremsstrahlung?

Increased quantity of brems photons.

What is the number one cause of tube failure?

Vaporized tungsten.

What is the benefit of metal envelopes in x-ray tubes?

They help extend tube life by eliminating tungsten vaporization.

What is the effect of excessive heat to rotor bearings?

Increase in friction and loss of anode rotation, leading to large pitting in one area.

What is the criteria for the least hazardous anode setting?

The setting with the lowest $HU$ (Heat Units) and largest focal spot.

What is the relationship between effective and actual focal spot size?

The effective (projected) focal spot is always smaller than the actual focal spot.

Where is the smallest effective focal spot located?

Smallest at the anode end of the tube, resulting in less blur and greatest spatial resolution.

What factors are affected by the anode angle?

Severity of heel effect, focused focal spot size, and heat loading capacity.

What does a decreased anode angle mean?

It refers to a steep or smaller angle.

What are the characteristics of off-focus radiation?

Occurs with photons not produced at the focal spot; also known as extrafocal or stem radiation; reduced by restricting the beam close to the source.

What is a method to reduce off-focus radiation?

Mount a pair of shutters (upper shutters) as close to the source as possible.

What do PSP plates and intensifying screens use?

$PSP$ plates do not use an intensifying screen.

What is the layer sequence of a PSP plate?

1. Protective layer

2. 2. Phosphor layer

3. 3. Conductor layer

4. 4. Support layer

5. 5. Light shield layer

6. 6. Backing layer

Which PSP layer records the radiographic image?

Phosphor layer.

What are PSP/IP front materials?

Magnesium, carbon fiber, or bakelite.

What are the major components of a CR reader?

Laser source, $IP$ transport mechanism & light channeling guide, photodetector & $ADC$, and f-theta lens.

What image changes occur from a larger input phosphor to the output phosphor?

Images are minified, inverted, and show an increase in brightness.

What is the effect of using a smaller input phosphor diameter?

The output screen image is magnified.

What is the effect of magnification on patient exposure?

Results in an increase in $\\text{mA}$, leading to greater patient exposure.

What is the relationship between FOV and spatial resolution?

As $FOV$ decreases, spatial resolution increases (and vice versa).

What is the requirement for magnification mode in fluoroscopy?

Use of smaller input phosphors.

What factors improve spatial resolution in II fluoroscopy?

Smaller diameter input phosphor, thin layer of cesium iodide, and use of magnification mode.

What is Automatic Exposure Rate Control (AERC)?

Compensates for changes in patient thickness, tissue attenuation, beam restriction, $OID$, and $FOV$ during flat-panel fluoro.

How much does digital fluoroscopy reduce patient dose?

Reduces patient dose by approximately $50\\%$.

What is the function of Automatic Brightness Control (ABC)?

Used to adjust $\\text{kV}$ and $\\text{mA}$.

What are the weaknesses of an Image Intensifier (II)?

Vignetting, pincushioning, blooming, and peripheral falloff.

How does CMOS compare to CCDs?

$CMOS$ is less expensive, much faster, but has poorer image quality than $CCDs$.

What is the formula for Total Brightness Gain?

$\\text{Minification Gain} \\times \\text{Flux Gain} = \\text{Total Brightness Gain}$.

What is interrogation time?

The time it takes for the tube to reach the required technical factors.

What is extinction time?

The time it takes for the x-ray tube to turn off.

What are the methods to achieve magnification fluoroscopy?

Select smaller diameter input phosphor, increase voltage to electrostatic lenses, or move $II$ focal point further from output phosphor.

What is the Inverse Square Law formula?

$\\frac{I\\_1}{I\\_2} = \\frac{(d\\_2)^2}{(d\\_1)^2}$.

What is Ohm's Law formula?

$V = I \\times R$.

What is the electromagnetic wave equation?

$c = f \\lambda$.

What is the transformer law formula?

$\\frac{V\\_s}{V\\_p} = \\frac{N\\_s}{N\\_p}$.

What is an alternative name for Compton scatter?

Modified scatter.

What is the Compton scatter effect?

A high-energy x-ray photon ejects or removes a loosely bound outer-shell electron.

What is the most common interaction in the human body?

Compton.

What is the photoelectric effect?

A relatively low energy photon uses all of its energy to eject/remove an inner shell electron.

What interaction contributes most to patient exposure?

Photoelectric absorption.

What is effective dose?

Equivalent whole-body dose.

What is the LET classification of diagnostic x-rays?

Relatively low energy and low $LET$.

What is the approximate LET of x-rays?

$3 \\text{ keV/\\mu m}$.

What is the acronym for cell radiosensitivity?

Little Stevie Eagerly Insists Everyone Oughta Store Female Mutants Near Cages.

What is the radiosensitivity rank from highest to lowest?

1. Hyperoxia, 2. Aerobic, 3. Hypoxic, 4. Anoxic.

What is the deterministic effects dose relationship?

Exhibit an increase in severity with an increase in dose.

What is the dose response relationship for deterministic effects?

Nonlinear, threshold.

What are somatic effects?

Effects of radiation on the body being irradiated.

What are genetic effects?

Effects upon future generations due to irradiation of germ cells in previous generations.

What is the dose response relationship for cataracts?

Nonlinear, threshold.

What are teratogenic effects?

Radiation exposure to a developing embryo/fetus after conception.

What are mutagenic effects?

Radiation exposure to human gametes prior to conception.

What is the pregnancy period for spontaneous abortion?

$0-2$ weeks ($0-9$ days); also called preimplantation.

What is the pregnancy period for induction of congenital abnormalities?

$2-8$ weeks.

What is the effect of 100 mGy exposure at 2-5 weeks of pregnancy?

Skeletal defects.

What is the pregnancy period for neurological deformities?

$6-8$ weeks.

What is the SID compensation for OID?

For every 1\\text{\"} of $OID$, you must use 7\\text{\"} of $SID$ to compensate.

What is the relationship between pixel size/pitch and spatial resolution?

Smaller pixel size/pitch means greater spatial resolution.

How does spatial resolution compare between analog and digital?

Analog film is superior in spatial resolution.

What is spatial resolution in direct digital systems?

Fixed and inversely related to the $TFT$ $DEL$ size.

What is the function of the TFT in a DEL?

Acts as the switch/gate to release charges for readout.

What is the effect of higher sampling frequency on spatial resolution?

Increases the spatial resolution.

What is the relationship between pixel size and resolution?

As pixel size decreases, resolution increases (and vice versa).

What is the independence of FOV and matrix size?

$FOV$ and matrix size are independent of one another.

What is a desirable Signal-to-Noise Ratio (SNR)?

High $SNR$ (meaning mAs is greater than the noise).

What is DQE (Detective Quantum Efficiency) / Speed Class?

The percentage of incoming x-ray photons that are detected and absorbed by the receptor.

What are the effects of increasing DQE/speed class?

The likelihood of noise increases while patient exposure decreases.

What is the Grid Conversion Factor (GCF) formula?

$\\frac{\\text{mAs}\\_1}{\\text{mAs}\\_2} = \\frac{\\text{GCF}\\_1}{\\text{GCF}\\_2}$.

What is the ARRT definition of dynamic range?

The range of exposures that may be captured by a detector.

What factors cause noise on a receptor?

Insufficient signal strength, excessive scatter, and excessive fog.

What are the components of the ARRT Standard of Ethics?

1. Code of Ethics (aspirational), 2. Rules of Ethics (mandatory and enforced).

What is the sequence for putting on PPE?

1. Gown, 2. Surgical mask/respirator, 3. Goggles/face shield, 4. Gloves.