X-Ray Production and The X-Ray Beam Study Guide Flashcards

Comprehensive 50-card Q&A practice flashcard deck covering x-ray production, tube construction, circuit components, target interactions, exposure factors, and heat units based on Chapters 2 and 3.

What electrical charge does the cathode carry, and what is its primary function?

The cathode carries a negative charge ($-$) and serves as the source of electrons.

What electrical charge does the anode carry, and what is its primary function?

The anode carries a positive charge ($+$) and attracts and stops or decelerates electrons.

What is thermionic emission in the context of an x-ray tube?

Thermionic emission is the release of electrons from the heated filament.

What is the space charge in an x-ray tube?

The space charge is the cloud of electrons surrounding the filament.

What is the function of the focusing cup?

The negatively charged focusing cup keeps the electron stream focused toward the anode.

What is the atomic number and melting point of tungsten used in the anode target?

Tungsten has an atomic number of $74$ and a melting point of about $3400\,^\circ\text{C}$.

What are the rotation speeds for standard and high-speed rotating anodes?

A standard rotating anode operates at $3\text{,}000\,\text{RPM}$, and a high-speed rotating anode operates at $10\text{,}000\,\text{RPM}$.

What is the position and job of the stator in the x-ray tube assembly?

The stator stays outside the glass housing and creates the magnetic field that rotates the rotor.

What is the second step in the 7-step sequence of x-ray production?

Electrons are released from the heated filament by thermionic emission.

What occurs when high-voltage electrons strike the target on the anode?

The electrons suddenly slow down (decelerate), producing x-rays and heat.

What is the correct circuit flow sequence from the main breaker to the x-ray tube?

Main breaker $\rightarrow$ Exposure switch $\rightarrow$ Autotransformer $\rightarrow$ Timer $\rightarrow$ Step-up transformer $\rightarrow$ Rectification $\rightarrow$ mA selector/resistor $\rightarrow$ Step-down transformer $\rightarrow$ X-ray tube.

What is the main job of the autotransformer?

It selects $\text{kVp}$ and provides induced voltage to the primary of the high-tension transformer.

What does a step-up transformer do in the x-ray circuit?

It increases voltage for the high-voltage section.

What does a step-down transformer do in the filament circuit?

It decreases voltage in the filament circuit, causing current to increase.

What formula expresses the Transformer Law?

$\frac{V_s}{V_p} = \frac{N_s}{N_p}$.

What is the formula for electrical power?

$P = I \times V$.

What is rectification in the x-ray circuit?

Rectification is the process of converting alternating current ($\text{AC}$) to direct current ($\text{DC}$).

What is the function of a diode?

A diode permits current to flow in only one direction, from cathode to anode.

What is voltage ripple, and how much ripple do high-frequency generators produce?

Voltage ripple is voltage fluctuation; high-frequency generators reduce ripple to less than $1\%$.

What proportion of the x-ray beam consists of Bremsstrahlung interactions?

Approximately $85\%$ of the x-ray beam.

What occurs during a Bremsstrahlung target interaction?

An incident electron is decelerated or slowed down near the nucleus of a target atom.

If an incoming electron has $120\,\text{keV}$ of energy and exits with $40\,\text{keV}$, what is the energy of the resulting Bremsstrahlung photon?

$120\,\text{keV} - 40\,\text{keV} = 80\,\text{keV}$.

What proportion of the x-ray beam consists of Characteristic interactions?

Approximately $15\%$ of the x-ray beam.

What occurs during a Characteristic target interaction?

An inner-shell electron is removed from a target atom, and an electron from an outer shell fills the vacancy.

If a K-shell electron binding energy is $69.5\,\text{keV}$ and an L-shell binding energy is $12.1\,\text{keV}$, what is the characteristic photon energy?

$69.5\,\text{keV} - 12.1\,\text{keV} = 57.4\,\text{keV}$.

What does it mean that the x-ray beam is polyenergetic?

It means that the x-ray beam contains a range of photon energies.

What are the approximate lowest photon energies present in the x-ray emission spectrum?

Approximately $15\text{--}20\,\text{keV}$.

What sets the maximum limit for photon energy in the x-ray emission spectrum?

The highest photon energy cannot exceed the selected $\text{kVp}$.

What is x-ray quantity?

X-ray quantity refers to the total number of x-ray photons in the beam.

What is x-ray quality?

X-ray quality refers to the penetrating power or energy of the x-ray beam.

How does $\text{kVp}$ affect x-ray quality and penetrability?

Higher $\text{kVp}$ increases electron speed, producing a more penetrating beam with greater x-ray quality.

How is $\text{mA}$ related to x-ray quantity?

$\text{mA}$ measures tube current and is directly proportional to quantity; doubling $\text{mA}$ doubles photon quantity.

What is the formula to calculate total $\text{mAs}$?

$\text{mAs} = \text{mA} \times \text{time}$.

Calculate the total $\text{mAs}$ for an exposure of $400\,\text{mA}$ and $0.25\,\text{s}$.

$400\,\text{mA} \times 0.25\,\text{s} = 100\,\text{mAs}$.

What is the actual focal spot?

The actual focal spot is the area of the anode target exposed to tube-current electrons.

What is the effective focal spot?

The effective focal spot is the focal spot size as measured directly under the anode target.

How does a smaller anode angle affect effective focal spot size and spatial resolution?

A smaller anode angle produces a smaller effective focal spot, which results in better spatial resolution.

What is the anode heel effect?

The anode heel effect is the variation in x-ray intensity where intensity is greater on the cathode side and decreases toward the anode side.

How should thick anatomic parts be positioned under the x-ray tube due to the anode heel effect?

The thicker anatomic area should be placed under the cathode side for a more even exposure.

What is total filtration in an x-ray tube?

Total filtration is the sum of inherent filtration and added filtration.

What effect does filtration have on low-energy photons?

Filtration absorbs low-energy photons, which decreases patient exposure.

How does increasing filtration affect beam quality and beam quantity?

Increasing filtration increases beam quality (higher average energy) while decreasing x-ray quantity.

What is beam hardening?

Beam hardening is the removal of weak (low-energy) photons from the beam, leaving a beam with a greater percentage of higher-energy photons.

What is Half-Value Layer (HVL)?

HVL is the amount of added filtration (usually in $\text{mm}$ aluminum) that reduces x-ray beam intensity to one-half ($50\%$) of its original value.

What percentage of original beam intensity remains after passing through $1$ HVL, $2$ HVLs, and $3$ HVLs?

$1\,\text{HVL} = 50\%$, $2\,\text{HVLs} = 25\%$, and $3\,\text{HVLs} = 12.5\%$.

What is the formula for calculating Heat Units (HU)?

$\text{HU} = \text{mA} \times \text{time} \times \text{kVp} \times \text{generator factor}$.

Calculate the Heat Units produced by $600\,\text{mA}$, $0.05\,\text{s}$, $75\,\text{kVp}$, and a generator factor of $1.35$.

$600 \times 0.05 \times 75 \times 1.35 = 3\text{,}037.5\,\text{HU}$.

What role do resistors play in the x-ray circuit?

Resistors regulate current/amperage and help maintain filament stability.

What is mutual induction in an x-ray transformer?

Mutual induction occurs when current flowing in primary coils creates current and voltage in secondary coils.

Name three operational methods to extend x-ray tube life.

Warm up the tube if applicable, avoid excessive heat generation, do not hold the rotor button without making an exposure, use lower $\text{mA}$ with longer exposure time, do not move the tube while energized, and report unusual noises.