Radiographic Imaging – Chapter 7

Question-and-Answer style flashcards covering key principles, equipment, exposure factors, digital imaging technologies, image quality parameters, and fluoroscopy from Chapter 7 Radiographic Imaging lecture notes.

In what year were X-rays discovered?

1895

Which part of the X-ray tube provides the source of electrons?

The tungsten filament on the cathode side

Name the four fundamental requirements for X-ray production.

1) Vacuum X-ray tube, 2) Source of electrons (filament), 3) High voltage to accelerate electrons, 4) Target to stop electrons and convert energy

What process releases electrons from the filament when current is applied?

Thermionic emission

What material is most commonly used for the X-ray tube target and why?

Tungsten, because of its high atomic number and high melting point

Which tube component focuses the electron cloud toward the anode?

The focusing cup on the cathode

What are the two classes of radiation that leave the patient and reach the image receptor?

Remnant radiation and scatter radiation

Define attenuation in radiography.

Loss of X-ray beam energy as it passes through an absorbing material

High-attenuation materials are called .

Radiopaque

Low-attenuation materials are called .

Radiolucent

List the three prime technical exposure factors.

mAs, kVp, and Source-to-Image Distance (SID)

What does mAs directly control?

Quantity of X-ray photons reaching the image receptor (IR exposure)

State the mAs reciprocity law.

Any combination of mA and time that yields the same mAs produces the same IR exposure

What does kVp primarily control?

X-ray beam penetration (beam quality) and affects image contrast and signal value

Write the inverse square law equation.

I₁ / I₂ = (D₂²) / (D₁²)

What formula is used to maintain exposure when SID changes?

mAs₁ / mAs₂ = (D₁²) / (D₂²)

Which two main digital image receptor systems exist?

Computed Radiography (CR) and Digital Radiography (DR)

What phosphor material is used in CR imaging plates?

Barium fluorohalide with europium (BaFBr:Eu)

What happens to the stored energy in a CR plate during reading?

A laser scans the plate, releasing stored energy as light that is converted to an electronic signal

Which DR technology uses amorphous selenium?

Direct-conversion DR

Which DR technology uses a scintillator such as cesium iodide?

Indirect-conversion DR

What two devices can capture light in indirect DR?

Charge-Coupled Device (CCD) and Thin-Film Transistor (TFT) array

What is the purpose of a histogram in digital imaging?

To graphically display the distribution of pixel values so the computer can rescale the image

Define quantum mottle.

Image noise caused by insufficient X-ray photons (underexposure)

Name four variables that affect signal value on the IR.

mAs, kVp/beam quality, patient factors (thickness/composition), and distance (SID)

What is beam filtration’s primary purpose?

To remove low-energy X-rays, reducing patient skin dose without affecting diagnostic photons

Define Half-Value Layer (HVL).

Thickness of absorbing material that reduces X-ray beam intensity to one-half its original value

Why are radiographic grids used?

To absorb scatter radiation before it reaches the IR, improving image contrast

What does fill factor refer to in a digital detector?

The percentage of each detector element dedicated to capturing X-ray signal; higher fill factor increases sensitivity

Do exposure indicator (EI or S#) values represent patient dose?

No; they represent the amount of radiation reaching the image receptor

How does the Exposure Index (EI) relate to exposure?

EI increases linearly and proportionally with exposure

How does the Sensitivity number (S#) relate to exposure?

S# decreases linearly and proportionally with exposure

What is automatic rescaling?

Computer adjustment of brightness and contrast to compensate for exposure variations

What monitor control adjusts image brightness?

Window Level (WL)

What monitor control adjusts image contrast?

Window Width (WW)

High image contrast is associated with window width and kVp.

Narrow window width; low kVp

What term describes the sharpness of structural edges on an image?

Spatial resolution (recorded detail)

List three factors that influence spatial resolution.

Temporal resolution (exposure time/motion), beam geometry (focal spot size, SID, OID), and detector characteristics (matrix/DEL size)

How does focal spot size affect spatial resolution?

Smaller focal spot size reduces penumbra and improves resolution

What two main types of distortion can affect a radiograph?

Size distortion (magnification) and shape distortion (elongation/foreshortening)

How can magnification be minimized?

Increase SID and decrease OID

Define temporal resolution in radiography.

Image sharpness as influenced by the time required to acquire the signal; shorter exposure times improve it

What imaging modality provides real-time visualization of anatomy and function?

Fluoroscopy

Name two types of fluoroscopic image receptors currently in use.

Image intensifier tubes and flat-panel detectors

What advantage do flat-panel detectors provide in fluoroscopy compared with image intensifiers?

Higher image quality, lower distortion, and immediate digital output

What is scatter radiation and why is it undesirable?

Radiation deflected from its original path after interacting with matter; it adds fog and reduces image contrast