X-ray Imaging and Computed Tomography Quiz
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Questions and Answers

What is the primary purpose of the oil surrounding the evacuated X-ray vessel?

  • For cooling and electrical isolation (correct)
  • To increase the X-ray output
  • To enhance image quality
  • To minimize radiation exposure

What is the range of potential difference applied between the anode and cathode during X-ray production?

  • 25 to 140 kV (correct)
  • 50 to 200 kV
  • 75 to 125 kV
  • 10 to 50 kV

Why is tungsten the preferred metal for the anode in X-ray tubes?

  • It is cost-effective compared to other metals
  • It has a low atomic number
  • It possesses high thermal conductivity and a high atomic number (correct)
  • It melts at low temperatures

What additional component is often used in tungsten anodes to enhance mechanical stability?

<p>Rhenium (A)</p> Signup and view all the answers

Which of the following describes the role of the cathode in an X-ray tube?

<p>To supply electrons through a tungsten wire (A)</p> Signup and view all the answers

What effect does a higher atomic number of the target metal have on X-ray production?

<p>Increases the efficiency of X-ray production (C)</p> Signup and view all the answers

How does the vacuum within the X-ray tube benefit the electron path?

<p>It provides an unimpeded path between the cathode and anode (D)</p> Signup and view all the answers

What is the typical melting point of tungsten, making it suitable for high-temperature applications in X-ray tubes?

<p>3370 °C (A)</p> Signup and view all the answers

What is the primary function of the cathode in an X-ray tube?

<p>To emit electrons (C)</p> Signup and view all the answers

Which component of the X-ray tube is responsible for converting electron energy into X-ray energy?

<p>The anode (D)</p> Signup and view all the answers

Why is it important for the X-ray tube to maintain an interior vacuum?

<p>To prevent air interference with electrons (A)</p> Signup and view all the answers

What material is commonly used for the filament in the cathode of an X-ray tube?

<p>Tungsten (A)</p> Signup and view all the answers

What is the role of the focusing cup in the X-ray tube's cathode?

<p>To concentrate emitted electrons (B)</p> Signup and view all the answers

Which of the following options does not describe a component of an X-ray tube?

<p>Radiation shield (B)</p> Signup and view all the answers

What is the purpose of the tube envelope in an X-ray tube?

<p>To maintain an interior vacuum (B)</p> Signup and view all the answers

Which statement about the X-ray energy spectrum generated by the tube is true?

<p>It consists of a range of energies, including low, medium, and high. (D)</p> Signup and view all the answers

Which material is used for the anode in digital mammography X-ray tubes?

<p>Molybdenum (B)</p> Signup and view all the answers

What is the effect of decreasing the bevel angle of the anode?

<p>Decreases the effective focal spot size (B)</p> Signup and view all the answers

What range of effective focal spot sizes is typically found for digital mammography?

<p>0.3 mm to 1.0 mm (C)</p> Signup and view all the answers

What phenomenon describes the intensity variation of the X-ray beam between the cathode-end and anode-end?

<p>Heel Effect (A)</p> Signup and view all the answers

Which of the following parameters does NOT affect the performance of an X-ray tube?

<p>Filtration type (A)</p> Signup and view all the answers

What is the typical range for tube current (mA) in planar radiography?

<p>50 to 400 mA (C)</p> Signup and view all the answers

Which mechanism for X-ray production is primarily responsible for producing a wide range of energies?

<p>Bremsstrahlung X-ray (B)</p> Signup and view all the answers

What kilovoltage peak (kVp) is typically used for digital mammography applications?

<p>25 kV (D)</p> Signup and view all the answers

Flashcards

X-ray Planar Radiography

A common medical imaging technique used to screen for injuries and diseases. It uses X-rays to create images of the inside body.

Bone Fracture Assessment

Using X-rays to determine the extent or severity of a bone fracture.

Lung Cancer/Emphysema Diagnosis

X-ray imaging can detect masses and changes associated with lung diseases like lung cancer or emphysema.

Kidney Stone Detection

X-rays are used to identify kidney stones.

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Gastrointestinal (GI) Diseases

X-rays can identify issues within the gastrointestinal tract.

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X-ray Tube

A specialized device that produces X-rays used for radiographic imaging.

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X-ray Tube Components

X-ray tubes have a cathode (electron source) anode (target), and a vacuum envelope.

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X-ray Imaging Contrast

Materials that absorb X-rays appear white, while materials that absorb fewer X-rays appear dark.

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X-ray production

X-rays are created when high-energy electrons strike a metal target.

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Cathode function

The cathode emits the electrons, often a tungsten wire.

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Accelerating voltage (kVp)

The voltage between cathode and anode that accelerates electrons.

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Anode material selection

Materials for the anode must withstand high temperatures and produce X-rays efficiently.

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Tungsten selection

Tungsten is a common anode material due to high atomic number, high melting point, good thermal conductivity, and low vapor pressure.

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Tungsten-rhenium alloy

A tungsten-rhenium alloy is used for improved mechanical stability in the target.

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Oil (x-ray tube) purpose

Surrounds the evacuated vessel for cooling and electrical insulation.

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Digital Mammography X-ray Anode Material

Molybdenum is used in digital mammography X-ray tubes instead of tungsten for low-energy X-rays.

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Anode Bevel Angle

The angle of the anode bevel, typically between 8° and 17°, controls the effective focal spot size and X-ray beam coverage.

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Effective Focal Spot Size

The apparent size of the X-ray focal point, affected by the anode bevel angle, and ranging from 0.3 mm in digital mammography to 0.6-1.2 mm in other imaging.

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Heel Effect

X-ray intensity is higher at the cathode-end and lower at the anode-end of the X-ray beam due to differences in travel distance through the target.

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X-ray Imaging Parameters

Three parameters controlled by the operator in X-ray imaging: accelerating voltage (kVp), tube current (mA), and exposure time.

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Tube Current Range

The current that travels from the cathode to anode, typically between 50-400 mA for planar radiography, and up to 1000 mA for CT.

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Kilovoltage Peak (kVp)

The maximum energy of the X-rays produced, ranging from ~25 kV for digital mammography to ~140 kV for bone and chest applications.

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Bremsstrahlung X-rays

One of two mechanisms for producing X-rays—X- rays generated by deceleration of electrons.

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Study Notes

X-ray Imaging and Computed Tomography

  • X-ray planar radiography is a key tool in radiology departments, providing initial screening for acute and chronic injuries/diseases.
  • Planar radiography (general X-rays) are used to assess bone fractures in acute injuries, presence of masses in lung cancer/emphysema, airway pathologies, kidney stones, and gastrointestinal (GI) tract diseases.
  • X-rays from a source are directed towards the patient, and those passing through are detected by a solid-state flat panel detector placed below the patient.
  • Detected X-ray energy is converted into light, voltage, and then digitized.
  • High contrast exists between bones (white, absorb X-rays) and lung tissue (dark, absorbs few X-rays).

X-ray Tube

  • X-ray source for both planar radiography and computed tomography (CT) is a specialized piece of equipment called an X-ray tube.
  • X-ray tubes consist of an electron source (heated tungsten filament), a focusing cup (cathode), a target/anode, and an envelope to maintain a vacuum inside.
  • Components are housed within an evacuated vessel surrounded by oil for cooling and electrical insulation, and a lead shield with a glass window for X-ray emission.
  • The X-ray tube's target (anode) must be efficient at producing X-rays and resistant to high temperatures.
  • Tungsten (atomic number 74) is the typical anode material due to high melting point (3370°C) and good thermal conductivity. A tungsten-rhenium alloy enhances mechanical stability.
  • For applications like digital mammography, molybdenum is sometimes used in the anode, as it requires lower X-ray energies.

X-ray Beam

  • The angle of the anode beveling affects the effective focal spot size (f) and coverage of the X-ray beam. Smaller bevel angles result in smaller focal spot sizes.
  • Effective focal spot size ranges from 0.3 mm (digital mammography) to 0.6-1.2 mm (planar radiography/CT).
  • Coverage is given by 2 x (source-patient distance) x tan(θ), where θ is the bevel angle.
  • X-ray beam intensity is higher at the cathode end than the anode end (Heel effect). This effect is due to differences in distances X-rays travel through the target.

X-ray Imaging Parameters

  • Three parameters for X-ray imaging are chosen by the operator: accelerating voltage (kVp), tube current (mA), and exposure time.
  • Typical tube current for planar radiography is 50-400 mA, and for CT up to 1000 mA.
  • kVp values vary from 25 kV (digital mammography) to ~140 kV (bone/chest).
  • X-ray tubes produce X-rays with a range of energies, up to a maximum determined by the kVp.

X-ray Production Mechanisms

  • X-ray production occurs through two mechanisms: Bremsstrahlung X-rays and characteristic X-rays.
  • Bremsstrahlung X-rays are produced when electrons passing near atomic nuclei lose kinetic energy and emit X-rays.
  • Characteristic X-rays are produced when an electron colliding with a tightly bound inner shell (e.g., K-shell) electron ejects it and an outer shell electron fills the vacancy, releasing the difference in energy as an X-ray.

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X-ray Imaging and Computed Tomography PDF

Description

Test your knowledge on X-ray imaging techniques and the functioning of X-ray tubes in radiology. This quiz covers the basics of planar radiography, how it is used in diagnosing various conditions, and the principles behind computed tomography. Perfect for students and professionals in the medical imaging field.

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