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Questions and Answers
What is the range of the large focal spot size in millimeters?
Which type of timer is known for being most complicated and accurate?
What is the primary material used for the target in X-ray tubes?
Which of the following features is true for mechanical timers?
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What is the melting point of tungsten?
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What characteristic makes tungsten a suitable target material for X-ray production?
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Which type of timer cannot be used for rapid serial exposure?
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What is the atomic number of tungsten?
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What is the primary function of the high voltage generator in an X-ray imaging system?
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Which component of the X-ray imaging system is primarily responsible for the quantity of X-rays produced?
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What is the primary function of an autotransformer in an x-ray system?
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Which term describes the penetrability of the X-ray beam?
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What material is commonly used for the anode in x-ray tubes?
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Which component of the x-ray tube is responsible for releasing electrons?
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What is the primary purpose of the protective housing in an X-ray tube?
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What does the abbreviation mAs stand for in an X-ray imaging system?
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What does the line compensator do in an x-ray system?
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Which of the following is NOT a basic control found on the operating console?
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What is the purpose of a focal spot in an x-ray tube?
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What component of the x-ray system converts alternating current to direct current?
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What is the typical size of an X-ray tube?
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During fluoroscopy, what happens to the X-ray tower?
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Which part of the cathode is responsible for directing the released electrons?
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What is the function of the ceiling support in an x-ray system?
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What is the primary function of diodes in an x-ray tube?
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What does kVp stand for in the context of x-ray technology?
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What is the effect of full-wave rectification compared to half-wave rectification?
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Which of the following statements about solid state rectifiers is true?
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How is mAs calculated in x-ray technology?
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What is a characteristic of 3 phase, 12 pulse power in x-ray generation?
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What does the Heat Unit (HU) calculation represent?
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What is the purpose of the House Cooling Chart?
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What is the main advantage of using three phase power for x-ray production compared to single phase power?
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How many pulses occur in three phase, 6 pulse power within one sixtieth of a second?
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Which formula correctly represents the heat unit calculation for single phase power?
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What does the Anode Cooling Chart indicate?
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What is the power rating formula for three phase power using a high-frequency generator?
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Study Notes
X-Ray Imaging System
-
3 Principal Parts
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Operating Console: Controls the x-ray tube current and voltage
- Components: On/off switch, mAs selection, kVp selection, voltmeter, exposure switch
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High Voltage Generator: Converts low voltage from the electric power company into high kilovoltage peak waveform
- Components: High Voltage Transformer, Filament Transformer, Rectifier
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X-ray Tube: Creates x-ray photons from electric energy supplied by the x-ray generator
- Quantity: Refers to the number of x-rays or intensity of the beam - controlled by mAs (directly proportional)
- Quality: Refers to the penetrability of the x-ray beam - controlled by kVp
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Operating Console: Controls the x-ray tube current and voltage
X-Ray Tube
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Protective Housing: Provides mechanical support to the x-ray tube, protects the x-ray tube from rough handling, reduces leakage radiation to less than 100 mR/hr at 1 meter
- Contains oil for electrical insulation and thermal cushioning
- Glass Envelope: Maintains a vacuum inside the x-ray tube, made of Pyrex glass
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Internal Structures
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Cathode: Negative side of the x-ray tube where electrons are released
- Filament: Releases electrons, made of Thoriated tungsten
- Focusing Cup: Metal cup where the filament is embedded
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Anode: Positive side of the x-ray tube, made of Tungsten and Rhenium
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Focal Spot: Actual source of radiation
- Effective Focal Spot: Projected to the patient and imaging receptor
- Small Focal Spot: Used for better spatial resolution (0.1 mm - 0.5 mm)
- Large Focal Spot: Used for high heat techniques (0.4 mm - 1.2 mm)
- Target: Area of the anode struck by the electrons
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Focal Spot: Actual source of radiation
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Cathode: Negative side of the x-ray tube where electrons are released
X-Ray Tube Operation
- Projectile Electrons: Electrons traveling from the cathode to the anode
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kVp: Energy that determines the penetrating ability of the x-ray beam
- kVp = (patient body/part thickness in cm) x 2 + machine constant
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mA: Measures the intensity of the x-ray beam and the number of x-ray photons
- mAs = milliAmpere x time (in seconds)
High Voltage Generator
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Autotransformer: Varies or controls the voltage to 100-200V
- Located on the secondary side of the autotransformer
- Major/minor kVp: Two separate series of connections
- Line Compensator: Supplies a precise voltage, located on the primary side of the autotransformer
- Pre-reading Voltmeter: Monitors voltage before exposure
X-Ray Tube Supporting Structures
- Ceiling Support: Two sets of rails mounted to the ceiling directly over the radiographic table
- Floor-to-Ceiling Support: Single column with rollers attached to each end, one on a ceiling-mounted rail and the other on a floor-mounted rail
- Floor Mount System: Alternative for the column mount
- Fluoroscopy: Mounted underneath the radiographic table, used during fluoroscopy
- C-Arm: X-ray tube mounted on a C-shaped support, used as a portable fluoroscopy unit
X-Ray Timers
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Mechanical Timers: Used in portable and dental units
- Synchronous Timers: Exposure time of 1/17 msec, cannot be used for rapid serial exposure
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Electronic Timers: Used for rapid serial exposure
- Contains diodes
- Self-Rectified: X-ray tube serves as a vacuum tube rectifier
- Full-Wave Rectification: Uses 2-4 diodes
Rectifiers
- Diodes: Electronic devices containing two electrodes that allow current to flow in one direction
- Solid State Rectifiers: More reliable and have a longer life than vacuum tubes
X-Ray Power
- Single Phase Power: Results in a pulsating x-ray beam
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Three Phase Power: More efficient than single phase, multiple voltage waveforms are superimposed:
- 6 pulses per one sixtieth of a second
- 12 pulses per one sixtieth of a second
X-Ray Heat Units
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Heat Unit Formula:
- Single Phase Power: Heat Unit (HU) = kVp x mAs
- Three Phase, 6 Pulse Power: Heat Unit (HU) = (1.35) kVp x mAs
- Three Phase, 12 Pulse Power: Heat Unit (HU) = (1.41) kVp x mAs
X-Ray Rating Charts
- Radiographic Rating Chart: Conveys safe and unsafe radiographic techniques for x-ray tube operation
- Anode Cooling Chart: Shows time required for a heated anode to cool; Thermal energy is measured in heat units (HUs) or Joules (J)
- House Cooling Chart: Similar to the anode cooling chart, used for the housing of the x-ray tube
X-ray Tube Failure
- Tungsten Vaporization with Internal Deposition: The most common cause of x-ray tube failure
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Description
Explore the essential components of the x-ray imaging system, including the operating console, high voltage generator, and x-ray tube. Learn how these parts work together to produce diagnostic images, and understand how they control both the quantity and quality of x-ray output.
