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x-ray production
production, interactions, and equipment
| Question | Answer |
|---|---|
| actual focal spot size | The size of the actual area on the anode where the x-ray beam is produced. |
| added filtration | The process of adding materials to the x-ray beam to remove low-energy photons. |
| anode heel effect | The variation in x-ray intensity along the beam due to the angle of the anode. |
| bremsstrahlung interactions | Interactions that occur when an incident electron slows down near the nucleus of a tungsten atom, producing x-ray photons. |
| characteristic interactions | Interactions that occur when an incident electron dislodges an inner-shell electron from a tungsten atom, resulting in the emission of x-ray photons. |
| compensating filters | Filters used to even out the intensity of the x-ray beam across the field of view. |
| dosimeter | A device used to measure exposure to ionizing radiation. |
| effective focal spot size | The size of the x-ray beam as it appears to the object being imaged, influenced by the anode angle. |
| electron transition | The movement of electrons between energy levels within an atom. |
| exposure time | The duration for which the x-ray beam is activated during imaging. |
| filament current | The current that heats the filament in the cathode to produce electrons through thermionic emission. |
| half-value layer (HVL) | The thickness of material needed to reduce the intensity of the x-ray beam by half. |
| heat unit (HU) | A measure of the amount of heat produced in the x-ray tube, calculated based on kVp, mA, and time. |
| inherent filtration | The filtration provided by the x-ray tube itself, including the glass or metal envelope. |
| kilovoltage | The peak voltage applied across the x-ray tube, influencing the energy of the x-ray photons produced. |
| line-focus principle | The principle that describes the relationship between the actual focal spot size and the effective focal spot size. |
| milliamperage (mA) | The measure of the tube current, which affects the quantity of x-rays produced. |
| space charge | The accumulation of electrons near the cathode that affects the flow of current in the x-ray tube. |
| space charge effect | The phenomenon where the space charge limits the number of electrons that can flow from the cathode to the anode. |
| thermionic emission | The process by which electrons are emitted from a heated filament. |
| total filtration | The sum of inherent and added filtration in the x-ray beam. |
| trough filter | A type of compensating filter that is shaped to provide uniform exposure across the imaging field. |
| tube current | The flow of electrons from the cathode to the anode, measured in milliamperes. |
| voltage ripple | The fluctuation in voltage output from the x-ray generator, which can affect image quality. |
| wedge filter | A type of compensating filter that tapers to provide varying levels of attenuation across the x-ray beam. |
| x-ray emission spectrum | The range of energies of x-ray photons produced by the x-ray tube. |
| Target interactions | The interactions that occur when electrons move from the cathode to the anode, producing x-rays upon striking tungsten atoms. |
| K-shell binding energy | The strongest binding energy in tungsten, measured at 69.5 keV, required for a projectile electron to eject a K-shell electron. |
| Energy of K-shell characteristic x-rays | K-shell characteristic x-rays have an energy range of approximately 57 to 69 keV. |
| Percentage of bremsstrahlung in x-ray beam | Approximately 85% of the x-ray beam results from bremsstrahlung interactions. |
| Percentage of characteristic x-rays in x-ray beam | Above 70 kVp, approximately 15% of the x-ray beam consists of characteristic x-rays. |
| Diagnostic energy range for x-ray interactions | The diagnostic energy range for most x-ray interactions is from 30 to 150 keV. |
| Energy calculation for bremsstrahlung x-ray photon | The energy of a bremsstrahlung x-ray photon can be found by subtracting the exit energy of the projectile electron from its entry energy. |
| Example of bremsstrahlung photon energy | If a projectile electron enters an atom with 120 keV and exits with 40 keV, the produced x-ray photon is 80 keV. |
| Example of lower bremsstrahlung photon energy | If a projectile electron enters with 120 keV and exits with 90 keV, the produced x-ray photon is 30 keV. |
| X-ray energy measurement | X-ray energy is measured in kiloelectron volts (keV), where 1 keV equals 1000 electron volts. |
| Low-energy bremsstrahlung x-ray photon | A type of x-ray photon produced when the incident electron travels farther from the nucleus, resulting in lower energy. |
| Rotating anode | A component in x-ray tubes that helps distribute heat and allows for higher x-ray production. |
| Focusing cup | A component that helps direct the electron beam towards the anode in an x-ray tube. |
| Incident electron | An electron that is accelerated towards the anode in an x-ray tube and interacts with tungsten atoms to produce x-rays. |
| X-ray photon | A quantum of electromagnetic radiation produced when electrons interact with atoms, typically in the context of x-ray production. |
| Tungsten atom | The target material in x-ray tubes, known for its high atomic number and effective x-ray production capabilities. |
| Binding energies for tungsten | Specific energy levels required to remove electrons from various shells of tungsten atoms. |
| M to K transition | An electron transition where an outer-shell electron drops into the K-shell position, contributing to x-ray production. |
| L to K transition | An electron transition where an outer-shell electron drops into the K-shell position, contributing to x-ray production. |
| K-shell | The innermost electron shell with a binding energy of 69.5 keV. |
| L-shell | The second electron shell with a binding energy of 12.1 keV. |
| M-shell | The third electron shell with a binding energy of 2.82 keV. |
| N-shell | The fourth electron shell with a binding energy of 0.6 keV. |
| O-shell | The fifth electron shell with a binding energy of 0.08 keV. |
| P-shell | The sixth electron shell with a binding energy of 0.008 keV. |
| Characteristic x-ray photons | Photons produced when a projectile electron removes an inner-shell electron and another electron fills the vacancy. |
| Photon energy calculation | The photon energy is equal to the difference in the binding energy of the shells involved. |
| Characteristic x-ray energy example | If a K-shell electron is removed (69.5 keV) and an L-shell electron fills the vacancy (12.1 keV), the energy of the K-shell characteristic x-ray photon produced is 57.4 keV. |
| kVp | The maximum energy of x-ray exposure cannot exceed the kVp set on the control panel. |
| X-ray energy range for 80 kVp | An 80 kVp x-ray exposure technique produces x-ray energies ranging from 15 to 80 keV. |
| Peak x-ray energies | The greatest number of x-ray energies occurs between 30 and 40 keV for an 80 kVp exposure. |
| Characteristic energy level | A characteristic energy level of approximately 69 keV is important when contrast media is used. |
| Thermionic cloud | The cloud of free electrons that forms around the filament due to thermionic emission. |
| Rotor | The part activated by the radiographer to start the stator that drives the rotor and rotating target. |
| Anode | The target in the x-ray tube that rotates and must reach top speed for x-ray production. |
| Deadman switches | Switches that require positive pressure to be applied during the entire x-ray exposure process. |
| X-ray exposure | Produced by a radiographer using two switches located on the control panel of the x-ray unit. |
| Cathode | The side of the x-ray tube where the filament is located and where electrons are emitted. |
| Rotating target | The anode that begins to turn rapidly after the rotor is activated. |
| Positive charge | Attracts electrons in the tube current on the anode side of the x-ray tube. |
| Negative charge | Repels electrons on the cathode side of the x-ray tube. |
| Exposure switch | The switch activated by the radiographer to initiate the x-ray exposure. |
| Electrical current | Induced across the filament in the cathode when the rotor is activated. |
| Milliamperes (mA) | The unit used to measure tube current. |
| X-rays | Produced when electrons strike the anode. |
| Heat | Produced alongside x-rays when electrons strike the anode. |
| Exposure process | Terminated immediately if the radiographer releases pressure on either of the deadman switches. |
| Top speed | The speed the rotating target must reach before an x-ray exposure can be made. |
| Seconds | The time it takes for the space charge to be produced and for the rotating target to reach its top speed. |
| Electromagnetic energy | Includes visible light and x-rays, varying in wavelength. |
| Wavelength | Ranges from 380 to 700 nanometers (10-6 m) for visible light. |
| Energy conversion | The process where kinetic energy of electrons is transformed into electromagnetic energy (x-rays) or thermal energy (heat). |
| Potential difference | The voltage difference between the anode and cathode that creates a charge attraction for electrons. |
| Quality of x-ray beam | Refers to the penetrating power of the x-ray beam, which is affected by the kVp setting. |
| Quantity of x-ray beam | Indicates the number of x-ray photons present in the primary beam. |
| Direct relationship | A relationship where one variable increases, the other also increases, but they are not proportional. |
| Speed of electrons | Increases as the kilovoltage applied across the x-ray tube increases, affecting the quality of x-rays produced. |
| Penetrability of x-ray photons | The ability of x-ray photons to pass through tissue, which increases with higher energy. |
| Energy level of radiation | Refers to the quality of the x-ray beam, which is influenced by the kVp setting. |
| X-ray photons | Particles of electromagnetic radiation produced when electrons interact with the anode target. |
| Thermal energy | The heat produced as a result of the kinetic energy of electrons striking the anode. |
| Manipulating prime exposure factors | Adjusting kVp, mA, and exposure time to control the quantity and quality of the x-ray beam. |
| X-ray production | The process initiated by the radiographer to generate x-rays using the x-ray tube. |
| Box 3.2 | A reference to the section that describes the initiation of x-ray exposure. |
| Box 3.3 | A reference to the section that outlines the relationship between kVp and x-ray quality. |
| Energy of X-Rays | The greater the energy of the x-rays produced, the greater the penetrability of the primary beam. |
| Penetrability of Primary Beam | The quality or energy of the x-rays in turn determines the penetrability of the primary beam (ease with which it moves through tissue). |
| Kilovoltage Accuracy | X-ray quality can be affected if the actual kilovoltage used is inaccurate. |
| Digital kVp Meter | A digital kVp meter measures the actual kilovoltage. |
| Maximum Variability of Kilovoltage | The maximum variability of the kilovoltage is ±5%. |
| kVp and Beam Penetrability | As kVp increases, beam penetrability increases; as kVp decreases, beam penetrability decreases. |
| X-Ray Production Efficiency | Increased kVp results in more x-rays being produced because it increases the efficiency of x-ray production. |
| X-Ray Generator | A generator is required to convert low voltage (volts) to high voltage (kilovolts) for x-ray production. |
| Single-Phase Generators | The voltage ripple for single-phase generators is said to be 100% because there is total variation in the voltage waveform, from peak voltage to zero voltage. |
| Three-Phase Generators | For three-phase generators, the voltage ripple is 13% for the 6-pulse mode and 4% for the 12-pulse mode. |
| High-Frequency Generators | High-frequency generators produce a voltage ripple of less than 1%. |
| Consistency of Voltage | The more consistent the voltage applied to the x-ray tube throughout the exposure, the greater the quantity and energy level (quality) of the x-ray beam. |
| mA | Milliamperage; higher mA results in more electrons moving in the tube current from the cathode to the anode. |
| Proportional Relationship of mA | The number of x-rays produced is directly proportional to mA. |
| X-Ray Emission Shift | Increasing the kVp from 72 to 82 shows an increase in the quantity of x-rays (amplitude), and the x-ray emission shifts toward the right, indicating an increase in the energy or quality of the beam. |
| Quality of x-rays | The mA does not affect the quality or energy of the x-rays produced. |
| Effect of exposure time on x-ray production | A longer exposure time results in more electrons moving in the tube current from the cathode to the anode, leading to more x-rays produced. |
| Mathematical expression of mAs | mAs is expressed as mA x s, where s represents the exposure time in fractions of a second or in seconds. |
| Calculating mAs | mAs = mA x seconds; for example, 200 mA x 0.25 s = 50 mAs. |
| Quality Control Check: Exposure Timer Accuracy | X-ray quantity can be affected if the actual exposure time used is inaccurate, with maximum variability of ±5% for times >10 ms and ±10% for times <10 ms. |
| X-ray quantity analogy | Producing x-rays is likened to plumbing, where water flow represents the quantity of x-rays produced. |
| Exposure time effects | Doubling the exposure time at a constant mA results in double the quantity of x-rays produced. |
| Millisecond conversion | Milliseconds (ms) of time must be converted to seconds to calculate mAs. |
| Example of mAs calculation | 500 mA x 2/5 s = 200 mAs. |
| X-ray energy relationship | Changing the mA results in a proportional change in the quantity (amplitude) of x-rays produced. |
| X-ray production and exposure time | The number of x-rays produced is directly proportional to the exposure time. |
| X-ray production analogy | When you turn on the faucet, water flows in gallons (liters) per minute, similar to how x-rays are produced. |
| Exposure time in seconds | Exposure time can be expressed in seconds or milliseconds, where 1 s = 1000 ms. |
| Example of x-ray production | An exposure time of 0.25 s at 400 mA hypothetically produces 5000 x-rays. |
| Doubling exposure time effect | Doubling the exposure time to 0.50 s at 400 mA would produce 10,000 x-rays. |
| Water amount after 30 seconds | Approximately 3 gallons (11.5 liters) of water in your sink. |
| Water amount after 45 seconds | Approximately 4.5 gallons (17 liters) of water in your sink. |
| mAs | Milliamperage-seconds, calculated by multiplying mA by exposure time. |
| Exposure time and x-ray quantity relationship | The quantity of electrons flowing from the cathode to the anode and the quantity of x-rays produced are directly proportional to the exposure time. |
| Effect of mAs on x-ray quantity | Higher mAs results in more electrons moving within the tube current from the cathode to the anode, producing more x-rays. |
| Quality of x-rays and mAs | mAs affects only the quantity of x-rays produced; it has no effect on the quality of the x-rays. |
| Reproducibility of exposure | Verifies the consistency of the radiation output for a given set of exposure factors with a maximum variability of +5%. |
| mAs reciprocity | Verifies the consistency of radiation intensity for changes in mA and exposure time with constant mAs, with a maximum variability of ±10%. |
| mA and exposure time linearity | Verifies that proportional changes in mA or exposure time change the radiation intensity, with a maximum variability of ±10%. |
| Importance of focal spot size | A large focal spot can withstand heat from large exposures, while a small one produces better image quality. |
| Maximum variability of linearity | ±10%. |
| Maximum variability of mAs reciprocity | ±10%. |
| Maximum variability of reproducibility of exposure | +5%. |
| Quantity of x-rays produced | Directly proportional to the quantity of electrons flowing from the cathode to the anode. |
| Effect of mA on x-ray production | An increase or decrease in mA directly affects the quantity of x-rays produced. |
| Quality control tests for radiation output | Typically performed with a dosimeter to evaluate radiation intensity. |
| Doubling mA or exposure time | Should double the radiation intensity. |
| Effective focal spot | A smaller effective focal spot yields better spatial resolution on the image. |
| Anode target angle | Typically ranges from 5 to 20 degrees and determines the size of the effective focal spot. |
| Larger target angle | Produces a larger effective focal spot. |
| Smaller target angle | Produces a smaller effective focal spot. |
| Intensity difference | The difference in x-ray intensities between the cathode and anode sides can be as much as 45%. |
| Cathode side intensity | X-rays are more intense on the cathode side of the tube. |
| Anode side intensity | X-ray intensity decreases toward the anode side. |
| Beam filtration | The process of adding filtration to the x-ray beam to attenuate low-energy photons. |
| Low-energy photons | Do not contribute to image formation and only increase patient dose. |
| Aluminum filtration | Absorbs more low-energy photons while allowing higher-energy photons to penetrate and exit. |
| Remnant beam | The x-ray beam that eventually records the body part onto the image receptor. |
| Polyenergetic x-rays | Consist of low-energy, medium-energy, and high-energy photons. |
| Patient dose | Increased by low-energy photons that do not contribute to image formation. |
| Thoracic spine imaging | Utilizes the anode heel effect by placing the patient's head under the anode end of the tube for more intense radiation toward the lower spine. |
| Image receptor | The device that records the x-ray image of the body part. |
| Spatial resolution | Improved by a smaller effective focal spot. |
| Heat loading | Both actual focal spot sizes can withstand the same heat loading. |
| X-ray beam | Produced at the anode and exits the tube housing to become the primary beam. |
| Intensity of x-ray beam | Greater on the cathode side and decreases toward the anode side. |
| X-ray tube | A device that produces X-rays. |
| Collimator | A beam restrictor located just below the X-ray tube. |
| Exit port | The opening through which the X-ray beam exits the tube. |
| Thinned wall of envelope of X-ray tube insert | Part of the X-ray tube that contributes to inherent filtration. |
| Insulating oil | Oil that surrounds the X-ray tube and contributes to inherent filtration. |
| Al-added filtration | Thin metal mirror of collimator offering additional filtration. |
| Minimum total filtration requirement | For X-ray tubes operating at or above 70 kVp, a minimum total filtration of 2.5 mm of aluminum or its equivalent is required. |
| X-ray beam quality | Increased by higher tube filtration, resulting in a greater percentage of high-energy X-rays. |
| HVL measurement | Expressed in millimeters of aluminum (mm-Al) and measured using a dosimeter. |
| NCRP Report #102 | Recommends that for equipment operated at or above 70 kVp, the required minimum total filtration should be at least 2.5 mm. |
| Normal HVL of general diagnostic beams | Ranges from 3 to 5 mm-Al. |
| Radiation protection | Achieved by the placement of inherent and added filtration in the path of the X-ray beam. |
| Polyenergetic beam | An X-ray beam that contains a range of energies. |
| Aluminum as a material for HVL | Chosen material for measuring X-ray beam intensity and quality. |
| X-ray beam intensity | Measured before and after adding aluminum filtration to determine HVL. |
| Beam half-value layer (HVL) | The amount of added filtration that reduces the beam intensity to half its original intensity. |
| X-ray system output tracking | An effective and relatively convenient method for tracking x-ray system output over time as a function of usage. |
| Generator Factor | A factor that accounts for the heat produced by different types of x-ray generators. |
| Single-phase generator factor | 1 |
| Three-phase generator factor | 1 |
| High-frequency generator factor | 1 |
| Calculating heat units | The process of determining heat units produced from an exposure using the formula HUMA × Timex kVpx Generator Factor. |
| Exposure example calculation | For a three-phase x-ray unit at 600 mA and 75 kVp over 0.05 s, HU = 600 × 0.05 × 75 × 1.35 = 3037.5 HU. |
| Tube-rating charts | Charts used to evaluate exposure technique selection to avoid excessive heat load in x-ray tubes. |
| X-ray tube aging | The process where the output of an x-ray system can decrease over time, particularly affecting the x-ray tube. |
| Annual HVL reassessment | The process of measuring and recording the HVL of an x-ray system annually by a qualified medical physicist. |
| Inherent filtration component | The component of the x-ray tube that increases due to metallic tungsten particles adhering to the inside of the x-ray tube glass envelope. |
| Unacceptable output level | The level at which the HVL indicates that the x-ray tube should be replaced after inspection by a qualified medical physicist. |
| X-ray exposure parameters | Factors that account for the entire x-ray beam makeup and influence the amount of added aluminum filtration required. |
| Anatomical areas imaging | The process of using compensating filters to produce more consistent exposure to the image receptor for nonuniform areas. |
| X-ray machine output | The overall output of an x-ray system, which can decrease over time, necessitating regular monitoring. |
| Technique Overload | A message seen by the radiographer indicating an inappropriate technique has been set. |
| Instantaneous-load tube-rating charts | Charts used to describe the exposure limits of x-ray tubes and determine safe exposure parameters. |
| Heat units | The quantity of heat generated during x-ray production, which can damage the x-ray tube. |
| Maximum kVp | The highest kilovoltage peak that can be used safely with specified mA and exposure time. |
| Maximum mA | The highest milliamperage that can be used safely with specified kVp and exposure time. |
| Maximum exposure time | The longest duration that can be used safely with specified kVp and mA. |
| Anode cooling charts | Charts that provide information on the cooling time required before initiating another exposure. |
| Microprocessor controls | Modern generator features that help prevent unacceptable exposure conditions and x-ray tube damage. |
| Warming up the tube | A procedure to prepare the x-ray tube for operation, especially if it has not been energized for 2 hours or more. |
| Excessive heat unit generation | The result of repeatedly using exposure techniques near the x-ray tube's limit, increasing the risk of damage. |
| Holding down the rotor button | An action that causes excessive wear on both the filament and the rotor if done without making an exposure. |
| Lower tube currents | Using reduced current with longer exposure times to minimize wear on the filament. |
| Moving the tube while energized | An action that can cause damage to the anode and anode stem due to torque. |
| Pitting of the anode track | Damage caused by consistent overloading of exposure factors, resulting in surface degradation. |
| Melting of the focal track | Damage caused by failure of the rotor to rotate the anode, often due to heat damage to rotor bearings. |
| Radiographer errors | Mistakes made by radiographers that can lead to x-ray tube failure and increased costs. |
| Downtime for a radiographic room | The period during which a radiographic room is not operational due to equipment failure. |
| Exposure limits | The maximum allowable settings for kVp, mA, and exposure time to prevent damage to the x-ray tube. |
| Safe exposure | An exposure that adheres to the limits set by the tube-rating chart to avoid damage. |
| Typical instantaneous-load tube-rating chart | A visual representation used to determine safe and unsafe exposures based on kVp, mA, and exposure time. |
| Bremsstrahlung | Primarily responsible for x-rays produced as electrons interact with tungsten atoms in the target. |
| Characteristic interaction | Type of target interaction responsible for some x-rays in the diagnostic beam. |
| Heat conversion percentage | Approximately 99% of the kinetic energy is converted to heat when moving electrons strike the anode target. |
| Target angle | As it decreases, the effective focal spot size decreases. |
| X-ray output due to characteristic radiation | Occurs at approximately 12 keV. |
| Aging of x-ray systems | As x-ray systems age due to usage, the HVL decreases. |
| mAs calculation | Produced when the radiographer sets a kVp of 70, an mA of 600, and an exposure time of 50 ms is 30 mAs. |
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