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Questions and Answers
Milliamperage measures the flow ________ of electrical current through a circuit.
Milliamperage measures the flow ________ of electrical current through a circuit.
quantity
The ________ control on the x-ray machine console is actually a selector which taps off a different resistor in the filament circuit.
The ________ control on the x-ray machine console is actually a selector which taps off a different resistor in the filament circuit.
mA
The set mA is applied to the filament in the x-ray tube cathode each time the ________ switch is depressed.
The set mA is applied to the filament in the x-ray tube cathode each time the ________ switch is depressed.
rotor
Higher mA causes greater friction and temperature of the filament, so more electrons are emitted through the process of ________________.
Higher mA causes greater friction and temperature of the filament, so more electrons are emitted through the process of ________________.
Liberated electrons form a ________ charge or electron ________ around the filament which is maintained at equilibrium as long as the rotor button is held down.
Liberated electrons form a ________ charge or electron ________ around the filament which is maintained at equilibrium as long as the rotor button is held down.
Ultimately, the intensity rate of the ________ beam is directly controlled by the mA station set at the console.
Ultimately, the intensity rate of the ________ beam is directly controlled by the mA station set at the console.
The exposure time is abbreviated ________.
The exposure time is abbreviated ________.
The radiographic term mAs derives from multiplying the ________ x ________.
The radiographic term mAs derives from multiplying the ________ x ________.
The term mAs refers to the ________ amount of electricity used during a radiographic exposure.
The term mAs refers to the ________ amount of electricity used during a radiographic exposure.
Primarily because it doesn't affect other factors, the mAs is considered the primary ________ over x-ray exposure.
Primarily because it doesn't affect other factors, the mAs is considered the primary ________ over x-ray exposure.
Doubling the mA makes a graph of the x-ray beam spectrum twice as ________.
Doubling the mA makes a graph of the x-ray beam spectrum twice as ________.
For a particular amount of exposure, mA and exposure time are ________ proportional to each other.
For a particular amount of exposure, mA and exposure time are ________ proportional to each other.
When the mA stations are listed in multiples of 100, to mentally find the mAs before multiplying you can move the decimal place in the exposure time to the ________ two places and the decimal place in the mA to the ________ two places.
When the mA stations are listed in multiples of 100, to mentally find the mAs before multiplying you can move the decimal place in the exposure time to the ________ two places and the decimal place in the mA to the ________ two places.
The x-ray beam is a shower of x-rays which have a ________ distribution just like the drops in a rain shower.
The x-ray beam is a shower of x-rays which have a ________ distribution just like the drops in a rain shower.
When exposure is very light and there are few photons striking the image receptor, one can see the ________ distribution of the exposure across the image.
When exposure is very light and there are few photons striking the image receptor, one can see the ________ distribution of the exposure across the image.
The grainy or 'blotchy' appearance caused by insufficient exposure is called ________ ________.
The grainy or 'blotchy' appearance caused by insufficient exposure is called ________ ________.
The best way to keep the SNR for the image high is to subdue quantum mottle by 'overwhelming it' with ________, so it makes a lesser percentage contribution to the overall image.
The best way to keep the SNR for the image high is to subdue quantum mottle by 'overwhelming it' with ________, so it makes a lesser percentage contribution to the overall image.
Anything which results in an insufficient amount of exposure at the image receptor plate can lead to mottle, including ________ kVp.
Anything which results in an insufficient amount of exposure at the image receptor plate can lead to mottle, including ________ kVp.
Because pixel values are amplified by digital imaging systems, only ________ underexposure can result in the appearance of quantum mottle.
Because pixel values are amplified by digital imaging systems, only ________ underexposure can result in the appearance of quantum mottle.
For all electronic display systems such as LCDs and CRTs, electronic ________ constitutes additional noise in the image.
For all electronic display systems such as LCDs and CRTs, electronic ________ constitutes additional noise in the image.
For digital images, the only means for the radiographer to become aware of overexposure due to the use of excessive mAs is to monitor the exposure ________ readout.
For digital images, the only means for the radiographer to become aware of overexposure due to the use of excessive mAs is to monitor the exposure ________ readout.
Since subject contrast is determined by the percentage contribution from each type of interaction to the total information reaching the IR, changes in ________ do not have any direct bearing upon contrast in the final image.
Since subject contrast is determined by the percentage contribution from each type of interaction to the total information reaching the IR, changes in ________ do not have any direct bearing upon contrast in the final image.
The mAs can have no relation whatever to any of the recognizability functions in the image, because they are all ________ factors, whereas the mAs is an electrical factor.
The mAs can have no relation whatever to any of the recognizability functions in the image, because they are all ________ factors, whereas the mAs is an electrical factor.
Although exposure time is not the direct cause of ________, the longer the exposure time, the greater chance there is for ________ to occur.
Although exposure time is not the direct cause of ________, the longer the exposure time, the greater chance there is for ________ to occur.
Since some types of motion cannot be controlled, exposure time is generally considered to be a ________ factor for motion blur during radiographic exposures.
Since some types of motion cannot be controlled, exposure time is generally considered to be a ________ factor for motion blur during radiographic exposures.
It is generally assumed that the shorter the exposure time, the ________ radiographic images are likely to be.
It is generally assumed that the shorter the exposure time, the ________ radiographic images are likely to be.
What is mA (milliamperage)?
What is mA (milliamperage)?
What is amperage?
What is amperage?
What does the rotor switch do?
What does the rotor switch do?
What is exposure time? (abbreviated 's')
What is exposure time? (abbreviated 's')
What is thermionic emission?
What is thermionic emission?
What is the electron cloud / space charge?
What is the electron cloud / space charge?
What is mAs considered to be?
What is mAs considered to be?
________ the mAs, mA or time raises the x-ray spectrum curve twice as high at every point.
________ the mAs, mA or time raises the x-ray spectrum curve twice as high at every point.
________ radiographs show a doubling in density for each doubling of the mAs.
________ radiographs show a doubling in density for each doubling of the mAs.
A disadvantage of ________ ________ is the lack of immediate feedback when doubling the mAs.
A disadvantage of ________ ________ is the lack of immediate feedback when doubling the mAs.
Sufficient exposure ensures a high ________________ ratio.
Sufficient exposure ensures a high ________________ ratio.
Anything which results in an insufficient exposure at the image receptor can lead to mottle, including: 1.________ 2.________ 3.________.
Anything which results in an insufficient exposure at the image receptor can lead to mottle, including: 1.________ 2.________ 3.________.
________ systems amplify the input from each pixel, making them highly sensitive to image noise such as mottle.
________ systems amplify the input from each pixel, making them highly sensitive to image noise such as mottle.
Result: Only slight underexposure can result in visible mottle for ________ systems.
Result: Only slight underexposure can result in visible mottle for ________ systems.
For all electronic display systems such as LCDs and CRTs, ________ constitutes additional noise in the image.
For all electronic display systems such as LCDs and CRTs, ________ constitutes additional noise in the image.
Overexposure is only detectable in digital systems by monitoring the ________.
Overexposure is only detectable in digital systems by monitoring the ________.
What end of the spectrum (exposure index values) does quantum mottle appear on? High or low end?
What end of the spectrum (exposure index values) does quantum mottle appear on? High or low end?
What is dose creep?
What is dose creep?
_________ is determined by these percentage contributions from the different interactions, so mAs does not affect ________.
_________ is determined by these percentage contributions from the different interactions, so mAs does not affect ________.
The set mAs is an _________, not a geometrical one. It therefore has no bearing upon the recognizability functions in the image: sharpness, magnification or distortion.
The set mAs is an _________, not a geometrical one. It therefore has no bearing upon the recognizability functions in the image: sharpness, magnification or distortion.
The set mAs does not directly affect: 1. ________ level at the IR 2. ________ brightness of the image 3. ________ mottle, and thereby noise level and SNR.
The set mAs does not directly affect: 1. ________ level at the IR 2. ________ brightness of the image 3. ________ mottle, and thereby noise level and SNR.
The greatest enemy to sharpness of recorded detail in the image is ________.
The greatest enemy to sharpness of recorded detail in the image is ________.
Exposure time is not a _________ cause of motion - it is the patient who moves.
Exposure time is not a _________ cause of motion - it is the patient who moves.
The _________ the exposure times, the sharper the images are likely to be.
The _________ the exposure times, the sharper the images are likely to be.
Define thermionic emission, space charge, and dual filament.
Define thermionic emission, space charge, and dual filament.
List image qualities which are not directly affected by mAs.
List image qualities which are not directly affected by mAs.
Explain quantum mottle and how to correct it.
Explain quantum mottle and how to correct it.
Explain the relationship between exposure time and motion unsharpness.
Explain the relationship between exposure time and motion unsharpness.
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Study Notes
Milliampere-seconds (mAs) Overview
- Milliamperage (mA) measures the quantity of electrical current through a circuit, impacting x-ray production.
- The mA control on an x-ray console selects different resistors in the filament circuit, influencing electron emission.
- Each time the rotor switch is pressed, the set mA is applied to the x-ray tube cathode, initiating a process for creating x-rays.
Thermionic Emission and Electron Dynamics
- Higher mA levels generate increased friction and temperature in the filament, resulting in thermionic emission and more electron ejection.
- Liberated electrons form a space charge or "cloud" around the filament, stabilizing while the rotor is engaged, crucial for defining x-ray beam intensity.
- The x-ray beam's intensity rate directly corresponds with the mA settings, with mAs represented as mA multiplied by exposure time (in seconds).
mAs and Exposure Relationships
- mAs indicates the total amount of electricity used during a radiographic exposure and is considered the primary control affecting x-ray exposure.
- Doubling the mA results in a graph of the x-ray beam spectrum being twice as dark, showing a direct correlation between mA and exposure level.
- Adjustments to mA and exposure time are inversely proportional; as one increases, the other decreases to maintain consistent exposure.
Image Quality and Exposure Effects
- Shorter exposure times generally yield sharper radiographic images, as longer times increase the likelihood of motion blur.
- Quantum mottle results from insufficient exposure, appearing as graininess in images, and is mitigated by ensuring good exposure.
- Digital imaging systems are sensitive to noise and only slight underexposure can lead to the visibility of quantum mottle.
Additional Considerations
- Various factors such as inadequate kVp settings or rectifier failures can result in insufficient exposure, leading to image mottle.
- Digital systems do not provide immediate feedback for overexposure, necessitating monitoring of exposure indicator readouts.
- Subject contrast is unaffected by mAs changes; it stems from differential interactions contributing to total image information.
Technical Definitions and Clarifications
- Motion, rather than exposure time, is the key factor affecting unsharpness in images, emphasizing the importance of managing motion during exposure.
- The electron cloud created by thermionic emission and the dual filament setup enhance x-ray production, offering a variety of exposures.
- mAs is not an influencing factor for specific image recognizability functions like sharpness, magnification, or distortion since it is an electrical factor.
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