Questions and Answers
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.
mA
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 ________________.
Signup and view all the answers
Liberated electrons form a ________ charge or electron ________ around the filament which is maintained at equilibrium as long as the rotor button is held down.
Signup and view all the answers
Ultimately, the intensity rate of the ________ beam is directly controlled by the mA station set at the console.
Signup and view all the answers
The exposure time is abbreviated ________.
Signup and view all the answers
The radiographic term mAs derives from multiplying the ________ x ________.
Signup and view all the answers
The term mAs refers to the ________ amount of electricity used during a radiographic exposure.
Signup and view all the answers
Primarily because it doesn't affect other factors, the mAs is considered the primary ________ over x-ray exposure.
Signup and view all the answers
Doubling the mA makes a graph of the x-ray beam spectrum twice as ________.
Signup and view all the answers
For a particular amount of exposure, mA and exposure time are ________ proportional to each other.
Signup and view all the answers
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.
Signup and view all the answers
The x-ray beam is a shower of x-rays which have a ________ distribution just like the drops in a rain shower.
Signup and view all the answers
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.
Signup and view all the answers
The grainy or 'blotchy' appearance caused by insufficient exposure is called ________ ________.
Signup and view all the answers
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.
Signup and view all the answers
Anything which results in an insufficient amount of exposure at the image receptor plate can lead to mottle, including ________ kVp.
Signup and view all the answers
Because pixel values are amplified by digital imaging systems, only ________ underexposure can result in the appearance of quantum mottle.
Signup and view all the answers
For all electronic display systems such as LCDs and CRTs, electronic ________ constitutes additional noise in the image.
Signup and view all the answers
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.
Signup and view all the answers
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.
Signup and view all the answers
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.
Signup and view all the answers
Although exposure time is not the direct cause of ________, the longer the exposure time, the greater chance there is for ________ to occur.
Signup and view all the answers
Since some types of motion cannot be controlled, exposure time is generally considered to be a ________ factor for motion blur during radiographic exposures.
Signup and view all the answers
It is generally assumed that the shorter the exposure time, the ________ radiographic images are likely to be.
Signup and view all the answers
What is mA (milliamperage)?
Signup and view all the answers
What is amperage?
Signup and view all the answers
What does the rotor switch do?
Signup and view all the answers
What is exposure time? (abbreviated 's')
Signup and view all the answers
What is thermionic emission?
Signup and view all the answers
What is the electron cloud / space charge?
Signup and view all the answers
What is mAs considered to be?
Signup and view all the answers
________ the mAs, mA or time raises the x-ray spectrum curve twice as high at every point.
Signup and view all the answers
________ radiographs show a doubling in density for each doubling of the mAs.
Signup and view all the answers
A disadvantage of ________ ________ is the lack of immediate feedback when doubling the mAs.
Signup and view all the answers
Sufficient exposure ensures a high ________________ ratio.
Signup and view all the answers
Anything which results in an insufficient exposure at the image receptor can lead to mottle, including: 1.________ 2.________ 3.________.
Signup and view all the answers
________ systems amplify the input from each pixel, making them highly sensitive to image noise such as mottle.
Signup and view all the answers
Result: Only slight underexposure can result in visible mottle for ________ systems.
Signup and view all the answers
For all electronic display systems such as LCDs and CRTs, ________ constitutes additional noise in the image.
Signup and view all the answers
Overexposure is only detectable in digital systems by monitoring the ________.
Signup and view all the answers
What end of the spectrum (exposure index values) does quantum mottle appear on? High or low end?
Signup and view all the answers
What is dose creep?
Signup and view all the answers
_________ is determined by these percentage contributions from the different interactions, so mAs does not affect ________.
Signup and view all the answers
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.
Signup and view all the answers
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.
Signup and view all the answers
The greatest enemy to sharpness of recorded detail in the image is ________.
Signup and view all the answers
Exposure time is not a _________ cause of motion - it is the patient who moves.
Signup and view all the answers
The _________ the exposure times, the sharper the images are likely to be.
Signup and view all the answers
Define thermionic emission, space charge, and dual filament.
Signup and view all the answers
List image qualities which are not directly affected by mAs.
Signup and view all the answers
Explain quantum mottle and how to correct it.
Signup and view all the answers
Explain the relationship between exposure time and motion unsharpness.
Signup and view all the answers
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.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
Test your knowledge of milliampere-seconds (mAs) with this set of flashcards focused on Chapter 15. Each card will help reinforce important concepts related to the flow of electrical current in radiology. Perfect for students preparing for exams in this field.