* kVp:
the power and strength of the x-ray beam
(quality of the x-rays). * mAs: the number of x-ray photons produced by the x-ray tube at the setting selected (quantity of x-rays). * time: how long the exposure lasts.
What does mAs mean in radiology?
Milliampere-seconds
, also more commonly known as mAs, is a measure of radiation produced (milliamperage) over a set amount of time (seconds) via an x-ray tube. It directly influences the radiographic density, when all other factors are constant.
Is kV and kVp the same?
One standard way to measure pulsating DC is its peak amplitude, hence kVp. Most modern X-ray generators apply a constant potential across the X-ray tube; in such systems,
the kVp and the steady-state kV are identical
.
What is the difference between mA and mAs in radiology?
The product of current (mA) and exposure time (seconds) is the familiar mAs and translates to the number of x-rays produced per second. For a given exposure time, the mAs (
current multiplied by time
) provides the quantity of x-rays used during that exposure.
What is the relationship between kVp and contrast?
Radiation quality or kVp: it has a great effect on subject contrast. A lower kVp will make the x-ray beam less penetrating. This will result
in a greater difference in attenuation between the different parts of the subject
, leading to higher contrast. A higher kVp will make the x-ray beam more penetrating.
How does kVp and mAs affect image quality?
The first experiment showed that, when the film density is kept constant, the higher the kVp, the lower the resolution and image contrast percentage; also, the
higher the mAs, the higher the resolution and image
contrast percentage.
Which would increase magnification?
It refers to the proportional increase in the dimensions of a radiographed object relative to the actual dimensions of that object and depends on the following factors:
Increasing object to film distance
only will result in an increase in magnification of the radiographic image.
What happens when kVp is increased?
The higher the kVp, the
more likely the x-ray beam will be able to penetrate through thicker or more dense material
. Low kVp photons are weak and easily absorbed by body tissues or filters that have been placed.
When is kVp increased?
When the kVp is increased at the control panel, a
larger potential difference
occurs in the x-ray tube, giving more electrons the kinetic energy to produce x-rays and increasing the kinetic energy overall. The result is more photons (quantity) and higher energy photons (quality).
What is high kVp technique?
Introduction. High kVp techniques, 15% or 10-kVp rules, are
well-known dose reduction methods
. Traditionally, the use of high tube potential (i.e. increased kVp) is associated with decreased radiographic contrast and overall image quality.
How is mAs calculated?
Milliampere-second (mAs) is an x-ray unit
determined by multiplying the milliamperes by the time the x-ray tube is generating x-rays
. On many x-ray machines this is a technique factor selected by the operator that together with kVp determines the exposure of patient and image receptor.
Does increasing mAs increase contrast?
The first experiment showed that, when the film density is kept constant, the higher the kVp, the lower the resolution and image contrast percentage; also, the higher the mAs,
the higher the resolution
and image contrast percentage.
How does Sid affect image quality?
The source image receptor distance (SID), is the distance of the tube from the image receptor,
affecting magnification
. The greater the SID, the less magnification the image will suffer.
Is kVp quality or quantity?
X-ray photons quality relates to the x-ray spectrum changes and the effective photon energy. The effective photon energy is approximately equal to between one third to one half of the maximum photon energy. Factors influencing x-ray quality include:
peak voltage
(kVp)
What is one of the benefits of using a higher kVp?
Higher kVp X-rays are less likely to interact with tissue and are described as more “penetrating.” Increasing kVp, thereby generating more penetrating radiation,
reduces the relative image contrast (or visible difference) between tissues of different densities
.
What is the difference between density and contrast in radiography?
Radiographic contrast is the
density difference between neighboring regions on a plain radiograph
. High radiographic contrast is observed in radiographs where density differences are notably distinguished (black to white).
