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A line, called the center line, is usually drawn on the face of the grid, which lets the radiographer know the direction of the grid lines, since they are hidden by the grid’s cover. The direction of the grid lines is very important to know when using the grid so the problem of grid cut-off can be avoided.
Oct 3, 2024 · Calculation Formula. The grid ratio (GRD) is determined using the formula: \ [ \text {GRD} = \frac {\text {HLS}} {\text {DS}} \] where: \ (\text {GRD}\) is the Grid Ratio, \ (\text {HLS}\) is the height of lead strips in inches, \ (\text {DS}\) is the distance between strips in inches.
- Overview of Technical Parameters
- MA
- KVP
- Sid
- Bucky Factor
- Golden Equation
As a technologist you are often faced with the situation where you need to make a change to a protocol but want to keep the exposure on the detector the same. In this scenario it is really important to understand the technical parameters and their influence the exposure, so that when changing parameters you do not end up under-exposing or over-expo...
The tube current and time in the x-ray exam are the parameters that are most frequently changed and you should consider this as your first go-to adjustment in order to change the x-ray exposure without impacting the quality of the exam in other ways. Increasing the tube current is actually just providing more electrons that with smash into the x-ra...
The kVp is the most important technical parameter as it has a very strong dependence on the x-ray exposure (kVp5). This strong dependence on the kVp for the exposure at the image receptor is because of the higher flux and stronger penetration of higher kVp imaging. Additionally, the kVp also changes the inherent contrast in the x-ray images. Since ...
The Source to Image Distance (SID) affects the exposure at the image receptor since the x-ray beam is divergent (i.e. spreading out as it gets further from the x-ray tube). Since the x-rays are spreading out the exposure depends on the SID as 1/SID2 . In our post on the basic x-ray properties we demonstrate how the divergent beam leads to the 1/R2d...
Finally, the Bucky factor is a unitless quantity which is the ratio of the x-ray exposure reaching the grid to the x-ray exposure reaching the image receptor. If no grid is used this definition will lead to a Bucky factor of 1.0. The Bucky factor for grids is dependent upon the grid ratio (grid height: grid spacing) and the kVp. It typically ranges...
Now that we have all pieces we can put these 5 simple relationshipstogether to make what we call the golden equation. You can give it your own cool name too. We just call it the golden equation since it has all of the factors that you need to consider so that as you change one factor you can compensate to keep your exposure constant. Also this is j...
The magnification is defines as the (Image Size)/ (Object Size). Since the x-rays are spreading out (i.e. diverging) the magnification will always be a number that is greater than 1 (i.e. the image size will always be larger than the object size).
Focused grids have lead strips that are oriented parallel at the center (along the x-ray central axis) and progressively slanted to the periphery to match the beam divergence from the focal spot .to the detector at a specific source to detector distance.
This formula, called the exposure maintenance formula, or the direct square law, allows the radiographer to calculate the new exposure factors to be used when the distance between the x-ray tube and the image receptor changes.
People also ask
What does the center line on a X ray grid mean?
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Antiscatter grids improve the X-ray image contrast at a cost of patient radiation doses. The choice of appropriate grid or its removal requires a good knowledge of grid characteristics, especially for pediatric digital imaging. The aim of this work ...
