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One of three interactions of radiation with the human body tissues. It occurs at low energy levels with energy transferred to the atom. Only about 5% of exposures is caused by this interaction. Also known as Thompson scatter.
One of three interactions of radiation with the human body tissues. In this effect, the x-ray photon is scattered from the body rather than going directly through to expose the film. This effect is undesirable in radiographic imaging.
A radiography of a very small area of the subject; used when fog compromises the ability to see specific details in a large body part.
A composite of two grids with the lead strips at right angles to each other; also called a crossed grid.
The range of source-image distances (SID) at which the grid will not absorb significant amounts of primary radiation.
Grid for general-purpose use; the lead strips are aligned to the direction of the diverging primary x-ray beam.
The distance at which the primary x-ray beam is parallel to the focused lead strips of the grid.
The relationship between the height of the lead strips and the width of the spaces between them; determines the effectiveness of the grid.
One of three interactions of radiation with the human body tissues. In this effect, the x-ray photon is totally absorbed in the body tissues.
Produced during photoelectric interactions and is considered secondary radiation.
In the diagnostic range of kVp used (50 to 100) the majority of radiation interactions with the body are ____ interactions.
The more ____ the absorbing matter is, the more scatter radiation that is produced because more of the primary beam is absorbed.
factors affecting scatter radiation fog
Tissue thickness, field size, milliampere-seconds, and kilovoltage.
other strategies for limiting scatter fog
Use of an air gap, limitation of the field size, and reduction of kVp.
____ x-rays not moving in the same direction as the primary x-ray beam are absorbed by the grid.
A grid is constructed of tiny, tissue-thin ____ strips, placed on edge separated by radiolucent interspacing material.
The ____ the grid ratio, the less variation is permitted and the greater is the efficiency of the grid.
two methods employed to prevent objectionable grid lines
Using a moving grid or using a grid with very high frequency.
Moving the grid during the exposure ____ the image of the grid lines so that the grid image is not visible on the film.
Grid cutoff occurs when the x-ray tube is centered to one side of the grid rather than to the ____.
Focal center line.
causes of cutoff
Lateral decentering, source-image receptor distance outside focal range, lateral angulation or grid level off, and grid reversed.
A crosshatch grid is desirable because it has an effective ratio ____ than the ratios of two grids combined.
for coned-down images what size IR and square field is used
8 x 10 IR and a 5- or 6-inch square field
standard control limit for collimator is that the x-ray light field and the radiation field must be within ____.
± 2% of the SID.
standard control limit for the tube's beam alignment is that the tube must be mounted so that the x-ray beam is within ____.
1 degree of perpendicular.
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