What is scatter radiation caused by

Scatter Radiation

Scatter radiation is a secondary radiation produced when an x- ray interact with the patient and the energy is not enough for an x- ray to reach the IR. X-rays that exit from the patient are remnant x-rays and those that exit and interact with the image receptor are called image-forming x-rays.

As scatter radiation increases, the radiograph loses contrast and appears gray and dull. Three primary factors influence the relative intensity of scatter radiation that reaches the image receptor: kVp, field size, and patient thickness.

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Scatter Radiation
Some x-rays interact with the patient and are scattered away from the image receptor (a). Others interact with the patient and are absorbed (b). X-rays that arrive at the image receptor are those transmitted through the patient without interacting (c)and those scattered in the patient (d). X-rays of types c and d are called image-forming x-rays.
Collimation of the x-ray beam results in less scatter radiation, reduced dose, and improved contrast resolution.
Patient Thickness
What is scatter radiation caused by quizlet?
Where does most scatter radiation come from?
Where is scatter radiation produced?

Some x-rays interact with the patient and are scattered away from the image receptor (a). Others interact with the patient and are absorbed (b). X-rays that arrive at the image receptor are those transmitted through the patient without interacting (c)and those scattered in the patient (d). X-rays of types c and d are called image-forming x-rays.

Three primary factors influence the relative intensity of scatter radiation that reaches the image receptor: kVp, field size, and patient thickness.

kVp

As x-ray energy is increased, the absolute number of Compton interactions decreases, but the number of photoelectric interactions decreases much more rapidly. Therefore, the relative number of x-rays that undergo Compton interaction increases.

Also, fewer x-rays reach the image receptor at low kVp—a phenomenon that is usually compensated for by increasing the mAs. The result is still higher patient dose.

With large patients, kVp must be high to ensure adequate penetration of the portion of the body that is being radiographed. If, for example, the normal technique factors for an AP examination of the abdomen are inadequate, the technologist has the choice of increasing mAs or kVp.

Increasing the mAs usually generates enough x-rays to provide a satisfactory image but may result in an unacceptably high patient dose. On the other hand, a much smaller increase in kVp is usually sufficient to provide enough x-rays, and this can be done at a much lower patient dose. Unfortunately, when kVp is increased, the level of scatter radiation also increases, leading to decreased image contrast.

Collimators and grids are used to reduce the level of scatter radiation.

Field Size
Another factor that affects the level of scatter radiation and is controlled by the radiologic technologist is x-ray beam field size. As field size is increased, scatter radiation also increases.

Collimation of the x-ray beam results in less scatter radiation, reduced dose, and improved contrast resolution.

Compared with a large field size, radiographic exposure factors may have to be increased for the purpose of maintaining the same OD when the exposure is made with a smaller field size. Reduced scatter radiation results in lower radiographic OD, which must be raised by increasing technique.

Patient Thickness

Imaging thick parts of the body results in more scatter radiation than imaging thin parts does. Compare a radiograph of the bony structures in an extremity with a radiograph of the bony structures of the chest or pelvis. Even when the two are taken with the same screen-film combination, the extremity radiograph will be much sharper because of the reduced amount of scatter radiation.

Patient Thickness

Scatter Radiation is a type of secondary radiation that occurs when the useful beam intercepts any object, causing some x-rays to be scattered. During an x-ray or fluoroscopic exam the patient is the most significant source of scatter radiation. Most of a technologists occupational exposure comes from scatter radiation; therefore using safety measures against scatter radiation will effectively lower a technologists occupational exposure.

Ways to protect yourself from scatter radiation are:

Always collimate to the area of interest, the larger the amount of tissue the beam is allowed to irradiate the more scatter radiation is produced.
Using high kVp and low mAs techniques produces less scatter
Use your protective equipment such as lead lined walls or lead aprons when you will be involved in an exam
During fluoroscopy exams always make sure the bucky slot cover is in place and the lead curtain is on the fluoro tower.
During mobile exams stand atleast 6 feet away and if possible at a 90 degree angle from the radiation source (the patient).
During c-arm procedures standing on the side of the image intensifier is safest because there is more scatter produced at the entrance surface side of the patient.

Examples of where to stand during exams:

This image illustrates the pattern of radiation during a fluoro exam, the safest place to stand is in the area of the black mark. This usually means standing behind the radiologist.

During a portable x-ray exam the safest place to stand would be the area of the black X, to the left or the right of the patient, but most importantly atleast 6 feet away.