Radiologic Technology: Geometric Properties

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Recorded detail

The distinctness or sharpness of the structurall lines that make up the recorded image.

Geometric unsharpness

a result of the relationship among the size of the focal spot, SID, and OID. Which alters the amount of unsharpness recorded in the film image.

Resolution

the ability of the imaging system to resolve or distinguish between two adjacent structures.

Spatial resolution

refers to the smallest detail that can be detected in an image.

Contrast resolution

refers to the ability of the imaging system to distinguish between small objects having similar subject contrast.

Blur

Unsharpness resulting from patient motion and is the most detrimental factor to maximizing recorded detail. two types voluntary and involuntary.

Size distortion/magnification

refers to an increase in the objects image size compared with its true, actual, size.

Magnification factor (MF)

indicates how much size distortion or magnification is demonstrated on a radiograph.

Elongation

refers to images of objects that appear longer than the true objects.

Foreshortening

refers to images that appear shorter than the true objects.

Source-to-object distance

refers to the distance from the x-ray source(focal spot) to the object being radiographed.

Geometric properties

the sharpness of structural lines recorded in the radiographic image. Is influenced by the relationship among focal spot, SID, and OID.

Focal spot size

refers to the size of the filament being used. And only affects the recorded detail.

Focal spot size and recorded detail

As focal spot size increases, unsharpness increases and recorded detail decreases. As focal spot size decreases, unsharpness decreases and recorded detail increases.

SID, Unsharpness, and Recorded Detail

Increasing the SID decreases the amount of unsharpness and increases the amount of recorded detail in the image whereas decreasing the SID increases the amount of unsharpness and decreases the recorded detail.

OID, unsharpness, and Recorded Detail

Increasing the OID increases the amount of unsharpness and decreases the recorded detail whereas decreasing the amount of OID decreases the amount of unsharpness and increases the recorded detail. OID also has a greater effect on the amount of geometric unsharpness.

Intensifying Film-Screen Speed, Recorded Detail, and Unsharpness.

Increasing the relative speed of he intesifying film screen system decreases the recorded detail and increases the amount of unsharpness recorded in the image. Decreasing the relative speed of the intensifying film-screen system increases the recorded detail and decreases the amount of unsharpness recorded in the image.

Motion Unsharpness

has the most detrimental effect on the recorded detail of the radiographic image. any motion whether its the tube, patient, part, or IR will greatly decrease the recorded detail.

Eliminating Motion

Using shorter exposure time compensated by higher mA. Good instructions, Using immobilization tools

Distortion

results from the radiographic misrepresentation of either the size(magnification) or shape of the anatomic part. When the image is distorted recorded detail is also reduced.

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