SOURCE TO IMAGE RECEPTOR DISTANCE

Source-to-image receptor distance (SID）

is the distance from the anode focal spot inside the x-ray tube to the IR.

SID

is an important technical consideration in the production of radiographs of optimal quality.

magnification of the anatomy on the image, spatial resolution, and patient dose

SID directly affects

the less the anatomy is magnified

the greater the SID

approximately 10%

the greater the spatial resolution with a reduction in patient dose of

SID of 40 inches (102 cm)

has been used traditionally for most conventional examinations.

SID less than 40 inches (<102 cm)

For a few radiographic projections,_ is desirable.

short SID of 30 inches (76 cm)

In certain examinations, such as examination of the odontoid in the open-mouth position.

greater magnification

This shorter SID results in differentially_, in the direction of beam divergence, of the anatomic structures closest to the tube.

greater field of view of the structures

the structures nearest to the image receptor (IR)

reduced SID

to demonstrate the body part with reduced superimposition of overlying structures.

approximately 0.5 inches

At a 30-inch SID,_ more anatomy is visible /seen.

longer than standard SID

used for some radiographic projections.

72 inch ( 183 cm ) SID

In chest radiography, a _ is the minimum

120 inches (305 cm)

in many departments, a distance up to _ is used.

source-to-skin distance (SSD)

The distance between the focal spot of the radiography tube and the skin of the patient is termed the

National Council on Radiation Protection (NCRP).

This distance affects the dose to the patient and is addressed by

• not be less than 12 inches (<30 cm)

• should not be less than 15 inches (<38cm)

Current NCRP recommendations state that the SSD shall

less than 12 inches (30 cm)

All modern radiographic and fluoroscopic equipment is constructed to prevent an SSD