SID, OID and Focal Spot relationship

SID

the distance from the x-ray source to the image receptor

Increased SID

Decreases magnification and geometric unsharpness, causing increased spatial resolution: ____ SID

Decreased SID

A ____ in SID will increases magnification and geometric unsharpness, causing decreased spatial resolution

magnification decreases

SID ↑ → _____ → blur ↓ → spatial resolution ↑

OID

the distance from the anatomy to the image receptor

Increased OID

Increases magnification and geometric unsharpness, causing decreased spatial resolution: ____ OID

Decreased OID

Decreases magnification and geometric unsharpness, causing increased spatial resolution: ____ OID

Magnification increases

OID ↑ → Magnificaion ___ → blur ↑ → spatial resolution ↓

Focal spot size

Size of the area on the anode where electrons strike and x-rays are produced

Small focal spot

Produces less geometric blur and better spatial resolution: ____ Focal Spot

Large focal spot

Produces more geometric blur and lower spatial resolution but handles more heat

geometric blur decreases

Focal spot size ↓ → Geo Blur ___ → spatial resolution ↑

Best combo for spatial resolution

Small focal spot + long SID + small OID

Worst combo for spatial resolution

Large focal spot + short SID + large OID

Short, Large

___ SID and ____ OID increase magnification

improves

Long SID, small OID, and small focal spot _____ image sharpness

Geometric unsharpness

Increases with a larger focal spot, shorter SID, or larger OID

improves, Decreases

Increasing SID____ spatial resolution, while increasing OID _____ spatial resolution

Long SOD

less magnification

Short SOD

more magnification