FUNDAMENTALS OF IMAGING
RAD 206
Geometric factors
What is focal spot? andWhat is effective focal spot ?
The smaller the beam towards the patient
The better the detail of image produced
FOCAL-SPOT BLURDependent on the size of the effective focal spotSmaller the effective focal spot results in:
• less Blur and •better spatial resolution
Focal spot Blur is the most important factor in determining spatial resolution
Smaller x-ray beam width will produce a sharper imageFine detail = small focal spot ( for small parts of the body )General radiography of large areas uses large focal spot
Experiment and compare between beam from a penlight with a beam from a flood light
Focal-Spot Blur is caused by the effective size of the focal spot, which is larger towards the cathode side of the image
Anode cathode
Effect of focal spot size on: PenumbraAnd Resolution
Anode cathode
Focal Spot Blur is smaller when the OID is smaller
OBJECT SHAPEObjects with structures coincide (aligned) with the x-ray beam has maximum detail