Image Production

range of exposure values that can be captured by an IR

dynamic range

range of exposure values that can produce a quality image at an appropriate patient dose

exposure latitude

compares amount of signal in an image to the amount of noise

signal to noise ratio

SNR

signal to noise ratio

info from remnant beam that represents the actual patient anatomy

signal

xray photon is completely absorbed by inner shell electron, creates contrast in image

photoelectric effect

incoming photon is slightly higher than binding energy of inner shell electron

photoelectric effect

non ioninzing interaction within the patient

photoelectric interaction

xray interaction that contributes to occupational dose

compton effect

xray photon energy is partially absorbed by outer shell electron and remitted as a scattered photon

compton effect

electron slows before nucleus and changes direction, the closer it is to the nucleus that higher resulting photon energy

Bremsstrahlung

90% of all xray production

Bremsstrahlung

“Braking” radiation

Bremsstrahlung

incident electron collides with K-shell electron, ejecting it and outer shell electron drops down, closer to nucleus, higher resulting photon energy

Characteristic

described how the xray beam intensity changes when distance changes

inverse square law

What formula does this picture represent?

inverse square law

A radiograph is made with a 72 inch SID
resulting in a receptor exposure of 0.01 mGy.
What will the receptor exposure be if the SID is
changed to 36 inches?

0.04 mGy

During a surgical procedure the x-ray
technologist stands at 1 meter from the c-arm for
1 hour and acquires an equivalent dose of 0.1
mSv. If the technologist had stood at a distance of
5 meters, what would their dose have been?

0.004 mSv

An x-ray source is producing an entrance skin
exposure of 3.1 mSv per hour at 15 cm from the
source. What is the entrance skin exposure at 10
meters from the source?

7.0 mSv per hour

describes how mAs changes when SID changes to maintain receptor exposure

direct square law

What formula does this picture represent?

direct square law

A portal chest x-ray is to be acquired on an ICU
patient. The technique chart indicates the
exposure should be made with 100 kVp, 3.5 mAs,
and a 72 inch SID. The room is small and the
exposure must be at 62 inches. How should the
technique be changed?

increase mAs to 2.6

A satisfactory x-ray of the cervical spine is made
at 40 inches using automatic exposure control.
The exposure time was 100 milliseconds. If the
exam is repeated at 60 inches, what will the new
exposure time be?

225 milliseconds

A technologist acquires an x-ray of the pelvis
using 30 mAs at 40 inches SID. The image shows
excessive magnification and the technologist
repeats the image at 60 inches SID and 45 mAs. If
the initial image showed good receptor exposure,
the new image will be:

under-exposed