A reduction in image quality at higher kVps is to be expected in
part due to reduced contrast as a result of the increased scatter. A
further influencing factor is likely to be the reduction in signal to
noise ratio due to the decreased mAs determined by the central AEC
chamber as the kVp rises.21 With the widespread introduction of
digital radiography systems the traditional relationship between
tube potential and image contrast (film-screen systems) has been
redefined. It is possible that if this investigation were to be
repeated, using digital radiography, then the decrease in image
quality seen at kVps in excess of 100 may potentially be less
significant.
There are further factors that must be considered prior to
implementing any changes to standard radiographic positioning.
The PA position of a patient for lumbar spine radiography will
require the careful consideration of the condition of the patient. It is
likely to be practically unsuitable for patients following trauma,
those with severe abdominal pain, serious respiratory difficulties or
mobility problems. Patient comfort is also another factor; intuitively
an AP position is likely to provide a more comfortable patient
position in which to undertake a radiographic image. If a PA position
is to be undertaken then due consideration of any steps that
could help minimise patient discomfort should be considered.