In our study, when increasing the X-ray beam energy both the
ESD and ED reduced (AP and PA). This trend has also been reported
by Doherty, O'Leary & Brennan.8 With respect to individual organ
doses an unexpected trend was noted for the testes. For AP projections,
at higher beam energies the absorbed dose to the testes
began to increase rather than decrease. A possible explanation for
this may be the fact that the testes are situated outside of the
collimated field during an AP lumbar projection.23 At higher beam
energies this increase in testicular (absorbed) dose may be due to
the greater intensity and surrounding penetration of scattered radiation.
This highlights an area which would warrant further
investigation. Dose calculations in this study were based on the
PCXMC software. PCXMC provides an option for calculating patients'
organ doses and the effective dose. It has several advantages
which should be noted. Firstly, as Servomaa and Tapiovaara (1998)
reported, dose calculations with PCXMC agree well with doses
calculations provided by the National Radiation Protection Board.24
Computation of organ doses can be undertaken for patients of different ages and sizes in freely adjustable X-ray projections and
can take into consideration other examination parameters.25 There
are, however, limitations which include possible mismatches between
the irradiated organs, e.g. if the field size is correct but the
irradiated organ volumes may be incorrect.