Morphometric X-ray absorptiometry (MXA) provides the potential to assess ve
rtebral deformity using a technique with much lower radiation dose to the p
atient than standard radiographic procedures. MXA overcomes many other limi
tations such as cone beam distortion observed in conventional plane radiogr
aphs. A phantom has been designed to assess the accuracy of the MXA techniq
ue, to monitor long-term precision and to assess inter- and intra-operator
variability. The phantom consists of two columns of 12 cylinders representi
ng the vertebral bodies, one of regular components and one representing ver
tebral deformities. Each column may be inserted, as required, into a Perspe
x torso-mimicking block. Initial assessment on the Lunar Expert-XL demonstr
ates that the phantom provides image parameters reflecting those found clin
ically. Measurement of vertebral height was found to be consistently under-
estimatedd by 4.9%. Operator precision ranged from 0.6% for posterior heigh
t measurement to 1.0% for middle height measurement of the regular componen
t column. The corresponding precision range for the column representing ver
tebral deformation was 0.6% (posterior) and 1.1% (middle). Analysis of 10 s
cans of each column by two independent operators demonstrated a few signifi
cant differences in height assessment confined to the 'thoracic' region of
the regular column. However, inter-operator variability was found to increa
se with increasing complexity of vertebral shape producing several differen
ces, particularly in posterior height assessment of the deformed column.