Cross-calibration, precision and patient dose measurements in preparation for clinical trials using dual energy X-ray absorptiometry of the lumbar spine
Sa. Cawte et al., Cross-calibration, precision and patient dose measurements in preparation for clinical trials using dual energy X-ray absorptiometry of the lumbar spine, BR J RADIOL, 72(856), 1999, pp. 354-362
Citations number
21
Categorie Soggetti
Radiology ,Nuclear Medicine & Imaging","Medical Research Diagnosis & Treatment
Large, multicentre clinical trials using DXA to monitor bone density follow
ing intervention are now common. At the same time, several different bone d
ensitometers and calibration phantoms are currently in use. The aim of this
study was to document the technical information required on cross-calibrat
ion of equipment, reproducibility and patient dose before commencing a mult
icentre clinical trial. To this end, we obtained an in vitro and in vivo cr
oss-calibration of two machines (a Hologic QDR 2000 and a Lunar DPX-L) that
were not significantly different. Interobserver and intraobserver precisio
n, and radiation dose were also measured and three commonly used phantoms a
ssessed for their usefulness in cross-calibration and quality assurance. Me
asured in vitro precision on the two machines (0.3-0.7%) was better than th
at specified by the manufacturers. In vivo precision was worse (1.4-2.1%),
as might be expected in patients with reduced bone mass. Mean entrance skin
radiation doses on each machine were 280 mu Sv for the QDR 2000 and 38 mu
SV for the DPX-L. No one phantom is ideal, but the European Spine Phantom o
r Lunar Aluminium Spine Phantom will provide an adequate cross-calibration
for a clinical trial. This study demonstrates that an adequate cross-calibr
ation can be obtained for use in groups of patients and that the equipment
used is reproducible with a low radiation output.