A comparative evaluation of the lunar bone densitometer software versions 1.3z and 4.7a following upgrade for Y2K compliance

Full text: Research departments perform software upgrades infrequently due to the need to maintain high consistency and precision. This study compares the results obtained on a Lunar DPX-L densitometer with v1.3z, and v4.7a installed to achieve Y2K compliance. The v4.7a provides improved image quality and femur edge detection algorithm with an expanded reference database. 30 previous studies on each region analysed on v1.3z were reanalysed on v4.7a. The paired data were evaluated using bivariate correlation. No differences existed in the bone mineral density (BMD) values, T-scores or Z-scores for the L2-L4 spine, radius (ultradistal), radius (33%) and total body (weight <75kg) (r=1, p<0.001). There is significant high correlation for the femoral neck and total body (weight >75kg) values (r>0.90; p<0.001). Although the mean femoral neck BMD difference was only 1% point, the individual difference ranged up to 22% points. Similarly, the mean differences in T- and Z-scores are small but the individual variation was up to 1.84 s.d. From the correlation equation, v7.4 software gave higher values for BMD above 1.00mg/cm2, and lower values below 1.00mg/cm2. The total body BMD for patients under 75kg of weight is unchanged. An extended analysis is recommended for patients greater than 75kg; software in v4.7 gave only minor variability (up to 5% points). Total lean and fat mass measurements show minimal variability. In conclusion, re-analysis of the femur and total body BMD (patients >75kg) of previous studies is needed to allow comparability with new studies as significant individual variation can occur even though the mean differences are small. Copyright (2000) The Australian and New Zealand Society of Nuclear Medicine Inc