Dual X-ray Absorptiometry
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The DMS Lexxos is the first cone-beam dual X-ray absorptiometry (DXA) system capable of performing bone mineral density (BMD) measurements of the spine and hip. By using a two-dimensional (2-D) detector array rather than the linear array used with conventional fan-beam DXA systems, image acquisition time on Lexxos is only 1.5 s. However, the need to correct for the large signal from scattered radiation reaching the detector is a potential source of error in cone-beam DXA. The aim of this clinical evaluation of the Lexxos bone densitometer was to investigate the relative accuracy of cone-beam BMD measurements compared with conventional DXA by performing an in vivo cross-calibration study with an established fan-beam system, the Hologic QDR-4500. Spine (L1–L4) and hip BMD measurements were performed in 135 patients (111 women, 24 men) referred for a bone densitometry examination. Duplicate Lexxos measurements were performed in 27 female patients to evaluate precision. On average, Lexxos spine and femoral neck BMD measurements were 2% lower than those on the QDR-4500, whereas total hip BMD was 5% higher. Larger differences were found for the trochanter and Ward’s triangle regions. For all sites, Lexxos BMD measurements showed a strong linear relationship with those measured on the QDR-4500 with correlation coefficients in the range r = 0.95 to 0.97 for the clinically important spine, femoral neck, and total hip regions. The root mean standard error (RMSE) between Lexxos and QDR-4500 BMDs ranged from 0.037 g/cm2 for the femoral neck to 0.060 g/cm2 for the spine, whereas Lexxos precision was 1.3% for total hip, 2.0% for femoral neck, and 2.3% for spine BMD. Although for the hip BMD sites the RMSE and precision of Lexxos measurements were similar to studies of pencil-beam and fan-beam DXA systems, the results for the spine were poorer than expected. The findings of this study suggest that Lexxos corrects accurately for the effects of scattered radiation at the detector, but that the precision of spine BMD measurements may be limited by involuntary patient movement between the high and low energy X-ray exposures.
KeywordsDual X-ray absorptiometry Cone-Beam DXA Cross-calibration
The authors wish to thank CML for the opportunity to evaluate the Lexxos DXA system and the DMS engineers for technical support.
- 5.Black, DM, Cummings, SR, Karpf, DB, Cauley, JA, Thompson, DE, Nevitt, MC, Bauer, DC, Genant, HK, Haskell, WL, Marcus, R, Ott, SM, Torner, JC, Quandt, SA, Reiss, TF, Ensrud, KE 1996Randomised trial of the effect of alendronate on risk of fracture in women with existing vertebral fracturesLancet34815351541CrossRefPubMedGoogle Scholar
- 6.Ettinger, B, Black, DM, Mitlak, BH, Knickerbocker, RK, Nickelsen, T, Genant, HK, Christiansen, C, Delmas, PD, Zanchetta, JR, Stakkestad, J, Gluer, CC, Krueger, K, Cohen, FJ, Eckert, S, Ensrud, KE, Avioli, LV, Lips, P, Cummings, SR 1999Reduction of vertebral fracture risk in postmenopausal women with osteoporosis treated with raloxifene: results from a 3-year randomized clinical trialJAMA282637645CrossRefPubMedGoogle Scholar
- 7.Harris, ST, Watts, NB, Genant, HK, McKeever, CD, Hangartner, T, Keller, M, Chesnut, CH, Brown, J, Eriksen, EF, Hoseyni, MS, Axelrod, DW, Miller, PD 1999Effects of risedronate treatment on vertebral and nonvertebral fractures in women with postmenopausal osteoporosisJAMA28213441352CrossRefPubMedGoogle Scholar
- 8.Neer, RM, Arnaud, CD, Zanchetta, JR, Prince, R, Gaich, GA, Reginster, J-Y, Hodsman, AB, Eriksen, EF, Ish-Shalom, S, Genant, HK, Wang, O, Mitlak, BH 2001Effect of recombinant human parathyroid hormone (1-34) fragment on spine and non-spine fractures and bone mineral density in postmenopausal osteoporosisN Engl J Med34414341441CrossRefPubMedGoogle Scholar
- 9.WHO Technical Report Series 843. (1994) Assessment of fracture risk and its application to screening for postmenopausal osteoporosis. World Health Organization, GenevaGoogle Scholar
- 10.Royal College of Physicians (2000) Osteoporosis: clinical guidelines for prevention and treatment. Update on pharmacological interventions and an algorithm for management. RCP, London, EnglandGoogle Scholar
- 21.Altman, DG 1991Practical statistics for medical researchChapman HallLondonGoogle Scholar