Cole Jacqueline H, Dowthwaite Jodi N, Scerpella Tamara A, van der Meulen Marjolein C H
Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY, USA.
J Clin Densitom. 2009 Jul-Sep;12(3):322-9. doi: 10.1016/j.jocd.2009.05.002.
As children grow, body and limb girths increase. For serial densitometric measurements, growth increases the distance between the bone region of interest and X-ray source over time, thereby increasing fan-beam magnification. To isolate bone accrual from magnification error in growing subjects, we developed a correction method based on waist girth, a common anthropometric measure. This correction was applied to dual-energy X-ray absorptiometry output obtained in a cohort of premenarcheal gymnasts and nongymnasts. After correcting for magnification, results for projected area and bone mineral content (BMC) increased by 0.4-1.1% at the lumbar spine and 8-16% at the femoral neck, decreasing areal bone mineral density (aBMD) by 0.4-2.3% at both sites. The effects of magnification correction were similar in magnitude to BMC and aBMD gains previously reported in longitudinal studies of normoactive children. Because of body size differences, the effect of correction for BMC and aBMD was 10-20% greater in nongymnasts than in gymnasts, which increased the observed aBMD differential between gymnasts and nongymnasts. Fan-beam magnification distorts true changes in bone mineral measures in growing premenarcheal girls and, therefore, may obscure additional activity-related changes during growth. Our correction technique may enhance detection of skeletal adaptation, particularly in pediatric populations.
随着儿童成长，身体和四肢周长会增加。对于系列密度测量，随着时间推移，生长会增加感兴趣骨区域与X射线源之间的距离，从而增加扇形束放大率。为了在生长中的受试者中分离出骨量增加与放大误差，我们基于腰围（一种常见的人体测量指标）开发了一种校正方法。该校正应用于一组月经初潮前体操运动员和非体操运动员获得的双能X射线吸收法输出结果。校正放大率后，腰椎的投影面积和骨矿物质含量（BMC）结果增加了0.4 - 1.1%，股骨颈增加了8 - 16%，两个部位的面积骨矿物质密度（aBMD）降低了0.4 - 2.3%。放大率校正的效果在幅度上与先前在正常活跃儿童纵向研究中报道的BMC和aBMD增加相似。由于体型差异，非体操运动员中BMC和aBMD校正的效果比体操运动员大10 - 20%，这增加了观察到的体操运动员和非体操运动员之间的aBMD差异。扇形束放大率会扭曲月经初潮前生长中女孩骨矿物质测量的真实变化，因此可能会掩盖生长过程中与活动相关的其他变化。我们的校正技术可能会增强对骨骼适应性的检测，尤其是在儿科人群中。
