Background

Bone strain index (BSI) is a tool measuring bone strain, derived from dual x-ray photon absorptiometry. It is able to characterise an aspect of bone quality that, joined to the quantity and quality parameters of bone mineral density (BMD) and trabecular bone score (TBS), permits an accurate definition of fracture risk. As no data are available about BSI precision, our aim was to assess its in vitro reproducibility.

Methods

A Hologic spine phantom was used to perform BSI scans with three different scan modes: fast array (FA), array (A), and high definition (HD). Different soft tissue thicknesses (1, 3, 6 cm) of fresh pork rind layers as a surrogate of abdominal fat were interposed. For each scan mode, the phantom was consecutively scanned 25 times without repositioning.

Results

In all scan modes (FA, A, HD) and at every fat thickness, BSI reproducibility was lower than that of BMD. The highest reproducibility was found using HD-mode with 1 cm of pork rind and the lowest one using HD-mode with 6 cm of pork rind. Increasing fat thickness, BSI reproducibility tended to decrease. BSI least significant change appeared to be about three times that of BMD in all modalities and fat thicknesses. Without pork rind superimposition and with 1-cm fat layer, BSI reproducibility was highest with HD-mode; with 3 or 6 cm fat thickness, it was higher with A-mode.

Conclusions

BSI reproducibility was worse than that of BMD, but it is less sensitive to fat thickness increase, similarly to TBS.

中文翻译：

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骨应变指数的可再现性和软组织厚度的影响：双重X射线光子吸收法幻象研究。

背景

骨应变指数（ BSI）是一种测量骨应变的工具，它是由双X射线光子吸收法得出的。它能够表征骨质量的一个方面，再加上骨矿物质密度（BMD）和小梁骨评分（TBS）的数量和质量参数，可以准确定义骨折风险。由于尚无有关BSI精度的数据，因此我们的目的是评估其BSI的体外可重复性。

方法

使用Hologic脊柱体模以三种不同的扫描模式执行BSI扫描：快速阵列（FA），阵列（A）和高清晰度（HD）。插入不同厚度的新鲜猪肉皮层（1、3、6厘米）作为腹部脂肪的替代物。对于每种扫描模式，幻像都连续扫描了25次而没有重新定位。

结果

在所有扫描模式（FA，A，HD）和每种脂肪厚度下，BSI的再现性均低于BMD。使用1厘米猪肉皮的HD模式时，再现性最高；使用6厘米猪肉皮的HD模式时，再现性最低。脂肪厚度增加，BSI重现性趋于降低。在所有方式和脂肪厚度上，BSI的最小显着变化似乎约为BMD的三倍。在没有猪皮叠加的情况下，脂肪层只有1厘米，HD模式的BSI重现性最高。脂肪厚度为3或6厘米时，在A模式下更高。

结论

BSI的可重复性比BMD差，但对脂肪厚度的增加不那么敏感，与TBS相似。