The CT's sample volume as an approximate, instrumental measure for density resolution in densitometry of the lung
The CT's sample volume as an approximate, instrumental measure for density resolution in densitometry of the lung
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DOI：
10.1118/1.597968
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发表时间：
1997-10-01
期刊：
影响因子：
3.8
通讯作者：
Lamers, RJS
中科院分区：
文献类型：
--
作者：
Kemerink, GJ;Kruize, HH;Lamers, RJS
最终，肺部CT密度测定应该在所有扫描仪上得到可比的结果。一个先决条件是使用相同的密度分辨率。不幸的是，密度分辨率作为性能指定参数是不切实际的，因为它取决于所扫描的细胞材料。因此，可用于扫描仪和协议表征且不依赖于特殊体模的另一个参数将是非常优选的。我们研究了CT的标称样本体积（V），根据CT制造商指定的切片厚度和平面内空间分辨率计算，可以作为密度分辨率的简单测量。使用泡沫和肺模型对6台CT扫描仪进行了研究。在所有扫描仪上，我们观察到泡沫的密度分辨率和V-12密度分辨率之间的近似线性关系在不同的扫描仪上有一定程度的变化。这些差异可解释为真实样品体积与标称值的偏差所致：例如，V=8 mm（3）的95%置信区间为4.6 mm（3）至16.9 mm（3）。这种扩散的可接受性取决于临床感兴趣的参数的结果，如像素和像素指数。为了评估这一点，我们使用了以前的患者研究的数据，直方图参数对样本量的依赖性。有了这些数据，它被发现，在直方图参数的大interscanner差异是可能的小值的V，用于薄切片密度。对于更大的V值，如更充分的密度分辨率所需，与肺密度测定中的其他变异性来源相比，差异要小得多，并且可能是可接受的。总之，对于至少2 mm的切片和平滑重建滤波器，对应于大于或接近8 mm的V（3），CT的标称样本量可用于扫描仪间和方案间密度分辨率的比较。(C)1997年美国医学物理学家协会。
Ultimately CT-densitometry of the lung should give comparable results on all scanners. One prerequisite for this is the use of the same density resolution. Unfortunately, density resolution is impractical as a performance specifying parameter because it depends on the cellular material scanned. Therefore, another parameter that can be used for scanner and protocol characterization, and that does not depend on a special phantom, would be highly preferable. We investigated how well the CT's nominal sample volume (V), calculated from section thickness and in-plane spatial resolution as specified by the CT manufacturer, can serve as a simple measure for density resolution. Six CT scanners were studied using foam and lung phantoms. On all scanners we observed for foam an approximately linear relation between density resolution and V-12 Density resolution on different scanners varied to some extent. These differences can be interpreted as being caused by deviations of the true sample volume from the nominal value: the 95%-confidence interval runs for instance for V=8 mm(3) from 4.6 mm(3) to 16.9 mm(3). Acceptability of this spread depends on the consequences for parameters of clinical interest, like percentiles and pixel indexes. To evaluate this we used data from a previous patient study on the dependence of histogram parameters on sample volume. With these data it is found that large interscanner differences in histogram parameters are possible for small values of V, as used in thin-section densitometry. For larger values of V, as required for a more adequate density resolution, the differences are much smaller and probably acceptable when compared to other sources of variability in lung densitometry. In conclusion, for sections of at least 2 mm and smooth reconstruction filters, corresponding to V greater than or similar to 8 mm(3), the CT's nominal sample volume might be used for interscanner and interprotocol comparison of density resolution. (C) 1997 American Association of Physicists in Medicine.