Kawai Tatsuya, Takeuchi Mitsuru, Hara Masaki, Ohashi Kazuya, Suzuki Hirochika, Yamada Kiyotaka, Sugimura Yuya, Shibamoto Yuta
Department of Radiology, Nagoya City University Graduate School of Medical Sciences, Nagoya.
Acta Radiol. 2013 Oct;54(8):954-60. doi: 10.1177/0284185113485068. Epub 2013 Apr 30.
The effects of a tin filter on virtual non-enhanced (VNE) images created by dual-energy CT have not been well evaluated.
To compare the accuracy of VNE images between those with and without a tin filter.
Two different types of columnar phantoms made of agarose gel were evaluated. Phantom A contained various concentrations of iodine (4.5-1590 HU at 120 kVp). Phantom B consisted of a central component (0, 10, 25, and 40 mgI/cm(3)) and a surrounding component (0, 50, 100, and 200 mgI/cm(3)) with variable iodine concentration. They were scanned by dual-source CT in conventional single-energy mode and dual-energy mode with and without a tin filter. CT values on each gel at the corresponding points were measured and the accuracy of iodine removal was evaluated.
On VNE images, the CT number of the gel of Phantom A fell within the range between -15 and +15 HU under 626 and 881 HU at single-energy 120 kVp with and without a tin filter, respectively. With attenuation over these thresholds, iodine concentration of gels was underestimated with the tin filter but overestimated without it. For Phantom B, the mean CT numbers on VNE images in the central gel component surrounded by the gel with iodine concentrations of 0, 50, 100, and 200 mgI/cm(3) were in the range of -19-+6 HU and 21-100 HU with and without the tin filter, respectively.
Both with and without a tin filter, iodine removal was accurate under a threshold of iodine concentration. Although a surrounding structure with higher attenuation decreased the accuracy, a tin filter improved the margin of error.
锡滤器对双能CT生成的虚拟平扫（VNE）图像的影响尚未得到充分评估。
比较有无锡滤器时VNE图像的准确性。
评估了两种由琼脂糖凝胶制成的不同类型的柱状体模。体模A含有不同浓度的碘（120 kVp时为4.5 - 1590 HU）。体模B由一个中心成分（0、10、25和40 mgI/cm³）和一个周围成分（0、50、100和200 mgI/cm³）组成，碘浓度可变。它们通过双源CT在常规单能量模式以及有无锡滤器的双能量模式下进行扫描。测量每个凝胶相应点的CT值，并评估碘去除的准确性。
在VNE图像上，体模A的凝胶CT值在单能量120 kVp、有锡滤器和无锡滤器时分别在626和881 HU以下的情况下落在 - 15至 + 15 HU范围内。当衰减超过这些阈值时，使用锡滤器时凝胶碘浓度被低估，而不使用时则被高估。对于体模B，在碘浓度为0、50、100和200 mgI/cm³的凝胶包围的中心凝胶成分中，VNE图像上的平均CT值在有锡滤器和无锡滤器时分别在 - 19至 + 6 HU和21至100 HU范围内。
无论有无锡滤器，在碘浓度阈值以下碘去除都是准确的。尽管具有较高衰减的周围结构会降低准确性，但锡滤器改善了误差范围。
