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Table 1 Hounsfield Unit (HU) values of segmented anatomy for conventional and VMI data from all four presented cases including ratio differential. Comparative and differential calculations were also made between the segmented ROI HU and the adjacent tissue material HU

From: Utility of virtual monoenergetic images from spectral detector computed tomography in improving image segmentation for purposes of 3D printing and modeling

Case

Conventional HU at ROI (C)

VMI HU at ROI (V)

HU value of tissue surrounding ROI (S)

HU Ratio Difference (C:V)

Δ HU Conventional HU to HU surrounding ROI (C-S)

Δ HU VMI HU to HU surrounding ROI (V-S)

1

89

206

62

1:2.3

27

144

2

308

666

250

1:2.2

58

416

3

148

451

87

1:3.0

61

364

4

698

66

NA*

1:0.11**

NA

NA

  1. *Case 4 was based on CT artifact reduction rather than surrounding tissue ROI differentiation and therefore HU value of tissue surrounding ROI was not calculated
  2. **The Ratio is less than one, because high keV VMI results in decreased ROI attenuation compared to conventional images