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Dual-layer dual-energy computed tomography for the assessment of hypovascular hepatic metastases: impact of closing k-edge on image quality and lesion detectability

  • Computed Tomography
  • Published:
European Radiology Aims and scope Submit manuscript

Abstract

Objectives

To evaluate the image quality of virtual-monoenergetic-imaging (VMI) from dual-layer dual-energy CT (DLCT) for the assessment of hypovascular liver metastases and its effect on lesion detectability.

Methods

Eighty-one patients with hypovascular-liver-metastases undergoing portal-venous-phase abdominal DLCT were included. Polyenergetic-images (PEI) and VMI at 40–200 keV (VMI40–200, 10-keV interval) were reconstructed. Image noise, tumor-to-liver contrast, and contrast-to-noise ratio (CNR) of hepatic parenchyma and metastatic nodules (n = 288) were measured to determine the optimal monoenergetic levels. Two radiologists independently and subjectively assessed the image quality (image contrast, image noise, and diagnostic confidence) of PEI and optimal VMI on 5-point scales to determine the best energy. For 38 patients having up to 10 metastases each with diameters < 25 mm (153 lesions), we compared blindly assessed lesion detectability and conspicuity between PEI and VMI at the best energy.

Results

Image noise of VMI40–200 was consistently lower than that of PEI (p < 0.01). Tumor-to-liver contrast and CNR increased as the energy decreased with CNR at VMI40–70 being higher than that observed on PEI (p < 0.01). The highest subjective score for diagnostic confidence was assigned at VMI40 followed by VMI50–70, all of which were significantly better than that of PEI (p < 0.01, kappa = 0.75). Lesion detectability at VMI40 was significantly superior to PEI, especially for lesions with diameters of < 10 mm (p < 0.01, kappa ≥ 0.6).

Conclusions

VMI40–70 provided a better subjective and objective image quality for the evaluation of hypovascular liver metastases, and the lesion detectability was improved with use of VMI40 compared with conventional PEI.

Key Points

• DLCT-VMI at 40–70 keV provides a superior subjective and objective image quality compared with conventional PEI for the assessment of hypovascular hepatic metastases during portal venous phase.

• Tumor-to-liver contrast and CNR of hypovascular hepatic metastases was maximized at 40 keV without a relevant increase in the image noise.

• VMI at 40 keV yields a superior lesion detectability, especially for small (< 1 cm) metastatic nodules compared with conventional PEI.

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Abbreviations

CNR:

Contrast-to-noise ratio

CTDIvol :

Volume CT dose index

DECT:

Dual-energy CT

DLCT:

Dual-layer dual-energy CT

PEI:

Polyenergetic image

ROI:

Region of interest

SSDE:

Size-specific dose estimate

VMI:

Virtual monoenergetic imaging

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Funding

The authors state that this work has not received any funding.

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Authors and Affiliations

  1. Department of Diagnostic Radiology, Graduate School of Medical Sciences, Kumamoto University, 1-1-1, Honjo, Chuo-ku, Kumamoto, 860-8556, Japan

    Yasunori Nagayama, Ayumi Iyama, Seitaro Oda, Narumi Taguchi, Takeshi Nakaura, Daisuke Utsunomiya, Yoko Kikuchi & Yasuyuki Yamashita

Authors
  1. Yasunori Nagayama
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  2. Ayumi Iyama
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  3. Seitaro Oda
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  4. Narumi Taguchi
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  5. Takeshi Nakaura
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  6. Daisuke Utsunomiya
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  7. Yoko Kikuchi
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  8. Yasuyuki Yamashita
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Correspondence to Yasunori Nagayama.

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The scientific guarantor of this publication is Yasuyuki Yamashita.

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The authors of this manuscript declare no relationships with any companies, whose products or services may be related to the subject matter of the article.

Statistics and biometry

No complex statistical methods were necessary for this paper.

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Institutional Review Board approval was obtained.

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Nagayama, Y., Iyama, A., Oda, S. et al. Dual-layer dual-energy computed tomography for the assessment of hypovascular hepatic metastases: impact of closing k-edge on image quality and lesion detectability. Eur Radiol 29, 2837–2847 (2019). https://doi.org/10.1007/s00330-018-5789-0

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  • DOI: https://doi.org/10.1007/s00330-018-5789-0

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