Utility of the iodine overlay technique and virtual nonenhanced images for the preoperative T staging of colorectal cancer by dual-energy CT with tin filter technology.

Chiao-Yun Chen,Jui-Sheng Hsu,Chien-Hung Lee,Chao-Hung Kuo,Ming-Lai Lai,Deng-Chyang Wu,Twei-Shiun Jaw,Yi-Ting Chen,Gin-Chung Liu,Ming-Chen Paul Shih,Qinghui Zhang

doi:10.1371/journal.pone.0113589

Abstract

ObjectivesTo evaluate the diagnostic accuracy and the potential radiation dose reduction of dual-energy CT (DECT) for tumor (T) staging of colorectal cancer (CRC) using iodine overlay (IO) and virtual nonenhanced (VNE) images.Materials and MethodsThis retrospective study included 103 consecutive patients who underwent nonenhanced CT and enhanced DECT for preoperative CRC staging. Enhanced weighted-average (WA), IO and VNE images were reconstructed from enhanced 80 kVp and Sn140 kVp scans. Two radiologists assessed image qualities of the true nonenhanced (TNE) and VNE images. For T-staging, another two radiologists independently interpreted all scans in two separate reading sessions: in the first session, only images derived from the single phase DECT acquisition (IO and VNE images) were read. In the second reading session after 30 to 50 (average:42) days, the same assessment was again performed with the TNE and enhanced WA images thereby simulating conventional dual-phase single-energy CT. The tumor node metastasis (TNM) system was used for staging with histopathologic reports as gold standard. Analysis of variance was used for statistical analysis.ResultsThe signal-to-noise ratios (SNRs) of the tumors and normal reference tissues showed significant correlation between the TNE and VNE images (P<0.01). The mean iodine overlay value (48.4 HU±12.2) and enhancement (49.4 HU±11.8) value of CRCs had no significant difference (P = 0.52).The mean image noise on TNE (5.0±1.1) and VNE (5.3±1.1) images were similar (P = 0.07). The quantitative qualities of the VNE images were mildly inferior to the TNE images. Overall accuracy of T-stage CRC when using single-phase acquisition was slightly better than the dual-phase acquisition (90.3% vs 87.4%) (P = 0.51). The mean dose of the single-phase DECT acquisition was 6.2mSv comparing with 14.3mSv of dual-phase.ConclusionSingle-phase DECT using IO and VNE images yields a high accuracy in T-staging of CRCs. Thereby, the radiation exposure of the patients can be reduced.

Highlights

The prognosis of patients with colorectal cancer (CRC) depends on the stage of disease at the time of diagnosis [1]
The overall diagnostic accuracies of T staging with multiplanar reformation (MPR) images was better in single-phase dual-energy CT (DECT) (VNE and iodine overlay (IO) images) than in dual-phase simulated single-energy CT (SECT) (TNE and enhanced WA images) (90.3% [93 of 103 neoplasms] vs. 87.4% [90 of 103 neoplasms]) (p50.51) (Fig. 5, 6)
Our results show that single-phase DECT using color-coded IO and virtual nonenhanced (VNE) images provide high accuracy in T-staging of CRC and suggest that VNE images could potentially replace true nonenhanced (TNE) images

Summary

Introduction

The prognosis of patients with colorectal cancer (CRC) depends on the stage of disease at the time of diagnosis [1]. Accurate preoperative staging is essential for the planning of optimal therapy [3, 4]. A standard CT imaging protocol usually includes nonenhanced and contrast-enhanced acquisitions [5,6,7]. Precontrast images are used as baseline density measurement of colon cancers, and providing information about the presence of fat [8], necrosis, calcium [9], or hemorrhage [10]. Previous reports found that contrastenhanced multidetector CT (MDCT) with multiplanar reformation (MPR) images could be used to assess suspected extensive colorectal cancers and identify invasion of pericolic fat planes and adjacent organs [5,6,7]

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