Differentiating Intrapulmonary Metastases from Different Primary Tumors via Quantitative Dual-Energy CT Based Iodine Concentration and Conventional CT Attenuation

Publication date: Available online 14 December 2018

Source: European Journal of Radiology

Author(s): Dominik Deniffel, Andreas Sauter, Julia Dangelmaier, Alexander Fingerle, Ernst J. Rummeny, Daniela Pfeiffer

ABSTRACT

Introduction

To investigate the utility of quantitative dual-energy spectral CT derived iodine concentration (IC), in comparison with conventional CT attenuation, for the differentiation of pulmonary metastases from different primary malignancies.

Materials and Methods

CT scans were performed on a dual-layer spectral CT. We retrospectively evaluated pulmonary metastases of 130 patients (77 men and 53 women, mean age 63, range 22 to 87) with primary bone (OS) (osteosarcoma; n = 6), breast (invasive-ductal adenocarcinoma; n = 17), colorectal (CRC) (adenocarcinoma; n = 27), head and neck (HNC) (squamous cell carcinoma; n = 17), kidney (RCC) (clear-cell renal cell carcinoma; n = 10), lung (adenocarcinoma; n = 12), pancreato-biliary (PBC) (adenocarcinoma; n = 18), prostate (adenocarcinoma; n = 5), soft tissue (undifferentiated pleomorphic sarcoma; n = 6), skin (malignant melanoma; n = 6), and urinary tract (transitional-cell carcinoma; n = 6) malignancies. Quantitative IC and conventional CT numbers (HU) were extracted and normalized to the thoracic aorta. Differences between the groups were assessed by pairwise t-tests with Holm-Sidak post-hoc p-value adjustment for multiple comparisons. Diagnostic accuracy was evaluated by receiver operating characteristic (ROC) analysis.

Results

Significant differences in IC and HU were noted for pulmonary metastases from RCC (IC: 2.83 mg/ml; HU: 93.12) versus breast cancer (IC: 1.47 mg/ml, adjusted p < 0.05; HU: 59.57, adjusted p < 0.05), CRC (IC: 1.23 mg/ml, adjusted p < 0.001; HU: 49.82, adjusted p < 0.001) and HNC (IC: 1.54 mg/ml, adjusted p < 0.05; HU: 58.91, adjusted p < 0.01). Based on IC alone, significant differences were further observed between metastatic lesions from CRC versus OS (IC: 2.36 mg/ml, adjusted p < 0.001), PBC (IC: 2.16 mg/ml, adjusted p < 0.001) and urinary tract carcinoma (IC: 2.21 mg/ml, adjusted p < 0.05). Based on IC and HU, pulmonary metastases from OS, HNC and RCC may be differentiated from other pulmonary metastases (area under ROC curve, 0.69-0.79). The diagnostic accuracy to discriminate between pulmonary metastases from PBC and those from other malignancies was significantly higher based on IC as compared to HU (area under ROC curve, 0.66; p < 0.05); no significant differences in diagnostic accuracy were noted for other differentiations.

Conclusions

Our findings demonstrate the utility of both dual-energy CT derived quantitative IC and conventional CT attenuation values for the differential diagnosis in suspected pulmonary metastases of unknown origin, however giving preference to the use of IC.

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