Improved Image Quality and Detectability of Hypovascular Liver Metastases on DECT with Different Adjusted Window Settings.

To investigate dual-energy CT of hypovascular liver metastases (LMs) with special focus on window settings (WSs). The aim of the study is to investigate the extent to which adapted WSs and the low-energy images of DECT improve the visibility especially of smaller LMs.  30 patients with LMs of colorectal cancer were investigated with DECT of the liver. In each patient contrast-enhanced DECT imaging with portal-venous delay was performed. The total number, mean number and conspicuity (1 = excellent - 5 = poor) of LMs were documented on 80-kVp images and virtual 120-kVp images with different WSs (25/200 HU, 50/200, 75/200 HU, 25/350 HU, 50/350 HU, 75/350 HU, 25/500 HU, 50/500 HU, 75/500 HU). The attenuation (HU) of LMs and several anatomic regions and the background noise on 80 kVp images and virtual 120 kVp images were documented. Signal (liver)/noise and liver/LM ratio (SNR/LLMR) were calculated. The total number of LMs depending on size (< 1 cm, 1 - 2 cm, > 2 cm) on 80 kVp images and virtual 120 kVp images with previously investigated best and regular WSs were documented.  The highest total number, mean number per patient and total number of LMs < 1 cm were detected with the WS 25/350 HU on 80kVp images (7.0; p = 0.02/218; p = 0.01/64;p < 0.001) compared to the WS 75/200 HU on virtual 120 kVp images and the regular WS 50/350 HU on 80 kVp images and virtual 120 kVp images. The best conspicuity of LMs on 80 kVp images was documented with the WS 25/350 HU compared to the best WS on virtual 120 kVp images with 75/200 HU (1.2 vs. 2.5; p = 0.01). HU of normal liver, aorta, SNR and LLMR differed significantly between 80 kVp images and virtual 120 kVp images (128.1 vs. 93.6; < 0.05/192.8 vs. 131.4; < 0.05/10.3 vs. 8.1; p < 0.05/2.8 vs. 2.1; p < 0.05).  Low kVp images of DECT datasets are more precise in detecting hypovascular liver metastases than virtual 120 kVp images. Dedicated window settings have a relevant influence on conspicuity. · DECT is a promising tool for detecting hypovascular liver metastases.. · The diagnostic value of low kVp image data can be significantly increased by using special window settings.. · Use of only the low kVp images would lead to reduced radiation exposure.. · Altenbernd Jens, Forsting Michael, Lauenstein Thomas et al. Improved Image Quality and Detectability of Hypovascular Liver Metastases on DECT with Different Adjusted Window Settings. Fortschr Röntgenstr 2017; 189: 228 - 232.