Liver contrast-enhancement on Computed tomography : a question of to be or not to be in the right phase

Abstract: Background: Computed tomography (CT), is commonly used imaging technique in cancer patients. In CT performed for tumour staging to detect the spread of tumours, the liver is a common place for metastases. There are two types of metastases in the liver, hypo- and hyper vascularised, which generally are best seen in the venous phase and the late arterial phase. Therefore, CT of the liver often includes a triple phase contrast-enhancement protocol.   Purpose: The aim of this study was to qualitatively and quantitatively examine, through image review and attenuation measurements, respectively, the overall image quality of CT examinations performed in conjunction with positron emission tomography, (PET)/CT and as separate, stand-alone CT-studies, at the Department of Nuclear Medicine and PET centre, Uppsala University Hospital.   Method: A retrospective cross-sectional patient records review was undertaken with a descriptive approach of the qualitatively and quantitative data. 286 examinations were included in the study.     Result: The examinations were of high-quality in terms of contrast-enhancement technique, 183/190 (96,3%) of late arterial phases and 211/286 (74%) of venous phases. Some characteristic differences in the contrast-enhancement of the liver and the metastases were found in the different CT phases, allowing for division into four separate categories based on their respective characteristics.   Conclusion: In summary, the performed CT examinations were in majority performed in the right phase. The image quality of Contrast-to-noise, (CNR) and Signal-to-noise (SNR) were satisfactory even if the CNR could be higher for a better distinguish and detected small structures in the images.