European Journal of Radiology 74 (2010) e132–e137 Contents lists available at ScienceDirect European Journal of Radiology journal homepage: www.elsevier.com/locate/ejrad Subtraction-multiphase-CT unbeneficial for early detection of colorectal liver metastases Martijn R. Meijerink a,∗ , Jan Hein T.M. van Waesberghe a , Richard P. Golding a , Lineke van der Weide b , Petrousjka van den Tol c , Sybren Meijer b , Cornelis van Kuijk a a Department of Radiology, Vrije Universiteit Medisch Centrum, Amsterdam, The Netherlands b Master of Oncology Program, Vrije Universiteit Medisch Centrum, Amsterdam, The Netherlands c Department of Surgical Oncology, Vrije Universiteit Medisch Centrum, Amsterdam, The Netherlands article info Article history: Received 22 November 2008 Received in revised form 30 March 2009 Accepted 7 May 2009 Keywords: Colorectal cancer Liver metastasis Computed tomography (CT) Digital subtraction CT abstract Purpose: To assess the value of multiphase-subtraction-CT for early detection of colorectal-liver- metastases (CRLM). Methods and materials: In 50 patients suspected of CRLM a routine pre-operative 4-phase-CT-scan of the upper abdomen was obtained. All 12 possible image subtractions between two different phases were constructed applying 3D-image-registration to decrease distortion artefacts induced by differences in inspiration volume. Two experienced radiologists initially reviewed the conventional 4-phase-CT for malignant and/or benign appearing lesions and at least 1-month hereafter the same 4-phase-CT now including the subtracted images. The results were compared to histology reports or to a combination of surgical exploration and intraoperative ultrasound together with results from pre-operative PET and follow-up examinations. Results: Although an additional number of 31 malignant appearing lesions were detected on the subtrac- tion images, none proved to represent a true CRLM. Interobserver agreement () decreased from 0.627 (good) to 0.418 (fair). Conclusion: Adding linearly co-registered subtraction-CT images to a conventional 4-phase-CT protocol does not improve detection of CRLM. © 2009 Elsevier Ireland Ltd. All rights reserved. 1. Introduction Until recently the only potentially curative strategy for patients with colorectal liver metastases (CRLM) was surgical resection. Dur- ing the last few years, several alternative local ablative therapies such as radiofrequency ablation have been suggested to improve survival [1,2]. The results of these forms of therapy strongly depend on the accuracy of pre- and intraoperative imaging. Any technique that will increase sensitivity and specificity for the detection of CRLM will therefore probably improve survival and may also pre- vent patients from receiving unnecessary procedures. In the past decades technological advances in computed tomography (CT) have improved our insights into the imaging char- acteristics and enhancement patterns for benign and malignant liver tumours. Understanding the principles of hepatic perfusion ∗ Corresponding author at: Department of Radiology, Vrije Universiteit Medisch Centrum (VUMC), De Boelelaan 1117, 1081 HV, Amsterdam, The Netherlands. Tel.: +31 20 4440362; fax: +31 20 4440399. E-mail address: mr.meijerink@vumc.nl (M.R. Meijerink). is quintessential for characterization and detection of focal and dif- fuse liver abnormalities. Based on physiological data from animal and human studies in healthy subjects the hepatic artery versus portal vein contribution is 25–30% versus 70–75%. Most primary and metastatic liver tumours receive their blood from the hep- atic artery [3]. With helical CT, it is possible to image the entire liver unenhanced and during distinct phases of contrast medium enhancement such as the hepatic arterial phase, the portal venous phase and the equilibrium phase. We refer to this sequence as a 4 phase study. Although colorectal liver metastases (CRLM) usually are detected as hypoattenuating lesions during the portal venous phase, the vascularity and therefore enhancement characteristics can be widely variable for reasons that are poorly understood [4–6]. Small CRLM often are hyperattenuating during the hepatic arterial phase whereas larger lesions will often show a hyperattenuating rim during the hepatic arterial phase and a hypoattenuating cen- tre representing diminished vascularity and/or tumour necrosis [7]. In theory image subtraction may increase contrast resolution and therefore improve lesion conspicuity between normal liver parenchyma and liver tumours [8,9]. 0720-048X/$ – see front matter © 2009 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ejrad.2009.05.009