Contents lists available at ScienceDirect Medical Hypotheses journal homepage: www.elsevier.com/locate/mehy Dynamic CT perfusion imaging for type 2 endoleak assessment after endograft placement Stavros Charalambous a, ⁎ , Nikolaos Kontopodis b , Kostas Perisinakis c , Antonios E. Papadakis c , Elias Kehagias a , Nikolaos Galanakis a , Nikolas Matthaiou a , Thomas G. Maris c , Christos V. Ioannou b , Dimitrios Tsetis a a Interventional Radiology Unit and Department of Medical Imaging, University Hospital of Heraklion, University of Crete Medical School, Greece b Vascular Surgery Unit and Department of Cardiothoracic and Vascular Surgery, University Hospital of Heraklion, University of Crete Medical School, Greece c Department of Medical Physics, University Hospital of Heraklion, University of Crete Medical School, Greece ARTICLE INFO Keywords: Abdominal aortic aneurysm Endovascular repair Endoleak Endoleak type 2 CT perfusion ABSTRACT Endovascular repair of abdominal aortic aneurysm is a widely performed treatment method due to its minimal invasiveness, reduced need for intensive care unit (ICU), shorter hospitalization and lower 30-day morbidity and mortality compared to open surgery. Endoleak is the drawback of this procedure and is considered the main culprit for re-interventions due to the risk of late aneurysm sac growth and rupture. Type 2 endoleak (T2EL) is the most common type of endoleak which is also the most controversial regarding its management. The aim of this paper is to investigate the potential of dynamic contrast-enhanced CT for the assessment of T2EL after endovascular aneurysm repair using qualitative and quantitative image analysis of the aneurysmal sac. Introduction Abdominal aortic aneurysmal disease is a major health problem associated with a certain risk of rupture and high mortality [1]. En- dovascular aneurysm repair (EVAR) is becoming the standard of care for the treatment of abdominal aortic aneurysm (AAA) since its initial introduction in 1991 [2]. The Achilles heel of EVAR is endoleak, which may be accompanied by a risk of late aortic rupture, being the main culprit for re-interventions [3,4]. Endoleak is defined as the presence of blood within the sac but outside the graft after EVAR. Five types of endoleaks have been de- scribed [5]. Type 2 endoleak (T2EL) is by far the most prevalent and it is characterized by retrograde perfusion of the aneurysmal sac from one or more aortic branches usually by inferior mesenteric and lumbar ar- teries and less commonly by sacral, gonadal and accessory renal arteries [3,6,7]. It is widely accepted that the risk of aneurysmal rupture in the presence of an isolated T2EL is exceptionally low [8]. This has led to the general practice that such lesions should be treated only if aneurysmal sac growth is observed [7,8]. Nevertheless, patients with T2EL are usually under close surveillance and strict follow-up protocols in order to observe the course of the endoleak and early detect any changes in the dimensions of the aneurysm sac. To date, the imaging method of choice after EVAR for endoleak detection and classification is computed tomography angiography (CTA). Doppler ultrasound (US) offers the possibility of repeated and reliable measurement of maximum aneurysm diameter at low cost without exposing the patient to ionizing radiation or nephrotoxic con- trast and, also, offers the possibility of detecting endoleaks, including flow direction and waveform [3]. Contrast-enhanced US is a new technique which has been reported to be equivalent to CTA in detecting endoleaks [9]. Recently, investigators suggested that magnetic re- sonance imaging (MRI) can be used in selected cases [10]. In a sys- tematic review comparing MR and CT examinations post-EVAR, MR appeared more sensitive for detection of endoleak, especially type 2 [11]. However, all these imaging techniques were mainly oriented in detection of an endoleak, but a portion of T2ELs will ever need further intervention and correction, thus, current research should focus on predictive factors identifying high-risk T2EL for sac expansion and/or rupture [10–13]. Dynamic CT perfusion (CTp) is a developing technique for quanti- tative evaluation of tissue blood perfusion and is routinely performed on patients with acute cerebral ischemia, coronary arterial disease as well as for diagnosis and evaluation of treatment response in patients with neoplasia (e.g. brain, liver, lung, prostate, and pancreas) [14–18]. To our knowledge, the blood perfusion characteristics have not been investigated so far in patients with endoleak. In this paper, we https://doi.org/10.1016/j.mehy.2020.109701 Received 15 February 2020; Received in revised form 21 March 2020; Accepted 30 March 2020 ⁎ Corresponding author. E-mail address: st.charalambous@hotmail.com (S. Charalambous). Medical Hypotheses 139 (2020) 109701 0306-9877/ © 2020 Elsevier Ltd. All rights reserved. T