AJR:193, November 2009 W437 detection of macrophages can contribute to identification of aneurysms at increased risk of growth or rupture. Although MRI with the macrophage-specific contrast agent ul- trasmall paramagnetic iron oxide (USPIO) has potential for noninvasive identification of macrophages in lymph nodes and athero- sclerotic plaques, little is known about US- PIO uptake in the aneurysm wall [9–12]. We studied USPIO uptake in the aortic wall of aneurysms and normal-sized aortas. Materials and Methods Patient Selection From January 2003 through September 2006, 239 patients with prostate cancer underwent CT angiography and USPIO-enhanced MRI in evalu- ation for lymph node metastasis. After retrospec- tive review of all USPIO-enhanced MRI data sets, the cases of 11 patients with an aortic (n = 6) or iliac (n = 5) aneurysm were identified. Because age is an important risk factor in atherosclerosis In Vivo Imaging of the Aneurysm Wall With MRI and a Macrophage- Specific Contrast Agent Maarten Truijers 1 Jurgen J. Fütterer 2 Satoru Takahashi 3 Roel A. Heesakkers 3 Jan D. Blankensteijn 1 Jelle O. Barentsz 3 Truijers M, Fütterer JJ, Takahashi S, Heesakkers RA, Blankensteijn JD, Barentsz JO 1 Department of Surgery and Vascular Surgery, Radboud University, Nijmegen Medical Center, Geert Grooteplein 10 zuid, PO Box 9101, Gelderland, 6500HB Nijmegen, The Netherlands. Address correspondence to M. Truijers (M.Truijers@chir.umcn.nl). 2 Department of Interventional Radiology, Radboud University, Nijmegen Medical Center, Gelderland, Nijmegen, The Netherlands. 3 Department of Radiology, Radboud University, Nijmegen Medical Center, Gelderland, Nijmegen, The Netherlands. Vascular฀and฀Interventional฀Radiology฀•฀Original฀Research WEB This is a Web exclusive article. AJR 2009; 193:W437–W441 0361–803X/09/1935–W437 © American Roentgen Ray Society A ccurate assessment of the risk of rupture of the aneurysm is essen- tial in selection of patients for prophylactic aneurysm repair [1, 2]. Although there is strong evidence that an- eurysm size correlates with rupture risk, small aneurysms do rupture [3, 4]. More- over, most patients with aneurysms have a short life expectancy and are likely to die with an intact large aneurysm [5]. To reduce the number of unanticipated ruptures with- out exposing all aneurysm patients to the risks of surgery, additional selection criteria are needed. Aneurysm rupture is associated with ex- tensive inflammation of the arterial wall [6]. Because of their capacity to secrete various cytokines, especially matrix metalloprotei- nases, infiltrated macrophages are consid- ered to play a central role in aneurysm for- mation, progression, and rupture [6–8]. Because of this important role, noninvasive Keywords: abdominal aortic aneurysm, macrophages, MRI, ultrasmall paramagnetic iron oxide DOI:10.2214/AJR.09.2619 Received February 22, 2009; accepted after revision April 15, 2009. OBJECTIVE. Because of their capability of secreting proteinases, macrophages play a central role in the growth and rupture of aneurysms. Noninvasive imaging of macrophages therefore may yield valuable information about the pathogenesis of aneurysm disease. We studied uptake of the macrophage-specific contrast agent ultrasmall paramagnetic iron oxide (USPIO) in the walls of aneurysms and normal-sized aortas. MATERIALS฀AND฀METHODS. Six patients with an aortic and five patients with an iliac aneurysm and 11 age-matched controls were identified in a database of 239 patients who underwent evaluations for the staging of prostate cancer. USPIO-enhanced MRI and contrast- enhanced MDCT were performed for all patients. The presence of USPIO was assessed with an iron-sensitive MRI sequence. Quantification consisted of counting the number of quad- rants with USPIO-induced subendothelial signal voids. A chi-square test was used to analyze the significance of the difference between the number of USPIO-positive quadrants in the an- eurysm group and that in the control group. RESULTS. The number of USPIO-positive quadrants was significantly higher in the an- eurysm than in the control group: 158 quadrants (4.2%) in the aneurysm group and 13 quad- rants (0.4%) in the control group ( p < 0.001). Two abdominal aortic aneurysms accounted for 90% (154/171) of all USPIO-positive quadrants. CONCLUSION. USPIO uptake is limited or absent in the wall of normal-sized aortas and most aneurysms. However, individual abdominal aortic aneurysms exhibit high levels of USPIO uptake, indicative of extensive macrophage infiltration in the aneurysm wall. Future research should focus on the predictive value of USPIO uptake for growth and rupture of aneurysms. Truijers et al. MRI of Aneurysm Wall Vascular and Interventional Radiology Original Research Downloaded from www.ajronline.org by 52.73.204.196 on 05/17/22 from IP address 52.73.204.196. Copyright ARRS. For personal use only; all rights reserved