PET Features of Aortic Diseases

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1 Nuclear Medicine/Molecular Imaging Pictorial Essay Hayashida et al. PET of ortic iseases Nuclear Medicine/Molecular Imaging Pictorial Essay ownloaded from by on 05/01/18 from IP address opyright RRS. For personal use only; all rights reserved Takeshi Hayashida 1 Eijun Sueyoshi 1 Ichiro Sakamoto 1 Masataka Uetani 1 Kenya hiba 2 Hayashida T, Sueyoshi E, Sakamoto I, Uetani M, hiba K Keywords: aortic diseases, aortitis, atherosclerosis, FG PET, periaortitis, thrombus OI: /JR Received November 12, 2009; accepted after revision ecember 17, epartment of Radiology, Nagasaki University School of Medicine, Sakamoto, Nagasaki , Japan. ddress correspondence to T. Hayashida (takeshi1@nagasaki-u.ac.jp). 2 Nishi-isahaya PET enter, Isahaya, Japan. JR 2010; 195: X/10/ merican Roentgen Ray Society PET Features of ortic iseases OJETIVE. Recently, several reports have highlighted the potential role of 18 F-FG PET for the assessment of various aortic diseases based on FG accumulation. In this article, we divided various aortic diseases into the following three groups on the basis of the mechanism of FG accumulation: atherosclerosis, aortitis or periaortitis, and thrombus. Elucidating the mechanisms and patterns of FG uptake in various aortic diseases provides valuable information for clinical management. ONLUSION. PET findings can provide additional information for the diagnosis of aortic diseases and valuable information for clinical management. It is essential to understand the characteristics of FG uptake in various aortic diseases for proper appreciation of PET findings. F G PET has been established as an effective technique for detecting various types of cancer and is rapidly becoming the standard technique of care for many cancers. FG PET is also being applied with increasing frequency to the evaluation of aortic diseases. However, various accumulation patterns have been shown for FG PET of aortic diseases. thorough knowledge of the mechanisms and patterns of 18 F-FG uptake in aortic diseases is essential for accurate image interpretation. The purpose of this article is to describe the characterization of aortic diseases using FG PET to provide valuable information for clinical management. therosclerosis Mechanism of FG ccumulation In atherosclerotic vessels, oxidized lowdensity lipoproteins destroy endothelial cells, and endothelial cell dysfunction causes migration of monocytes and T lymphocytes into the intima. Then, monocytes are transformed into intimal macrophages, which are activated by T lymphocytes, and FG accumulates in such activated macrophages. ortic neurysm ortic aneurysms are occasionally characterized by transmural inflammation involving lymphocytes and macrophage aggregation, and FG accumulates in the aggregated macrophages. Increased inflammation in the aortic aneurysm wall can be shown by FG. Hence, the absence of FG uptake in the aortic wall may indicate that the aneurysm wall is stable, whereas the presence of FG uptake may indicate an unstable aneurysm wall (Fig. 1). Sakalihasan et al. [1] showed a possible association between increased FG uptake and abdominal aortic aneurysm expansion and rupture. ortitis or Periaortitis Mechanism of FG ccumulation In aortitis, the main inflammatory lesions originate in the media or periaorta because of cellular infiltration by T lymphocytes, natural killer cells, monocytes, or granulocytes. FG mainly accumulates in monocytes. In active aortitis, FG uptake is higher in the large vessels than in the liver [2]. hronic Periaortitis hronic periaortitis is a clinical pathologic entity characterized by a fibroinflammatory reaction that extends from the adventitia of the abdominal aorta and the common iliac arteries into the retroperitoneum and that often leads to the encasement of adjacent structures (i.e., the ureter and inferior vena cava). The following three main entities are included: idiopathic retroperitoneal fibrosis, inflammatory abdominal aortic aneurysms, and perianeurysmal retroperitoneal fibrosis [3]. FG accumulates in the monocytes associated with chronic periaortitis (Fig. 2). JR:195, July

2 Hayashida et al. ownloaded from by on 05/01/18 from IP address opyright RRS. For personal use only; all rights reserved Giant ell rteritis Giant cell arteritis (G) affects large and medium-sized vessels and is best known for its manifestation in the extracranial branches of the carotid artery. The systemic manifestations of G include fever, malaise, and weight loss. rticles in the literature suggest that clinically manifested aortic disease occurs in 10 15% of G patients, about one third of whom present with aortic dissection or rupture, which most commonly affects the proximal thoracic aorta. linically manifested large-artery (i.e., the aorta and proximal branches) complications have been reported in up to 27% of patients with G [4]. PET can be used as a sensitive and reasonably specific diagnostic test for largevessel G (Fig. 3) because FG accumulates in areas of inflammation in the aortic wall. Takayasu rteritis Takayasu arteritis is a chronic inflammatory arteritis that primarily involves the aorta and its main branches [5]. PET is a wellestablished functional imaging technique that provides data on glucose metabolism in lesions (Fig. 4) and allows the visualization of inflammatory cells. Increased FG accumulation allows detection of active inflammation of the aorta in patients with early-phase Takayasu arteritis [6]. dditionally, the ability to visualize FG accumulation in activated inflammatory cells makes PET a promising technique for evaluating disease activity and the response to therapy in patients with Takayasu arteritis. Thrombus Mechanism of FG ccumulation In resting platelets, selectins are stored; on activation, they are redistributed to the platelet surface and initiate adhesion to Ws. FG accumulates in Ws. Intramural Hematoma Intramural hematoma may be differentiated from aortic dissection in that hemorrhaging of the aortic wall occurs in the absence of intimal disruption. Focal FG uptake in the wall of the aorta can be seen in intramural hematoma [7] (Fig. 5). lthough patients with intramural hematoma usually present with sudden back or chest pain, we encountered a patient with an intramural hematoma that was discovered by PET examination for cancer screening. In that case, PET examination allowed early diagnosis of the intramural hematoma and enabled appropriate treatment. Graft Thrombus Vascular prosthesis infection is a serious complication with high morbidity and mortality. Vascular graft infections are usually detected by T or MRI, but there is growing interest in PET as an imaging technique for the detection of infections. Increased FG uptake can be seen in areas of activated granulocytes [8]. onsequently, PET has the potential to depict vascular graft infections, as illustrated in several reports [9 11]; however, synthetic grafts provoke chronic lowgrade inflammation and thrombus. This chronic inflammation and thrombus constitute a potential site for FG uptake and, therefore, a potential risk of false-positive PET results (Fig. 6). onclusion FG PET findings can provide additional information for the diagnosis of aortic diseases and valuable information for clinical management. It is essential to understand the characteristics of FG uptake in various aortic diseases for proper appreciation of PET findings. References 1. Sakalihasan N, Van amme H, Gomez P, et al. Positron emission tomography (PET) evaluation of abdominal aortic aneurysm (). Eur J Vasc Endovasc Surg 2002; 23: Walter M, Melzer R, Schindler, et al. The value of [ 18 F]FG-PET in the diagnosis of largevessel vasculitis and the assessment of activity and extent of disease. Eur J Nucl Med Mol Imaging 2005; 32: Salvarani, Pipitone N, Versari, et al. Positron emission tomography (PET): evaluation of chronic periaortitis. rthritis Rheum 2005; 53: Janssen SP, omans EH, Voskuyl E, Wisselink W, Smulders YM. Giant cell arteritis: heterogeneity in clinical presentation and imaging results. J Vasc Surg 2008; 48: Webb M, hambers, l-nahhas, et al. The role of 18 F-FG PET in characterising disease activity in Takayasu arteritis. Eur J Nucl Med Mol Imaging 2004; 31: Iwabu M, Yamamoto Y, obashi H, Kameda T, Kittaka K, Nishiyama Y. F-18 FG PET findings of Takayasu arteritis before and after immunosuppressive therapy. lin Nucl Med 2008; 33: Ryan, Mcook, Sholosh, et al. cute intramural hematoma of the aorta as a cause of positive FG PET/T. lin Nucl Med 2007; 32: van der Vaart MG, Meerwaldt R, Slart RH, van am GM, Tio R, Zeebregts J. pplication of PET/SPET imaging in vascular disease. Eur J Vasc Endovasc Surg 2008; 35: Wassélius J, Malmstedt J, Kalin, et al. High 18 F- FG uptake in synthetic aortic vascular grafts on PET/T in symptomatic and asymptomatic patients. J Nucl Med 2008; 49: Liberatore M, Iurilli P, Ponzo F, et al. linical usefulness of technetium-99m-hmpo-labeled leukocyte scan in prosthetic vascular graft infection. J Nucl Med 1998; 39: Prats E, anzo J, bós M, et al. iagnosis of prosthetic vascular graft infection by technetium 99m-HMPO-labeled leukocytes. J Nucl Med 1994; 35: JR:195, July 2010

3 PET of ortic iseases ownloaded from by on 05/01/18 from IP address opyright RRS. For personal use only; all rights reserved Fig year-old man with atherosclerotic aortic aneurysm., oronal maximum-intensity-projection PET image shows continuous FG uptake at vessel together with abdominal aortic aneurysm., xial PET image shows focal FG uptake in right lateral aspect of abdominal aortic aneurysm (arrow). Heterogeneous uptake strongly suggests presence of atherosclerotic plaques because FG accumulates in inflammatory cells in atherosclerotic plaques., xial PET/T fusion image shows focal FG uptake in right lateral aspect of abdominal aortic aneurysm (arrow). FG accumulates in inflammatory cells in atherosclerotic plaques. Fig year-old woman with chronic periaortitis., oronal maximum-intensity-projection PET image shows visible FG uptake at abdominal aorta (arrow)., xial PET image shows FG uptake in periaortic mass (arrow); this finding is suggestive of chronic periaortitis., xial PET/T fusion image shows FG uptake in periaortic mass (arrow); this finding is suggestive of chronic periaortitis. JR:195, July

4 Hayashida et al. ownloaded from by on 05/01/18 from IP address opyright RRS. For personal use only; all rights reserved Fig year-old woman with giant cell arteritis., oronal maximum-intensity-projection PET image shows linear continuous FG uptake at wall of aorta and its branches (arrows)., xial PET image shows FG uptake in walls of ascending and descending aorta (arrows)., xial PET/T fusion image shows FG uptake in walls of ascending and descending aorta (arrows)., MR angiography image shows severe bilateral subclavian arteries stenosis (arrows). Fig year-old woman with Takayasu arteritis., xial PET/T fusion image shows high focal uptake in thoracic descending aorta (arrow)., xial T image shows wall thickening of thoracic descending aortic wall (arrow)., Follow-up axial PET/T fusion image obtained after patient had undergone corticoid therapy shows FG uptake is no longer present in aorta (arrow)., Follow-up axial T image obtained after patient had undergone corticoid therapy shows aortic wall (arrow) is not thickened. 232 JR:195, July 2010

5 PET of ortic iseases ownloaded from by on 05/01/18 from IP address opyright RRS. For personal use only; all rights reserved Fig year-old man with intramural hematoma., oronal maximum-intensity-projection PET image shows focal FG uptake at wall of aortic arch (arrow). hest pain had occurred 3 days before PET examination., xial T image shows intramural hematoma of aortic arch (arrow)., PET image shows focal high FG uptake in intramural hematoma (arrow)., PET/T fusion image shows high FG uptake in intramural hematoma (arrow). E, ontrast-enhanced T image shows intramural hematoma with ulcerlike projection (arrow). Surgical intervention was performed, and obtained 3 months after. Surgical findings and specimens confirmed diagnosis of intramural hematoma. Fig year-old man who had undergone surgery for thoracic and abdominal aortic aneurysms presented with inflammation and thrombus of graft. Patient had no symptoms or signs suggesting infection., oronal maximum-intensity-projection PET image shows focal FG uptake at vascular grafts (arrows)., xial PET image shows FG uptake at right brachiocephalic artery (arrow). We speculate that observed FG uptake is attributable to inflammation and thrombus in graft., xial PET/T fusion image shows FG uptake in right brachiocephalic artery (arrow). This FG uptake may be attributable to inflammation and thrombus in graft., xial PET image shows FG uptake in vascular graft (arrow). This FG uptake may be attributable to inflammation and thrombus in graft. E, xial PET/T fusion image shows FG uptake in vascular graft (arrow). This FG uptake may be attributable to inflammation and thrombus in graft. E E JR:195, July