title: Characteristics of immunoglobulin G4-related aortitis/periaortitis and periarteritis on fluorodeoxyglucose positron emission tomography/computed tomography co-registered with contrast-enhanced computed tomography.
abstract: BACKGROUND
  We aimed to assess the positivity, distribution, quantitative degree of vessel inflammation, and clinical characteristics of IgG4-related aortitis/periarteritis and periarteritis (IgG4-aortitis), and to examine the difference in these characteristics between cases with and without IgG4-aortitis, using fluorodeoxyglucose positron-emission tomography/computed tomography (FDG-PET/CT) co-registered with contrast-enhanced CT (CECT). We retrospectively evaluated 37 patients with IgG4-related disease (IgG4-RD) who underwent both FDG-PET/CT and CECT. The arterial SUVmax and its value normalized to the background venous blood pool (BP)-the target-to-background ratio (TBR) in the entire aorta and the major first branches-were measured. Active vascular inflammation was considered in cases with a higher FDG uptake than BP and a thickened arterial wall (>2 mm).
  
  
  RESULTS
  Fifteen (41%) patients exhibited IgG4-aortitis. Most patients (80%) showed multiple region involvement. The entire aorta, including the major first branches, were involved, typically showing a thickened wall and high FDG uptakes. The most common site was the iliac arteries (35%), followed by the infrarenal abdominal aorta (33%), thoracic aorta (8%), first branches of the thoracic aorta (8%), suprarenal abdominal aorta (6%), and the first branches of the abdominal aorta (5%). The IgG4-aortitis-positive vessel regions were thickened, with an average maximal wall thickness of 6.3 ± 2.9 mm. The SUVmax and TBR values were significantly higher in the IgG4-aortitis-positive regions (median 3.7 [1.6-5.5] and 2.1 [1.4-3.7], respectively) than in the IgG4-aortitis-negative regions (median 2.1 [1.2-3.7] and 1.3 [0.9-2.3], respectively; p < 0.0001). The IgG4-aortitis-positive group patients were older (69.5 ± 6.0 vs. 63.3 ± 12.6 years, respectively) and had a higher male predominance (80 vs. 55%, respectively) than the negative group, although the differences were not significant (p = 0.17 and p = 0.06, respectively).
  
  
  CONCLUSIONS
  We investigated the image characteristics of IgG4-aortitis. The entire aorta and major branches can be involved with more than 2-fold higher FDG uptake than the venous background pool, and with wall thickening. The most common involved site is the iliac arteries, followed by the infrarenal abdominal aorta.
authors.affiliation: Department of Radiation Medicine, Hokkaido University Graduate School of Medicine, N15 W7, Kita-Ku, Sapporo, 060-8638, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Yabusaki
authors.affiliation: Department of Diagnostic and Interventional Radiology, Hokkaido University Hospital, N14 W5, Kita-Ku, Sapporo, 060-8648, Japan. norikooyama@med.hokudai.ac.jp.
authors.forename: Noriko
authors.initials: N
authors.lastname: Oyama-Manabe
authors.affiliation: Department of Nuclear Medicine, Hokkaido University Hospital, N14 W5, Kita-Ku, Sapporo, 060-8648, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Manabe
authors.affiliation: Department of Nuclear Medicine, Hokkaido University Hospital, N14 W5, Kita-Ku, Sapporo, 060-8648, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Hirata
authors.affiliation: Department of Diagnostic and Interventional Radiology, Hokkaido University Hospital, N14 W5, Kita-Ku, Sapporo, 060-8648, Japan.
authors.forename: Fumi
authors.initials: F
authors.lastname: Kato
authors.affiliation: Department of Radiation Medicine, Hokkaido University Graduate School of Medicine, N15 W7, Kita-Ku, Sapporo, 060-8638, Japan.
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Miyamoto
authors.affiliation: Department of Surgical Pathology, Hokkaido University Hospital, N14 W5, Kita-Ku, Sapporo, 060-8648, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Matsuno
authors.affiliation: Department of Diagnostic and Interventional Radiology, Hokkaido University Hospital, N14 W5, Kita-Ku, Sapporo, 060-8648, Japan.
authors.forename: Kohsuke
authors.initials: K
authors.lastname: Kudo
authors.affiliation: Department of Nuclear Medicine, Hokkaido University Hospital, N14 W5, Kita-Ku, Sapporo, 060-8648, Japan.
authors.forename: Nagara
authors.initials: N
authors.lastname: Tamaki
authors.affiliation: Department of Radiation Medicine, Hokkaido University Graduate School of Medicine, N15 W7, Kita-Ku, Sapporo, 060-8638, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Shirato
keywords: Contrast-enhanced CT; FDG-PET/CT; IgG4-related disease; IgG4-related vascular disease