title: Altered carotid plaque signal among different repetition times on T1-weighted magnetic resonance plaque imaging with self-navigated radial-scan technique.
abstract: BACKGROUND
  Magnetic resonance (MR) plaque imaging for carotid arteries is usually performed by using an electrocardiograph (ECG)-gating technique to eliminate pulsation-related artifacts, which can affect the plaque signals because of varied repetition time (TR) among patients. Hence, we investigated whether differences in TR causes signal alterations of the carotid plaque by using a non-gated plaque imaging technique.
  
  
  METHODS
  We prospectively examined 19 patients with carotid stenosis by using a T1-weighted self-navigated radial-scan technique with TRs of 500, 700, and 900 ms. The signal intensity of the carotid plaque was measured, and the contrast ratio (CR) relative to the adjacent muscle was calculated.
  
  
  RESULTS
  CRs of the carotid plaques were 1.39 +/- 0.39, 1.29 +/- 0.29, and 1.23 +/- 0.24 with TRs of 500, 700, and 900 ms, respectively, and were significantly different. Among the plaques, those with a hyperintensity signal (CR > 1.5) and moderate-intensity signal (CR 1.2-1.5) at 500 ms showed a TR-dependent signal decrease (hyperintensity plaques, 1.82 +/- 0.26; 1.61 +/- 0.19; and 1.48 +/- 0.17; moderate-intensity plaques, 1.33 +/- 0.08; 1.26 +/- 0.08; and 1.19 +/- 0.07), while those with an isointensity signal (CR < 1.2) remained unchanged regardless of TR (0.96 +/- 0.12, 0.96 +/- 0.11, and 0.97 +/- 0.13).
  
  
  CONCLUSIONS
  The signal intensity of the carotid plaque on T1-weighted imaging significantly varies among different TRs and tends to decrease with longer TR. MR plaque imaging with short and constant TR settings that the ECG-gating method cannot realize would be preferable for evaluating plaque characteristics.
authors.affiliation: Department of Neurology and Gerontology, Iwate Medical University, 19-1 Uchimaru, Morioka, Japan.
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Narumi
authors.forename: Makoto
authors.initials: M
authors.lastname: Sasaki
authors.forename: Hideki
authors.initials: H
authors.lastname: Ohba
authors.forename: Kuniaki
authors.initials: K
authors.lastname: Ogasawara
authors.forename: Jiro
authors.initials: J
authors.lastname: Hitomi
authors.forename: Kiyofumi
authors.initials: K
authors.lastname: Mori
authors.forename: Kazumasa
authors.initials: K
authors.lastname: Ohura
authors.forename: Ayumi
authors.initials: A
authors.lastname: Ono
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Terayama
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016893:Carotid Stenosis / Q000473:pathology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D013997:Time Factors