title: Parotid fat contents in healthy subjects evaluated with iterative decomposition with echo asymmetry and least squares fat-water separation.
abstract: OBJECTIVE
  To evaluate the effectiveness of three fat measurement methods for parotid glands in healthy subjects, with or without metallic dental implants.
  
  
  METHODS
  The institutional review board approved this study, with informed consent obtained from 114 volunteers undergoing magnetic resonance (MR) imaging at 1.5 T. Fat-saturated (FS) and non-fat-saturated (NFS) fast spin-echo T1-weighted imaging (T1 method), FS and NFS T2-weighted periodically rotated overlapping parallel lines with enhanced reconstruction fast spin-echo imaging (T2 method), and gradient-echo imaging with fat-water separation using iterative decomposition with echo asymmetry and least squares (IDEAL) method were used to derive parotid fat contents. Two raters examined the homogeneity of fat saturation to determine whether parotid fat quantification was successful, with the success rate in the 114 subjects recorded for each protocol. In subjects whose fat quantification was successful with all three imaging methods, linear regression was used to analyze the correlation between any pair of the three parotid fat content measurement methods.
  
  
  RESULTS
  Success rates in parotid fat measurements by using T1, T2, and IDEAL methods were 87.7% (100 of 114), 87.7% (100 of 114), and 100% (114 of 114), respectively. The means of measured parotid fat contents revealed significant differences (P < .001) between any pair of the three measurement methods. The parotid fat contents measured with the three methods were significantly correlated with each other between any pair of combinations.
  
  
  CONCLUSIONS
  The IDEAL method provided a high success rate for parotid fat measurements, even in subjects with metallic dental implants.
authors: Department of Electrical Engineering and Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, No. 1, Sec 4, Roosevelt Road, MD-624, Taipei, Taiwan.
authors: Hing-Chiu
authors: HC
authors: Chang
authors: Chun-Jung
authors: CJ
authors: Juan
authors: Hui-Chu
authors: HC
authors: Chiu
authors: Yi-Jui
authors: YJ
authors: Liu
authors: Cheng-Chieh
authors: CC
authors: Cheng
authors: Su-Chin
authors: SC
authors: Chiu
authors: Cheng-Yu
authors: CY
authors: Chen
authors: Guo-Shu
authors: GS
authors: Huang
authors: Hsiao-Wen
authors: HW
authors: Chung
mesh_terms: D000273:Adipose Tissue / Q000033:anatomy & histology*; D015921:Dental Implants; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007091:Image Processing, Computer-Assisted; D016018:Least-Squares Analysis; D016014:Linear Models; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008670:Metals; D008875:Middle Aged; D010306:Parotid Gland / Q000033:anatomy & histology*; D011446:Prospective Studies
chemical_list: D015921:Dental Implants; D008670:Metals