title: Investigation of motion artifacts associated with fat saturation technique in 3D flash imaging.
abstract: OBJECTIVE
  Fast low-angle shot (FLASH) imaging is widely used in dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) because it permits fast and accurate T1 measurement in vivo. Suppression of the fat signal is necessary for most FLASH applications; otherwise, fat will appear hyperintense. The fat saturation technique is one popular method to reduce fat images on clinical scanners. However, fat saturation combined with the 3D FLASH sequence in breast DCE-MRI scans results in heavy ghosting artifacts caused by heartbeat. We used simulation and experimental scans to determine the cause of these artifact-enhancement phenomena.
  
  
  METHODS
  We simulated imaging of motion in the x, y, and z directions, with and without fat saturation, to investigate the origin of artifacts. Fourier transform (FT) of the whole field of view was used in the simulation, and we assumed that the uniform phantom was static during one TR. The amplitude of each echo was considered a factor in the FT data. Images were reconstructed using FT data from different phantom positions multiplied by the amplitude factor. Phantom experiments and volunteer studies were implemented to verify the conclusion.
  
  
  RESULTS
  Both phantom and volunteer results showed artifacts similar to those in simulation images. We found that FLASH sequence without fat saturation is insensitive to motion. Fat saturation radiofrequency pulses placed before each group of echoes disrupted the steady state of the signal amplitude and produced a low-pass filter effect that enhanced the motion artifacts.
  
  
  CONCLUSIONS
  We conclude that the low-pass filter effect associated with the fat saturation technique is responsible for dramatically increased motion artifacts.
authors.affiliation: Beijing City Key Lab of Medical Physics and Engineering, Beijing University, Beijing 100871, China.
authors.forename: Kaining
authors.initials: K
authors.lastname: Shi
authors.forename: Kun
authors.initials: K
authors.lastname: Zhou
authors.forename: Xueming
authors.initials: X
authors.lastname: Niu
authors.forename: Bei
authors.initials: B
authors.lastname: Luo
authors.forename: Hui
authors.initials: H
authors.lastname: Han
authors.forename: Shanglian
authors.initials: S
authors.lastname: Bao
authors.forename: Jingfei
authors.initials: J
authors.lastname: Ma
mesh_terms: D000273:Adipose Tissue / Q000033:anatomy & histology; D016477:Artifacts; D055592:Biophysical Phenomena; D001940:Breast / Q000033:anatomy & histology; D003287:Contrast Media; D005260:Female; D005583:Fourier Analysis; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods* / Q000706:statistics & numerical data; D008279:Magnetic Resonance Imaging / Q000379:methods* / Q000706:statistics & numerical data; D009038:Motion; D019047:Phantoms, Imaging; D012984:Software
chemical_list: D003287:Contrast Media