title: Segmented TOF at 7 T MRI: Technique and clinical applications.
abstract: OBJECTIVE
  Time-of-flight (TOF) MR angiography has an advantage of contrast and resolution in ultra-high field (7 T) MRI systems. However, increased specific absorption rate (SAR) prohibits the application of spatial saturation band, leading to venous contamination in maximum intensity projection (MIP) images.
  
  
  METHODS
  A segmented k-space filling scheme with sparse venous saturation pulses was developed for 7 T TOF-MRA. The effectiveness of the segmented TOF sequence was verified by Bloch equation simulation and experiments on 3 T. The protocol on 7 T was optimized and applied for healthy volunteers and patients with vascular diseases.
  
  
  RESULTS
  Segmented TOF achieved equivalent contrast and venous suppression effect as conventional methods, while SAR values had a remarkable reduction and obeyed the limit of a 7 T MRI system. The decreased number of saturation pulses allowed shorter acquisition time than existing solutions. The comparison of segmented TOF and conventional TOF revealed flow direction in vascular diseases.
  
  
  CONCLUSIONS
  Segmented TOF is proved to be a time-efficient way to achieve high-resolution angiograms without venous contamination at ultra-high field. The sequence holds strong promise for non-contrast clinical diagnosis on cerebrovascular diseases.
authors.affiliation: State Key Laboratory of Brain and Cognitive Science, Beijing MR Center for Brain Research, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China; Graduate School, University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Zihao
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing 100050, China.
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Deng
authors.affiliation: Siemens Shenzhen Magnetic Resonance Ltd., Shenzhen 518057, China.
authors.forename: Dehe
authors.initials: D
authors.lastname: Weng
authors.affiliation: Siemens Shenzhen Magnetic Resonance Ltd., Shenzhen 518057, China.
authors.forename: Jing
authors.initials: J
authors.lastname: An
authors.affiliation: State Key Laboratory of Brain and Cognitive Science, Beijing MR Center for Brain Research, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Zhentao
authors.initials: Z
authors.lastname: Zuo
authors.affiliation: State Key Laboratory of Brain and Cognitive Science, Beijing MR Center for Brain Research, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Brain and Cognitive Science, Beijing MR Center for Brain Research, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China; Graduate School, University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Ning
authors.initials: N
authors.lastname: Wei
authors.affiliation: Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing 100050, China.
authors.forename: Jizong
authors.initials: J
authors.lastname: Zhao
authors.affiliation: State Key Laboratory of Brain and Cognitive Science, Beijing MR Center for Brain Research, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China; Beijing Institute for Brain Disorders, Beijing 100053, China. Electronic address: rxue@bcslab.ibp.ac.cn.
authors.forename: Rong
authors.initials: R
authors.lastname: Xue
mesh_terms: D000328:Adult; D002561:Cerebrovascular Disorders / Q000473:pathology*; D003287:Contrast Media; D005260:Female; D006801:Humans; D007089:Image Enhancement; D018810:Magnetic Resonance Angiography; D008297:Male; D055815:Young Adult
chemical_list: D003287:Contrast Media
keywords: 7T; MR angiography; SAR; Segmented TOF; Venous suppression