title: Refocused turbo spin-echo for noncontrast peripheral MR angiography.
abstract: OBJECTIVE
  To develop and assess a three-dimensional refocused turbo spin-echo (rTSE) sequence for generating peripheral angiograms. This sequence combines the rapid T2 -weighting of TSE and the better flow performance of the fully-refocused gradients of balanced steady state free precession (bSSFP), along with bSSFP-style phase alternation of refocusing radiofrequency (RF) pulses.
  
  
  METHODS
  The signal behavior generated by such a sequence was explored through Bloch equation simulations. The rTSE and TSE sequences were both used to generate peripheral angiograms in nine normal volunteers. The signal to noise ratio, contrast resolution, and vessel sharpness of the resulting images were used as bases for comparison. Additionally, the rTSE sequence was applied in four patients with peripheral artery disease to preliminarily assess its efficacy in a clinical setting through quality scoring by two experienced radiologists.
  
  
  RESULTS
  The rTSE's RF phase alternation approach out-performs a simple balanced-gradient CPMG (Carr-Purcell-Meiboom-Gill) -style TSE sequence in the presence of B0 and B1 inhomogeneities. In volunteers, the rTSE sequence yielded better arterial-venous contrast (0.378 ± 0.145 versus 0.155 ± 0.202; P < 0.01) and increased vessel sharpness (0.340 ± 0.034 versus 0.263 ± 0.034; P < 0.005) over TSE images. Stenoses visible in conventional angiographic images in patients were successfully imaged with the rTSE sequence; however, image quality scores in patients were lower than in volunteers (1.2 ± 0.38 versus 3.0 ± 1.0; P < 0.05).
  
  
  CONCLUSIONS
  The rTSE sequence generates nonsubtractive, flow-independent, peripheral MR angiograms with better arterial-venous contrast and vessel sharpness in normal volunteers than a conventional TSE sequence.
authors.affiliation: Department of Biomedical Engineering, University of Virginia, Charlottesville, Virginia, USA.
authors.forename: Samuel W
authors.initials: SW
authors.lastname: Fielden
authors.forename: John P
authors.initials: JP
authors.lastname: Mugler
authors.forename: Klaus D
authors.initials: KD
authors.lastname: Hagspiel
authors.forename: Patrick T
authors.initials: PT
authors.lastname: Norton
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Kramer
authors.forename: Craig H
authors.initials: CH
authors.lastname: Meyer
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D007866:Leg / Q000098:blood supply / Q000473:pathology; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D015588:Observer Variation; D016491:Peripheral Vascular Diseases / Q000175:diagnosis*; D015203:Reproducibility of Results; D059629:Signal-To-Noise Ratio; D055815:Young Adult
keywords: MR angiography; flow-independent angiography; noncontrast angiography; peripheral angiography; vascular disease