title: Precision, signal-to-noise ratio, and dose optimization of magnitude and phase arterial input functions in dynamic susceptibility contrast MRI.
abstract: OBJECTIVE
  To determine optimal conditions for precise measurement of arterial input function (AIFs) in dynamic susceptibility contrast (DSC) perfusion MRI.
  
  
  METHODS
  Magnitude-based (DeltaR(2)*) and phase-based (Deltaphi) AIFs were numerically simulated for several doses and baseline MRI noise levels [SNR(I(0))]. Random noise (1000 realizations) was added to real/imaginary MRI signals (derived from an internal carotid AIF), and AIF signal, noise, and signal-to-noise ratio (SNR) were determined. The optimal dose was defined as the dose that maximizes mean AIF SNR over the first-pass (SNR(mean)), rather than SNR at the AIF peak (SNR(peak)) because, compared to SNR(peak), doses predicted by SNR(mean) reduced the AIF-induced variability in cerebral blood flow (CBF) by 24% to 40%.
  
  
  RESULTS
  The AIF SNR is most influenced by choice of AIF signal, then optimal dosing, each with little penalty. Compared to DeltaR(2)*, Deltaphi signal has 4 to 80 times the SNR over all doses and time points, and approximately 10-fold SNR(mean) at respective optimal doses. Optimal doses induce 85% to 90% signal drop for the DeltaR(2)* method, and 70% to 75% for Deltaphi, with two-fold dose errors causing approximately 1.7-fold loss in SNR(mean). Increases in SNR(I(0)) proportionally increase AIF SNR, but at a cost.
  
  
  CONCLUSIONS
  AIF SNR is affected most by signal type, then dosing, and lastly, SNR(I(0)).
authors.affiliation: Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
authors.forename: Melanie S
authors.initials: MS
authors.lastname: Kotys
authors.forename: Erbil
authors.initials: E
authors.lastname: Akbudak
authors.forename: Joanne
authors.initials: J
authors.lastname: Markham
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Conturo
mesh_terms: D000328:Adult; D002343:Carotid Artery, Internal / Q000033:anatomy & histology* / Q000473:pathology; D002560:Cerebrovascular Circulation / Q000502:physiology; D003198:Computer Simulation; D003287:Contrast Media / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D008954:Models, Biological; D009942:Organometallic Compounds; D012016:Reference Values; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D013997:Time Factors
chemical_list: D003287:Contrast Media; D009942:Organometallic Compounds; C112666:gadoversetamide