title: Comprehensive population-averaged arterial input function for dynamic contrast-enhanced vmagnetic resonance imaging of head and neck cancer.
abstract: OBJECTIVE
  To generate a population-averaged arterial input function (PA-AIF) for quantitative analysis of dynamic contrast-enhanced MRI data in head and neck cancer patients.
  
  
  METHODS
  Twenty patients underwent dynamic contrast-enhanced MRI during concurrent chemoradiation therapy. Imaging consisted of 2 baseline scans 1 week apart (B1/B2) and 1 scan after 1 week of chemoradiation therapy (Wk1). Regions of interest (ROIs) in the right and left carotid arteries were drawn on coronal images. Plasma concentration curves of all ROIs were averaged and fit to a biexponential decay function to obtain the final PA-AIF (AvgAll). Right-sided and left-sided ROI plasma concentration curves were averaged separately to obtain side-specific AIFs (AvgRight/AvgLeft). Regions of interest were divided by time point to obtain time-point-specific AIFs (AvgB1/AvgB2/AvgWk1). The vascular transfer constant (Ktrans) and the fractional extravascular, extracellular space volume (Ve) for primaries and nodes were calculated using the AvgAll AIF, the appropriate side-specific AIF, and the appropriate time-point-specific AIF. Median Ktrans and Ve values derived from AvgAll were compared with those obtained from the side-specific and time-point-specific AIFs. The effect of using individual AIFs was also investigated.
  
  
  RESULTS
  The plasma parameters for AvgAll were a1,2 = 27.11/17.65 kg/L, m1,2 = 11.75/0.21 min(-1). The coefficients of repeatability (CRs) for AvgAll versus AvgLeft were 0.04 min(-1) for Ktrans and 0.02 for Ve. For AvgAll versus AvgRight, the CRs were 0.08 min(-1) for Ktrans and 0.02 for Ve. When AvgAll was compared with AvgB1/AvgB2/AvgWk1, the CRs were slightly higher: 0.32/0.19/0.78 min(-1), respectively, for Ktrans; and 0.07/0.08/0.09 for Ve. Use of a PA-AIF was not significantly different from use of individual AIFs.
  
  
  CONCLUSIONS
  A PA-AIF for head and neck cancer was generated that accounts for differences in right carotid artery versus left carotid artery, day-to-day fluctuations, and early treatment-induced changes. The small CRs obtained for Ktrans and Ve indicate that side-specific AIFs are not necessary. However, a time-point-specific AIF may improve pharmacokinetic accuracy.
authors.affiliation: Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina.
authors.forename: Jennifer D
authors.initials: JD
authors.lastname: Onxley
authors.affiliation: Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina.
authors.forename: David S
authors.initials: DS
authors.lastname: Yoo
authors.affiliation: iCAD Inc., Nashua, New Hampshire.
authors.forename: Naira
authors.initials: N
authors.lastname: Muradyan
authors.affiliation: Department of Radiology, Duke University Medical Center, Durham, North Carolina.
authors.forename: James R
authors.initials: JR
authors.lastname: MacFall
authors.affiliation: Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina; Department of Surgery, Duke University Medical Center, Durham, North Carolina.
authors.forename: David M
authors.initials: DM
authors.lastname: Brizel
authors.affiliation: Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina. Electronic address: Oana.Craciunescu@duke.edu.
authors.forename: Oana I
authors.initials: OI
authors.lastname: Craciunescu
mesh_terms: D000465:Algorithms; D002294:Carcinoma, Squamous Cell / Q000098:blood supply* / Q000628:therapy; D002339:Carotid Arteries / Q000033:anatomy & histology / Q000502:physiology*; D059248:Chemoradiotherapy; D003287:Contrast Media / Q000493:pharmacokinetics; D005110:Extracellular Space / Q000502:physiology; D006258:Head and Neck Neoplasms / Q000098:blood supply* / Q000628:therapy; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D012039:Regional Blood Flow; D018709:Statistics, Nonparametric; D013997:Time Factors
chemical_list: D003287:Contrast Media