title: Arterial input function and gray matter cerebral blood volume measurements in children.
abstract: OBJECTIVE
  To investigate how arterial input functions (AIFs) vary with age in children and compare the use of individual and population AIFs for calculating gray matter CBV values. Quantitative measures of cerebral blood volume (CBV) using dynamic susceptibility contrast (DSC) magnetic resonance imaging (MRI) require measurement of an AIF. AIFs are affected by numerous factors including patient age. Few data presenting AIFs in the pediatric population exists.
  
  
  METHODS
  Twenty-two previously treated pediatric brain tumor patients (mean age, 6.3 years; range, 2.0-15.3 years) underwent DSC-MRI scans on a 3T MRI scanner over 36 visits. AIFs were measured in the middle cerebral artery. A functional form of an adult population AIF was fitted to each AIF to obtain parameters reflecting AIF shape. The relationship between parameters and age was assessed. Correlations between gray matter CBV values calculated using the resulting population and individual patient AIFs were explored.
  
  
  RESULTS
  There was a large variation in individual patient AIFs but correlations between AIF shape and age were observed. The center (r = 0.596, P < 0.001) and width of the first-pass peak (r = 0.441, P = 0.007) were found to correlate significantly with age. Intrapatient coefficients of variation were significantly lower than interpatient values for all parameters (P < 0.001). Differences in CBV values calculated with an overall population and age-specific population AIF compared to those calculated with individual AIFs were 31.3% and 31.0%, respectively.
  
  
  CONCLUSIONS
  Parameters describing AIF shape correlate with patient age in line with expected changes in cardiac output. In pediatric DSC-MRI studies individual patient AIFs are recommended.
authors.affiliation: RRPPS, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK.|Birmingham Children's Hospital, Birmingham, UK.|Cancer Sciences, University of Birmingham, Birmingham, UK.
authors.forename: Stephanie B
authors.initials: SB
authors.lastname: Withey
authors.affiliation: Birmingham Children's Hospital, Birmingham, UK.|Cancer Sciences, University of Birmingham, Birmingham, UK.
authors.forename: Jan
authors.initials: J
authors.lastname: Novak
authors.affiliation: Birmingham Children's Hospital, Birmingham, UK.
authors.forename: Lesley
authors.initials: L
authors.lastname: MacPherson
authors.affiliation: Birmingham Children's Hospital, Birmingham, UK.|Cancer Sciences, University of Birmingham, Birmingham, UK.
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Peet
mesh_terms: D000293:Adolescent; D001811:Blood Volume Determination; D001921:Brain / Q000098:blood supply* / Q000000981:diagnostic imaging; D001932:Brain Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D002560:Cerebrovascular Circulation; D002648:Child; D002675:Child, Preschool; D066128:Gray Matter / Q000000981:diagnostic imaging / Q000473:pathology*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007223:Infant; D008279:Magnetic Resonance Imaging; D015203:Reproducibility of Results
keywords: arterial input function (AIF); cerebral blood volume (CBV); dynamic susceptibility contrast (DSC) MRI; pediatric; perfusion