title: Quality control within the multicentre perfusion CT study of primary colorectal cancer (PROSPeCT): results of an iodine density phantom study.
abstract: OBJECTIVE
  To assess the cross-centre consistency of iodine enhancement, contrast-to-noise ratio and radiation dose in a multicentre perfusion CT trial of colorectal cancer.
  
  
  METHODS
  A cylindrical water phantom containing different iodine inserts was examined on seven CT models in 13 hospitals. The relationship between CT number (Hounsfield units, HU) and iodine concentration (milligrams per millilitre) was established and contrast-to-noise ratios (CNRs) calculated. Radiation doses (CTDIvol, DLP) were compared across all sites.
  
  
  RESULTS
  There was a linear relationship between CT number and iodine density. Iodine enhancement varied by a factor of at most 1.10, and image noise by at most 1.5 across the study sites. At an iodine concentration of 1 mg ml(-1) and 100 kV, CNRs ranged from 3.6 to 4.8 in the 220-mm phantom and from 1.4 to 1.9 in the 300-mm phantom. Doses varied by a factor of at most 2.4, but remained within study dose constraints. Iterative reconstruction algorithms did not alter iodine enhancement but resulted in reduced image noise by a factor of at most 2.2, allowing a potential dose decrease of at most 80% compared to filtered back projection (FBP).
  
  
  CONCLUSIONS
  Quality control of CT performance across centres indicates that CNR values remain relatively consistent across all sites, giving acceptable image quality within the agreed dose constraints.
  
  
  CONCLUSIONS
  Quality control is essential in a multicentre setting to enable CT quantification. CNRs in a body-sized phantom had the recommended value of at least 1.5. CTDIs and DLPs varied by factors of 1.8 and 2.4 respectively.
authors.affiliation: Medical Physics Department, Guy's & St. Thomas' NHS Foundation, Trust, London, UK.
authors.forename: Maria
authors.initials: M
authors.lastname: Lewis
authors.forename: Vicky
authors.initials: V
authors.lastname: Goh
authors.forename: Shaun
authors.initials: S
authors.lastname: Beggs
authors.forename: Andrew
authors.initials: A
authors.lastname: Bridges
authors.forename: Philip
authors.initials: P
authors.lastname: Clewer
authors.forename: Anne
authors.initials: A
authors.lastname: Davis
authors.forename: Trevelyan
authors.initials: T
authors.lastname: Foy
authors.forename: Karen
authors.initials: K
authors.lastname: Fuller
authors.forename: Jennifer
authors.initials: J
authors.lastname: George
authors.forename: Antony
authors.initials: A
authors.lastname: Higginson
authors.forename: Ian
authors.initials: I
authors.lastname: Honey
authors.forename: Gareth
authors.initials: G
authors.lastname: Iball
authors.forename: Steve
authors.initials: S
authors.lastname: Mutch
authors.forename: Shellagh
authors.initials: S
authors.lastname: Neil
authors.forename: Cat
authors.initials: C
authors.lastname: Rivett
authors.forename: Andrew
authors.initials: A
authors.lastname: Slater
authors.forename: David
authors.initials: D
authors.lastname: Sutton
authors.forename: Nick
authors.initials: N
authors.lastname: Weir
authors.forename: Sarah
authors.initials: S
authors.lastname: Wayte
mesh_terms: D000465:Algorithms; D015179:Colorectal Neoplasms / Q000000981:diagnostic imaging*; D006801:Humans; D007455:Iodine; D019047:Phantoms, Imaging; D011786:Quality Control; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D007455:Iodine