Quality control within the multicentre perfusion CT study of primary colorectal cancer (PROSPeCT): results of an iodine density phantom study

Maria Lewis, Vicky Goh, Shaun Beggs, Andrew Bridges, Philip Clewer, Anne Davis, Trevelyan Foy, Karen Fuller, Jennifer George, Antony Higginson, Ian Honey, Gareth Iball, Steve Mutch, Shellagh Neil, Cat Rivett, Andrew Slater, David Sutton, Nick Weir, Sarah Wayte, PROSPeCT InvestigatorsSusan Mallett

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)


OBJECTIVES: 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.

MATERIALS AND 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.

KEY POINTS: 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.

Original languageEnglish
Pages (from-to)2309-18
Number of pages10
JournalEuropean Radiology
Issue number9
Publication statusPublished - Sept 2014


  • Algorithms
  • Colorectal Neoplasms
  • Humans
  • Iodine
  • Phantoms, Imaging
  • Quality Control
  • Radiation Dosage
  • Radiographic Image Interpretation, Computer-Assisted
  • Reproducibility of Results
  • Tomography, X-Ray Computed


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