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

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.

The use of clinical broadband UV radiometers for optical radiation hazard measurements.

The implementation of the UK Control of Artificial Optical Radiation at Work Regulations 2010 requires the employer to perform a risk assessment of workers' exposure to UV radiation from phototherapy equipment in the hospital environment. The objective of this study was to demonstrate that, where the source spectrum is known, an assessment of exposure to UV sources commonly used in hospitals, including assessment of reflections and transmission through personal protective equipment, may be performed with sufficient reliability by radiometer measurement rather than by complex spectroradiometric measurements. An intercomparison of radiometer and spectroradiometer measurements of exposure to UV sources was carried out. Direct exposure was considered, as well as exposure to reflected or scattered beams and that transmitted through eyewear. Assessment by radiometer of direct exposure and exposure to reflections demonstrated an acceptable measurement error in the context of the inherent uncertainty in the assumptions of the exposure scenario. Assessment of transmitted beams may result in a greater measurement error due to spectral mismatch; however, for typical exposure scenarios the error remained acceptable in comparison with the exposure limit value. The methodology presented reduces the complexity of the measurement of UV hazard levels for common phototherapy equipment.