...issue 17 of the journal for medical imaging professionals worldwide. For the future, the Editorial Board is supporting a change to web-based distribution of C2I2, in line with trends in medical publishing and with the increasing preference of readers to read and file electronic papers. The Board views this transition as a very positive move that reflects the growing international readership and will allow all readers to receive the journal promptly as soon as it is published. This will be the last issue to be printed so please be sure to register for the electronic version at the website: www.c2i2.org

• Dr David Sutton, a physicist, discusses the public health risk associated with radiation exposure from CT scans, a subject that is becoming increasingly important with the escalating use of CT scanning. He explains the methodology used to estimate the increased risk of cancer, reviews the available evidence and discusses the risk from both patient and population perspective. He concludes that the challenge of reducing the radiation dose in CT has not yet been fully met.
• The association between gadolinium-based contrast agents and the occurrence of nephrogenic systemic fibrosis in patients with renal impairment has become a hot topic since it was first suggested in 2006. Dr Adrian Holden reviews our current understanding of the condition and discusses some of the theories that have been proposed to explain it. He concludes that there is no evidence that any gadolinium product is safer than any other with respect to NSF and points out that the decrease in new cases since 2006 may reflect a cautious use of gadolinium agents, in line with recommendations to avoid use in patients with severe renal failure.
• Dr Sam Firoozi and Dr Stephen Brecker consider the place of percutaneous closure in the management of patients with patent foramen ovale (PFO). As well as describing the technique itself and the closure devices available, they also review the role of PFO in stroke, migraine and decompression illness and discuss the selection of patients who will benefit from closure.

In this issue