Dalton Discussion 15 – Metal ions in medical imaging: optical, radiopharmaceutical and MRI contrast, 8^th–10^th September 2014, York

Dalton Discussion 15 – Metal ions in medical imaging: optical, radiopharmaceutical and MRI contrast was held in York on 8^th–10^th September with over 100 delegates attending from around the world and particularly strong representation from the UK and France, demonstrating the current relevance of research in this area.

Medical imaging techniques are central to our understanding of disease and the application of new medicines and treatments. Chemical entities can be used in a variety of different ways to report on their environment. The balance of resolution, sensitivity, quantitation and depth of tissue penetration characterises each of the techniques available with no single optimal technique. New technologies, such as the recently commercialised simultaneous positron emission tomography (PET)/magnetic resonance imaging (MRI) scanner, bring different combinations into practice and extend research opportunities in this area.

There is a diverse challenge in the design of metal containing contrast or reporting agents which can be administered to cells, animals or patients. Radiopharmaceutical imaging agents allow highly sensitive detection and with a growing range of isotopes available offer scope for optimised chelator design and exploitation of different targeting/conjugation methodology. MRI does not require a chemical agent to provide a signal, however reporting contrast agents are providing significant scope to gain more information from this widely used technique. Optical imaging has issues with tissue penetration in human patients but is ideal for cell and small animal studies and is more commonly being incorporated as part of a multimodal imaging approach.

The themes of the four sessions followed the main imaging techniques and also drew focus on the pathway to translate chemical advances into clinical trials and practice (optical imaging; MR imaging probes; radiopharmaceuticals; translational applications). The papers from the ‘keynote’ speakers gave an essential briefing on each of the topic areas. Prof. David Parker gave an inspirational talk showing what can be achieved in the design of optimised optical imaging probes discussing the development of the brightest europium(III) complexes and applications in cellular imaging and new bioassays. Prof. Peter Caravan detailed his work on enhancement of the signal generating capacity of MRI probes, including activation and protein targeting. Prof. Phil Blower demonstrated the increasing potential for new radiopharmaceuticals in nuclear medicine with a tour of the periodic table highlighting both the current applications and the future opportunities and challenges with the increasing range of available metal radioisotopes. Prof. Helmut Mäcke was unfortunately unable to join us due to illness but provided some excellent slides allowing his contribution to the discussion and some excellent examples of translational research to be shared. Other invited speakers gave excellent talks showing the use of transition metal complexes in cellular imaging (Prof. Kenneth Kam-Wing Lo), extending our understanding of optimised MR agent relaxivity (Prof. Mauro Botta), radiopharmaceutical imaging approaches in neurodegenerative disorders (Prof. Paul Donnelly) and the potential for future widespread translation of radiometal conjugates into clinical use (Prof. David Brasse). The majority of the remaining papers were of the highest standard with other selected topics covered giving us insight into chelator design for ⁸⁹Zr⁴⁺ PET tracers (Dr Michelle Ma), combined imaging and therapy agents (presentations from Dr Christine Goze and Dr Francesca Bryden), picolinate pendant arms in MRI agent design (Dr Gyula Tircso) and carbonic anhydrase targeting radiopharmaceuticals (Dr Sofia Pascu). We hope that this special issue of Dalton Transactions allows the delegates to reflect again on an excellent meeting but more importantly offers an excellent collection of articles to inspire the wider community to apply their chemical skills to this burgeoning area.

We would like to give special thanks to the scientific organising committee for DD15 (in no particular order: Profs. Eva Toth, Nick Long, Loic Charbonniere and Peter Edwards) for their organisation and invaluable contribution to animated discussion and debate, and to the RSC staff who facilitated the meeting and organised the smooth running sessions (Dr Richard Walker and Gemma Wilkins were the key contributors). We also thank RSC publishing staff for all of their hard work following the meeting to compile the papers, guide them through peer review and produce this special issue which will offer a lasting record of this fruitful meeting. Finally, the participants themselves deserve congratulations for contributing to lively discussion and debate after every talk and in front of the numerous posters, identifying the key issues for the design of the next generation metal complexes to use in medical imaging applications. We came away inspired but tempered with some sadness that this would be the final Dalton Discussion meeting. We hope that the key strengths of the format, including the in depth analysis allowed by prolonged discussion, will transfer to other meetings in the future.

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