We are grateful to have received for analysis datasets from several different sites and systems. Preliminary findings were shown by Philip Kilner at the EuroCMR meeting in Lisbon in May 2008.
The findings were important as they confirmed that there can be significant background phase offset errors in more than one CMR system that is in clinical use. But they also showed that it is not straightforward to acquire data at different sites that is comparable in all necessary respects.
The group is therefore in the process of modifying the instructions for a second round of static gel phantom studies, to be run during July 2008. The new studies will include, if possible, fully predetermined acquisition protocols, prepared in advance and saved digitally using each CMR system and software package that is to be tested.
Please contact Philip Kilner by email if you are interested in running such phantom tests on your own system.
Bear in mind, however, that we are not offering to send phantoms that consist mainly of 10kg of water round the world, so we ask participating sites to make their own. They consist of: 500g of dried gelatin (giving about twice a typical ‘jelly’ strength) plus gadolinium (100ml of 0.5M Gd-DTPA, which can be from out-dated stock), all dissolved in 10L of water and allowed to set inside a suitable screw top 10L rectangular plastic container (eg a 10L plastic ‘jerrycan’, as sold by Gelert).
We already have several participating Siemens sites, and are interested in recruiting more sites using Phillips or GE systems.
The Initiative Group on Flow Measurement of the Working Group EuroCMR is being established by Philip Kilner (picture) of the Royal Brompton Hospital in London working with his colleague Peter Gatehouse and members of the EuroCMR Nucleus Group.
It aims to work towards the optimization of CMR phase contrast velocity mapping for clinical investigation, across sites and manufacturers and across international boundaries. Measurement of flow in large vessels is potentially a valuable strength of CMR, but measurements can be subject to inaccuracy due to background phase errors. These errors vary depending on the CMR system used, the position of measurement in the magnet and other acquisition parameters.
Aims
- The overall aim is to work towards the optimization, across sites, manufacturers and national boundaries, of CMR phase contrast velocity mapping for clinical investigation.
- To define and initiate cross-site studies using specified types of velocity acquisition and specified types of static phantom. These static phantom ‘flow’ studies aim to test the relative susceptibility of any particular CMR system to background phase errors which could adversely affect clinical measurements of flow.
- To collect, collate and discuss the results of cross-site phantom studies.
- Depending on the findings and subject to the agreement of participating centres, the CMR Flow Taskforce would aim to publish cross-site information, in appropriately anonymized form, with a view to:
- help the CMR community and the manufacturers to identify the nature and degree of inaccuracies, and so to make improvements through appropriate hardware and software design,
- avoiding the clinical use of inaccurate and potentially misleading methods.
- To work towards the publication of guidelines on the clinical use, potential limitations and the optimization of methods for blood flow measurement by CMR phase velocity mapping
Further information on the causes and correction of flow errors is given in two papers published in the Journal of Cardiovascular Magnetic Resonance, accessible here:
Please note that PDF copies are available upon request