Moving the goalposts for MRI


A new class of MRI (magnetic resonance imaging) contrast agents developed by scientists in the UK is promising to deliver clearer images in less time. ‘In any NMR experiment you are chasing sensitivity. We have enhanced the intrinsic ability to observe an MRI probe signal by a factor of 20,’ explains David Parker of Durham University who led the study.

MRI is used in clinical settings to image the inside of the body. It uses strong magnetic fields and radio waves to probe the behaviour of nuclei that possess nuclear spin. Chemical shifts from proton NMR normally fall between 0–12ppm but water and fat resonate at 4.7 and 1.3ppm, respectively, and can overlap with MRI probe signals. Parker’s new probes shunt the spectral window of MRI scans well away from these interfering signals, a concept he describes as ‘moving the goalposts’. The probes consist of lanthanide complexes with a t-butyl group and the distance between the lanthanide and t-butyl group was fixed to optimise the rate of decay of the t-butyl signal as well as move its chemical shift. Data acquisition was possible just a few minutes after administering the probe and the signal from the lanthanide induced relaxation of the nine protons in the t-butyl groups has been shifted by up to 80ppm.

Proton NMR spectra showing the shifted t-butyl resonances in some of the new dysprosium and thulium complexes

Janet Morrow, who develops inorganic complexes for MRI imaging at the University of Buffalo in New York, US, says the study is ground-breaking because it shows that lanthanide-based paramagnetic chemical shift agents can be imaged at concentrations typically used for gadolinium contrast agents. ‘They have carefully considered intramolecular nuclear relaxation rates and coordination chemistry to optimise the complexes for imaging.’

Another advocate of the work is Kenneth Raymond, an inorganic chemist at the University of California, Berkeley, in the US: ‘their careful choice of lanthanide and ligand system can enhance acquisition time and sensitivity, which in turn necessitates lower contrast agent dosages and results in better sensitivity.’

Parker is confident the combination of the probes’ speed with their superior levels of sensitivity could lead to the development of new imaging experiments in which the probes can localise for defined periods of time in particular regions of the body.


Related Content

Small and sensitive nanoparticles

14 February 2011 News Archive

news image

Putting individual nanoparticles inside micelles could make improved contrast agents for imaging in the body

Picture perfect

29 January 2007 Premium contentFeature

news image

Medical imaging now promises to take us to the molecular level, thanks to new, powerful MRI machines and clever contrast agen...

Most Read

Isotope effect produces new type of chemical bond

22 October 2014 Research

news image

Evidence emerges for vibrational bond first proposed 30 years ago

DNA 'barcodes' used to track food

30 October 2014 Research

news image

Milk has been successfully tracked as it is turned into cheese and yogurt in an advance that could fight food fraud

Most Commented

Square planar iron complex breaks inorganic dogma

31 October 2014 Research

news image

Unusual spin state could open the door to new and exciting chemistry

Indian U-turn on diabetes drug ban

16 August 2013 News and Analysis

news image

Suspension of cheap and popular medicine reversed but will now come with new safety warnings