Two 'eyes' see better than one

Combining more than one type of imaging in a single system provides a sort of quality control facet to independently track the dynamics of the same contrast agent. EU-funded scientists developed a multimodal dynamic imaging system within the context of the project 'DOT/MRI dual-modality cancer imaging using a bifunctional contrast agent' (UNLU_IRG2010).

The team extended the capabilities of their combined diffuse optical tomography (DOT) and magnetic resonance imaging (MRI) system to measure dynamic information from exogenous probes. Contrast between tissue types is a critical part of the imaging process, whether due to external contrast agents or endogenous, natural difference in tissue properties. To take full advantage of the imaging system, researchers developed new polymer-based mono- (optical) and bifunctional (optical and magnetic resonance) agents to act as a platform for new contrast agents.

Investigators produced two polymer-based bifunctional contrast agents, one large and one medium-sized, for a combined DOT/MRI system at the University of California, Irvine. Enhancement kinetics, reflecting the haemodynamic features of a lesion due to its greater absorption of contrast agent, is an important indicator of cancerous tissue abnormalities. The combined DOT/MRI system successfully measured the enhancement kinetics of both the mono- and bifunctional contrast agents. It also detected the endogenous difference between normal and cancerous tissue due to differences in haemoglobin content and scattering.

Finally, a study in a rat tumour model with simultaneous acquisition of data from both the DOT and the MRI modes showed that enhancement kinetics measured were similar but not exactly the same. In particular, contrast wash-in rate and time of peak enhancement overlapped, but wash-out was faster for the MRI kinetic curve compared to the optical one. These results support the usefulness of the multimodal imaging system and also highlight the specific parameters that can be compared in a straightforward manner.

UNLU_IRG2010 developed a novel multimodal imaging system and suitable contrast agents that should increase the accuracy of cancer detection and diagnosis. Eventual commercialisation will thus have important benefits for patients as well as for their families and national health care systems.