Catharina Gerda Klose, Presenter: Nothing to Disclose

Monika Huhndorf, Abstract Co-Author: Nothing to Disclose

Marcel Dommaschk, Abstract Co-Author: Nothing to Disclose

Christian Riedel, Abstract Co-Author: Nothing to Disclose

Olav Jansen MD, PhD, Abstract Co-Author: Nothing to Disclose

Rainer Herges, Abstract Co-Author: Nothing to Disclose

We investigated a new molecule that can change its magnetic properties from diamagnetic to paramagnetic and vice and versa by illuminating it with different wavelengths of visible light. The purpose was to find out if this magnetic switch can change T1 relaxivity in a way that it can be used as a switchable MRI contrast agent.

We used a nickel complex as a molecular spin switch that can change between diamagnetic and paramagnetic state by exposing it with blue-green light (500 nanometers) and violet-blue light (435nm). The process leads to stable states and is fully reversible without fatigue. We designed a closed loop flow system attached to a light source and a pump outside our 3T MRI scanner (Achieva, Philips Medical Systems, Best , The Netherlands). The flow system also contained a reservoir enclosed in a head phantom inside the MRI Scanner. We repeatedly scanned the reservoir containing a solution of the molecule using T1 weighted sequences in order to evaluate the contrast dynamics. Outside the scanner the solution was permanently illuminated while being pumped through the flow system. This was repeated for different concentrations of the solution.

The T1w signal intensity in the reservoir increased significantly during the illumination with wavelengths of 500 nm as the molecules changed their magnetic state from diamagnetic to paramagnetic. In the same way, the T1w signal intensity decreased during illumination with a wavelength of 435 nm. While at high concentration (2.4 mmol) we found a signal-to-noise ratio (SNR) of 10.2, at lower concentration (0.9 mmol) the SNR dropped to 5.9. In addition, we could show that the molecules were much faster switched off than switched on. The half- life period was 2 min for switching off versus 8 min for switching on. The switching process was also concentration dependent. At a concentration of 0.9 mmol the half-life period for switching the contrast off was 2 minutes versus 7 minutes at a concentration of 2.4 mmol.

Our switchable molecule allows for generating noticeable T1w contrast differences within a period of time comparable to a standard MRI pulse sequence.

Switchable contrast agent could be used to better delineate contrast enhancement by subtracting the tissue background because the molecule can be switched on and off as often as necessary.

Klose, C, Huhndorf, M, Dommaschk, M, Riedel, C, Jansen, O, Herges, R, Turning T1- weighted Contrast on and off – An in Vitro MRI Study Using a New Molecule Switchable by Visible Light.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14019224.html