Harald Ittrich MD, Presenter: Nothing to Disclose

Oliver T. Bruns, Abstract Co-Author: Nothing to Disclose

Alexander Bartelt, Abstract Co-Author: Nothing to Disclose

Kersten Peldschus MD, Abstract Co-Author: Nothing to Disclose

Michael Gerhard Kaul, Abstract Co-Author: Nothing to Disclose

Gerhard B. Adam MD, Abstract Co-Author: Nothing to Disclose

Jorg Heeren PhD, Abstract Co-Author: Nothing to Disclose

To evaluate new USPIO-labeled lipoprotein complexes for an in-vivo monitoring of lipid metabolism in different tissues with real time dynamic MRI in a mouse model.

Triglycerid-rich lipoprotein nanosomes (TRL-NS) were designed in-vitro using a superparamagnetic iron oxide core (USPIO) coated by a lipid layer with lipoproteins. In-vivo dynamic MRI using a T2*w 2D gradient echo sequence (temporal resolution 3.2 sec., TA 15 min.) was performed before, during, and after the bolus i.v. application of TRL-NS in cold-exposed wildtype mice using a clinical 3T scanner (Philips Intera) with a custom made small animal solenoid coil. SNR in vena cava, aorta, portal vein, liver, white (WAT) and brown adipose tissue (BAT), skeletal muscle, myocardium and myelon were measured for estimation of biodistribution and metabolism of TRL-NS. Relative SNR changes (rΔSNR) of all tissues were measured and last 30 SNR values were tested in comparison to baseline (bl) for statistical significance (t-test). MR measurements were matched with y-counts of tissues after application of radioactive TRL-NS (59Fe-SPIO), histology (H&E, Prussian blue) and electron microscopy.

TRL-NS is a potent MR contrast agent with comparable properties to TRL. Dynamic in-vivo MR measurements after application of TRL-NS showed a two phase SNR change with a rapid exponential SNR decrease in order of vena cava, aorta, portal vein followed by a protracted SNR recovery in all vessels. Liver and BAT showed an exponential SNR decline (rΔSNRliver= -0.60±0.14 (p<0.01); rΔSNRBAT= -0.74±0.13 (p<0.01)) indicating high metabolism, that was confirmed with radioactive measurements. Skeletal muscle (rΔSNR= -0.08±0.18), myocardium (rΔSNR= -0.10±0.15) and WAT (rΔSNR= -0.05±0.11) showed a non-significant decline trend in contrast to significant uptake measured by y-counting. Brain showed no significant SNR changes in correlation to radioisotope counting. Corresponding to MR imaging histology and electron microscopy confirmed a predominantly accumulation of TRL-NS in liver and brown adipose tissue.  

Distribution and metabolism of USPIO-marked lipoproteins can be monitored by real time MRI in a preclinical mouse model at a clinical 3T MR System.

The study demonstrates the potential of USPIO-labeled TRL in combination with realtime in-vivo MRI for the enhancement of tissue specific metabolic activity and pathways in lipoprotein metabolism.

Ittrich, H, Bruns, O, Bartelt, A, Peldschus, K, Kaul, M, Adam, G, Heeren, J, Real-Time MR Imaging of Lipoprotein Distribution and Metabolism in Different Tissues Using USPIO-labeled Lipoproteins at 3T.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12033940.html