Conclusion

A macrophage-specific MR contrast agent allows the detection of small and otherwise undetectable lymph node metastases in patients with cancer. This has an important clinical impact, as the diagnosis will be more precise and less invasive to obtain. Subsequently, this will reduce morbidity and health care costs. However, thorough knowledge of sequence parameters and planes, lymph node anatomy, appearance of normal and abnormal nodes and pitfalls is essential when using this technique. This...

Physicochemical Properties of Superparamagnetic Iron Oxide Particles

Recently, several authors explored the possible application of Superparamag-netic Iron Oxide Particles (SPIO) as MR imaging tool for atherosclerosis. These particles are internalized by macrophages and the biological amplification through intracellular accumulation results in a strong signal reduction in T2 T2*-weighted MR images (Corot et al., 2004). These nanoparticles consist of a small iron oxide core with a diameter of 4-10 nm stabilized with a biodegradable coating to prevent particle...

Optimal Size of the Agents

In order to determine the optimal size of Gd-dendrimer for lymphatic vessel and lymph node imaging, each agent was tested in vivo. Intracutaneous injection at the phalanges revealed that larger nano-sized agents worked better for visualizing the lymphatic vessels than smaller agents. MR lymphangiograms with the largest agent studied (G8 13 nm) showed the best depiction of the lymphatic system among all the tested agents (Figure 2.2). The relatively large size of these molecules meant that once...

Upper Gastrointestinal Cancer

One published study has documented the application of USPIO-MRI for the pre-operative staging and assessment of lymph node metastases in 17 patients with advanced gastric cancer (Tatsumi et al., 2006). Of 781 lymph nodes dissected during surgery, the imaging results of 194 nodes were correlated with their histopathological findings. Fifty-nine lymph nodes from 11 patients had histopathological metastases. In non-affected normal lymph nodes, a dark signal intensity on MRI was evidently caused by...

Info

Studies should be carefully weighed since imaging equipment and parameters were not uniform among institutions (Table 4.2). 4.3.2.1. SPIO-MRI vs Non-enhanced MRI In the early years of SPIO-enhanced MR imaging, Stark et al. reported that SPIO-enhanced images of the liver obtained with standard pulse sequence techniques significantly increased the number of hepatic lesions detected and reduced the threshold size for detection to 3 mm (Stark et al., 1988). SPIO-enhanced MR imaging is more accurate...

Mechanism of Action

After IV injection, the ferumoxtran-10 particles are taken up by macrophages, and are transported to the interstitial space and from there through the lymph vessels to the lymph nodes (Figure 3.1). Thus, this contrast agent is cell-specific for macrophages. Once within normally functioning nodes, the intracellular Figure 3.1. Uptake mechanism of ferumoxtran-10. IV injected particles slowly extravasate from vascular to interstitial space (1) and are then transported to lymph nodes via lymphatic...

Paramagnetic Complexes as High Field Contrast Agents

With the advent of high-field whole body magnets 3-9.4 T and animal systems up to 21 T , with the potential for increased sensitivity, it will be important to translate these technological improvements directly into enhanced molecular and cellular images. Among the lanthanide ions, Gd is known as the best low-field T1 relaxation agent because of its long electronic relaxation time. Complexes with other paramagnetic lanthanides III have been commonly used as shift agents in NMR spectroscopy or...

List of Contributors

Department of Radiology, UMCN, Nijmegen, The Netherlands J.Barentsz rad.umcn.nl Department of Biomedical Engineering, University of California, Davis, CA, USA Department of Nuclear Medicine, Radboud University Nijmegen Medical Russell H. Morgan Department of Radiology and Radiological Science, Division of MR Research and the Institute for Cell Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD, USA jwmbulte mri.jhu.edu Philips Medical Systems, Cleveland, OH, USA...