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Published online by Cambridge University Press: 01 February 2011
Certain diseases have been associated with the administration of heavy elements as contrast agents to patients undergoing medical imaging procedures. Recently, the presence of gadolinium (Gd) administered as a paramagnetic contrast agent for MRI contrast studies was associated with the incidence of Nephrogenic Fibrosing Dermopathy (NFD), also called Nephrogenic Systemic Fibrosis (NSF). To determine specific causation, Gd and other metallic nanoparticles in various tissues must be detected directly and characterized in-situ. This is done to develop specific mechanisms for the chemical modification of the metal elements as the result of a biologic response. Fixed biopsies embedded in paraffin were sectioned at 3-5 μm thick, deparaffinized by hand (xylene and 100% ethyl alcohol), placed on carbon planchettes, and allowed to air dry. Deparaffinized tissues were examined using a field emission SEM (FE-SEM) to directly detect and image the presence of Gd as well as other metals. Backscatter electron (BSE) imaging (20kV) was used to discern metal particles within tissues. Energy dispersive spectroscopy (EDS) (15kV) was used to verify the specific elements present. This allowed for the spatial characterization of the nanoparticles within the tissues but due to the physical limitations of SEM/EDS, quantification of the amount of metal was not possible. Mass concentration of the metal elements was determined using inductively coupled plasma mass spectrometry (ICP-MS) on digested tissues. Thick tissue sections, >30 μm, were used for ICP-MS to provide enough mass for detection. These sections were taken from the histology blocks adjacent to the thin sections used in the FE-SEM. Gadolinium was detected in skin, heart, lung and liver tissues. The highest concentrations were found in heart and skin; both had average tissue concentrations greater than 200μg/g (100-450μg/g range). In skin, gadolinium nano-particulates were readily seen near cell body locations in autopsy samples and within the cells in biopsy samples. The cells where gadolinium was most easily found were along blood vessels. In the cells the agglomerates appear granular with a size of less than 100 nm. They are diffused throughout the cell but as of this time not associated with any particular cell structure. Subsequent work using TEM will examine that aspect as well as the specific ultrastructure and chemistry of the nanoparticles. In this investigation, gadolinium was detected in the tissues of a number of patients with NSF. Although neither dispositive of a pathophysiologic mechanism, nor proof of causation, the detection and quantification of gadolinium within tissues of NSF patients is supportive of the epidemiologic association between exposure to gadolinium containing contrast material and development of the disease.
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