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Chapter-26 Metallopharmaceuticals as Exogenous Contrast Agents

BOOK TITLE: Biomedical Magnetic Resonance: Proceedings of the International Workshop

Author
1. Sharma RK
2. Mishra AK
3. Mathur R
ISBN
9788180614989
DOI
10.5005/jp/books/10100_26
Edition
1/e
Publishing Year
2005
Pages
10
Author Affiliations
1. Army Hospital (Research and Referral), Delhi Cantt, Assisted Reproductive Technology (ART) Centre, Armed Forces Medical College (AFMC), Pune, Maharashtra, India, Assisted Reproduction Technologies (ART) Centre, AH (R and R), New Delhi, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow (UP), Retina Foundation, Ahmedabad, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Raebareli Road, Lucknow, Uttar Pradesh, India, Defence Research Laboratory, Tezpur, Assam, India, Institute of Nuclear Medicine and Allied Sciences, Delhi, India, University School of Medicine, Philadelphia, United States, ART Center, CH (SC), Pune, Maharashtra, India, Institute of Reproductive Medicine and IVF Center, Primus Super Speciality Hospital, Chanakyapuri, New Delhi, India, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India, Primus Super Speciallity Hospital, New Delhi; Army Hospital (R&R), New Delhi and Command Hospital (SC), Armed Forces Medical College, Pune, Maharashtra,
2. Institute of Nuclear Medicine and Allied Sciences, Delhi, India
3. Institute of Nuclear Medicine and Allied Sciences, Delhi, India
Chapter keywords
molecular science, medical diagnosis and therapeutics, physiological and biochemical manifestations, molecular imaging, pathological processes, subcellular level, medical imaging techniques, positron emission tomography (PET), optical imaging, magnetic resonance imaging (MRI), molecular process, flow-sensitive pulse sequences, MR angiography, blood flow, vascular anatomy, functional MR imaging, micro-vascular hemodynamics, paramagnetic materials, paramagnetic metal ions, unpaired electrons, paramagnetic heavy metal ions, toxicity, superparamagnetic iron oxide (SPIO), colloids, nonstoichiometric microcrystalline magnetite cores, dextrans, siloxanes, hemodynamic disruption, ligand, protein, tissue-specific contrast agents, porphyrins, metabolic disorders, photodynamic therapy, tumors, metalloporphyrins, rapid bolus injection, paramagnetic ECF agent, vascular space, interstitium

Abstract

Developments in molecular science are shifting the detection horizon of medical diagnosis and therapeutics to the earliest physiological and biochemical manifestations of disease. Molecular imaging is the in vivo diagnosis of complex pathological processes by detection of unique biological signatures at the subcellular level. A wide range of medical imaging techniques like positron emission tomography (PET), optical imaging, and magnetic resonance imaging (MRI) can be used for molecular imaging and the choice will be determined by the specific molecular process that is being targeted. Magnetic resonance imaging (MRI) offers the unique opportunity to extract both anatomic and physiological information simultaneously. Flow-sensitive pulse sequences and MR angiography yield data about blood flow, as well as displaying the vascular anatomy. A particularly powerful paradigm for functional MR imaging of micro-vascular hemodynamics incorporates paramagnetic materials that create significant image contrast. Paramagnetic metal ions do show suitable effect which depends on number of unpaired electrons in the ion. The main problem with paramagnetic heavy metal ions in their native form is their toxicity. Another, relatively new type of paramagnetic contrast agents is so-called superparamagnetic iron oxide (SPIO) based colloids. They consist of nonstoichiometric microcrystalline magnetite cores, which are coated with dextrans or siloxanes. The mechanism of toxicity could involve hemodynamic disruption. Potential improvement also lies in the idea of covalently coupling the ligand to protein to generate tissue-specific contrast agents. Porphyrins have been known for decades as indicators of various metabolic disorders and disease states. They are used in photodynamic therapy of tumors. Low toxicity of metalloporphyrins and their selective retention in tumors have led recently to their study as an MRI contrast media. MR angiography usually requires a rapid bolus injection of a paramagnetic ECF agent since these agents rapidly redistributes from the vascular space into the interstitium.

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