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Contrast enhancement agents and radiopharmaceuticals
Published in A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha, Clark’s Procedures in Diagnostic Imaging: A System-Based Approach, 2020
A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha
To understand fully the physics and chemistry of contrast agents for MRI goes beyond the scope of this book. However, it is perhaps of value at this stage to consider the difference between paramagnetic and ferromagnetic compounds. Paramagnetic compounds can be defined as pertaining to the property of any substance (excluding iron and other materials that attract a magnetic field very strongly) that displays a tendency to move to the strongest part of a non-uniform magnetic field. Gadolinium, a paramagnetic compound, may be considered for use as MRI contrast. These agents are chosen for use in medical imaging because of their magnetic susceptibility, low toxicity and therefore good tolerance by patients, in addition to their relatively low cost. Gadolinium is a rare earth metal possessing high relaxivity, i.e. an ability to alter relaxation times on adjacent protons in tissue. Paramagnetic media may be considered as ‘positive’ enhancement, increasing image intensity on T1-weighted images. Gadolinium is also referred to as a T1 contrast agent, as its greatest effect is on T1 relaxation.
Nanotheranostics: Implications of Nanotechnology in Simultaneous Diagnosis and Therapy
Published in Alok Dhawan, Sanjay Singh, Ashutosh Kumar, Rishi Shanker, Nanobiotechnology, 2018
Brahmeshwar Mishra, Ravi R. Patel
Borgman et al. designed Arg-Gly-Asp (RGD)-HPMA-Indium-111 (In-111)-conjugated nanotheranostics by the copolymerization method for targeted delivery of radiotherapeutics to alpha(v)beta(3) integrin-expressed solid tumors, which was confirmed by scintigraphy (Borgman et al. 2008). Gadolinium is also used as an effective contrast agent for MRI. Gadolinium-tagged HPMA conjugates were also prepared for targeting integrin αvβ3 by functionalizing with c(RGDfK) peptide, which has shown increased blood circulation time with active targeting, indicating the potential of conjugates for tumor therapy monitoring (Zarabi et al. 2009). Very recently, Yuan et al. developed Cu-64 (intrinsic theranostic agent)-conjugated HPMA copolymers for active targeting of tumor angiogenesis. They have utilized RGD as a targeting ligand. The targeting potential was quantitatively confirmed by measuring the Cu-64 radioactivity with the aid of positron emission tomography (PET), which showed significantly higher tumor localization of RGD-bound nanotheranostics as compared to a bare one upon intravenous administration in human prostate cancer cells bearing mice xenografts. Further, HPMA conjugates exhibited an enhanced pharmacokinetic profile of Cu-64; approximately onefold in the tumor region (Yuan et al. 2013). Likewise, RGD4C-conjugated HPMA copolymer was radiolabeled with 99mTc, which indicated retention of conjugated structure for a prolonged time during scintigraphic imaging (Mitra et al. 2005, Wang et al. 2014).
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Published in Mara Cercignani, Nicholas G. Dowell, Paul S. Tofts, Quantitative MRI of the Brain: Principles of Physical Measurement, 2018
Leonidas Georgiou, David L. Buckley
The types of low-molecular-weight contrast agents used in most clinical applications in the brain are paramagnetic gadolinium-based contrast agents with either linear chemical structures, Gd-DTPA (gadopentetate dimeglumine), Gd-DTPA-BMA (gadodiamide), Gd-DTPA-BMEA (gadoversetamide) and Gd-BOPTA (gadobenate dimeglumine) or cyclic structures, Gd-DOTA (gadoterate meglumine), Gd-BT-DO3A (gadobutrol) and Gd-HP-DO3A (gadoteridol). Until recently, these agents were all considered to be very safe for human use. However, since 2010 the European Medicines Agency (EMA) have recommended against the use, or at least minimisation of the use, of these agents in patients with severe kidney problems or patients undergoing liver transplants. Such patients are at risk of a condition known as nephrogenic systemic fibrosis believed to be caused by gadolinium contained in these agents. Moreover, in March 2017 the EMA recommended suspension of the marketing authorisation for the four linear agents because of increasing evidence that small amounts of gadolinium may accumulate in the brain following multiple contrast agent administrations. As a result it seems likely that future studies will employ cyclic agents only.
Impregnated activated carbon for the adsorption of Gd(III) radionuclides from aqueous solutions
Published in Particulate Science and Technology, 2018
Ghada M. Rashad, Mamdoh R. Mahmoud, Reda R. Sheha
Gadolinium, a rare earth element (Gd(III)), has found many applications in nuclear and industrial fields. Because it has the highest neutron cross-section among other stable nuclides, gadolinium is used in the nuclear field for shielding in neutron radiography and in nuclear reactors (Aghayan, Khanchi, and Mahjou 2013). In the nonnuclear field, gadolinium was found to play an important role in manufacturing appliances, computer hardware, networking and medical imaging (Radhika et al. 2012). Despite its innumerable benefits, gadolinium shows adverse effects if leaked in the environment. Gadolinium ions show toxicity in the human body due to interfering with a number of calcium-ion channel-dependent processes. It lead to a rare and serious illness called nephrogenic systematic fibrosis. It can damage the cell membrane and the reproduction system of animals thriving in aqueous bodies. Gadolinium also affects the lung metabolism and can be threat to the liver (Gupta, Singh, and Kumawat 2013). Owing to these detrimental effects, gadolinium is considered a hazardous material. Therefore, gadolinium should be removed from wastewaters before discharge into the environment.
Solvent Extraction, Sequential Separation and Trace Determination of La (III), Ce (III), Nd (III) and Gd (III) with 2, 14-bis[m-nitrophenyl]-Calix[4]Resorcinarene-8, 20-bis[N- phenylbenzo]-dihydroxamic Acid
Published in Solvent Extraction and Ion Exchange, 2023
C. R. Sharma, R. N. Patadia, Y. K. Agrawal
Gadolinium is used in magnetic resonance imaging (MRI) as a contrast agent. Its high magnetic moment allows it to produce strong signals in MRI scans, making it useful for detecting tumors, inflammation, and other abnormalities.[9,10] Gadolinium compounds are also used in some types of optical fibers and in certain types of lasers. Additionally, gadolinium has been proposed for use as a neutron absorber in nuclear reactors.[11] Overall, gadolinium has many unique properties and potential applications in many different fields of science and technology.