![]() However, sonographic evaluations can be non-effective or give ambiguous results. Ultrasound (US) is currently the imaging system of choice for pregnant patients. Medical imaging encompasses different technologies to image the human body for the diagnosis, course of treatment management, and follow-up of diseases. Pregnancy is a delicate state, during which timely investigation of possible physiological anomalies is essential to reduce the risk of maternal and fetal complications. Some agents are also capable of targeting other organs, inflammation as well as specific tumors. ![]() A number of contrast agents have been developed to selectively distinguish liver pathologies. According to biodistribution and applications, MRI contrast agents may be categorised into three types: extracellular fluid, blood pool and target/organ-specific agents. MRI contrast agents may be administered orally or intravenously. MRI contrast agents incorporating chelating agents reduces storage in the human body, enhances excretion and reduces toxicity. The enhanced parts appear darker on T2-weighted images. Dysprosium, superparamagnetic agents and ferromagnetic agents are negative contrast agents. These agents shorten the T1, so the enhanced parts appear bright on T1-weighted images. ![]() Most paramagnetic contrast agents are positive agents. These elements shorten the T1 or T2 relaxation time, thereby causing increased signal intensity on T1-weighted images or reduced signal intensity on T2-weighted images. The majority of these agents are either paramagnetic ion complexes or superparamagnetic magnetite particles and contain lanthanide elements such as gadolinium (Gd3+) or transition metal manganese (Mn2+). Magnetic resonance imaging (MRI) contrast agents are categorised according to the following specific features: chemical composition including the presence or absence of metal atoms, route of administration, magnetic properties, effect on the magnetic resonance image, biodistribution and imaging applications. ![]()
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