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Microcomputed Tomography
Published in George C. Kagadis, Nancy L. Ford, Dimitrios N. Karnabatidis, George K. Loudos, Handbook of Small Animal Imaging, 2018
To improve the contrast for imaging soft tissue and vasculature, iodinated contrast agents can be introduced to alter the x-ray attenuation characteristics of the target organ or tissue. Although there are clinically available iodinated contrast agents, they are not often used due to the relatively long scan times required for imaging compared with the metabolic rate of the rodent. To ensure constant enhancement through the imaging session, the clinical agents must be introduced via a power injection with a constant infusion rate. Alternatively, blood pool agents have been developed for preclinical applications. These blood pool agents, injected via the tail vein, recirculate in the vasculature for hours to provide exquisite contrast between the blood and surrounding tissue.
Nanomaterials in Imaging
Published in Sourav Bhattacharjee, Principles of Nanomedicine, 2019
The blood pool agents (BPAs), also known as intravascular contrast agents (polymeric Gd-chelates, albumin-binding Gd complexes, etc.), are typically of very high molecular weights [73], which, unlike most other contrast agents, prevents their leakage through vascular walls into interstitial spaces. In addition, these molecules typically demonstrate higher relaxivity compared to conventional contrast agents [74]. Hence, these molecules remain longer within vascular compartments and enable the imaging of vasculature with higher resolution.
Comparison of fast field-cycling magnetic resonance imaging methods and future perspectives
Published in Molecular Physics, 2018
Markus Bödenler, Ludovic de Rochefort, P. James Ross, Nicolas Chanet, Geneviève Guillot, Gareth R. Davies, Christian Gösweiner, Hermann Scharfetter, David J. Lurie, Lionel M. Broche
All these results demonstrate the potential of FFC-MRI in the field of contrast agents, to improve the sensitivity and specificity of contrast agent detection over a wide range of field strengths. Although approximately 40% of clinical MRI exams employ Gadolinium-based CAs [53], the availability of clinical approved CAs suitable for FFC-MRI is rather limited. The aforementioned gadofosveset was designed as blood pool agent for contrast-enhanced MR angiography and is approved for a clinical use [54]. This agent shows favourable dispersive properties in the clinical field range between 1.5 T and 3 T, but the manufacturer discontinued the production in 2017 [55]. Iron oxide nanoparticles also show dispersive properties in the clinical field range. For example, ferumoxytol is approved by the United States Food and Drug Administration (FDA) for treatment of iron deficiency anaemia in adult patients and its off-label use as MRI contrast agent has rapidly grown [56,57]. Over the years, significant effort has gone into the development of new MRI contrast agents but sophisticated toxicology and pharmaceutical investigations are necessary to take the step from preclinical development to approval for clinical use.