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MR Imaging
Published in George C. Kagadis, Nancy L. Ford, Dimitrios N. Karnabatidis, George K. Loudos, Handbook of Small Animal Imaging, 2018
Sodium MRI is highly sensitive to 23Na compartmentalization and can provide early markers of cell damage in neurological and treatment response studies (Schepkin et al. 2012). 23Na MRI has relatively high sensitivity due to large γ and short T1 of 23Na spins. On the other hand, an extremely short 23Na T2 time in biological system requires application of ultrashort echo-time imaging sequences, and currently a novel strategy of spatial encoding such as twisted projection has been developed for 23Na MRI (Yushmanov et al. 2009).
Animal Models and Imaging of Intervertebral Disc Degeneration
Published in Raquel M. Gonçalves, Mário Adolfo Barbosa, Gene and Cell Delivery for Intervertebral Disc Degeneration, 2018
Marion Fusellier, Johann Clouet, Olivier Gauthier, Catherine Le Visage, Jerome Guicheux
The following techniques are being developed and need further evaluation before coming into routine use. Biochemical imaging techniques such as CEST, sodium imaging, and dGEMRIC can assess GAG content. In the CEST method, exchangeable protons are saturated, and the saturation is transferred by chemical exchange to the bulk water of their environment, inducing a considerable contrast enhancement of bulk water. GAG CEST has been used to evaluate GAG content and pH changes during DDD in vitro (Saar et al. 2013) and in vivo (Schleich et al. 2016; Zhou et al. 2016). Sodium MRI consists in quantification of the 23Na concentration by MRI (Ooms et al. 2008). In IVD, the sodium concentration correlates with the GAG concentration (Shapiro et al. 2002) and disc degeneration induces a decrease in IVD 23Na content (Haneder et al. 2014). This technique is feasible on small-animal models such as rabbits (Moon et al. 2012). dGEMRIC was initially developed for examination of articular cartilage after intravenous administration of gadolinium. In IVD, gadolinium diffuses from the capillaries of the EP and can provide an estimation of the in vivo GAG content of disc tissue (Vaga et al. 2008).
Methods for Evaluating Articular Cartilage Quality
Published in Kyriacos A. Athanasiou, Eric M. Darling, Grayson D. DuRaine, Jerry C. Hu, A. Hari Reddi, Articular Cartilage, 2017
Kyriacos A. Athanasiou, Eric M. Darling, Grayson D. DuRaine, Jerry C. Hu, A. Hari Reddi
Methods such as diffusion MRI have been used to assess extracellular matrix content and alignment (Nieminen et al. 2001;de Visser et al. 2008). For example, diffusion imaging used to evaluate autologous chondrocyte transplantation was able to discern differences between transplanted and native cartilages (Mamisch et al. 2008). Sodium MRI is another technique that has been correlated with extracellular matrix content in articular cartilage. As proteoglycans are lost during the progression of osteoarthritis, the negative fixed charge density of cartilage is reduced, resulting in a loss of sodium ions, and this can be measured using sodium MRI (Wheaton et al. 2004). Fluid-suppressed sodium MRI signals have also been correlated with Kellgren-Lawrence scores of osteoarthritis (Madelin et al. 2013). Also, collagen is a highly anisotropic matrix component in articular cartilage, and collagen fibers can impose anisotropic translational and rotational motions on sodium ions. For the detection of osteoarthritis, use of sodium MRI appears to depend on subject age and whether the fields assessed include synovial fluid (Newbould et al. 2012, Newbould et al. 2013). To summarize, for the evaluation of articular health and disease, techniques to independently assess both glycosaminoglycan content and collagen content must be developed.
Clinical applications of ultra-high field magnetic resonance imaging in multiple sclerosis
Published in Expert Review of Neurotherapeutics, 2018
Matilde Inglese, Lazar Fleysher, Niels Oesingmann, Maria Petracca
Several 3 T sodium MRI studies from different laboratories around the world [58–64] have showed a widespread brain increase of total tissue sodium concentration (TSC) in patients with MS, suggesting that this might reflect changes in cellular and metabolic integrity of both lesions and normal-appearing brain tissue. While in the early disease stage TSC increase is prevalent in macroscopic lesions [60], it spreads to normal-appearing white matter, cortical and deep gray matter as the disease progresses [58–61]. TSC increase in lesions might be explained by gliosis, tissue disruption, and replacement with extracellular fluid, whereas TSC increase in normal-appearing brain tissue is related not only to increased extracellular space, caused by demyelination and axonal loss, but also to intra-axonal 23Na increase.
Dynamic Volume Assessment of Hepatocellular Carcinoma in Rat Livers Using a Clinical 3T MRI and Novel Segmentation
Published in Journal of Investigative Surgery, 2018
Lorenzo A. Orci, Graziano Oldani, Stephanie Lacotte, Florence Slits, Iris Friedli, Wolfgang Wirth, Christian Toso, Jean-Paul Vallée, Lindsey A. Crowe
For MRI assessment alone, studies of HCC exist using both negative contrast agents (such as iron oxide nanoparticles [9, 10]) and positive contrast agents (such as Gadolinium either as a conventional contrast agent or nanoparticles [11, 12]). However, many techniques involving the use of contrast agents other than commercial gadolinium complexes are not widely available outside research [13]. On the other hand, data on radiological techniques without exogenous contrast agent to quantify the growth of liver tumor are scarce. For instance, diffusion-weighted MRI (DWI) can be used to track changes in HCC volume [14, 15] but this technique is hampered by abdominal organ motion, susceptibility to artifacts, and limits on resolution in a reasonable scan time [16, 17]. In a recent study, three-dimensional (3D) reconstructions, by interpolating 2D multi-slice images, were combined with DWI and sodium MRI to monitor HCC growth rate [15]. However, this study still calculated tumor volume based on an ellipsoid assumption [18] which oversimplifies the often complex morphology of tumor nodules.