Magnetic Resonance Angiography MRA

Magnetic resonance angiography (MRA) is a method of imaging blood vessels in the presence of certain diseases, such as angiogenesis, tumors, atherosclerosis, coronary arteries [100], myocardium infarction, vascular injury, and blood flow reduction. Blood pool CA enhanced MRA increases the vessel-to-background ratio [101]. Blood pool CAs can be classified into two types, namely, low molecular weight Gd-based CAs and macromolecular CAs. 

The percentage binding of MS-325 is species dependent [105]. It has a binding range of 64-91%, but preferentially binds to human pig rabbit dog rat mouse [106]. Its in vitro relaxivity is 53.5, 32.5, 28.0, and 22.6 mM s at 20MHz in human plasma, rabbit plasma, rat plasma, and mouse plasma, respectively [104]. The first clinical trial demonstrated MS-325 to have a good CNR for DCE-MRI at a dose of 0.05mmolkg [107]. Its excretion half-life is 2-3 h [105]. 

DCE-MRA using MS-325 displays a long blood pool retention and allows steady-state imaging, which improves the vascular, arterial, and venous contrast enhancement [108]. This combination has been used for imaging the whole heart [109] and for cardio-venous imaging [110]. The pattern of contrast enhancement for cardiovascular imaging also depends on the type of CAused [111]. 

The differences between low molecular weight Gd-based CAs and macromolecular CAs stem mainly from their pharmacodynamic and pharmacokinetic properties, that is, what the CA does to the body, and vice versa. In addition to the observed relaxivity, the dynamic relaxivity is another parameter that is used in contrast-enhanced MRA in the presence of different types of CAs. The dynamic relaxivity describes the relaxivity results from both bound and non-bound complexes. For example, a comparison of the strongly HSA-bound MS-325 with the non-HSA-bound P792 in rabbit showed P792 to have a more constant dynamic relaxivity [114], A constant pharmacokinetics profile is also favorable for MRA analysis. 

Ideal blood pool agents display moderate HSA binding and a good dynamic relaxivity, a reasonably long blood residence time, no diffusion via the endothelium or reduced interstitial diffusion, a smaller dose and injection volume requirement, and efficient excretion. These qualities enable high-resolution MRA and an increase in vessel-to-background contrast, and thus a better visualization of smaller vessels and vascular pathology. 

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Both chelates have been launched as extracellular contrast agents using doses up to 3 mmol/kg body weight. Both can be formulated as 1.0 molar aqueous solutions with acceptable viscosity (Table 2). These highly concentrated agents are useful in fast dynamic studies such as brain perfusion and fast magnetic resonance angiography (MRA). 

These highly concentrated solutions are useful in fast dynamic studies such as brain perfusion and in magnetic resonance angiography (MRA) [56,57]. 

Contrast-enhanced magnetic resonance angiography (MRA) could be an interesting alternative to conventional X-ray angiography, for both safety and financial considerations [3]. 

Magnetic resonance angiography (MRA) This technique is used to image the arteries and blood flow, and using computer reconstmction it is even possible to display blood vessels in 3D. Thus, MRA is useful for evaluation of abnormal... 

Magnetic resonance angiography (MRA)— A noninvasive method to evaluate the patency of blood vessels using magnetic resonance imaging. 

Ma, L., et al., Can baseline magnetic resonance angiography (MRA) status become a foremost factor in selecting optimal acute stroke patients for recombinant tissue plasminogen activator (rt-PA) thrombolysis beyond 3 hours Neurol Res, 2009. 31(4) p. 355-61. 

Houkin K, Aoki T, Takahashi A, Abe H, Koiwa M, Kashiwaba T (1994) Magnetic resonance angiography (MRA) of ruptured cerebral aneurysm. Acta Neurochir 128 132-136 Housepian E, Pool J (1958) A systematic analysis of intracranial aneurysms from the autopsy file of the Presbyterian Hospital, 1914 to 1956. J Neuropathol Exp Neurol 17 409-423... 

Magnetic resonance angiography (MRA) and venography (MRV) provide visualization of arteries and veins. The images produced can help physicians evaluate potential health problems such as narrowing of the vessels or vessel walls at risk of rupture as in an aneurysm. The most common arteries and veins examined are the m or vessels in the head, neck, abdomen, kidneys, and legs. 

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