Items tagged “needs review”

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MRI (an abbreviation of magnetic resonance imaging) is an imaging modality that uses non-ionizing radiation to create useful diagnostic images. MRI was initially called nuclear magnetic resonance (NMR) imaging after its early use for chemical analysis. The initial "nuclear" part was dropped abou...

Gradient echo sequences

Gradient echo sequences (GRE) are an alternative technique to spin echo sequences, differing from it in two principal points: utilization of gradient fields to generate transverse magnetisation flip angles of less than 90° Compared to the spin echo and inversion recovery sequences, gradient e...

Gastrointestinal MRI contrast agents

Gastrointestinal MRI contrast agents are varied and can be either positive or negative agents. Acceptance of the use of MRI in abdominal imaging has been limited in part by difficulty in distinguishing bowel from intra-abdominal masses and normal organs. The use of enteric contrast agents can ai...

Intravascular (blood pool) MRI contrast agents

Intravascular MRI contrast agents normally remain confined to the intravascular space, compared to Gd-DTPA which distributes throughout the extracellular fluid space. This is a result of intravascular agents having a molecular weight of approximately 70,000 and above, compared to a molecular wei...

Reticuloendothelial MRI contrast agents

Reticuloendothelial MRI contrast agents can best be discussed in terms of those used for liver and spleen imaging and those for lymph node imaging. Liver and spleen The use of Gd-DTPA with routine imaging sequences of the liver is unsatisfactory. Particulate contrast agents targeted to the ret...

Tumor specific MRI contrast agents

Tumor specific MRI contrast agents are pharmaceuticals that are targeted to tumors, either specifically or nonspecifically. Monoclonal antibodies are targeted to specific tumors such as adenocarcinoma of the colon. Metalloporphyrins exhibit affinity for many tumor types including carcinoma, sarc...

Phase contrast imaging

Phase contrast imaging is an MRI technique that can be used to visualize moving fluid. It is typically used for MR venography as a non-IV-contrast requiring technique.  Spins that are moving in the same direction as a magnetic field gradient develop a phase shift that is proportional to the vel...

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