摘要:

The use of contrast agents in MRI is well established as a means to improve diagnosis. MRI diflers from other imaging modalities because signal and contrast are multiparametric in both the properties of the tissue and the method of measurement. Contrast depends on differences in proton-spin density, magnetic susceptibility, molecular diffusion and perfusion, and T1 and T2 relaxation times. Relaxivity contrast agents, those that focus, on shortening relaxation times, are most commonly employed in the form of paramagnetic chelates and depend on a variety of mechanisms, including concentration, number of ion-coordination sites, spin quantum number, magnetic moment, ion-to-proton distance, and correlation time constants characteristic of the chemical and molecular structure. A sound understanding of the principles of general contrast mechanisms, contrast agent design, and MRI techniques used in conjunction with contrast agents is vital to ensure proper enhancement and optimal diagnostic results.

ISSN:0899-3459    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

The clinical utility of paramagnetic metal ion chelates for contrast enhancement in MRI of the brain is well established Contrast administration provides both improved sensitivity and specificity wilh respect to diagnosis in neoplasia. infection, demyelinating disease, infarction, and arteriovenous abnormalities. On the basis of results from prospective studies, use of enhanced scans, in addition to baseline precontrast T1− and T2-weighted scans, is advocated in all patient studies in which there is a high index of suspicion with respect to intracranial pathology.

ISSN:0899-3459    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

MRI of the spine and its contents is fast becoming the study of choice over CT myelography for the evaluation of spinal pathology. MRI is able to generate sagittal and coronal images in addition to axial images, to image the entire spine, and to produce a myelogramlike picture. These capabilities give MRI a distinct advantage over CT myelography not only because no intrathecal contrast injection is needed but also because intramedullary lesions, edema, and syrinx may be differentiated from each other by conventional, noncontrast, spin-echo MRI. This article reviews the current philosophies regarding contrast-enhanced MRI with gadopentate dimeglumine in the evalution of the spine and its contents. It will provide an imaging strategy and approach to evaluation, briefly discuss spin-echo and gradient-echo pulse sequences, and give contrast indications focusing on disorders that benefit from the use of injected, intravenous gadopentate dimeglumine. Potential imaging artifacts related to spin-echo and gradient-echo imaging pertinent to imaging of the spine will also be discussed.

ISSN:0899-3459    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Although parenteral contrast agents are now widely used in the central nervous system, progress in the development of applications in the remainder of the body has been slow. Both intravenous Gd-DTPA and magnetic iron oxide particles have many potential applications but the former will probably require faster imaging techniques and the latter will require reformulation to produce a less toxic preparation. In spite of these problems methods have been developed for the diagnosis of myocardial infarction, breast carcinoma, and musculoskeletal tumors. Interesting preliminary results are available for other applications of contrast agents in the body and many of these are likely to become routine over the next 5 years.

ISSN:0899-3459    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

In June 1988 Gd DTPA became the first MR contrast agent to be approved for clinical use in adult patients in the United States. Initial approval was given for its use in imaging of the head. One year later approval was extended to include spine studies. This was soon followed by approval for use in children aged 2 years and older. Research is continuing to expand the applications of Gd DTPA in MR imaging of the musculoskeletal system, abdomen, and in MR angiography. Research is ongoing in the development of new agents, attempting to reduce toxicity, permit increased doses, or target specific organs. Gd DOTA has been in clinical use in Europe for approximately 1 year. Two neutral (nonionic) agents, Gd HP-DO3A and Gd DTPA-BMA, have just completed phase Ml clinical trials. Mn DPDP and AMI-25 are two targeted compounds that have entered clinical trials. Formulations intended for opacirication of the gastrointestinal tract, with both Gd DTPA and magnetic particles, have been evaluated in Europe and in the United States.

ISSN:0899-3459    

出版商:OVID    

年代:1991

数据来源: OVID

ISSN:0899-3459    

出版商:OVID    

年代:1991

数据来源: OVID

ISSN:0899-3459    

出版商:OVID    

年代:1991

数据来源: OVID