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At least 1,117 records · Page 62Linked to original sources
PubMed1990

Metalloporphyrin magnetic resonance contrast agents. Feasibility of tumor-specific magnetic resonance imaging.

The criteria for tumor-specific MRI contrast agents are considered. The metalloporphyrins have been shown to be potential tumor-specific contrast agents due to their selective retention by cancer cells. The Mn(III) water-soluble porphyrin complexes are preferred on the basis of relaxivity and stability. Protein binding in human plasma enhances the relaxivity of Mn(III)-tetraphenylsulfonato-porphyrin (MnTTPS). In preliminary work this agent was shown to enhance MRI contrast at 0.5 T in subcutaneous human colon carcinomas grown in nude mice. Here we report further evidence of enhanced contrast in the same system, and extend this work to human breast tumors in nude mice using a 2 T animal imager. Questions of metalloporphyrin stability, toxicity and dose-contrast relationship are discussed.

Animals↗
PubMed1990

[Obstacles to the routine use of magnetic resonance imaging--results of a multicenter study for evaluating nuclear magnetic resonance tomography].

Within the framework of this study, the factors that impair the value of MR scans were also investigated and analysed. It was found that artifacts occurred in a large number of examinations that exercised a negative effect on the results. Artifacts are particularly seen in the thorax (54%) and upper abdomen (57%), but they have also been reported in 23% of the CNS examinations. The sources of such artifacts were mainly movements in the investigated layer, whereas other causes were negligible. In the 21,633 examined patients no undesirable effects caused by the examination were noted that would have impaired the patient or the course of the study. On an average, 88% of the examinations were performed with normal tolerance of the examination. In the remaining cases there was motor unrest or claustrophobia requiring special measures, thus hampering the course of the examination.

Diagnosis, Differential↗
PubMed1990

[Evaluating magnetic resonance tomography studies of the extremities--results of a multicenter study for evaluating nuclear magnetic resonance tomography].

MR examinations of the extremities occupy the first place in whole body examinations via MR. Highest accuracy quotas in this area with an average of 93.8% were obtained for tumours, trauma and necroses of the bones. These high accuracy quotas, however, were achieved only if sufficient preliminary information was available. Other statistically significant factors were found to be the field strength, the combined use of spin echo and fast imaging sequences and the use of the multislice technique.

Bone Neoplasms↗
PubMed1985

[Checklist for understanding magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS)].

Overview on informations which are necessary to interpret MRI and MRS. The approach is related rather to application than it is a physical one. The central steps in comprehending MR are presented, e.g. frequency decomposition in order to obtain local information with MRI or chemical information with MRS, the spin echo in order to differentiate instrumental dephasation from dephasation by molecular interference, perfusion in MRI, and the components of sensitivity in measuring different nuclei etc. The report terminology is based on the description of grey scale pictures, but one has to consider that the information is not one-dimensional but multiparametric. Therefore new terms have to be developed, a problem similar to that of describing scintigraphic time sequences in nuclear medicine.

Electron Spin Resonance Spectroscopy↗
PubMed1986

[Phantom substances in the quantitative evaluation of magnetic resonance T-images. II. Effect of relaxation times on magnetic resonance T-intensity values].

Reference material for quantitative MR Imaging (paramagnetic agar gel) is examined with regard to effects of small T1 and T2 variations on MRI signals. For some pulse sequences that are important in clinical practice, it can be shown that SE images are very sensitive to T2 variations, whereas IR images are influenced by both T1 and T2.

Electron Spin Resonance Spectroscopy↗