No abstract

Physiologically inert perfluorinated gases may be used for lung ventilation imaging by Nuclear Magnetic Resonance (NMR). Because the nuclear concentration in the gas is lower than in tissue, signals from large gas volumes must be integrated to produce an acceptable image quality. After a series of phantom studies, preliminary dog studies have been carried out, using breathable mixtures of CF4 and O2. The resulting images have been compared with Xe ventilation scans. Furthermore, perfluorinated solutions were imaged using phantoms. The results are described and the future potential of the technique discussed.

The authors summarise their experience of four clinical studies with a negative oral contrast agent for magnetic resonance imaging of the abdomen and pelvis. 140 patients were enrolled in the studies. These were partly comparative studies pre- and post-contrast, partly at 0.5 and 1.5 T, partly pre-injection and post-injection of glucagon. All patients received 800 ml of a suspension of oral magnetic particles "OMP". The distribution of this contrast agent was homogeneous throughout the entire GI tract. A complete or partial signal void was observed in all patients in T1, T2-, and intermediately weighted images. Generally, diagnostic information was higher after contrast. Artifacts caused by peristalsis and movement of the diaphragm were fewer after contrast. After contrast metallic artifacts were observed in a minority of patients. Adverse events after contrast were minimal; they included nausea and vomiting.

A multiple spin-echo-sequence has been evaluated in diagnosis of demyelinating diseases. TE in these MR-experiments was between 14 and 336 msec, TR between 860 and 1660 msec. Three groups of patients were examined, and it could be shown that the probability to detect MS-plaques grows with long TE's up to 300 msec. T2-relaxation-time-values range between 126 and 250 msec. Different MS-plaques in the same patient might show different T2-values.

In a patient population of some 450 with definite, probable, and possible multiple sclerosis referred to us for MRI, some 40 suffering from definite MS were chosen randomly for relaxation time measurements of plaque-free grey and white matter. T1 values could not be used for diagnostic purposes owing to their broad standard deviation. Overall white matter T2 was slightly higher in MS patients than in a non-MS population (94 ms versus 89 ms). Because these changes are not visible in MR images, relaxation time measurements may prove valuable for differential diagnosis.