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Biomedical subjects

A Sivula

Publications and source records attributed to A Sivula.

83 records · Page 5Linked to original sources
PubMedDate not supplied

Low field (0.02 T) nuclear magnetic resonance imaging of the brain.

Many technical and instrumental alternatives are available to obtain good spatial and contrast resolution in magnetic resonance (MR) imaging. Optimum field strength remains a controversial question. In spite of its inherent low signal-to-noise ratio, low field imaging exhibits some advantages. It is well established that the relaxation times are dependent on the magnetic field strength. In low fields the relaxation times, especially T1, are shorter and the relative differences of T1 between different tissues are larger. Other benefits are the ease of installation of the device, its cost effectiveness, and the obvious avoidance of hazards caused by the magnetic field. In this report we describe six cases of cerebral lesions studied with an MR imager operating at a field strength of 0.02 T (200 G). This is the lowest field strength reported in clinical MR imaging. The information obtained was equal to that of the CT studies performed on the same patients.

Adult↗
PubMedDate not supplied

Intracranial hematomas studied by MR imaging at 0.17 and 0.02 T.

The contrast in magnetic resonance (MR) images relies mainly on the relaxation time differences between the tissues. The relative differences in relaxation times T1 are bigger at lower field strengths, although the absolute values of T1 are smaller. A shorter T1 is also advantageous for the contrast of the T2 and proton density weighted images because of the more complete recovery of the spin system during the repetition time TR. Scrutiny of the clinical results of MR shows some unsolved problems in the specificity of diagnosing fresh intracranial hematomas. Low field MR imaging at 0.02 T seems to offer new vistas in this sense. Fresh subdural hematoma was more easily detected and differentiated at 0.02 T than at 0.17 T. The T2 of fresh intracranial hematomas was rather short compared with cerebrospinal fluid and edema and, unlike T1, was not highly dependent on magnetic field strength. The different visualization of acute versus late intracerebral hematoma and the changes during the resorption were demonstrated in follow-up studies of two patients at 0.17 T and of one at 0.02 T. In one patient the same lesion was imaged successively at both field strengths, showing the divergent contrast in the inversion recovery images at 0.02 and 0.17 T.

Cerebral Hemorrhage↗