Abstruct-In this papier the dependence of electromagnetic energy absorption at 900 IMHz in the human head on its anatomy and its modeling are investigated for RF-sources operating in the very close proximity of the head. Different numerical head phantoms based on MRI scans of three different adults were used with voxel sizes down to 1 mm:'. Simulations of the absorption were performed by distinguishing the electrical properties of up to 13 tissue types. In addition simulations with modified electric parameters and reduced degrees of complexity were performed. Thus, the phantoms greatly differ from each other in terms of shape, size, and internal anatomy. The numerical results are compared with those of measurements in a multitissue phantom and two homogeneous phantoms of different shapes and sizes. The results demonstrate that size and shape are of minor importance. Although local SAR values depend significantly on local inhomogeneities and elecctric properties, the volume-averaged spatial peak SAR obtained with the homogeneous phantoms only slightly overestimates that of the worst-case exposure in the inhomogeneous phantoms.
Proximal myotonic myopathy (PROMM) is an autosomal dominantly inherited multisystemic disorder characterized by myotonia, proximal muscle weakness, and cataracts. This disorder is not linked to the gene locus of myotonic dystrophy (DM). We describe three new families with PROMM. In all patients, CTG repeats of the DM gene in DNA from blood leukocytes were normal. MRI of the brain revealed a consistent pattern of marked white matter hyperintensity on T2-weighted images in four patients; two additional patients had similar but mild to moderate MRI abnormalities. The morphology of these abnormalities is unknown. Clinical symptoms of brain disease were not consistent and included mental changes with hypersomnia, parkinsonian features, stroke-like episodes, and seizures. The causative relationship of these clinical features with the MRI white matter abnormalities remains to be established. Our observations suggest that PROMM may involve the brain.
Two brothers are described with a distal myopathy different from the known hereditary distal myopathies. Early adult onset, beginning in the distal leg muscles with marked elevation of creatine kinase (CK) activity (20 to 30-fold) were the characteristic features. The parents of the patients had no symptoms or signs of myopathy. Their serum CK-activity was in the normal range. There was parental consanguinity, so the distal myopathy in these brothers is probably an autosomal recessive inheritance.
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