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Biomedical subjects

F Schmitt

Publications and source records attributed to F Schmitt.

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

Physiological effects of fast oscillating magnetic field gradients.

To evaluate the physiological thresholds of neuromuscular stimulation relevant to very fast NMR imaging studies that use gradient switching at frequencies of 1-2 kHz and a maximum magnetic field of up to 10 mT, a series of studies were done with human volunteers using an experimental echo planar gradient coil set. The threshold for induction of localized and momentary sensations in the human back and abdomen for 10 subjects is 60 T/s for sinusoidally oscillating magnetic fields at 1.27 kHz. The threshold relates to an E field of 6 V/m and is shown to vary with number of oscillations and frequency in accord with theory. Using a simple model of E field induction, the threshold for stimulation of cardiac electrical events should be greater than 4 times this value.

Abdomen↗
PubMedDate not supplied

Peripheral nerve stimulation by time-varying magnetic fields.

PURPOSE: A study was performed to assess the stimulation threshold for healthy adults using sinusoidally oscillating gradients. METHOD: One hundred thirteen healthy adults were examined in the study. ECG and physiological parameters were measured. All measurements were performed of both the head and the abdomen. The subjects were measured in the supine position with the region of interest positioned in the center of the gradient coils. The measurement was performed for three orthogonal, four oblique, and double oblique orientations. RESULTS: No volunteer reported painful, severe stimulation. The mean thresholds for peripheral stimulation in head and body measurement were similar: 85.5% of stimulation during examination of the head and 87.6% during measurements of the abdomen were reported when the y-gradient was used. CONCLUSION: The greatest frequency of reported stimulations occurs when the y-gradient is used. This was confirmed by the results and supports the hypothesis that orthogonal to the y-axis the body has its largest conductive loop, resulting in the strongest peripheral stimulation.

Adult↗
PubMedDate not supplied

Rhabdomyosarcoma mimicking Wilms' tumor.

A case of a 6 year old child, with a pleomorphic rhabdomyosarcoma involving simultaneously the leg muscles and the kidney is reported. The renal tumor distorted the pyelocalycial system and Wilms' tumor was the clinical diagnosis. The authors discuss on the possible primary site of the tumor.

Child↗