Site Survey

SERVICES

Magnetic survey and vibration measurements on site.

Before finally deciding on the location of an MRI room, a magnetic survey and vibration measurements generally need to be carried out.

The fluctuations of magnetic fields are measured in all three axes using a fluxgate sensor in a frequency range extending from DC (0 Hz) to 1000 Hz. The sensor has a range of ±10 µT and a typical noise level of <10 pTRMS.

Vibration is measured in the floor of the magnetic room in a frequency range of 0.2 Hz to 5 kHz depending on the sensor used. The sensitivity of the vibration measuring instrument (sensor and FFT analyser) is 9.78 V/g and the resolution 0.000001 g.

Four to eight hours are needed to conduct a full survey. A report is provided containing results of the survey which include the largest fluctuations during the measurement period in the time domain and typical amplitude spectrum, in the case of magnetic fields in a frequency range of 0…1000 Hz and in the case of vibration in frequency ranges of 0…100 Hz and 10 Hz…5 kHz.

Conditions:

IMEDCO AG is fully equipped to measure fringe magnetic fields.

This can be necessary for subsequently checking the effectiveness of a magnetic shield or to record the lines of force to which other equipment is subjected.

Three independent sensors of the Hall effect-type designed to measure DC fields of the kind generated by MRI equipment are embedded in the probe and individually connected to the evaluation equipment.

Generally, the 0.5 mT and 0.1 mT fringe field contours are of interest.

The program includes models of the fringe fields generated by the main types of magnets available.

The geometry of the magnetic shield is entered using the integrated CAD program. The system then applies the finite element method to calculate the leakage field around the shield and prints a plot of the lines of force. Two and three-dimensional calculations can be performed.

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