Radio-Frequency Magnetic Field Probes

Medical magnetic nanoparticle hyperthermia treatment requires applying an external radio-frequency magnetic field to the patient.

It is therefore essential to measure and map the field within the treatment volume.

Firstly, to ensure there is sufficient field density throughout the location of the tumour.

Secondly, to make sure there are no 'hot-spots' i.e. locations where the field density is too high, which can cause excessive eddy-current heating of healthy tissue.

FluxMetrix engineers designed a world-leading RF magnetic field probe system. The novel design allows safe operation in very high fields.

A probe takes the guesswork out of magnetic nanoparticle heating measurements. It gives an independent measurement of operating frequency and magnetic field density at the exact sample position, to corroborate indicated or calculated values. Use of the probe to set the test field improves confidence in the quality and repeatability of measurements.

To ensure the reproducibility of measurements, the probe allows you to:

Determine the maximum magnetic field density within the test volume
Map field density within the test volume
Determine the region of acceptable homogeneous field
Ensure that samples are tested at a consistent field density from test-to-test
Ensure that testing is consistent between different locations or test machines

Single Axis probe

The probe is a complete and compact system, consisting of the probe wand, USB oscilloscope, notebook computer and software. It comes with interconnect leads and a universal-input power supply.

Featuring small flux-sensors, it will detect local variations in field strength, not normally evident. This allows accurate measuring and mapping of test volumes.

Amplitude is detected with a proprietary lock-in amplifier technology implemented in the laptop software, this provides great resolution.

Probes will operate over a wide frequency range, from 40kHz to 1MHz.

Probes can operate safely at magnetic flux density levels far higher than alternative products.

The field amplitude can be displayed in Teslas, Amps/Metre, Oersted or Gauss. The display can be averaged from 1 measurement to the rolling average of 2, 4, 8, 16, 32, 64, 128, 256 or 512 consecutive readings. This allows stable readings if (for example) the magnetic field amplitude is modulated by power-supply ripple.

Specifications:

Operating frequency range: 40kHz to 1MHz (Range extension is possible).

Field frequency (kHz) is measured and displayed, selectable to 2, 3 ,4, 5 or 6 significant figures.

Field RMS amplitude is measured (uniaxial flux). Display units: mT, A/m, Oe or G selectable.

2, 3, 4 or 5 significant figures are selectable.

Dynamic range / resolution:

(100kHz) 250mT to 10uT

(1MHz) 25mT to 1uT (range scales with frequency).

Display modes:

RUN (continuous update)

STOP (freeze current display)

SINGLE (start one capture).

Initial Calibration: +/-1% compared to in-house ab-initio reference.

Probe Diagnostic Version

An enhanced version of the field probe is available. This is a very powerful analytic and diagnostic tool, for analysing the quality of the RF magnetic field.

Additional features:

Waveform: Normalised display of one cycle of the flux waveform, superimposed on a perfect sinusoid, also showing +/- 10% window range.

Envelope: Shows the envelope of the operating frequency on 100ms, 1s or 10s timebase

Harmonics: Shows a normalised spectral analysis of the operating frequency, showing the relative amplitudes of the first 30 harmonics. Also a calculation of Total Harmonic Distortion (THD) is given, as well as [THD + noise], as a percentage and in –dBc.

Over thirty of these probe units have been sold to research organisations worldwide. These systems can operate with various probe wands, both longitudinal and transverse, to suit the application.

3-Axis omnidirectional probe

A 3-axis probe has been proven and is in the final stages of development. This measures the X, Y and Z-axis components of a RF magnetic field and also calculates the absolute magnitude of the flux vector |B| at that location.

The output is an analog DC voltage proportional to RMS flux density, for the X, Y, Z axes and vector magnitude.

Long cables up to 5m are supported.

Contact us to discuss your requirements