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. 2014 Feb 25;5(3):876-81.
doi: 10.1364/BOE.5.000876. eCollection 2014 Mar 1.

Optical multichannel room temperature magnetic field imaging system for clinical application

G Lembke  1 , S N Erné  1 , H Nowak  1 , B Menhorn  2 , A Pasquarelli  3
Affiliations

Optical multichannel room temperature magnetic field imaging system for clinical application

G Lembke et al. Biomed Opt Express. .

Abstract

Optically pumped magnetometers (OPM) are a very promising alternative to the superconducting quantum interference devices (SQUIDs) used nowadays for Magnetic Field Imaging (MFI), a new method of diagnosis based on the measurement of the magnetic field of the human heart. We present a first measurement combining a multichannel OPM-sensor with an existing MFI-system resulting in a fully functional room temperature MFI-system.

Keywords: (120.0120) Instrumentation, measurement, and metrology; (170.0170) Medical optics and biotechnology; (230.0230) Optical devices.

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Figures

Fig. 1
Fig. 1
Left: Photo of a single module. OM: Optical module containing a lens for collimating the light, two linear polarizers for intensity adjustment and a λ/4-plate for circularly polarizing the light, PD: Photodiode, Cs-Cell: cesium-cell. FB: Indicated position of the feedback coils. Right: Photo of the lowest sensor plane.
Fig. 2
Fig. 2
Layout of the sensor array. Left: 3D-display of all three levels with a spacing of 70 mm. Right: Top view on lowest sensor plane. At the positions marked with + the reference sensors in the second and third level are located.
Fig. 3
Fig. 3
Schematics of the data processing. PD: photodiode, PA: preamplifier, ADC: Analog-Digital-Converter, x: Multiplier, LPF: Low-pass-filter, PI: Proportional-integral controller, DAC: Digital-Analog-Converter, FB: Feedback-coils, PC: workstation for data recording.
Fig. 4
Fig. 4
Root noise density of one single channel with (green) and without (red) active compensation. A square-wave signal with amplitude of 6 nT and a frequency of 1 Hz was used as test signal.
Fig. 5
Fig. 5
First MFI-measurement of a healthy test person performed with the optical sensor head. The data was recorded for 10 minutes and averaged. The arrow indicates the position of the test person’s head.
Fig. 6
Fig. 6
Evaluation of the first optical MFI-measurement of a healthy test person. Upper part: Three channels with the averaged heart signal and magnetic field map. Upper left: Signal with maximum amplitude. Upper right: “Butterfly plot” of all relevant channels. Middle left: Channel with highest fragmentation. Middle right: Magnetic field map. Lower part: As result, the fragmentation index is displayed in comparison to the normal range of healthy test persons.
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