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A feasibility study of altered spatial distribution of losses induced by eddy currents in body composition analysis.

Blomqvist KH, Sepponen RE - Biomed Eng Online (2010)

Bottom Line: The rate of loss as a function of frequency was observed to be approximately three times larger for a phantom with fat in the middle of its volume than for one with fat in its outer shell volume.At higher frequencies the major signal contribution can be shifted toward outer shell volume.The authors expect that the loss changing rate over frequency can be a potential index for body composition analysis.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Electronics, Aalto University, PO BOX 13340, 00076 Aalto, Finland. kim.h.blomqvist@tkk.fi

ABSTRACT

Background: Tomographic imaging has revealed that the body mass index does not give a reliable state of overall fitness. However, high measurement costs make the tomographic imaging unsuitable for large scale studies or repeated individual use. This paper reports an experimental investigation of a new electromagnetic method and its feasibility for assessing body composition. The method is called body electrical loss analysis (BELA).

Methods: The BELA method uses a high-Q parallel resonant circuit to produce a time-varying magnetic field. The Q of the resonator changes when the sample is placed in its coil. This is caused by induced eddy currents in the sample. The new idea in the BELA method is the altered spatial distribution of the electrical losses generated by these currents. The distribution of losses is varied using different excitation frequencies. The feasibility of the method was tested using simplified phantoms. Two of these phantoms were rough estimations of human torso. One had fat in the middle of its volume and saline solution in the outer shell volume. The other had reversed conductivity distributions. The phantoms were placed in the resonator and the change in the losses was measured. Five different excitation frequencies from 100 kHz to 200 kHz were used.

Results: The rate of loss as a function of frequency was observed to be approximately three times larger for a phantom with fat in the middle of its volume than for one with fat in its outer shell volume.

Conclusions: At higher frequencies the major signal contribution can be shifted toward outer shell volume. This enables probing the conductivity distribution of the subject by weighting outer structural components. The authors expect that the loss changing rate over frequency can be a potential index for body composition analysis.

Show MeSH
Q of the resonator. Quality factor characteristic of the resonator from 100 kHz to 400 kHz.
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Figure 12: Q of the resonator. Quality factor characteristic of the resonator from 100 kHz to 400 kHz.

Mentions: The quality factor characteristic of the tuned coil is shown in Figure 12. There was no significant change in Q over the bandwidth of interest when the coil was laid on a table or placed upright on the floor.


A feasibility study of altered spatial distribution of losses induced by eddy currents in body composition analysis.

Blomqvist KH, Sepponen RE - Biomed Eng Online (2010)

Q of the resonator. Quality factor characteristic of the resonator from 100 kHz to 400 kHz.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2992533&req=5

Figure 12: Q of the resonator. Quality factor characteristic of the resonator from 100 kHz to 400 kHz.
Mentions: The quality factor characteristic of the tuned coil is shown in Figure 12. There was no significant change in Q over the bandwidth of interest when the coil was laid on a table or placed upright on the floor.

Bottom Line: The rate of loss as a function of frequency was observed to be approximately three times larger for a phantom with fat in the middle of its volume than for one with fat in its outer shell volume.At higher frequencies the major signal contribution can be shifted toward outer shell volume.The authors expect that the loss changing rate over frequency can be a potential index for body composition analysis.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Electronics, Aalto University, PO BOX 13340, 00076 Aalto, Finland. kim.h.blomqvist@tkk.fi

ABSTRACT

Background: Tomographic imaging has revealed that the body mass index does not give a reliable state of overall fitness. However, high measurement costs make the tomographic imaging unsuitable for large scale studies or repeated individual use. This paper reports an experimental investigation of a new electromagnetic method and its feasibility for assessing body composition. The method is called body electrical loss analysis (BELA).

Methods: The BELA method uses a high-Q parallel resonant circuit to produce a time-varying magnetic field. The Q of the resonator changes when the sample is placed in its coil. This is caused by induced eddy currents in the sample. The new idea in the BELA method is the altered spatial distribution of the electrical losses generated by these currents. The distribution of losses is varied using different excitation frequencies. The feasibility of the method was tested using simplified phantoms. Two of these phantoms were rough estimations of human torso. One had fat in the middle of its volume and saline solution in the outer shell volume. The other had reversed conductivity distributions. The phantoms were placed in the resonator and the change in the losses was measured. Five different excitation frequencies from 100 kHz to 200 kHz were used.

Results: The rate of loss as a function of frequency was observed to be approximately three times larger for a phantom with fat in the middle of its volume than for one with fat in its outer shell volume.

Conclusions: At higher frequencies the major signal contribution can be shifted toward outer shell volume. This enables probing the conductivity distribution of the subject by weighting outer structural components. The authors expect that the loss changing rate over frequency can be a potential index for body composition analysis.

Show MeSH