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DIELECTRIC PROPERTIES OF HUMAN COLOSTRUM AT MICROWAVE FREQUENCIES

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					DIELECTRIC PROPERTIES OF HUMAN COLOSTRUM
        AT MICROWAVE FREQUENCIES

          Anil Lonappan1, Chadrasekharan Rajasekharan2, Vinu Thomas1,
                Gopinathan Bindu1 and Kattackal Thomas Mathew
    1
     Department of Electronics, Microwave Tomography and Materials Research Laboratory
             Cochin University of Science and Technology, Kochi-682 022, India
                                      anil@cusat.ac.in
              2
               Department of Medicine, Medical College, Trivandrum- 695 011

        This article communicates the study of both the dielectric properties of human colostrums
and breast milk at microwave frequencies. The colostrum samples were taken immediately after child
birth and breast milk samples were collected at weekly intervals following the delivery. Rectangular
cavity perturbation technique is used for the measurements of dielectric properties at the S-band of
microwave frequency. The dielectric constants of the colostrums samples and breast milk samples
are found to increase as weeks elapse, which is attributed to the reduced fat content and increased
lactose concentration. The conductivity of these samples is similarly found to increase due to the
increased dilution.


                                                                       Submission Date: 10 October 2006
                                                                          Acceptance Date: 19 June 2007
                                                                        Publication Date: 30 August 2007


INTRODUCTION                                               ditional application of microwave energy, the
                                                           dielectric properties of the tissues that determine
Proper knowledge of the dielectric properties              the absorption and propagation of EM energy
of biological systems is essential for either de-          through the tissues must be taken into consid-
termining safe levels for personal exposure to             eration. Thus, from the knowledge of dielectric
electromagnetic radiation or for effectively em-           constants, tissue properties can be characterized
ploying electromagnetic radiation in beneficial            in the microwave frequency range.
biomedical applications. Thus, the measurement                  Electromagnetic radiation has been used as
of the dielectric properties of biological tissues         a therapeutic agent in medicine for many years.
would play a significant role in any well-founded          Recently, several studies of the biological effects
effort involving tissue interaction with electro-          of microwave radiation and the possibilities of
magnetic energy. It is widely recognized that              its use in medicine have been made. Microwave
radio frequency and microwave energy can                   radiation could be a useful thermogenic agent
be effectively used in the treatment of many               in the practice of physiotherapy if the problems
diseases. In order to develop the use and ad-              of dosage measurement and method of applica-
                                                           tion to patients are solved [Heath, 1974]. Con-
Keywords: Colostrums, breast milk, dielectric constant     currently, the search for any specific action of
cavity perturbation, S- band


41-2-30                         Journal of Microwave Power & Electromagnetic Energy          Vol. 41, No. 2, 2007
intense microwave fields on microorganisms,         2005]. In this experiment a transmission type
virus and other biological molecules has been       cavity resonator is employed. The number of
investigated [Campanella et al., 2003]. From the    resonant frequencies depends on the length of
point of view of microwave propagation, most        the resonator. The resonator is excited in the
materials of biological interest can be regarded    TE10P mode. The resonant frequency fo and the
as lossy dielectrics, which are frequently mac-     corresponding quality factor Qo of each reso-
roscopically or microscopically heterogeneous.      nant peak of the cavity resonator with the empty
The processes by which dielectric loss occurs       sample holder placed at the maximum electric
and thereby energy is transferred to the medium     field are noted. The shape of the sample holder
depend on the nature of the material and the        is in the form of a capillary tube flared to a disk
frequency range of radiations in use. Exhaus-       shaped bulb to facilitate easy movement of the
tive studies of dielectric parameters of various    same through the non-radiating cavity slot. The
human tissues and body fluids at different RF       sample holder filled with a known amount of the
frequencies have been reported [Gabriel et          sample is introduced into the cavity resonator.
al., 1996; Cook, 1951]. In addition, different      The resonant frequencies of the sample-loaded
measurement techniques have been developed          cavity are selected and the position of the sample
for the measurement of dielectric properties of     is adjusted for maximum perturbation (i.e. maxi-
biological samples at various bands of frequen-     mum shift of resonant frequency with minimum
cies [Burdette et al., 1980]. Active and passive    amplitude for the peak). The new resonant fre-
microwave imaging for disease detection and         quency fs and the corresponding quality factor Qs
treatment require proper knowledge of body tis-     are determined. The same procedure is repeated
sues’ dielectric properties at the microwave fre-   for other resonant frequencies.
quencies [Bolomey et al., 1983; Land, 1987].
     This paper reports a comprehensive study       THEORY
of the dielectric properties of human colostrums
and breast milk at microwave frequencies. The       When a material is introduced into a resonant
samples (all donors being Indian women) were        cavity, the cavity field distribution and resonant
collected at weekly intervals following child       frequency change; a change that is dependent
birth. Measurements are made at the S-band of       upon geometry, electromagnetic properties and
microwave frequency. The measurements reveal        its position in the fields of the cavity. Dielectric
that dielectric constant and conductivity of the    material interacts only with the electric field in
colostrums and breast milk samples are found        the cavity.
to increase as weeks elapse. These samples               According to the theory of cavity perturba-
are simultaneously subjected to chemical tests      tion [Mathew, 2005] the real and imaginary parts
which reveal that fat content decreases with the    of the complex permittivity can be expressed
passing of time.                                    as:
                                                                            f −f V 
MEASUREMENT TECHNIQUE                                             ε'r − 1 = 0 s  c 
                                                                             2fs  Vs 
                                                                                                   (1)
The measurement set-up consists of an S-band
rectangular cavity resonator connected to a HP                            Vc  Q0 − Qs 
8714 ET network analyzer. The rectangular                        ε"r =                
                                                                         4 Vs  Q0Qs 
                                                                                                  (2)
cavity resonator consists of a rectangular wave
guide with one or both ends closed, and being ei-
ther a transmission or a reflection type [Mathew,   where ε'r is the real part of the relative complex


International Microwave Power Institute                                                          41-2-31
                          Table 1. Quantitative analysis of breast milk - Sample 1.

                              Week 1
     Constituents                          Week 2     Week 3      Week 4    Week 5     Week 6      Week 7    Week 8
                            Colostrum
          Milk fat            13.6%         12.4%      11.3%      10.2%       9.8%          9.1%    8.3%       8.2%
   Milk solids not fat         8.5%            8.9%     9.3%       9.9%      11.2%      13.4%      13.2%      13.4%
          Protein              3.3%            3.6%     3.4%       3.3%       3.6%          3.3%    3.5%       3.1%


                          Table 2. Quantitative analysis of breast milk - Sample 2.

                              Week 1
     Constituents                          Week 2     Week 3      Week 4    Week 5     Week 6      Week 7    Week 8
                            Colostrum
          Milk fat            12.5%         12.1%      11.8%      11.2%      10.8%      10.1%       9.9%       9.7%
   Milk solids not fat        10.2%         10.7%      11.3%      11.3%      11.8%      12.1%      12.3%      12.7%
          Protein              3.0%            3.2%     3.4%       3.1%       3.4%          3.5%    3.4%       3.3%




permittivity, which is known as the dielectric                   breast milk samples. The samples were collected
constant, and ε"r is the imaginary part of the                   from the donors at weekly intervals from the first
relative complex permittivity associated with                    to the eighth week following child birth. From
the dielectric loss of the material, hence the                   Figures 1 and 2 it is found that the dielectric
complex dielectric permittivity is given by                      constant of the breast milk samples increases
εr = ε 'r − jε "r . The volumes of the sample and                as weeks elapse, while the dielectric constant
the cavity resonator are Vs and Vc , respectively.               colostrum samples is lower than that of the breast
The resonance frequency and the quality factors                  milk. This increase indicates that the fat content
of the cavity with and without the sample are fs                 in the breast milk decreases and there is a rise in
                                                                 the concentration of lactose as time elapses. The
and Qs , and f0 and Q0 , respectively. The con-
                                                                 results suggest that this method is an indirect way
ductivity can be related to the imaginary part of
                                                                 of comparing the fat content rather than going for
the complex dielectric permittivity as follows:
                                                                 traditional chemical examination, which is time
                                                                 consuming. From Figures 3 and 4 it is seen that
                    σ e = ωε " = 2 πfsε0ε "r             (3)
                                                                 the conductivity of the colostrum is lower than
                                                                 that of the breast milk The conductivities of the
Where ε0 is the dielectric permittivity of the                   breast milk samples increase as weeks elapse.
vacuum.                                                          This is attributed to the increased dilution of the
                                                                 breast milk with time.
RESULTS AND DISCUSSION
                                                                 CONCLUSION
The microwave studies of the human colostrums
and breast milk samples are done using the                       This experiment is an alternative in vitro method
cavity perturbation technique and the results                    of analyzing human colostrums and breast
are shown in Figures 1-4. Tables 1 and 2 show                    milk samples to the conventional techniques
the chemical results of typical colostrums and


41-2-32                               Journal of Microwave Power & Electromagnetic Energy             Vol. 41, No. 2, 2007
   Dielectric Constant εrʹ




                                                                        Frequency [MHz]

                                                 Figure 1. Dielectric Constant variations of Sample 1.
                                                               ������������������������������������������

                                  ��




                                  ��
       Dielectric Constant εrʹ




                                  ��
       ������������������������




                                  ��




                                  ��




                                  ��
                                                    ��������        ��������              ��������          ��������

                                                    ��������        ��������              ��������          ��������
                                  ��
                                   ����   ����         ����      ����          ����         ����     ����              ����   ����
                                                                         ��������������
                                                                        Frequency [MHz]

                                                 Figure 2. Dielectric constant variations of Sample 2.


International Microwave Power Institute                                                                                              41-2-33
    Conductivity (S/m)




                                           Frequency [MHz]

                         Figure 3. Conductivity variations of Sample 1.
    Conductivity (S/m)




                                           Frequency [MHz]

                         Figure 4. Conductivity variations of Sample 2.


41-2-34                    Journal of Microwave Power & Electromagnetic Energy   Vol. 41, No. 2, 2007
of chemical analysis. The technique is quick,                Land D. V., “ A clinical microwave thermography system
simple and accurate and requires less volume                     IEE Proc. 134A pp 193-200, 1987
                                                             K. T. Mathew, “Perturbation Theory”, Encyclopedia of
of the samples. The dielectric constants of the                  RF and Microwave Engineering, Wiley-Interscience,
colostrums samples and breast milk samples                       USA Vol.4, pp 3725-3735,2005.
are found to increase as weeks elapse, which is
attributed to the reduced fat content and increased
lactose concentration. The conductivity of these
samples is similarly found to increase due to the
increased dilution.

ACKNOWLEDGMENTS

Author Anil Lonappan acknowledges Council
of Scientific and Industrial Research (CSIR),
Government of India for providing Senior Re-
search Fellowship.

REFERENCES

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International Microwave Power Institute                                                                     41-2-35

				
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