G. Bindu

ACTIVE MICROWAVE IMAGING FOR BREAST CANCER DETECTION

Active microwave imaging is explored as an imaging modality for early detection of breast cancer. When exposed to microwaves, breast tumor exhibits electrical properties that are significantly different from that of healthy breast tissues. The two approaches of active microwave imaging — confocal microwave technique with measured reflected signals and microwave tomographic imaging with measured scattered signals are addressed here. Normal and malignant breast tissue samples of same person are subjected to study within 30 minutes of mastectomy. Corn syrup is used as coupling medium, as its dielectric parameters show good match with that of the normal breast tissue samples. As bandwidth of the transmitter is an important aspect in the time domain confocal microwave imaging approach, wideband bowtie antenna having 2:1 VSWR bandwidth of 46% is designed for the transmission and reception of microwave signals. Same antenna is used for microwave tomographic imaging too at the frequency of 3000 MHz. Experimentally obtained time domain results are substantiated by finite difference time domain (FDTD) analysis. 2-D tomographic images are reconstructed with the collected scattered data using distorted Born iterative method. Variations of dielectric permittivity in breast samples are distinguishable from the obtained permittivity profiles.

Dielectric Studies of Corn Syrup for Applications in Microwave Breast Imaging

Permittivity and conductivity studies of corn syrup in various concentrations are performed using coaxial cavity perturbation technique over a frequency range of 250 MHz-3000 MHz. The results are utilized to estimate relaxation time and dipole moments of the samples. The stability of the material over the variations of time is studied. The measured specific absorption rate of the material complies with the microwave power absorption rate of biological tissues. This suggests the feasibility of using corn syrup as a suitable, cost effective coupling medium for microwave breast imaging. The material can also be used as an efficient breast phantom in microwave breast imaging studies.

Nondestructive Measurement of Human Blood at Microwave Frequencies

This letter reports a novel in vitro test of blood analysis based on the measurement of the dielectric properties at microwave frequencies. The measurements were made using rectangular cavity perturbation technique at the S-band of microwave frequency with the different samples of blood obtained from healthy donors as well as from patients. It is observed that an appreciably change in the dielectric properties of patient samples with the normal healthy samples and this measurements were in good agreement with clinical analysis. This measurement technique is nondestructive in nature. These results indicate an alternative in-vitro method of diagnosing blood abnormalities using microwaves.

Analysis of human cerebro spinal fluid at the ism band of frequencies

The effect of the electromagnetic fields on the human brain due to the usage of mobile phones is an active research area. These effects are a direct function of the electrical properties of the brain tissue which depends on the bound water content. This paper reports the microwave study of cerebrospinal fluid (CSF), the main constituent of which is water. Both normal and pathologically abnormal CSF samples are subjected to the microwave study and a study of the variation of the dielectric parameters of CSF with frequency is done for both the normal and pathologically different samples. In this communication, in vitro measurements using cavity perturbation technique is employed. The frequency range employed is between 2 to 3 GHz. It is seen that in the band of frequencies employed for the study, the normal and abnormal CSF samples exhibit distinctive behavior for the variation of dielectric constant and conductivity with frequency.

Diagnosis of Diabetes Mellitus using Microwaves

This paper reports a novel in vitro analysis of urine based on the measurement of the dielectric properties at microwave frequencies. The measurements were made using rectangular cavity perturbation technique at the S-band of microwave frequency with the different samples of urine obtained at different intervals of time from healthy persons as well as from patients having diabetes mellitus. It is found that an appreciably change in the dielectric properties of patient samples with the normal healthy samples and this measurements were in good agreement with clinical analysis. This measurement technique an alternative in-vitro method of diagnosing diabetes mellitus using microwaves.

ANALYSIS OF HUMAN SEMEN USING MICROWAVES

Microwave engineering now a days plays a vital tool in diagnostic and therapeutic medicine. A quality evaluation of human semen at microwave frequencies using the measurements made at different intervals of time by cavity perturbation technique in the S- band of microwave spectrum is presented in this paper. Semen samples were also examined in the microscopic as well as macroscopic level in clinical laboratory. It is observed that conductivity of semen depends upon the motility of sperm and it increases as time elapses, which finds applications in forensic medicine.

Analysis of Human Breast Milk at Microwave Frequencies

In this communication a comprehensive study of the dielectric properties of human breast milk at microwave frequencies is reported. The samples are collected at weekly intervals following child birth. Measurements are made at the S-band of microwave frequency employing the rectangular cavity perturbation technique. The dielectric constants of the 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 the breast milk samples is similarly found to increase due to the increased dilution.

A Novel Technique for Localizing the Scatterer in Inverse Profiling of Two Dimensional Circularly Symmetric Dielectric Scatterers Using Degree of Symmetry and Neural Networks

A novel technique for localizing the scatterer in microwave imaging of two-dimensional circularly symmetric dielectric scatterers using degree of symmetry and neural networks is presented. The degree of symmetry for a transmitter position is computed as a function of the difference between the first half and the spatially reflected second half of the measured scattered field vector. A Probabilistic Neural Network (PNN) classifier is trained with the degree of symmetry vectors for the different object configurations. It classifies the degree of symmetry vector of the unknown circularly symmetric scatterer presented to it into one of the classes that indicate the radius and location of the centre of the scatterer. Thus the scatterer is localized in the imaging domain. This not only reduces the degrees of freedom in the inversion for the unknown object, thereby aiding the global convergence of the solution, but also results in a reduction in computation time. The technique has been tested on synthetic data and the results are promising.

Microstripline fed circular sector dielectric resonator antenna

A microstripline fed circular sector dielectric resonator antenna is investigated. A 180/spl deg/ sector of a cylindrical DR on a ground plane has been used for the study. The proposed configuration offers an increase in bandwidth (24%) with broadside radiation pattern. In addition, the configuration offers simple feed structure, compact size and thus easy integration with handheld communication equipment.

DIELECTRIC PROPERTIES OF HUMAN COLOSTRUM AT MICROWAVE FREQUENCIES

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.