Dielectric Blood Measurement Detects HIV/AIDS

DESPITE THE FACT THAT HIV/AIDS has grown into a worldwide pandemic, Elisa and Western Blot tests are still the only tests available for detecting it. Yet a new testing method could be based on the measurement of the dielectric properties of blood at microwave frequencies. Behind this proposed method are the efforts of C. Rajasekaran from the Department of Medicine at Medical College (Kerala, India) together with Anil Lonappan, Vinu Thomas, G. Bindu, Joe Jacob, and K.T. Mathew from the Microwave Tomography and Materials Research Laboratory and Cochin University of Science and Technology (Kerala, India).

In their research, this team made measurements at S-band using a rectangular cavity perturbation technique with samples of blood from healthy donors as well as from HIV/AIDS patients. Compared to the healthy samples, an appreciable change was observed in the dielectric properties of the patient samples. The measurements were shown to agree with clinical results.

At the core of this setup was a transmissiontype S-band rectangular cavity resonator connected to an HP 8714 ET network analyzer from Agilent Technologies (www.agilent.com). The cavity resonator is a transmission line with one or both ends closed. The number of resonant frequencies is determined by the resonator's length. In this setup, the resonator was excited by the TE10P mode. In a normal blood sample, for example, the CD4 + was in the range of 500 to 1500 cells/L. For HIV/ AIDS patients, however, that count was only on the order of 30 to 180 cells/L. Such variations also show up in the glucose level and lipid and electrolyte profiles.

In addition, the conductivity of HIV/AIDS blood samples was found to be above the conductivity of normal blood samples. Such increased conductivity is due to the presence of HDL and VLDL cholesterol as well as triglycerides. Compared to the healthy samples, the measurements succeeded in showing an appreciable change in the dielectric properties of HIV/AIDS blood samples. Thus, an alternative in-vitro method of diagnosing HIV/ AIDS could be leveraged using microwaves. See "A Novel Method of Detecting HIV/AIDS Using Microwaves," Microwave And Optical Technology Letters, March 2008, p. 557.

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