Detection of Kidney Cancer Using Circularly Polarized Patch Antenna Array

Abstract

The use of a circularly polarized patch antenna array to detect kidney cancer by microwave techniques is proposed in this paper. A four-element linear antenna array is designed and fabricated at the ISM frequency of 2.4 GHz. The dimensions of the antenna array are 200 mm × 78 mm. The single element is a square patch with side length of 30 mm. The distance between patches is chosen to be 20 mm which ensures that mutual coupling between any two adjacent patches is less than 20 dBs. The substrate is a FR-4 material of relative permittivity 4.3 and thickness 1.6 mm. The circular polarization has an axial ratio of 0.8 dB at 2.4 GHz. The bandwidth at S₁₁ = -10 dB is 7.23 %. Renal system phantom consisting of kidney cortex, renal capsule, ureter, adrenal gland, muscle, fat, and skin is used. Four stages of renal cancer tumors are considered depending upon the tumor size in each stage. The presence of a tumor causes an increase in the reflection coefficient (S₁₁) and a shift in resonance frequency, which can be used to identify cancer. The increase in reflection coefficient and the shift in resonance frequency are calculated for each stage of the cancer tumors. The shift in resonance frequency for the early stages is too small. Therefore, detection depends mainly on the increase in S₁₁. The shift in resonance frequency and increase in S₁₁ are large for advanced stages of the tumor, which makes detection easier. Computed specific absorption rate (SAR) is found to be less than the safety levels, which means this technique is safe to use. Overall, this work suggests a new simple detection technique of kidney cancer. The advantages of this technique are safety, compact, fast, inexpensive, comfortable examination, non-invasive, and finally non- ionizing radiation during measurement.