Performance Assessment of a First Generation Breast Microwave Imaging System: Study of Breast Abnormalities Detection

Overview

The main goal of this project is to assess the ability of a recently developed Breast Microwave Imaging (BMI) system to detect abnormalities in a human breast. These trials will be performed by recruiting fourteen volunteers that have been diagnosed with breast abnormalities using x-ray mammography. The breast presenting the abnormality will be imaged using the BMI system in a controlled and comfortable environment. As this is a feasibility study of the technology, and has the main goal to evaluate the diagnostic accuracy of this technology. The data collected from this study will be used to: (1) evaluate the overall participant experience during the BMI imaging procedure, (2) optimize the design of the BMI imaging system (both hardware and software), (3) open discussions with other medical professionals (e.g. radiologists) about the clinical feasibility of this emerging diagnostic imaging modality.

The Breast Microwave Imaging (BMI) system that will be used in this study is designed to detect breast abnormalities using low power microwave waveforms. The system is formed by three main components: 1. Patient bed. The volunteer will be positioned in this bed in a prone position where with the breast to be imaged in a pendant position. 2. Instrumentation rack. This component contains all the microwave instrumentation and motion mechanisms required to illuminate the breast using an ultrawide band waveform and record the responses from the breast structures. 3. Control computer. This component is used to control the motion of the mechanical components of the system and to retrieve the responses from the breast structures from the microwave instruments and store them in an electronic format. The system takes between 7.5 to 10 minutes to collect a three dimensional dataset from a single breast. The BMI system used in the study operates in the frequency range of 20 megahertz (MHz) to 9 gigahertz (GHz). Canadian safety limits for the interaction of these non-ionizing electromagnetic waves with humans are outlined in the Health Canada publication "Safety Code 6: Limits of Human Exposure to Radiofrequency Electromagnetic Energy in the Frequency Range from 3 kilohertz (kHz) to 300 GHz \[1\]. For unregulated environments, the Specific Absorption Rate (SAR) limit set by Health Canada is 1.6 W/Kg. In the system used in this study, radio-frequency energy is generated via the Vector Network Analyzer (VNA). If the VNA is set at its maximum output power, which is 3.2 milliwatt (mW), the power received at 5 cm from the antenna (which is the distance where the breast will be) was measured to be 890 microwatt, which would yield a SAR value of 0.0196 W/kg. References \[1\] Consumer and Clinical Radiation Protection Bureau, Limits of Human Exposure to Radiofrequency Electromagnetic Energy in the Frequency Range from 3 kHz to 300 GHz, Health Canada, Ottawa, Ontario, 2015.

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