Jeff M. Sill

Tissue Sensing Adaptive Radar for Breast Cancer Detection—Experimental Investigation of Simple Tumor Models

Microwave breast cancer detection is based on differences in electrical properties between healthy and malignant tissues. Tissue sensing adaptive radar (TSAR) has been proposed as a method of microwave breast imaging for early tumor detection. TSAR senses all tissues in the volume of interest and adapts accordingly. Simulation results have shown the feasibility of this system for detecting tumors of 4 mm in diameter. In this paper, the second-generation experimental system for TSAR is presented. Materials with electrical properties similar to those in the breast are used for the breast model. A resistively loaded Wu–King monopole antenna is fabricated, and reflections from the breast model over the frequency range of 1–10 GHz are recorded. The reflected signals are processed with the TSAR algorithm, which includes improved skin subtraction and TSAR focusing algorithms. Various tumor models are examined; specifically, a 1-cm tumor is detected with a signal-to-clutter ratio of 10.41 dB. Tumor detection with the experimental system is evaluated and compared to simulation results.

Experimental feasibility study of confocal microwave imaging for breast tumor detection

Initial experimental verification of confocal microwave imaging for breast tumor detection is described. Simple phantoms, consisting of a PVC pipe and objects representing tumors, are scanned with resistively loaded monopole or horn antennas. Successful reduction of clutter and detection of a variety of two-dimensional objects is demonstrated.

A prototype system for measuring microwave frequency reflections from the breast

Microwave imaging of the breast is of interest for monitoring breast health, and approaches to active microwave imaging include tomography and radar-based methods. While the literature contains a growing body of work related to microwave breast imaging, there are only a few prototype systems that have been used to collect data from humans. In this paper, a prototype system for monostatic radar-based imaging that has been used in an initial study measuring reflections from volunteers is discussed. The performance of the system is explored by examining the mechanical positioning of sensor, as well as microwave measurement sensitivity. To gain insight into the measurement of reflected signals, simulations and measurements of a simple phantom are compared and discussed in relation to system sensitivity. Finally, a successful scan of a volunteer is described.

Breast Surface Estimation for Radar-Based Breast Imaging Systems

Radar-based microwave breast-imaging techniques typically require the antennas to be placed at a certain distance from or on the breast surface. This requires prior knowledge of the breast location, shape, and size. The method proposed in this paper for obtaining this information is based on a modified tissue sensing adaptive radar algorithm. First, a breast surface detection scan is performed. Data from this scan are used to localize the breast by creating an estimate of the breast surface. If required, the antennas may then be placed at specified distances from the breast surface for a second tumor-sensing scan. This paper introduces the breast surface estimation and antenna placement algorithms. Surface estimation and antenna placement results are demonstrated on three-dimensional breast models derived from magnetic resonance images.

Preliminary investigations of tissue sensing adaptive radar for breast tumor detection

Tissue sensing adaptive radar detects tumors based on the differences in electrical properties of healthy and malignant breast tissues. This paper presents results for simple experimental models and computer simulations of a larger diameter cylindrical model and more realistic hemispherical model. The results suggest that TSAR imaging is a promising method for breast tumor detection.

Tissue sensing adaptive radar for breast cancer detection: preliminary experimental results

Microwave breast cancer detection records the differences in electrical properties between healthy and malignant tissue. Tissue sensing adaptive radar (TSAR) has been proposed as a method for early tumor detection. Reflections from the differences in electrical properties between healthy and diseased tissue (tumors) are time-shifted and summed to create images. In this paper, the TSAR second generation experimental system is presented. An antenna is tested and characterized, reflections are recorded and the image formation algorithms are tested. Finally, preliminary tumor detection with the experimental setup is evaluated.

Phantoms for testing radar-based microwave breast imaging

In order to test and improve radar-based microwave imaging systems, realistic breast phantoms have been developed. Eight hemispherical and four realistic breast models were created utilizing tissue-mimicking materials introduced in [1]. Implementing a stepwise procedure and creating various molds allowed phantoms with skin, gland, fat and tumour materials to be constructed and imaged.

Safety assessment of ultra-wideband antennas for microwave breast imaging

This article deals with the safety assessment of several ultra-wideband (UWB) antenna designs for use in prototype microwave breast imaging systems. First, the performances of the antennas are validated by comparison of measured and simulated data collected for a simple test case. An efficient approach to estimating the specific energy absorption (SA) is introduced and validated. Next, SA produced by the UWB antennas inside more realistic breast models is computed. In particular, the power levels and pulse repetition periods adopted for the SA evaluation follow the measurement protocol employed by a tissue sensing adaptive radar (TSAR) prototype system. Results indicate that the SA for the antennas examined is below limits prescribed in standards for exposure of the general population; however, the difficulties inherent in applying such standards to UWB exposures are discussed. The results also suggest that effective tools for the rapid evaluation of new sensors have been developed.

Antenna performance for ultra-wideband microwave imaging

Numerous antenna designs have been proposed for microwave breast imaging utilizing an ultra-wideband frequency range. The antennas are typically compact, operate in an immersion medium, and have a band covering at least 2–10 GHz. We have developed 3 antennas for our UWB microwave breast imaging system. In this contribution, we compare the performance of the antennas in order to gain insight into the relationship between antenna performance metrics and image quality.

Experimental feasibility of breast tumor detection and localization

Microwave breast imaging with radar-based techniques has been proposed for breast tumor detection. The feasibility study reported in this paper is designed to evaluate detection and localization of objects in three dimensions (3D). Experimental setups consisting of a PVC pipe (skin) and wood spheres (tumors) are illuminated with a resistively loaded monopole antenna. Improved image reconstruction algorithms are applied to the measured data, and the resulting images demonstrate detection and localization of smaller 3D tumor models.