Electromagnetic breast imaging: results of a pilot study in women with abnormal mammograms.

PURPOSE: To prospectively assess quantitatively the inherent contrast of electromagnetic (EM) properties that can be imaged by using available technology in women with abnormal findings at conventional breast imaging who underwent subsequent biopsy. MATERIALS AND METHODS: The protocol was HIPAA compliant and approved by the institutional review board. All participants provided informed consent. Fifty-three women with normal (Breast Imaging Reporting and Data System [BI-RADS] category 1) and ninety-seven women with abnormal (BI-RADS category 4 or 5) screening mammograms were imaged with three EM imaging methods: electrical impedance spectroscopy (EIS), microwave imaging spectroscopy (MIS), and near-infrared spectral tomography (NIR). A region-of-interest (ROI) analysis was used to assess the EM image properties for comparison of findings with conventional image findings and correlation with specific pathologic parameters for women with abnormal findings. Statistical analyses were conducted. RESULTS: One hundred fifty participants (age range, 35-81 years) were included. EM image property contrast ratios of 150%-200% were found in breast abnormality ROIs relative to the ipsilateral breast background. Analysis of variance demonstrated significant differences in ROI image summaries of mammographically normal versus abnormal breasts for EIS, across diagnostic groups for NIR, and for MIS (analysis restricted to lesions larger than 1 cm(3)). Receiver operating curve (ROC) analysis of the EM properties for cancers among subjects with BI-RADS category 4 or 5, compared with the EM properties for the subjects with normal breasts (BI-RADS category 1), yielded areas under the ROC curve ranging from 0.67 to 0.81. Pathologic correlations with mean vessel density, mean vessel area, and epithelium-to-stroma ratio suggest a biological origin of the EM image properties associated with disease. CONCLUSION: Results from EM breast examinations provide statistical evidence of a mean increase in image contrast of 150%-200% between abnormal (benign and malignant) and normal breast tissue.

Electromagnetic breast imaging: average tissue property values in women with negative clinical findings.

Representative data are provided for three electromagnetic breast imaging techniques-near-infrared spectroscopy, electrical impedance spectroscopy, and microwave imaging spectroscopy-to serve as potential benchmarks for future investigation. The breasts of 23 women without clinical or mammographic findings of disease were imaged in the coronal plane with nonionizing radiation of varying frequencies. Average electromagnetic property values were reconstructed at each frequency on the basis of computational models of light diffusion, current flow, and microwave propagation. Electromagnetic properties were correlated with subject characteristics and between techniques. Each technique yielded information on breast tissue features (eg, conductivity, permittivity, light scattering, and absorption) that had not previously all been measured in the same individuals.

Electrical impedance spectroscopy of the breast: clinical imaging results in 26 subjects.

Electrical impedance spectroscopy (EIS) is a potential, noninvasive technique to image women for breast cancer. Studies have shown characteristic frequency dispersions in the electrical conductivity and permittivity of malignant versus normal tissue. Using a multifrequency EIS system, we imaged the breasts of 26 women. All patients had mammograms ranked using the American College of Radiology (ACR) BIRADS system. Of the 51 individual breasts imaged, 38 were ACR 1 negative, six had ACR 4-5 suspicious lesions, and seven had ACR 2 benign findings such as fibroadenomas or calcifications. A radially translatable circular array of 16 Ag/AgCl electrodes was placed around the breast while the patient lay prone. We applied trigonometric voltage patterns at ten frequencies between 10 and 950 kHz. Anatomically coronal images were reconstructed from this data using nonlinear partial differential equation methods. Typically, ACR 1-rated breasts were interrogated in a single central plane whereas ACR 2-5-rated breasts were imaged in multiple planes covering the region of suspicion. In general, a characteristic homogeneous image emerged for mammographically normal cases while focal inhomogeneities were observed in images from women with malignancies. Using a specific visual criterion, EIS images identified 83% of the ACR 4-5 lesions while 67% were detected using a numerical criterion. Overall, multifrequency electrical impedance imaging appears promising for detecting breast malignancies, but improvements must be made before the method reaches its full potential.

Imaging the breast with EIS: an initial study of exam consistency.

Use of electrical impedance spectroscopy (EIS) to image the breasts of women with both normal and abnormal conditions requires the ability to deliver a consistent and repeatable exam. To investigate the degree to which our current imaging system can meet this requirement we conducted an initial study of exam consistency. The trial involved the imaging of 25 breasts stratified into four separate substudies with increasing levels of electrode placement uncertainty. The degree of complexity ranged from single-placement single-session imaging to multiple-placement single-session imaging to multiple-placement multiple-session imaging. Both visual analysis and quantitative comparisons using mean squared difference (MSD) measures between pairs of permittivity and conductivity images were performed. A new breast interface with the improved vertical and radial electrode array positioning capability required to complete this study is described. Not surprisingly, the results show a dominant trend of increased image variability with increased electrode placement uncertainty. Importantly, quantitative levels of image consistency are reported through MSD analysis. On average across all frequencies analysed, MSDs for single placements are well below 1%, near 2-3% for repositioned breasts during the same session and approximately 15% for re-examined breasts in multiple sessions conducted over time. Overall, these results suggest that EIS breast exams are consistent provided the electrode placement is well controlled, typically with better than 1 cm accuracy.