Microwave imaging for neoadjuvant chemotherapy monitoring: Initial clinical experience

Breast cancer research: BCR (Impact Factor: 5.49). 04/2013; 15(2):R35. DOI: 10.1186/bcr3418
Source: PubMed


Microwave tomography recovers images of tissue dielectric properties, which appear to be specific for breast cancer, with low-cost technology that does not present an exposure risk, suggesting the modality may be a good candidate for monitoring neoadjuvant chemotherapy.

Eight patients undergoing neoadjuvant chemotherapy for locally advanced breast cancer were imaged longitudinally five to eight times during the course of treatment. At the start of therapy, regions of interest (ROIs) were identified from contrast-enhanced magnetic resonance imaging studies. During subsequent microwave examinations, subjects were positioned with their breasts pendant in a coupling fluid and surrounded by an immersed antenna array. Microwave property values were extracted from the ROIs through an automated procedure and statistical analyses were performed to assess short term (30 days) and longer term (four to six months) dielectric property changes.

Two patient cases (one complete and one partial response) are presented in detail and demonstrate changes in microwave properties commensurate with the degree of treatment response observed pathologically. Normalized mean conductivity in ROIs from patients with complete pathological responses was significantly different from that of partial responders (P value = 0.004). In addition, the normalized conductivity measure also correlated well with complete pathological response at 30 days (P value = 0.002).

These preliminary findings suggest that both early and late conductivity property changes correlate well with overall treatment response to neoadjuvant therapy in locally advanced breast cancer. This result is consistent with earlier clinical outcomes that lesion conductivity is specific to differentiating breast cancer from benign lesions and normal tissue.

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    • "Microwave tomography (MT) is a nonionizing imaging modality capable of noninvasively recovering a wide range of dielectric property (DP) values [1] [2] [3]. An observable contrast exists between the dielectric properties (e.g., permittivity and conductivity) of healthy and abnormal breast tissue [4– 8], and MT has shown great promise as a clinical imaging technique for applications initially related to breast-cancer detection [9], diagnosis [8], and chemotherapy monitoring [10]. Current breast-imaging investigations at Dartmouth College (Hanover, NH, USA) now focus on multimodal MR- MT techniques [11] [12] [13] [14], with the advent of MT providing specificity information to the high-resolution noncontrast enhanced MR images. "
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    ABSTRACT: We have developed a simple mechanism incorporating feedline bends and rotary joints to enable motion of a monopole antenna within a liquid-based illumination chamber for tomographic imaging. The monopole is particularly well suited for this scenario because of its small size and simplicity. For the application presented here a full set of measurement data is collected from most illumination and receive directions utilizing only a pair of antennas configured with the rotating fixture underneath the imaging tank. Alternatively, the concept can be adapted for feed structures entering the tank from the sides to allow for measurements with vertically and horizontally polarized antennas. This opens the door for more advanced imaging applications where anisotropy could play an important role such as in bone imaging.
    International Journal of Antennas and Propagation 06/2014; 2014(431602):8. DOI:10.1155/2014/431602 · 0.66 Impact Factor
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    • "Even more unfortunate are the implications of these results on interpretations being made and conclusions being drawn from the data reported in [10,11]. These widely cited studies are often considered to be the definitive data on the electromagnetic properties of breast tissue/tumor, and while they do represent the largest and most systematic effort completed to date to probe the dielectric properties of breast surgical specimens, the results presented here suggest that those measurements are surface-property biased, and likely do not represent the effective dielectric properties of the volume averaged tissue that could, for example, be recovered on a cm-scale through non-invasive microwave imaging methods [14,15,17]. "
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    ABSTRACT: Background Tissue dielectric properties are specific to physiological changes and consequently have been pursued as imaging biomarkers of cancer and other pathological disorders. However, a recent study (Phys Med Biol 52:2637–2656, 2007; Phys Med Biol 52:6093–6115, 2007), which utilized open-ended dielectric probing techniques and a previously established sensing volume, reported that the dielectric property contrast may only be 10% or less between breast cancer and normal fibroglandular tissue whereas earlier data suggested ratios of 4:1 and higher may exist. Questions about the sensing volume of this probe relative to the amount of tissue interrogated raise the distinct possibility that the conclusions drawn from that study may have been over interpreted. Methods We performed open-ended dielectric probe measurements in two-layer compositions consisting of a background liquid and a planar piece of Teflon that was translated to predetermined distances away from the probe tip to assess the degree to which the probe produced property estimates representative of the compositional averages of the dielectric properties of the two materials resident within a small sensing volume around the tip of the probe. Results When Teflon was in contact with the probe, the measured properties were essentially those of pure Teflon whereas the properties were nearly identical to those of the intervening liquid when the Teflon was located more than 2 mm from the probe tip. However, when the Teflon was moved closer to the probe tip, the dielectric property measurements were not linearly related to the compositional fraction of the two materials, but reflected nearly 50% of those of the intervening liquid at separation distances as small as 0.2 mm, and approximately 90% of the liquid when the Teflon was located 0.5 mm from the probe tip. Conclusion These results suggest that the measurement methods reported in the most recent breast tissue dielectric property study are not likely to return the compositional averages of the breast tissue specimens evaluated, and thus, the conclusions reached about the expected dielectric property contrast in breast cancer from this specimen study may not be correct.
    BMC Medical Physics 06/2014; 14(3). DOI:10.1186/1756-6649-14-3
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    • "Low and radio frequency dielectric properties evaluation appeared as non ionizing and low cost potential tools for non invasive body sensing. Currently, microwave tomography is an established field in biomedical imaging [2] [3] [4] [5] [6] [7] [8] [9]. Particularly for bone, the first clinical microwave tomographic images of the calcaneus were recently published [10]. "
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    ABSTRACT: In this paper, the dielectric properties of human trabecular bone are evaluated under physiological condition in the microwave range. Assuming a two components medium, simulation and experimental data are presented and discussed. A special experimental setup is developed in order to deal with inhomogeneous samples. Simulation data are obtained using finite difference time domain from a realistic sample. The bone mineral density of the samples are also measured. The simulation and experimental results of the present study suggest that there is a negative relation between bone volume fraction (BV/TV) and permittivity/conductivity: the higher the BV/TV, the lower the permittivity/conductivity. This is in agreement with the recently published in vivo data.
    Medical & Biological Engineering 03/2014; DOI:10.1007/s11517-014-1145-y · 1.73 Impact Factor
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