Evaluation of breast tumor response to neoadjuvant chemotherapy with tomographic diffuse optical spectroscopy: case studies of tumor region-of-interest changes.

PURPOSE: To evaluate two methods of summarizing tomographic diffuse optical spectroscopic (DOS) data through region-of-interest (ROI) analysis to differentiate complete from incomplete responses in patients with locally advanced breast cancer undergoing neoadjuvant treatment and to estimate the standard deviations of these methods for power analysis of larger study designs in the future. MATERIALS AND METHODS: Subjects participating in the HIPAA-compliant imaging study, approved by the institutional review board, provided written informed consent and were compensated for their examination participation. Seven of 16 cases in women with complete study data were analyzed by using both fixed- and variable-size (full-width-at-half-maximum) ROI measures of the DOS total hemoglobin concentration (Hb(T)), blood oxygen saturation, water fraction, optical scattering amplitude, and scattering power in the ipsilateral and contralateral breasts. Postsurgical histopathologic analysis was used to categorize patients as having a complete or incomplete treatment response. RESULTS: Average normalized change in Hb(T) was the only DOS parameter to show significant differences (P < or = .05) in the pathologic complete response (pCR) and pathologic incomplete response (pIR) outcomes in seven patients. Mean values of the changes for fixed-size ROIs were -64.2% +/- 50.8 (standard deviation) and 16.9% +/- 38.2 for the pCR and pIR groups, respectively, and those for variable-size ROIs were -96.7% +/- 91.8, and 14.1% +/- 26.7 for the pCR and pIR groups, respectively. CONCLUSION: Tomographic DOS may provide findings predictive of therapeutic response, which could lead to superior individualized patient treatment. SUPPLEMENTAL MATERIAL: http://radiology.rsnajnls.org/cgi/content/full/2522081202/DC1.

Measurement of pressure-displacement kinetics of hemoglobin in normal breast tissue with near-infrared spectral imaging.

Applying localized external displacement to the breast surface can change the interstitial fluid pressure such that regional transient microvascular changes occur in oxygenation and vascular volume. Imaging these dynamic responses over time, while different pressures are applied, could provide selective temporal contrast for cancer relative to the surrounding normal breast. In order to investigate this possibility in normal breast tissue, a near-infrared spectral tomography system was developed that can simultaneously acquire data at three wavelengths with a 15 s time resolution per scan. The system was tested first with heterogeneous blood phantoms. Changes in regional blood concentrations were found to be linearly related to recovered mean hemoglobin concentration (Hb(T)) values (R(2)=0.9). In a series of volunteer breast imaging exams, data from 17 asymptomatic subjects were acquired under increasing and decreasing breast compression. Calculations show that a 10 mm displacement applied to the breast results in surface pressures in the range of 0-55 kPa depending on breast density. The recovered human data indicate that Hb(T) was reduced under compression and the normalized change was significantly correlated to the applied pressure with a p value of 0.005. The maximum Hb(T) decreases in breast tissue were associated with body mass index (BMI), which is a surrogate indicator of breast density. No statistically valid correlations were found between the applied pressure and the changes in tissue oxygen saturation (S(t)O(2)) or water percentage (H(2)O) across the range of BMI values studied.

The correlation of in vivo and ex vivo tissue dielectric properties to validate electromagnetic breast imaging: initial clinical experience.

Electromagnetic (EM) breast imaging provides low-cost, safe and potentially a more specific modality for cancer detection than conventional imaging systems. A primary difficulty in validating these EM imaging modalities is that the true dielectric property values of the particular breast being imaged are not readily available on an individual subject basis. Here, we describe our initial experience in seeking to correlate tomographic EM imaging studies with discrete point spectroscopy measurements of the dielectric properties of breast tissue. The protocol we have developed involves measurement of in vivo tissue properties during partial and full mastectomy procedures in the operating room (OR) followed by ex vivo tissue property recordings in the same locations in the excised tissue specimens in the pathology laboratory immediately after resection. We have successfully applied all of the elements of this validation protocol in a series of six women with cancer diagnoses. Conductivity and permittivity gauged from ex vivo samples over the frequency range 100 Hz-8.5 GHz are found to be similar to those reported in the literature. A decrease in both conductivity and permittivity is observed when these properties are gauged from ex vivo samples instead of in vivo. We present these results in addition to a case study demonstrating how discrete point spectroscopy measurements of the tissue can be correlated and used to validate EM imaging studies.

Digital breast tomosynthesis: initial experience in 98 women with abnormal digital screening mammography.

OBJECTIVE: The purpose of our study was to compare the image quality of tomosynthesis with that of conventional mammography and to estimate the recall rate of screening when tomosynthesis is used in addition to mammography. MATERIALS AND METHODS: Women with an abnormal screening mammography were recruited sequentially. Consenting women underwent tomosynthesis of the affected breast corresponding to the views obtained with diagnostic mammography. The study radiologist compared the image quality, including lesion conspicuity and feature analysis, of tomosynthesis with diagnostic film-screen mammography and assessed the need for recall when tomosynthesis was added to digital screening mammography. Screening recalls were considered unnecessary when tomosynthesis did not show a corresponding abnormality or allowed definitely benign lesion characterization. Fisher's exact test was used to determine the association of equivalence and recall status with mammographic finding type. RESULTS: There were 99 digital screening recalls in 98 women. The image quality of tomosynthesis was equivalent (n = 51) or superior (n = 37) to diagnostic mammography in 89% (88/99). Finding type was significantly (p < 0.001) associated with equivalence. Approximately half--52/99 (52%)--of the findings would not have been recalled when digital screening mammography was supplemented with tomosynthesis. When adjusting for confounding conditions, the recall reduction was 40% (37/92). The likelihood of recall was also dependent on finding type (p = 0.004). CONCLUSION: Subjectively, tomosynthesis has comparable or superior image quality to that of film-screen mammography in the diagnostic setting, and it has the potential to decrease the recall rate when used adjunctively with digital screening mammography.

Initial clinical experience with microwave breast imaging in women with normal mammography.

RATIONALE AND OBJECTIVES: We have developed a microwave tomography system for experimental breast imaging. MATERIALS AND METHODS: In this article, we illustrate a strategy for optimizing the coupling liquid for the antenna array based on in vivo measurement data. We present representative phantom experiments to illustrate the imaging system's ability to recover accurate property distributions over the range of dielectric properties expected to be encountered clinically. To demonstrate clinical feasibility and assess the microwave properties of the normal breast in vivo, we summarize our initial experience with microwave breast exams of 43 women with negative mammography according to the Breast Imaging Reporting and Data System (BI-RADS 1). RESULTS: The clinical results show a high degree of bilateral symmetry in the whole breast average microwave properties. Focal assessments of microwave properties are associated with breast tissue composition evaluated through radiographic density categorization verified through magnetic resonance image correlation in selected cases. Specifically, both whole-breast average and local microwave properties increase with increasing radiographic density, in which the latter exhibits a more substantial rise. CONCLUSION: These findings support our hypothesis that water content variations in the breast play an influential role in dictating the overall dielectric property distributions and indicate that the microwave properties in the breast are more heterogeneous than previously believed based on ex vivo property measurements reported in the literature.

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.