Abstract P6-02-03: Interpretation schema for optical coherence tomography images in breast tissue

Purpose

Optical coherence tomography (OCT) is an attractive technology for surgical imaging because it permits the real-time visualization of microscopic tissue morphology with a handheld probe without the need for exogeneous agents, tissue manipulation, ionizing radiation, or histological processing. While initial studies have shown that OCT is an effective margin-evaluation tool for breast conserving surgery (BCS), image interpretation and feature identification have not been directly studied. In this work, breast pathologies were assessed with a handheld OCT probe and the images were compared to histology.

Methods

Mastectomy and BCS specimens from 26 women were imaged with a handheld OCT probe, and histology slides from the same region were digitally photographed. OCT and histology images from the same region were paired by selecting the best structural matches. Because image characteristics in OCT are akin to those in ultrasound, descriptive OCT image feature terminology similar to that of ultrasound was developed. Each of these characteristics was used to select and describe OCT-histology image matches.

Results

In total, 2880 OCT images were acquired from 26 breast specimens, and 48 matching OCT-histology image pairs were identified. These matched image pairs illustrate tissue types including adipose tissue, dense fibrosis, fibroadipose tissue, blood vessels, regular and hyperplastic ducts and lobules, cysts, fibroadenoma, IDC, ILC, DCIS, calcifications, and biopsy cavities. Differentiation between pathologies was achieved by considering feature boundaries, interior appearance, posterior shadowing or enhancement, and overall morphologic patterns.

Conclusions

This is the first work to systematically catalog the features of breast OCT images. The results indicate that OCT can be used to identify important structures and distinguish between benign and malignant breast pathologies.

Citation Format: Yemul KS, Zysk AM, Richardson AL, Tangella KV, Jacobs LK. Interpretation schema for optical coherence tomography images in breast tissue [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-02-03.

Interpretation of Optical Coherence Tomography Images for Breast Tissue Assessment

PURPOSE

Initial studies have shown that optical coherence tomography (OCT) is an effective margin-evaluation tool for breast-conserving surgery, but methods for the interpretation of breast OCT images have not been directly studied. In this work, breast pathologies were assessed with a handheld OCT probe. OCT images and corresponding histology were used to develop guidelines for the identification of breast tissue features in OCT images.

METHODS

Mastectomy and breast-conserving surgery specimens from 26 women were imaged with a handheld OCT probe. During standard pathology specimen dissection, representative 1-cm × 1-cm tissue regions were grossly identified, assessed with OCT, inked for orientation and image-matching purposes, and processed. Histology slides corresponding to the OCT image region were digitally photographed. OCT and histology images from the same region were paired by selecting the best structural matches.

RESULTS

In total, 2880 OCT images were acquired from 26 breast specimens (from 26 patients) and 48 matching OCT-histology image pairs were identified. These matched image pairs illustrate tissue types including adipose tissue, dense fibrosis, fibroadipose tissue, blood vessels, regular and hyperplastic ducts and lobules, cysts, cyst, fibroadenoma, invasive ductal carcinoma, invasive lobular carcinoma, ductal carcinoma in situ, calcifications, and biopsy cavities. Differentiation between pathologies was achieved by considering feature boundaries, interior appearance, posterior shadowing or enhancement, and overall morphologic patterns.

CONCLUSIONS

This is the first work to systematically catalog the critical features of breast OCT images. The results indicate that OCT can be used to identify and distinguish between benign and malignant features in human breast tissue.

Abstract P1-11-04: Looking beyond the margins: Economic costs and complications associated with repeated breast-conserving surgeries

Background: Although considerable attention has been drawn to the problem of repeat breast-conserving surgery (BCS), the costs and complications due to these additional operations are not well-characterized. In this work, a retrospective review of insurance claims data for BCS patients was performed to assess complications and economic outcomes.

Methods: Private claims data were analyzed for 9,837 women undergoing BCS for breast carcinoma between January 2010 and December 2013. Patients enrolled in insurance plans in IL, TX, NM, and OK were included. Patients undergoing a second open breast surgery (mastectomy or BCS) within 90 days of the initial BCS were classified as having a repeat surgery. Complications were identified via a set of 8 CPT and 25 ICD9 diagnosis and procedure codes related to breast cancer treatment. The analysis included these complications and the total cost of all allowed healthcare claims within two years following diagnosis.

Results: 7,555/9,837 patients (77% ±0.8%, 95% confidence interval) had one BCS operation, and 2,282 patients (23% ±0.8%) had at least one repeat surgery. The mean patient age was 53 years. Women who underwent an additional operation waited an average of 24 days for the procedure.

The mean two-year total costs for patients undergoing a single BCS was $89,016 (±$1,884), and the cost for patients undergoing a repeat breast surgery was $105,088 (±$3,680; p < 0.0001), $100,637 (±$4,219) for a second BCS and $115,292 (±$7,259) for subsequent mastectomy. The mean added cost due to a repeat surgery was $16,072.

The percentage of patients experiencing at least one complication was 23.6% (±1.0%) for those undergoing one BCS only and 34.8% (±2.0%) for those undergoing a repeat operation (p < 0.0001). Patients undergoing repeated surgery were 88% more likely to experience multiple complications (5.5% ±0.5% vs. 10.4% ±1.3%) and nearly three times as likely to experience fat necrosis (2.5% ±0.4% vs. 7.2% ±1.1%). Infection, hematoma/seroma, and breast pain were the most common complications for patients who did not undergo a repeated surgery (9.9% ±0.7%, 8.7% ±0.6%, 6.9% ±0.6%). For patients undergoing a repeated surgery, infection, hematoma/seroma, and fat necrosis were the most common complications (15.3% ±1.5%, 13.9% ±1.4%, 7.2% ±1.1%).

Conclusions: For the 23% of women undergoing a second operation after BCS, complications were 48% more common, and the mean total cost of surgery was $16,072 more, demonstrating statistically-significant evidence of a patient-centered and fiscal imperative to reduce reoperations in BCS for breast cancer.Background: Although considerable attention has been drawn to the problem of repeat breast-conserving surgery (BCS), the costs and complications due to these additional operations are not well-characterized. In this work, a retrospective review of insurance claims data for BCS patients was performed to assess complications and economic outcomes.

Methods: Private claims data were analyzed for 9,837 women undergoing BCS for breast carcinoma between January 2010 and December 2013. Patients enrolled in insurance plans in IL, TX, NM, and OK were included. Patients undergoing a second open breast surgery (mastectomy or BCS) within 90 days of the initial BCS were classified as having a repeat surgery. Complications were identified via a set of 8 CPT and 25 ICD9 diagnosis and procedure codes related to breast cancer treatment. The analysis included these complications and the total cost of all allowed healthcare claims within two years following diagnosis.

Results: 7,555/9,837 patients (77% ±0.8%, 95% confidence interval) had one BCS operation, and 2,282 patients (23% ±0.8%) had at least one repeat surgery. The mean patient age was 53 years. Women who underwent an additional operation waited an average of 24 days for the procedure.

The mean two-year total costs for patients undergoing a single BCS was $89,016 (±$1,884), and the cost for patients undergoing a repeat breast surgery was $105,088 (±$3,680; p < 0.0001), $100,637 (±$4,219) for a second BCS and $115,292 (±$7,259) for subsequent mastectomy. The mean added cost due to a repeat surgery was $16,072.

The percentage of patients experiencing at least one complication was 23.6% (±1.0%) for those undergoing one BCS only and 34.8% (±2.0%) for those undergoing a repeat operation (p < 0.0001). Patients undergoing repeated surgery were 88% more likely to experience multiple complications (5.5% ±0.5% vs. 10.4% ±1.3%) and nearly three times as likely to experience fat necrosis (2.5% ±0.4% vs. 7.2% ±1.1%). Infection, hematoma/seroma, and breast pain were the most common complications for patients who did not undergo a repeated surgery (9.9% ±0.7%, 8.7% ±0.6%, 6.9% ±0.6%). For patients undergoing a repeated surgery, infection, hematoma/seroma, and fat necrosis were the most common complications (15.3% ±1.5%, 13.9% ±1.4%, 7.2% ±1.1%).

The impact of repeated breast-conserving surgeries BCS, No RepeatRepeat BCSConvert to MastectomyPatients76.8% (7,555)16.2% (1,589)7.0% (693)Mean Two-Year Cost Per Patient$89,016$100,637$115,292Patients with any Complication(s)23.6% (1,783)32.5% (516)40.3% (279)Patients with Infection9.9% (746)14.0% (222)18.3% (127)Patients with Hematoma/Seroma8.7% (655)12.8% (203)16.6% (115)Patients with Breast Pain6.9% (525)7.0% (111)6.1% (42)Patients with Fat Necrosis2.5% (187)7.6% (120)6.5% (45)

Conclusions: For the 23% of women undergoing a second operation after BCS, complications were 48% more common, and the mean total cost of surgery was $16,072 more, demonstrating statistically-significant evidence of a patient-centered and fiscal imperative to reduce reoperations in BCS for breast cancer.

Citation Format: Metcalf LN, Zysk AM, Underwood HR, Edelman G, Vu L, Cittadine AJ, Hyer KB, Thompson AM. Looking beyond the margins: Economic costs and complications associated with repeated breast-conserving surgeries [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P1-11-04.

Filtering for unwrapping noisy Doppler optical coherence tomography images for extended microscopic fluid velocity measurement range

In this Letter, we report the first application of two phase denoising algorithms to Doppler optical coherence tomography (DOCT) velocity maps. When combined with unwrapping algorithms, significantly extended fluid velocity dynamic range is achieved. Instead of the physical upper bound, the fluid velocity dynamic range is now limited by noise level. We show comparisons between physical simulated ideal velocity maps and the experimental results of both algorithms. We demonstrate unwrapped DOCT velocity maps having a peak velocity nearly 10 times the theoretical measurement range.

Optical Biopsy of Lymph Node Morphology using Optical Coherence Tomography

Optical diagnostic imaging techniques are increasingly being used in the clinical environment, allowing for improved screening and diagnosis while minimizing the number of invasive procedures. Diffuse optical tomography, for example, is capable of whole-breast imaging and is being developed as an alternative to traditional X-ray mammography. While this may eventually be a very effective screening method, other optical techniques are better suited for imaging on the cellular and molecular scale. Optical Coherence Tomography (OCT), for instance, is capable of high-resolution cross-sectional imaging of tissue morphology. In a manner analogous to ultrasound imaging except using optics, pulses of near-infrared light are sent into the tissue while coherence-gated reflections are measured interferometrically to form a cross-sectional image of tissue. In this paper we apply OCT techniques for the high-resolution three-dimensional visualization of lymph node morphology. We present the first reported OCT images showing detailed morphological structure and corresponding histological features of lymph nodes from a carcinogen-induced rat mammary tumor model, as well as from a human lymph node containing late stage metastatic disease. The results illustrate the potential for OCT to visualize detailed lymph node structures on the scale of micrometastases and the potential for the detection of metastatic nodal disease intraoperatively.

Real-time Imaging of the Resection Bed Using a Handheld Probe to Reduce Incidence of Microscopic Positive Margins in Cancer Surgery

Wide local excision (WLE) is a common surgical intervention for solid tumors such as those in melanoma, breast, pancreatic, and gastrointestinal cancer. However, adequate margin assessment during WLE remains a significant challenge, resulting in surgical reinterventions to achieve adequate local control. Currently, no label-free imaging method is available for surgeons to examine the resection bed in vivo for microscopic residual cancer. Optical coherence tomography (OCT) enables real-time high-resolution imaging of tissue microstructure. Previous studies have demonstrated that OCT analysis of excised tissue specimens can distinguish between normal and cancerous tissues by identifying the heterogeneous and disorganized microscopic tissue structures indicative of malignancy. In this translational study involving 35 patients, a handheld surgical OCT imaging probe was developed for in vivo use to assess margins both in the resection bed and on excised specimens for the microscopic presence of cancer. The image results from OCT showed structural differences between normal and cancerous tissue within the resection bed following WLE of the human breast. The ex vivo images were compared with standard postoperative histopathology to yield sensitivity of 91.7% [95% confidence interval (CI), 62.5%-100%] and specificity of 92.1% (95% CI, 78.4%-98%). This study demonstrates in vivo OCT imaging of the resection bed during WLE with the potential for real-time microscopic image-guided surgery.

Intraoperative Assessment of Final Margins with a Handheld Optical Imaging Probe During Breast-Conserving Surgery May Reduce the Reoperation Rate: Results of a Multicenter Study

BACKGROUND

A multicenter, prospective, blinded study was performed to test the feasibility of using a handheld optical imaging probe for the intraoperative assessment of final surgical margins during breast-conserving surgery (BCS) and to determine the potential impact on patient outcomes.

METHODS

Forty-six patients with early-stage breast cancer (one with bilateral disease) undergoing BCS at two study sites, the Johns Hopkins Hospital and Anne Arundel Medical Center, were enrolled in this study. During BCS, cavity-shaved margins were obtained and the final margins were examined ex vivo in the operating room with a probe incorporating optical coherence tomography (OCT) hardware and interferometric synthetic aperture microscopy (ISAM) image processing. Images were interpreted after BCS by three physicians blinded to final pathology-reported margin status. Individual and combined interpretations were assessed. Results were compared to conventional postoperative histopathology.

RESULTS

A total of 2,191 images were collected and interpreted from 229 shave margin specimens. Of the eight patients (17 %) with positive margins (0 mm), which included invasive and in situ diseases, the device identified all positive margins in five (63%) of them; reoperation could potentially have been avoided in these patients. Among patients with pathologically negative margins (>0 mm), an estimated mean additional tissue volume of 10.7 ml (approximately 1% of overall breast volume) would have been unnecessarily removed due to false positives.

CONCLUSIONS

Intraoperative optical imaging of specimen margins with a handheld probe potentially eliminates the majority of reoperations.

A computational model to generate simulated three-dimensional breast masses

PURPOSE

To develop algorithms for creating realistic three-dimensional (3D) simulated breast masses and embedding them within actual clinical mammograms. The proposed techniques yield high-resolution simulated breast masses having randomized shapes, with user-defined mass type, size, location, and shape characteristics.

METHODS

The authors describe a method of producing 3D digital simulations of breast masses and a technique for embedding these simulated masses within actual digitized mammograms. Simulated 3D breast masses were generated by using a modified stochastic Gaussian random sphere model to generate a central tumor mass, and an iterative fractal branching algorithm to add complex spicule structures. The simulated masses were embedded within actual digitized mammograms. The authors evaluated the realism of the resulting hybrid phantoms by generating corresponding left- and right-breast image pairs, consisting of one breast image containing a real mass, and the opposite breast image of the same patient containing a similar simulated mass. The authors then used computer-aided diagnosis (CAD) methods and expert radiologist readers to determine whether significant differences can be observed between the real and hybrid images.

RESULTS

The authors found no statistically significant difference between the CAD features obtained from the real and simulated images of masses with either spiculated or nonspiculated margins. Likewise, the authors found that expert human readers performed very poorly in discriminating their hybrid images from real mammograms.

CONCLUSIONS

The authors' proposed method permits the realistic simulation of 3D breast masses having user-defined characteristics, enabling the creation of a large set of hybrid breast images containing a well-characterized mass, embedded within real breast background. The computational nature of the model makes it suitable for detectability studies, evaluation of computer aided diagnosis algorithms, and teaching purposes.

Abstract P2-03-11: In situ imaging of the tumor cavity during breast lumpectomy using optical coherence tomography

Re-operation rates for breast lumpectomy procedures are exceedingly high, often over 30%, depending on the institution and surgical technique. Because current standard-of-care relies on post-operative histopathology to provide a microscopic view and assessment of surgical margins, there has been great interest in developing new imaging solutions to visualize tissues intraoperatively with high-resolution, and provide real-time feedback on the margin status. While it is possible to use a variety of microscopic imaging methods in the operating suite, including frozen-section histology, touch-prep cytology, confocal or scattering-based microscopy, all these techniques are limited to visualizing margins on ex vivo resected specimens, and do not provide a means for visualizing the in situ tumor cavity for evidence of positive margins or residual disease.

Optical coherence tomography (OCT) is a high-resolution, real-time, optical biomedical imaging technology that is the optical analogue to ultrasound imaging, except images are based on backscattered near-infrared light. OCT is capable of performing optical biopsies of in situ tissue at resolutions that approach those in histopathology. With the use of an advanced computed imaging technique called ISAM (Interferometric Synthetic Aperture Microscopy), even higher imaging resolution over larger depths is possible, commensurate with the depths (1-2 mm) visualized by pathologists to determine negative, close, or positive margins. Past studies by our group and others have demonstrated the feasibility of intraoperative OCT for assessing tumor margin and lymph node status during breast cancer surgery, but to date, all studies have been performed on resected lumpectomy tissue.

In this study, we report the development of a novel handheld surgical imaging probe that enables 2-D and 3-D OCT/ISAM imaging of the in situ tumor cavity, in addition to the margins of excised specimens. To date, this handheld OCT/ISAM probe has been used in 10 breast cancer surgeries where both in situ and ex vivo imaging was performed. Four of these cases involved in situ imaging of the cavity margin after a suspicious area was visually and tactically identified, and was subsequently resected, followed by ex vivo imaging and validating post-operative histopathology. Representative cases included fibroadipose tissue, fibroadenomas, and high-grade ductal carcinoma in situ.

Distinct microstructural features identified on OCT/ISAM and confirmed with histopathology demonstrate that this technique can visualize the in situ tumor cavity, as well as the surgical margins on resected specimens, with micron-scale resolution. OCT/ISAM has the potential to determine margin status in real-time during the surgical procedure, when further surgical resection to establish clear margins and reduce re-operation rates is possible.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P2-03-11.

Nondestructive volumetric imaging of tissue microstructure with benchtop x-ray phase-contrast tomography and critical point drying

The in vitro investigation of many optically opaque biological microstructures requires 3D analysis at high resolution over a large field of view. We demonstrate a new nondestructive volumetric imaging technique that eliminates the structural and computational limitations of conventional 2D optical microscopy by combining x-ray phase-contrast tomography with critical point drying sample preparation. We experimentally demonstrate the enhancement of small features afforded by phase-contrast imaging and show the contrast improvement afforded by the drying of a hydrated specimen. We further demonstrate the biological application of this technique by imaging the microstructure of the accommodative apparatus in a primate eye using a benchtop phase-contrast tomography system.

Imaging of poly(α-hydroxy-ester) scaffolds with X-ray phase-contrast microcomputed tomography

Porous scaffolds based on poly(α-hydroxy-esters) are under investigation in many tissue engineering applications. A biological response to these materials is driven, in part, by their three-dimensional (3D) structure. The ability to evaluate quantitatively the material structure in tissue-engineering applications is important for the continued development of these polymer-based approaches. X-ray imaging techniques based on phase contrast (PC) have shown a tremendous promise for a number of biomedical applications owing to their ability to provide a contrast based on alternative X-ray properties (refraction and scatter) in addition to X-ray absorption. In this research, poly(α-hydroxy-ester) scaffolds were synthesized and imaged by X-ray PC microcomputed tomography. The 3D images depicting the X-ray attenuation and phase-shifting properties were reconstructed from the measurement data. The scaffold structure could be imaged by X-ray PC in both cell culture conditions and within the tissue. The 3D images allowed for quantification of scaffold properties and automatic segmentation of scaffolds from the surrounding hard and soft tissues. These results provide evidence of the significant potential of techniques based on X-ray PC for imaging polymer scaffolds.

Adaptation of a clustered lumpy background model for task-based image quality assessment in x-ray phase-contrast mammography

PURPOSE

Since the introduction of clinical x-ray phase-contrast mammography (PCM), a technique that exploits refractive-index variations to create edge enhancement at tissue boundaries, a number of optimization studies employing physical image-quality metrics have been performed. Ideally, task-based assessment of PCM would have been conducted with human readers. These studies have been limited, however, in part due to the large parameter-space of PCM system configurations and the difficulty of employing expert readers for large-scale studies. It has been proposed that numerical observers can be used to approximate the statistical performance of human readers, thus enabling the study of task-based performance over a large parameter-space.

METHODS

Methods are presented for task-based image quality assessment of PCM images with a numerical observer, the most significant of which is an adapted lumpy background from the conventional mammography literature that accounts for the unique wavefield propagation physics of PCM image formation and will be used with a numerical observer to assess image quality. These methods are demonstrated by performing a PCM task-based image quality study using a numerical observer. This study employs a signal-known-exactly, background-known-statistically Bayesian ideal observer method to assess the detectability of a calcification object in PCM images when the anode spot size and calcification diameter are varied.

RESULTS

The first realistic model for the structured background in PCM images has been introduced. A numerical study demonstrating the use of this background model has compared PCM and conventional mammography detection of calcification objects. The study data confirm the strong PCM calcification detectability dependence on anode spot size. These data can be used to balance the trade-off between enhanced image quality and the potential for motion artifacts that comes with use of a reduced spot size and increased exposure time.

CONCLUSIONS

A method has been presented for the incorporation of structured breast background data into task-based numerical observer assessment of PCM images. The method adapts conventional background simulation techniques to the wavefield propagation physics necessary for PCM imaging. This method is demonstrated with a simple detection task.

Framework for computing the spatial coherence effects of polycapillary x-ray optics

Despite the extensive use of polycapillary x-ray optics for focusing and collimating applications, there remains a significant need for characterization of the coherence properties of the output wavefield. In this work, we present the first quantitative computational method for calculation of the spatial coherence effects of polycapillary x-ray optical devices. This method employs the coherent mode decomposition of an extended x-ray source, geometric optical propagation of individual wavefield modes through a polycapillary device, output wavefield calculation by ray data resampling onto a uniform grid, and the calculation of spatial coherence properties by way of the spectral degree of coherence.

Optical coherence tomography: the intraoperative assessment of lymph nodes in breast cancer

During breast-conserving surgeries, axillary lymph nodes draining from the primary tumor site are removed for disease staging. Although a high number of lymph nodes are often resected during sentinel and lymph-node dissections, only a relatively small percentage of nodes are found to be metastatic, a fact that must be weighed against potential complications such as lymphedema. Without a real-time in vivo or in situ intraoperative imaging tool to provide a microscopic assessment of the nodes, postoperative paraffin section histopathological analysis currently remains the gold standard in assessing the status of lymph nodes. This paper investigates the use of optical coherence tomography (OCT), a high-resolution real-time microscopic optical-imaging technique, for the intraoperative ex vivo imaging and assessment of axillary lymph nodes. Normal (13), reactive (1), and metastatic (3) lymph nodes from 17 human patients with breast cancer were imaged intraoperatively with OCT. These preliminary clinical studies have identified scattering changes in the cortex, relative to the capsule, which can be used to differentiate normal from reactive and metastatic nodes. These optical scattering changes are correlated with inflammatory and immunological changes observed in the follicles and germinal centers. These results suggest that intraoperative OCT has the potential to assess the real-time node status in situ, without having to physically resect and histologically process specimens to visualize microscopic features.

Analysis of ideal observer signal detectability in phase-contrast imaging employing linear shift-invariant optical systems

Phase-contrast imaging methods exploit variations in an object's refractive index distribution to permit the visualization of subtle features that may have very similar optical absorption properties. Although phase-contrast is often viewed as being desirable in many biomedical applications, its relative influence on signal detectability when both absorption- and phase-contrast are present remains relatively unexplored. In this work, we investigate the ideal Bayesian observer signal-to-noise ratio in phase-contrast imaging for a signal-known-exactly/background-known exactly detection task involving a weak signal. We demonstrate that this signal detectability measure can be decomposed into three contributions that have distinct interpretations associated with the imaging physics.

Transport of intensity and spectrum for partially coherent fields

Transport-of-intensity and transport-of-spectrum equations are derived using the coherent mode decomposition for paraxial fields having an arbitrary state of coherence. We give a simple example that demonstrates the difference between a partially coherent and a fully coherent transport of intensity or spectrum. The results presented here may be used to estimate the intensity response in a variety of phase-contrast imaging modalities and may form the basis for improved phase-retrieval techniques.

Intraoperative evaluation of breast tumor margins with optical coherence tomography

As breast cancer screening rates increase, smaller and more numerous lesions are being identified earlier, leading to more breast-conserving surgical procedures. Achieving a clean surgical margin represents a technical challenge with important clinical implications. Optical coherence tomography (OCT) is introduced as an intraoperative high-resolution imaging technique that assesses surgical breast tumor margins by providing real-time microscopic images up to 2 mm beneath the tissue surface. In a study of 37 patients split between training and study groups, OCT images covering 1 cm(2) regions were acquired from surgical margins of lumpectomy specimens, registered with ink, and correlated with corresponding histologic sections. A 17-patient training set used to establish standard imaging protocols and OCT evaluation criteria showed that areas of higher scattering tissue with a heterogeneous pattern were indicative of tumor cells and tumor tissue in contrast to lower scattering adipocytes found in normal breast tissue. The remaining 20 patients were enrolled into the feasibility study. Of these lumpectomy specimens, 11 were identified with a positive or close surgical margin and 9 were identified with a negative margin under OCT. Based on histologic findings, 9 true positives, 9 true negatives, 2 false positives, and 0 false negatives were found, yielding a sensitivity of 100% and specificity of 82%. These results show the potential of OCT as a real-time method for intraoperative margin assessment in breast-conserving surgeries.

Clinical feasibility of microscopically-guided breast needle biopsy using a fiber-optic probe with computer-aided detection

Needle biopsy of small or nonpalpable breast lesions has a high nondiagnostic sampling rate even when needle position is guided by stereotaxis or ultrasound. We assess the feasibility of using a near-infrared fiber optic probe and computer-aided detection for the microscopic guidance of needle breast biopsy procedures. Specimens from nine consented patients undergoing breast-conserving surgery were assessed intraoperatively using a needle device with an integrated fiber-optic probe capable of assessing two physical tissue properties highly correlated to pathology. Immediately following surgical resection, specimens were probed by inserting the optical biopsy needle device into the tissue, simulating the procedure used to position standard biopsy needles. Needle positions were marked and correlated with histology, which verified measurements obtained from 58 needle positions, including 40 in adipose and 18 in tumor tissue. This study yielded tissue classifications based on measurement of optical refractive index and scattering. Confidence-rating schemes yielded combined sensitivity of 89% (16/18) and specificity of 78% (31/40). Refractive index tests alone identified tumor tissue with a sensitivity of 83% (15/18) and specificity of 75% (30/40). Scattering profiles independently identified tumor tissue with a sensitivity of 61% (11/18) and specificity of 60% (24/40). These results show that a biopsy needle with an integrated fiber optic probe can be used to identify breast tumor tissue for sampling. Integration of this probe into current practices offers the potential to reduce nondiagnostic sampling rates by directly evaluating in situ microscopic tissue properties in real-time, before removal.

Optical coherence tomography (OCT) as a diagnostic tool for the real-time intraoperative assessment of breast cancer surgical margins

Abstract #802

Background: The decrease in the number of breast cancer deaths has largely been attributed to increased awareness, earlier detection, and improved treatment options. However, as the number of breast-conserving surgeries rose over the years, the need for negative margins and little or no residual disease has become critical to help reduce the chances of local recurrence. OCT is a high resolution imaging modality that has been used to image tumor margins in an NMU-carcinogen-induced rat mammary tumor model. Due to the location of breast lesions, the use of needle-based imaging probes may be used to further extend the reach of the OCT imaging beam by incorporating an optical fiber into biopsy needle tips, providing real-time information to guide biopsies or to place localization wires.
 Material & Methods: A clinical spectral domain OCT system was developed with a super luminescent diode light source centered at 1310 nm with a bandwidth of 92 nm yielding an axial resolution of 8.3 µm. The beam delivery sample arm uses a 60 mm achromatic lens to focus 4.75 mW of light to a 35.0 µm spot size (transverse resolution) with a confocal parameter of 1.47 mm. The patients included in this study had primary breast tumors diagnosed by needle-biopsy and were in need of surgical resection, as determined by their physicians. At Carle Foundation Hospital, the OCT system was placed inside the operating room during breast conserving surgical procedures to image the tissue specimens. The OCT images were evaluated by a single operator allowing for consistent classification based on the level of scattering intensity and heterogeneity, scattering profile, and physical extent of the highly scattering area.
 Results: An initial training data set of OCT images from 17 patients was used to establish standard imaging protocols and standard evaluation criteria of the surgical margins. Of the 20 additional tissue specimen imaged for the feasibility study, 11 were identified as having a positive or close surgical margin and nine as a negative margin under OCT. In comparing to the H&E histology, there were 9 true positives, 9 true negatives, 2 false positives, and 0 false negatives yielding a sensitivity of 82% and specificity of 100%.
 Discussion: With an imaging penetration depth of 2-3 mm, equivalent to that used for histological assessment, OCT provides unique real-time cellular-level imaging to identify positive and close margins. In these studies, areas of higher scattering tissue with an irregular or heterogeneous pattern were identified, differentiating them from the abundant adipose tissue found in normal breast tissue. The small nucleus to cytoplasm (N/C) ratio is observed with low-scattering adipocytes compared with the larger N/C ratio found from highly-scattering tumor cells. These intraoperative imaging studies have demonstrated the ability for OCT to identify positive surgical margins.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 802.

Group refractive index reconstruction with broadband interferometric confocal microscopy

We propose a novel method of measuring the group refractive index of biological tissues at the micrometer scale. The technique utilizes a broadband confocal microscope embedded into a Mach-Zehnder interferometer, with which spectral interferograms are measured as the sample is translated through the focus of the beam. The method does not require phase unwrapping and is insensitive to vibrations in the sample and reference arms. High measurement stability is achieved because a single spectral interferogram contains all the information necessary to compute the optical path delay of the beam transmitted through the sample. Included are a physical framework defining the forward problem, linear solutions to the inverse problem, and simulated images of biologically relevant phantoms.

Optical coherence tomography: a review of clinical development from bench to bedside

Since its introduction, optical coherence tomography (OCT) technology has advanced from the laboratory bench to the clinic and back again. Arising from the fields of low coherence interferometry and optical time- and frequency-domain reflectometry, OCT was initially demonstrated for retinal imaging and followed a unique path to commercialization for clinical use. Concurrently, significant technological advances were brought about from within the research community, including improved laser sources, beam delivery instruments, and detection schemes. While many of these technologies improved retinal imaging, they also allowed for the application of OCT to many new clinical areas. As a result, OCT has been clinically demonstrated in a diverse set of medical and surgical specialties, including gastroenterology, dermatology, cardiology, and oncology, among others. The lessons learned in the clinic are currently spurring a new set of advances in the laboratory that will again expand the clinical use of OCT by adding molecular sensitivity, improving image quality, and increasing acquisition speeds. This continuous cycle of laboratory development and clinical application has allowed the OCT technology to grow at a rapid rate and represents a unique model for the translation of biomedical optics to the patient bedside. This work presents a brief history of OCT development, reviews current clinical applications, discusses some clinical translation challenges, and reviews laboratory developments poised for future clinical application.

Needle-based reflection refractometry of scattering samples using coherence-gated detection

We present a novel method for in situ refractive index measurement of scattering samples using a needle device. The device employs a fiber-based reflectance refractometer and coherence-gated detection of the reflected optical signal that eliminates scattering-dependent backreflection contributions. Additionally, birefringence changes induced by fiber movement are neutralized by randomizing the source polarizations and averaging the measured Fresnel reflection coefficients over many incident polarization states. Experimental measurements of Intralipid scattering solutions are presented and compared with Monte Carlo simulations.

Needle-based refractive index measurement using low-coherence interferometry

We present a novel needle-based device for the measurement of refractive index and scattering using low-coherence interferometry. Coupled to the sample arm of an optical coherence tomography system, the device detects the scattering response of, and optical path length through, a sample residing in a fixed-width channel. We report use of the device to make near-infrared measurements of tissues and materials with known optical properties. The device could be used to exploit the refractive index variations of tissue for medical and biological diagnostics accessible by needle insertion.

Computational methods for analysis of human breast tumor tissue in optical coherence tomography images

Optical coherence tomography (OCT) has been demonstrated as a promising means of identifying the boundaries between normal and diseased breast tissue. This capability has yielded promise for the development of OCT techniques for biopsy guidance, surgical margin assessment, and minimally invasive evaluation of disease states. We present methods for the assessment of human breast tissue based on spatial and Fourier-domain analysis. Derived from preliminary OCT data, these methods are aimed at the development of automated diagnostic tools that will aid in the translation of this technology into the clinical environment.

Refractive index of carcinogen-induced rat mammary tumours

Near-infrared optical techniques for clinical breast cancer screening in humans are rapidly advancing. Based on the computational inversion of the photon diffusion process through the breast, these techniques rely on optical tissue models for accurate image reconstruction. Recent interest has surfaced regarding the effect of refractive index variations on these reconstructions. Although many data exist regarding the scattering and absorption properties of normal and diseased tissue, no measurements of refractive index appear in the literature. In this paper, we present near-infrared refractive index data acquired from N-methyl-N-nitrosourea-induced rat mammary tumours, which are similar in pathology and disease progression to human ductal carcinoma. Eight animals, including one control, were employed in this study, yielding data from 32 tumours as well as adjacent adipose and connective tissues.

Eikonal method for calculation of coherence functions

A method is presented for computing the cross-spectral density of a special class of partially coherent fields in which the coherent modes obey an eikonal equation. This method allows for statistical analysis of optical systems based on simple ray tracing.

Projected index computed tomography

Projected index computed tomography (PICT) is a new imaging technique that provides a computed reconstruction of the index of refraction of a sample. PICT makes use of data from standard optical coherence tomography images taken from several view angles to determine a mapping of the refractive indices of the sample. A rectilinear propagation model is assumed, so the data are understood to be related to the line integral of the refractive index in the beam paths. These data thus provide a set of angular projections of the sample. The spatial distribution of the index of the object may then be reconstructed by use of standard filtered backprojection techniques. The resultant PICT images are free of the spatial distortion that is inherent in standard optical cross-sectional images and correspond well to the manufactured dimensions of specific samples.