Heterodyne frequency-domain multispectral diffuse optical tomography of breast cancer in the parallel-plane transmission geometry

PURPOSE

The authors introduce a state-of-the-art all-optical clinical diffuse optical tomography (DOT) imaging instrument which collects spatially dense, multispectral, frequency-domain breast data in the parallel-plate geometry.

METHODS

The instrument utilizes a CCD-based heterodyne detection scheme that permits massively parallel detection of diffuse photon density wave amplitude and phase for a large number of source-detector pairs (10(6)). The stand-alone clinical DOT instrument thus offers high spatial resolution with reduced crosstalk between absorption and scattering. Other novel features include a fringe profilometry system for breast boundary segmentation, real-time data normalization, and a patient bed design which permits both axial and sagittal breast measurements.

RESULTS

The authors validated the instrument using tissue simulating phantoms with two different chromophore-containing targets and one scattering target. The authors also demonstrated the instrument in a case study breast cancer patient; the reconstructed 3D image of endogenous chromophores and scattering gave tumor localization in agreement with MRI.

CONCLUSIONS

Imaging with a novel parallel-plate DOT breast imager that employs highly parallel, high-resolution CCD detection in the frequency-domain was demonstrated.

CHOP THERAPY INDUCED MITOCHONDRIAL REDOX STATE ALTERATION IN NON-HODGKIN'S LYMPHOMA XENOGRAFTS

We are interested in investigating whether cancer therapy may alter the mitochondrial redox state in cancer cells to inhibit their growth and survival. The redox state can be imaged by the redox scanner that collects the fluorescence signals from both the oxidized-flavoproteins (Fp) and the reduced form of nicotinamide adenine dinucleotide (NADH) in snap-frozen tissues and has been previously employed to study tumor aggressiveness and treatment responses. Here, with the redox scanner we investigated the effects of chemotherapy on mouse xenografts of a human diffuse large B-cell lymphoma cell line (DLCL2). The mice were treated with CHOP therapy, i.e., cyclophosphamide (C) + hydroxydoxorubicin (H) + Oncovin (O) + prednisone (P) with CHO administration on day 1 and prednisone administration on days 1-5. The Fp content of the treated group was significantly decreased (p = 0.033) on day 5, and the mitochondrial redox state of the treated group was slightly more reduced than that of the control group (p = 0.048). The decrease of the Fp heterogeneity (measured by the mean standard deviation) had a border-line statistical significance (p = 0.071). The result suggests that the mitochondrial metabolism of lymphoma cells was slightly suppressed and the lymphomas became less aggressive after the CHOP therapy.

P2-10-03: Non-Invasive In Vivo Characterization of Cancer-Cell Proliferation & Angiogenesis in Cancer-Cell-Surrounding Stromal Microenvironment In-Vivo Using Diffuse Optical Tomography

Background: Cancer cell proliferation and stromal microenvironment changes have been shown to indicate tumor growth (Orimo, Weinberg et al., Cell, 2005, Coussens and Werb, Nature, 2002). However, most studies were performed using excised tissue samples or cultured cells. In-vivo characterization of these properties in human breast cancer could magnify the importance of recent findings from in-vitro tissues. Diffuse Optical Tomography (DOT) provides quantitative three-dimensional (3D) images of the physiological and pathological properties of breast cancer tissues in vivo. In this study, we investigate the relationship between DOT measured physiological parameters, such as hemoglobin & tissue oxygenation that differentiate malignant, benign and normal breast tissues (Choe, Yodh et al. JBO, 2009), and histologically quantified Ki67 expression in cancer cell nuclei and vasculature in the stromal microenvironment surrounding breast cancer cells.

Methods: DOT was employed to measure 20 infiltrating ductal carcinoma patients. DOT utilizes non-ionizing low power near infrared light to examine a subject laying in the prone position on a bed with her breasts inside a breast box. DOT quantifies oxy- and deoxy-hemoglobin concentration and tissue oxygenation. Cancer proliferation was quantified by calculating Ki67 stained nuclei percent and vascular area (calculated by detecting CD34 stained vascular structure using automated RGB based software).

Results: The ratio of Ki67 expression in cancer cells to surrounding normal cells was correlated with DOT-measured tumor-to-normal ratio of volume-averaged oxy-hemoglobin and tissue oxygen saturation (R=0.72, p-value: 0.0197 and R=0.68, p-value: 0.0293, respectively, N=10). The vascular area (μm2) the surrounding stroma was correlated with total hemoglobin concentration and oxy-hemoglobin (R=0.49, p-value: 0.1238 and R=0.43, p-value: 0.1819, respectively, N=11). Additionally, cancer-to-normal ratio of nuclei compactness and cancer micro-vessel density was correlated with tumor-to-normal ratio of oxy-hemoglobin concentration (R=0.43, p-value: 0.056 and R=0.43, p-value:0.058, respectively, N=20).

Discussion: The positive correlations between Ki67 cancer-proliferation-marker and tissue oxy-hemoglobin concentration indicate that DOT detects increased oxygenated environment for proliferating cells. The observation that nuclei compactness increases with oxy-hemoglobin concentration also supports the statement above, and, the correlation between hemoglobin concentration and vascular area in surrounding stroma suggests that DOT measures tumor growth stimulated by stromal micro-environment changes. The difference between the field of view needed to calculate a parameter value (i.e., macroscopic (cm3) for DOT and microscopic (|im3) for histology) likely lowers the correlation between the two technologies. However, the results of this study clearly suggest that DOT measures tumor growth due to proliferation of cancer cells and angiogenesis in cancer-cell-surrounding stroma. This work was supported by NIH and the Susan G. Komen for the Cure foundation.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-10-03.

Diffuse Optics for Tissue Monitoring and Tomography

This review describes the diffusion model for light transport in tissues and the medical applications of diffuse light. Diffuse optics is particularly useful for measurement of tissue hemodynamics, wherein quantitative assessment of oxy- and deoxy-hemoglobin concentrations and blood flow are desired. The theoretical basis for near-infrared or diffuse optical spectroscopy (NIRS or DOS, respectively) is developed, and the basic elements of diffuse optical tomography (DOT) are outlined. We also discuss diffuse correlation spectroscopy (DCS), a technique whereby temporal correlation functions of diffusing light are transported through tissue and are used to measure blood flow. Essential instrumentation is described, and representative brain and breast functional imaging and monitoring results illustrate the workings of these new tissue diagnostics.

Differentiation of benign and malignant breast lesions by in-vivo three-dimensional diffuse optical tomography

Abstract #805

Background: Diffuse optical tomography (DOT) uses near-infrared light to non-invasively image total hemoglobin concentration and blood oxygen saturation in the human breast. Given its low cost, ease of use, and possibility of repeated measured over time, DOT is a promising adjunctive imaging modality for screening, diagnosis and monitoring of neoadjuvant therapy. In this study we explored the performance of DOT to differentiate benign and malignant breast lesions.
 Method and Materials: Forty-seven women with clinical or mammographic abnormalities were prospectively recruited for DOT. Most patients underwent gadolinium-enhanced MRI examination. Three-dimensional oxy-, deoxy-hemoglobin, total hemoglobin concentration, blood oxygen saturation and scattering coefficient images of each breast were reconstructed. Tumor-to-normal (T/N) ratios of these parameters were computed by defining tumor regions with guidance from MRI and radiology reports. In addition, optical index was constructed based on these parameters to maximize the T/N contrast. Only the biopsy-proven lesions were selected (51 breast lesions) and classified into three groups: benign lesions (N=10), malignant lesions where DOT preceded core biopsy (N=20) and malignant lesions where DOT was performed after core-biopsy (N=21). We fit a mixed effects model that estimated the mean optical T/N ratios and optical index for each group, and using the resulting standard errors developed 95% confidence intervals and tested the hypothesis that each optical contrast parameter was unity.
 Results: Malignant cancers showed statistically significant higher total hemoglobin concentration, scattering, oxy-hemoglobin concentration and optical index (P=0.01-0.04) compared to normal tissue. Furthermore, malignant lesions exhibited a two-fold average increase in an optical index derived from the endogenous optical parameters (95% CI: 1.4 - 2.4). To test whether bleeding due to core biopsy influence DOT results, we compared if there was statistically significant differences between two groups measured before or after core-biopsy. There were no statistically significant differences in these groups, suggesting that post biopsy hemorrhage did not alter the DOT results. Benign tumors did not show statistical significance in all of the T/N ratios. AUC of total hemoglobin concentration, scattering, oxy-hemoglobin and optical index suggested good discriminatory power with values between 0.90 and 0.99.
 Discussion: The data demonstrates the feasibility of differentiating benign and malignant lesions by quantitative three-dimensional DOT when the tumor location information is provided by other imaging modality. The main drawback of this study is the small number of benign lesions, which warrants further study. DOT technology is still at its developing stage and needs more investigation to find its niche in breast imaging.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 805.

Three-dimensional diffuse optical tomography in the parallel plane transmission geometry: evaluation of a hybrid frequency domain/continuous wave clinical system for breast imaging

Three-dimensional diffuse optical tomography (DOT) of breast requires large data sets for even modest resolution (1 cm). We present a hybrid DOT system that combines a limited number of frequency domain (FD) measurements with a large set of continuous wave (cw) measurements. The FD measurements are used to quantitatively determine tissue averaged absorption and scattering coefficients. The larger cw data sets (10(5) measurements) collected with a lens coupled CCD, permit 3D DOT reconstructions of a 1-liter tissue volume. To address the computational complexity of large data sets and 3D volumes we employ finite difference based reconstructions computed in parallel. Tissue phantom measurements evaluate imaging performance. The tests include the following: point spread function measures of resolution, characterization of the size and contrast of single objects, field of view measurements and spectral characterization of constituent concentrations. We also report in vivo measurements. Average tissue optical properties of a healthy breast are used to deduce oxy- and deoxy-hemoglobin concentrations. Differential imaging with a tumor simulating target adhered to the surface of a healthy breast evaluates the influence of physiologic fluctuations on image noise. This tomography system provides robust, quantitative, full 3D image reconstructions with the advantages of high data throughput, single detector-tissue coupling path, and large (1L) imaging domains. In addition, we find that point spread function measurements provide a useful and comprehensive representation of system performance.

Bulk optical properties of healthy female breast tissue

We have measured the bulk optical properties of healthy female breast tissues in vivo in the parallel plate, transmission geometry. Fifty-two volunteers were measured. Blood volume and blood oxygen saturation were derived from the optical property data using a novel method that employed a priori spectral information to overcome limitations associated with simple homogeneous tissue models. The measurements provide an estimate of the variation of normal breast tissue optical properties in a fairly large population. The mean blood volume was 34 +/- 9 microM and the mean blood oxygen saturation was 68 +/- 8%. We also investigated the correlation of these optical properties with demographic factors such as body mass index (BMI) and age. We observed a weak correlation of blood volume and reduced scattering coefficient with BMI: correlation with age, however, was not evident within the statistical error of these experiments. The new information on healthy breast tissue provides insight about the potential contrasts available for diffuse optical tomography of breast tumours.

Optic disk characteristics before the occurrence of disk hemorrhage in glaucoma patients

PURPOSE

To evaluate qualitatively the structural characteristics and the associated features that antedate the occurrence of a disk hemorrhage in patients with glaucoma.

METHODS

Retrospective observational case series. A total of 4018 pairs of stereoscopic optic disk images obtained over 15 years were reviewed. All eyes with optic disk images before the occurrence of a disk hemorrhage were enrolled. The disk images were evaluated in a masked fashion with respect to the general neural rim and peripapillary appearance.

RESULTS

The optic disk characteristics and associated features that most antedate the disk hemorrhage in 33 eyes of 26 patients that had previous optic disk images for evaluation are focal neural rim notch (36%), thin sloping rim (42%), peripapillary atrophy (79%), and superior-inferior rim asymmetry (73%). In eyes with preexisting focal rim notches, all subsequent disk hemorrhages were identified at or adjacent to the notches.

CONCLUSIONS

Focal rim notching may precede the occurrence of a disk hemorrhage.

Modeling photon transport in transabdominal fetal oximetry

The possibility of optical oximetry of the blood in the fetal brain measured across the maternal abdomen just prior to birth is under investigation. Such measurements could detect fetal distress prior to birth and aid in the clinical decision regarding Cesarean section. This paper uses a perturbation method to model photon transport through an 8-cm-diam fetal brain located at a constant 2.5 cm below a curved maternal abdominal surface with an air/tissue boundary. In the simulation, a near-infrared light source delivers light to the abdomen and a detector is positioned up to 10 cm from the source along the arc of the abdominal surface. The light transport [W/cm2 fluence rate per W incident power] collected at the 10 cm position is Tm = 2.2 x 10(-6) cm(-2) if the fetal brain has the same optical properties as the mother and Tf = 1.0 x 10(-6) cm(-2) for an optically perturbing fetal brain with typical brain optical properties. The perturbation P=(Tf - Tm)/Tm is -53% due to the fetal brain. The model illustrates the challenge and feasibility of transabdominal oximetry of the fetal brain.

Paired parallel locking forceps

We describe an instrument used to prevent contact between an antimetabolite and the conjunctiva-Tenon's wound edge in filtering surgery. Paired parallel locking forceps were used to keep the everted conjunctival-Tenon's wound edge from touching the antimetabolite sponge during limbal-based filtering surgery while enabling manipulation of the antimetabolite sponge. This allows the surgeon to more easily avoid the conjunctival edge, making antimetabolite touch easier and safer.