Diaphanography in benign breast disorders. Correlation with clinical examination, mammography, cytology and histology

The development of breast radiology: the Acta Radiologica perspective

The encouraging results of modern breast cancer care builds on tremendous improvements in diagnostics and therapy during the 20th century. Scandinavian countries have made important footprints in the development of breast diagnostics regarding technical development of imaging, cell and tissue sampling methods and, not least, population screening with mammography. The multimodality approach in combination with multidisciplinary clinical work in breast cancer serve as a role model for the management of many cancer types worldwide. The development of breast radiology is well represented in the research published in this journal and this historical review will describe the most important steps.

Spatial and Spectral Information in Optical Mammography

This article reviews our research activities in the area of optical mammography and relates them to the historical developments and the current state and trends in the field. The guiding threads for this article are the roles played in optical mammography by spatial and spectral information. The first feature, spatial information, is limited by the diffusive nature of light propagation but can take advantage of the exceptionally high optical contrast featured by blood vessels and blood-rich areas in the breast. We describe a method to correct for edge effects, a spatial second-derivative algorithm, and a two-dimensional phased-array approach that enhance the image contrast, the spatial resolution, and the depth discrimination in optical mammograms. The second feature, spectral information, is the most powerful and unique capability of optical mammography, and allows for functional measurements associated with hemoglobin concentration and oxygenation, water concentration, lipids content, and the wavelength dependence of tissue scattering. We present oxygenation-index images obtained from multi-wavelength optical data that point to the diagnostic potential of oxygenation information in optical mammography. The optimization of the spatial and spectral information in optical mammography has the potential to create a role for this imaging modality in the detection and monitoring of breast cancer.

Near-infrared spectral imaging of the female breast for quantitative oximetry in optical mammography

We present a hybrid continuous-wave, frequency-domain instrument for near-infrared spectral imaging of the female breast based on a tandem, planar scanning of one illumination optical fiber and one collection optical fiber configured in a transmission geometry. The spatial sampling rate of 25 points/cm(2) is increased to 400 points/cm(2) by postprocessing the data with a 2D cubic spline interpolation. We then apply a previously developed spatial second-derivative algorithm to an edge-corrected intensity image (N-image) to enhance the visibility and resolution of optical inhomogeneities in breast tissue such as blood vessels and tumors. The spectral data at each image pixel consist of 515-point spectra over the 650-900 nm wavelength range, thus featuring a spectral density of two data points per nanometer. We process the measured spectra with a paired-wavelength spectral analysis method to quantify the oxygen saturation of detected optical inhomogeneities, under the assumption that they feature a locally higher hemoglobin concentration. Our initial measurements on two healthy human subjects have generated high-resolution optical mammograms displaying a network of blood vessels with values of hemoglobin saturation typically falling within the 60%-95% range, which is physiologically reasonable. This approach to spectral imaging and oximetry of the breast has the potential to efficiently exploit the high intrinsic contrast provided by hemoglobin in breast tissue and to contribute a useful tool in the detection, diagnosis, and monitoring of breast pathologies.

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.

Influence of a superficial layer in the quantitative spectroscopic study of strongly scattering media

We have experimentally investigated the meaning of the effective optical absorption [mu(a)((eff))] and the reduced scattering [mu(s)?((eff))] coefficients measured on the surfaces of two-layered turbid media, using the diffusion equation for homogeneous, semi-infinite media. We performed frequency-domain spectroscopy in a reflectance geometry, using source-detector distances in the range 1.5-4.5 cm. We measured 100 samples, each made of one layer (thickness in the range 0.08-1.6 cm) on top of one semi-infinite block. The optical properties of the samples were similar to those of soft tissues in the near infrared. We found that the measured effective optical coefficients are representative of the underlying block if the superficial layer is less than ~0.4 cm thick, whereas they are representative of the superficial layer if it is more than ~1.3 cm thick.

Breast carcinoma and benign breast lesions. Diaphanography and quantitative evaluation using the computer-controlled image scanner OSIRIS

A total of 110 diaphanograms from women with breast carcinoma and 154 diaphanograms from women with benign breast disorders were quantitatively evaluated using the OSIRIS image scanner. Optical density values in the green and red spectral bands were recorded. The malignant and the benign groups, were statistically evaluated using linear discriminant analysis. Correct classification was obtained in 73.5 per cent of women with breast carcinoma and in 84.6 per cent of women with benign breast disorders. Visual interpretation of the findings alone classified 84.5 per cent of the malignant lesions correctly and 90.8 per cent of the benign lesions correctly. Quantitative evaluation combined with visual interpretation improved the accuracy of classification of breast carcinoma (91.8%), but not of benign breast disorders, which was about the same (83.8%).

Physical interpretation of diaphanograms using the computer-controlled image scanner OSIRIS

Experiments have shown that the light recorded in diaphanography covers approximately the wavelength region of 645 to 900 nm. No significant change in image quality was noted by changing the camera distance between 10 and 25 cm and the light source aperture between 5 and 30 mm. Experiments using polarising filters indicated that the breast is optically isotropic; therefore the results cannot be improved by using polarising filters. In a comparison of various films. Kodak Ektachrome Infrared Film gave the best results. No degradation or variation in image quality was observed when different batches were compared or when the exposed film was stored for 3 weeks before processing. The exposure level is a critical factor and a series of 3 images is needed for optimum evaluation of diaphanograms. The experiments indicate that diaphanography gives consistent results.

Diaphanography in various breast disorders. Clinical and experimental observations

Diaphanograms of various breast disorders were obtained and investigations were made concerning the ways in which changes in skin temperature, fine needle aspiration biopsy and surgery as well as anti-oestrogen treatment affect the findings. A lowering of the skin temperature made it impossible to detect some of the vessels in the breast and more difficult to interpret the diaphanograms. Cooling of the breast should therefore be avoided in diaphanography. Mastitis, haemorrhage after fine needle aspiration biopsy or an induced haemorrhagic cyst will result in the appearance of a shadow on the diaphanogram suggestive of malignancy. The shadow of a haemorrhagic cyst disappeared immediately after the cyst was emptied and diminished gradually in the other cases. Thus the nature of the breast disorder may be determined by diaphanography if it is repeated at short intervals. Fine needle aspiration biopsy may yield false positive findings and should therefore not be made until diaphanography has been performed.