Horst Siebold

Spatial second-derivative image processing: an application to optical mammography to enhance the detection of breast tumors

We present an image-processing method that enhances the detection of regions of higher absorbance in optical mammograms. At the heart of this method lies a second-derivative operator that is commonly employed in edge-detection algorithms. The resulting images possess a high contrast, an automatic display scale, and a greater sensitivity to smaller departures from the local background absorbance. Moreover, the images are free of artifacts near the breast edge. This second-derivative method enhances the display of structural information in optical mammograms and may be used to robustly select areas of interest to be further analyzed spectrally to determine the oxygenation level of breast lesions.

Near-infrared imaging of the human breast: complementing hemoglobin concentration maps with oxygenation images

We have previously reported a comparison between edge-corrected near-infrared optical mammograms and those that have undergone a further image-processing step based on a spatial second derivative. In this work, we go a step further by combining the second-derivative images from four wavelengths (690, 750, 788, and 856 nm) to obtain oxygenation-index images. While the spatial second derivative improves contrast and allows for visibility of fine structures in the images, thereby improving the sensitivity to tumor detection, additional information is needed to avoid false-positive results. The oxygenation-index images are introduced to address this issue. Oxygenation information may help discriminate benign from malignant breast lesions, thereby effectively complementing single-wavelength optical mammograms that display optically dense regions within the breast with high sensitivity.

Using Near-Infrared Light to Detect Breast Cancer

Frequency-domain optical mammography is a safe and painless technique that may one day become a valuable tool for the detection and diagnosis of breast cancer.

Apparatus for adjustably mounting coils of a magnet system for nuclear spin tomography

An adjusting and holding assembly for magnet coils in a nuclear spin tomography system includes mechanical adjusting devices connected to a frame structure for the mutual alignment of the connected to a frame structure for the mutual alignment of the base field magnet coils. In order to enable a relatively simple adjustment of the individual magnet coils to produce a highly homogeneous base field, at least one of the magnet coils is rigidly connected to the frame structure, while each adjustable or positionable magnet coil is held at three points via at least one support device and three adjusting devices within the frame structure. Each support device comprises a support element in the form of a spherical sector rotatably mounted to a respective coil and slidably resting on a horizontal support surface of the frame structure. The support points of the adjustable magnet coils are longitudinally spaced from the center of gravity line of the respective magnet coil so that an additional tilting force is brought about.

Clinical applications of frequency-domain optical mammography

We present clinical results obtained with a frequency-domain (70 MHz), four-wavelength (690, 750, 788, 856 nm) prototype for optical mammography. The 2D projection images are taken on the slightly compressed breast in craniocaudal and oblique projections, similar to what is done in x-ray mammography. The amplitude and phase images are combined to enhance the contrast and the tumor detectability by reducing the edge effects caused by the breast thickness variations within the scanned area. The analysis of the first set of clinical data (63 patients) has yielded encouraging results. The success rate in the detection of breast cancer was 73%, and specificity was 49%. A comparison of the optical mammograms at the four wavelengths in the range 690 - 856 nm suggests that spectral information may allow for the discrimination of benign and malignant breast lesions, thereby enhancing specificity.

Optical mammography with single-wavelength contrast enhancement and multiwavelength oxygenation assessment

We present a combination of (1) single-wavelength optical mammograms representing either the optical absorbance (N-images) or its spatial second-derivative (N’’-images), and (2) oxygenation-index images based on optical data at four wavelengths (690, 750, 788, and 856 nm). The enhanced contrast of the second-derivative images with respect to the absorbance images is complemented by the functional information provided by the oxygenation-index images. In a number of clinical cases, we have found that breast cancer is often associated with relatively low oxygenation indices, while benign breast lesions correspond to areas with relatively high oxygenation indices. However, the relative nature of the oxygenation-index presented in this work does not allow for a comparison of oxygenation values in different images, for which absolute oxygenation measurements would be needed.