Michiel van Beek

Linear image reconstruction for a diffuse optical mammography system in a noncompressed geometry using scattering fluid

Diffuse optical tomography (DOT) is a potential new imaging modality to detect or monitor breast lesions. Recently, Philips developed a new DOT system capable of transmission and fluorescence imaging, where the investigated breast is hanging freely into the measurement cup containing scattering fluid. We present a fast and robust image reconstruction algorithm that is used for the transmission measurements. The algorithm is based on the Rytov approximation. We show that this algorithm can be used over a wide range of tissue optical properties if the reconstruction is adapted to each patient. We use estimates of the breast shape and average tissue optical properties to initialize the reconstruction, which improves the image quality significantly. We demonstrate the capability of the measurement system and reconstruction to image breast lesions by clinical examples.

Radiation-induced carbon contamination of optics

In this work molecular contamination of optical components such as e.g. reflective mirrors for extreme ultraviolet (EUV) lithography was experimentally studied using irradiation with keV electrons. Since secondary electrons are known to initiate most of the surface chemistry, radiation with EUV photons or electrons often gives similar results. Due to presence of hydrocarbon molecules in a vacuum system, carbon growth will occur at each irradiated surface. The carbon growth rate for various molecules was measured by in-situ Auger electron spectroscopy and Rutherford backscattering spectroscopy (RBS) analyzing the influence of the two main parameters being radiation dose and partial pressure of hydrocarbons. The latter was varied over a large range from 10-5 until 10-11 mbar. Furthermore the structure of the resulting carbon films was analyzed by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy indicating the formation of a nanocrystalline graphite-like structure independent of the original hydrocarbon molecule.

Optical Fluorescence Imaging of Breast Cancer

We report on the first results obtained with the Philips diffuse optical tomography system and Schering AGs Omocianine fluorescent dye.

Automated 3D whole-breast ultrasound imaging: results of a clinical pilot study

We present the first clinical results of a novel fully automated 3D breast ultrasound system. This system was designed to match a Philips diffuse optical mammography system to enable straightforward coregistration of optical and ultrasound images. During a measurement, three 3D transducers scan the breast at 4 different views. The resulting 12 datasets are registered together into a single volume using spatial compounding. In a pilot study, benign and malignant masses could be identified in the 3D images, however lesion visibility is less compared to conventional breast ultrasound. Clear breast shape visualization suggests that ultrasound could support the reconstruction and interpretation of diffuse optical tomography images.

Image reconstruction and evaluation of system performance for optical fluorescence tomography

Diffuse optical tomography is a non-invasive method aiming at the detection of breast cancer. The sensitivity and specificity of the method can be increased if a fluorescent contrast agent is used that accumulates in malignant lesions. Recently, Philips developed an optical scanner, where the patient is lying on a bed, with one breast hanging freely in a cup containing an optical matching fluid. 507 optical fibers are mounted in the surface of the measurement cup. The breast is illuminated sequentially by half of these fibers while the other half is used to collect the light that is emanating from the breast. The system uses near-infrared light of continuous wave solid-state lasers to illuminate the breast at four different wavelengths. A complete measurement takes less than ten minutes and involves five breast scans: transmission data are collected for four wavelengths, and fluorescence data for excitation at one wavelength. Here, we present the image reconstruction scheme and a novel method to assess the system performance in terms of lesion detectability. This method uses a statistical significance test on simulated data with and without a lesion. It allows the quantification of the detectability of lesions for different size, position, or contrast of the lesion. It also allows to analyze the potential impact of system improvements or to judge the performance of an image reconstruction algorithm.

Non-Invasive Blood Analysis Using Raman Spectroscopy

We have developed a non-invasive blood analysis method based on combined imaging and confocal Raman spectroscopy. With this technology, in-vivo Raman spectra can be obtained that resemble in-vitro spectra with respect to shape and intensity.