Martin B. van der Mark

Estimation of lipid and water concentrations in scattering media with diffuse optical spectroscopy from 900 to 1600 nm

We demonstrate a method to estimate the concentrations of water and lipid in scattering media such as biological tissues with diffuse optical spectra acquired over the range of 900 to 1600 nm. Estimations were performed by fitting the spectra to a model of light propagation in scattering media derived from diffusion theory. To validate the method, spectra were acquired from tissue phantoms consisting of lipid and water emulsions and swine tissues ex vivo with a two-fiber probe.

Development of an air gap servo system for high data transfer rate near field optical recording

This paper describes development of a bi-axial actuator-based air gap servo system for a near field optical recording system using a blue laser and a solid immersion lens (SIL). We first present a new pull-in procedure ensuring smooth air gap servo start-up without lens-disc collision. Furthermore, a memory-loop control technique has been employed to realize a high-speed air gap servo system guaranteeing a high data transfer rate.

Near-field read-out of a 50-GB first-surface disc with NA=1.9 and a proposal for a cover-layer-incident, dual-layer near-field system

We present read-out results of a 50 GB disk with a blue laser and a NA=1.9 Solid Immersion Lens in a conventional focus and tracking actuator. Furthermore, we show a light path and a disk design that enable cover-layer incident near field recording on dual-layer disks with a capacity of 300 GB on a double-sided disk.

First results from the Philips optical mammoscope

The Philips Optical Mammoscope Prototype is a versatile CW optical mammography apparatus with which fully 3D images of breast tissue can be obtained at several wavelengths. We present the properties of the machine, and show the first images obtained with it. We elaborate on the tissue parameter that can be quantitatively reconstructed from the measurements, and show some preliminary research into the natural variation of this parameter.

Diffuse Optical Tomography of the Breast: Initial Validation in Benign Cysts

PurposeThe purpose of this study was to validate a newly developed diffuse optical tomography (DOT) system on benign cysts in the breast.ProceduresEight patients with 20 benign cysts were included. Study procedures consisted of optical breast imaging and breast magnetic resonance imaging (MRI) for comparison. A reconstruction algorithm computed three-dimensional images for each of the four near-infrared wavelengths used by our DOT system (Philips Healthcare, Best, The Netherlands). These images were combined using a spectroscopic model to assess tissue composition and lesion size.ResultsTwenty cysts were analyzed in eight patients. By using the spectroscopic information, 13 of 20 cysts (65%) were visualized with DOT, confirming their high water and low total hemoglobin content. Lesion size and location showed good agreement with MRI; Pearson correlation coefficient was 0.7 (p < 0.01).ConclusionsDOT can visualize benign cysts in the breast and elucidate their high water and low total hemoglobin content by spectroscopic analysis.

Near Field Recording on First-Surface Write-Once Media with a NA=1.9 Solid Immersion Lens

We present a single-wavelength near field recording set-up with a blue laser and a NA=1.9 solid immersion lens in a conventional focus and tracking actuator. The most important aspects to realize such a near field recording system are discussed, in particular, gap error signal normalization and correction of chromatic aberration of the objective lens. First recording results demonstrate that the set-up is fully operational.

Multiple scattering of light from polymer dispersed liquid crystal material

Light scattering from polymer dispersed liquid crystal (PDLC) material has been studied experimentally and by Monte Carlo simulation. Light scattering was measured as a function of both scattering angle and cell thickness. The cell thicknesses of practical interest are in an intermediate regime where neither single scattering nor light diffusion applies. Both the angular and the thickness dependence of the scattering intensity can be described accurately by a Monte Carlo simulation of multiple scattering from a homogeneous distribution of independent scatterers. The model smoothly interpolates between the single scattering limit for thin cells and the diffusion limit for thick cells. It can easily be extended to include any specific feature of a scattering display system.

Optical mammography combined with fluorescence imaging: lesion detection using scatterplots

Using scatterplots of 2 or 3 parameters, diffuse optical tomography and fluorescence imaging are combined to improve detectability of breast lesions. Small or low contrast phantom-lesions that were missed in the optical and fluorescence images were detected in the scatterplots. In patient measurements, all tumors were visible and easily differentiated from artifacts and areolas in the scatterplots. The different rate of intake and wash out of the fluorescent contrast agent in the healthy versus malignant tissues was also observed in the scatterplot: this information can be used to discriminate malignant lesion from normal structures.

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.

Optical image reconstruction with deconvolution in light diffusing media

We describe a simple reconstruction method for diffuse optical imaging based on modified back-projection approach for medical tomography. These modifications are based primarily on the deconvolution of the broadened image by a point spread function which is dependent on the scattering of light in tissue. The nonlinearities in the image formation are handled empirically by coordinate transformations. Although our method is an approximate image reconstruction technique, it may provide a basis for rapid, real time medical monitoring by using optical projections. We have applied this method to experimental projections taken by parallel and fan beam tomography geometries on biomedical phantoms with multiple objects. The results presented in this report indicate considerable improvement in image resolution.