Philips Journal of Research最新文献

For the enhancement of digital subtraction angiography (DSA) images, registration of mask and contrast image prior to subtraction is a pre-requisite. One of the main requirements of this task is that the region-of-interest used for the calculation of the registration parameters should contain the vascular structures of interest. This, however, is also one of the main problems in DSA because the contrasted vascular structures can be regarded as a distortion that makes the images to be compared dissimilar. In this paper we present a comparison between three frequently used similarity measures and histogram-based similarity measures. This reveals the advantages of the latter. The data-driven approach is especially suitable for registration of two images which are identical except for some structures visible in one but not in the other image. Based on an energy similarity measure, a motion vector field is obtained by template matching, which gives a set of homologous landmarks or control points in the mask and contrast image. A point-based registration is performed fitting the parameter of an appropriate transformation for patient motion correction. An affine and an elastic transformation are compared for an abdominal fluoroscopic scene.

The diagnostic value of medical images significantly depends on the signal-to-noise ratio (SNR). Especially in fluoroscopic tomography, the SNR is limited by the radiation dose (Computer Tomography), or by the suitable acquisition techniques (Magnetic Resonance Imaging). The purpose of this paper is to introduce a projection-based method for the motion-compensated SNR enhancement applied in Radon space. It is based on a projection-based motion estimation with subsequent motion-compensated, edge-preserving filtering of the measured projections. The effect of temporal filtering as well as spatial filtering will be presented. In contrast to the recently introduced image-based approach, this method allows a very efficient computational implementation, likely to be used in real time imaging. It will be shown that a significant increase of the SNR can be achieved without introducing additional motion artifacts or blurring in the reconstructed images. The proposed technique has the potential to be used for SNR enhancement in low-dose fluoroscopy applications in CT as well as for SNR improvements in MR fluoroscopy using projection reconstruction based techniques.

This paper describes the outline of a method for simulating the electromagnetic behaviour of ICs fabricated in the RF passive integration process. The theory is an extension of that used in the CAD package Fasterix. This is modified to take account of the losses and other aspects of the IC process. The new theory is then applied to the design of a power amplifier for a mobile phone handset, and the results presented demonstrate its accuracy, speed and flexibility. Further results demonstrate that use of this powerful new model can lead to improved electrical performance of real RF applications.

An improved version of motion-adapted gating useful in MR imaging is presented. Compared to other gating approaches, this advances method shows an improved ability to suppress motion artefacts at a reduced scan time. It is based on a k-space dependent weighting function and a real-time system feedback. During MR data acquisition patient motion is monitored and only those profiles are accepted whose respiratory motion induced displacements are below a pre-defined threshfold (gating) function. The displacements are measured relative to a reference position, which is automatically determined during the initial phase of the MR scan. While MR data are acquired, the object motion is statistically analysed in parallel by calculating the histogram of the displacement distribution for consecutive time intervals. This information can be used to interfere with the measurement process in the case that motion statistics changes during the scan. Initial in-vivo results are presented and compared to conventional techniques.

The first thin film heads produced commercially by Philips were of the socalled sensor-first type, the sensor being processed on the substrate and the remaining parts of the head being processed on top of the sensor. This design has various drawbacks in comparison with a design where the sensor is processed at the end (sensor-last), such as a higher power consumption (low head efficiency) and limitations of use of high-temperature processes/materials. However, initially, topographic structures, step coverage and problems with wet chemical etching were obstacles in realizing the sensor-last design. The introduction of planarization in wafer processing technology opened the way to the sensor-last design. The design was introduced in heads for the DIGAMAX^TM system and showed all the expected advantages in comparison with the sensor-first design. It also offers the possibility of applying new materials in the head, an option which is necessary for realizing new generations of recording systems.

Applications of the passive integration technology are described. A broad range of specific application examples are chosen with the aim of illustrating the possibilities for functional integration within this technology. The discussion is technical rather than commercial, to underline the advantages as well as the limitations of a passive integration approach. This paper is directly complementary to those on the technology of passive integration and on electromagnetic simulations of passive IC's in this edition.

Polymer light-emitting diodes have become feasible when suitable materials were available. The various relevant properties are interrelated parameters. The solubility can be improved in various ways but here the introduction of side-chains has been found most successful. Colour tuning is achieved by attaching electron withdrawing or donating side-chains. Some polymer defects in PPV are shown. Special functionalities can be built-in. As an example a self-doped PPV is given.

The technology of magnetoresistive element (MRE) fabrication and integration as well as some experimental results on the performance of anisotropic and giant magnetoresistive elements are discussed. Most emphasis is put on isolated MREs in specially designed test structures, although results on completed heads will also be discussed. Aspects such as output signal level, noise level, distortion and magnetic stability are the performance indicators considered.

The sensitivity of magnetoresistive read heads can be increased by using layered magnetic materials showing the giant magnetoresistance effect, instead of a single magnetic film showing the anisotropic magnetoresistance effect. For this purpose, exchange-biased spin-valve layered structures are very suitable. For well-chosen compositions and nanometer-scale layer thicknesses these materials combine a fair giant magnetoresistance effect with a very small field interval in which the resistance change takes place. In this paper we give an overview of aspects which determine the functioning of materials of this class in read heads, including their preparation, magnetotransport properties and the magnetic interactions which determine the magnetization reversal process.