A novel 3D multi-scale lineness filter for vessel detection.

The branching pattern and geometry of coronary microvessels are of high interest to understand and model the blood flow distribution and the processes of contrast invasion, ischemic changes and repair in the heart in detail. Analysis is performed on high resolution, 3D volumes of the arterial microvasculature of entire goat hearts, which are acquired with an imaging cryomicrotome. Multi-scale vessel detection is an important step required for a detailed quantitative analysis of the coronary microvasculature. Based on visual inspection, the derived lineness filter shows promising results on real data and digital phantoms, on the way towards accurate computerized reconstructions of entire coronary trees. The novel lineness filter exploits the local first and second order multi-scale derivatives in order to give an intensity-independent response to line centers and to suppress unwanted responses to steep edges.

Model-based cartilage thickness measurement in the submillimeter range.

Current methods of image-based thickness measurement in thin sheet structures utilize second derivative zero crossings to locate the layer boundaries. It is generally acknowledged that the nonzero width of the point spread function (PSF) limits the accuracy of this measurement procedure. We propose a model-based method that strongly reduces PSF-induced bias by incorporating the PSF into the thickness estimation method. We estimated the bias in thickness measurements in simulated thin sheet images as obtained from second derivative zero crossings. To gain insight into the range of sheet thickness where our method is expected to yield improved results, sheet thickness was varied between 0.15 and 1.2 mm with an assumed PSF as present in the high-resolution modes of current computed tomography (CT) scanners [full width at half maximum (FWHM) 0.5-0.8 mm]. Our model-based method was evaluated in practice by measuring layer thickness from CT images of a phantom mimicking two parallel cartilage layers in an arthrography procedure. CT arthrography images of cadaver wrists were also evaluated, and thickness estimates were compared to those obtained from high-resolution anatomical sections that served as a reference. The thickness estimates from the simulated images reveal that the method based on second derivative zero crossings shows considerable bias for layers in the submillimeter range. This bias is negligible for sheet thickness larger than 1 mm, where the size of the sheet is more than twice the FWHM of the PSF but can be as large as 0.2 mm for a 0.5 mm sheet. The results of the phantom experiments show that the bias is effectively reduced by our method. The deviations from the true thickness, due to random fluctuations induced by quantum noise in the CT images, are of the order of 3% for a standard wrist imaging protocol. In the wrist the submillimeter thickness estimates from the CT arthrography images correspond within 10% to those estimated from the anatomical sections. We present a method that yields virtually unbiased thickness estimates of cartilage layers in the submillimeter range. The good agreement of thickness estimates from CT images with estimates from anatomical sections is promising for clinical application of the method in cartilage integrity staging of the wrist and the ankle.

Visualisation of intramural coronary vasculature by an imaging cryomicrotome suggests compartmentalisation of myocardial perfusion areas.

A technique is presented for the 3D visualisation of the coronary arterial tree using an imaging cryomicrotome. After the coronary circulation of the excised heart was filled with a fluorescent plastic, the heart was frozen and mounted in the cryomicrotome. The heart was then sliced serially, with a slice thickness of 40 microm, and digital images were taken from each cutting plane of the remaining bulk material using appropriate excitation and emission filters. Using maximum intensity projections over a series of images in the cutting plane and perpendicular plane, the structural organisation of intramural vessels was visualised in the present study. The branching end in the smallest visible vessels, which define tissue areas that are well delineated from each other by 1-2 mm wide bands populated only by vessels less than 40 microm in diameter. The technique presented here allows further quantification in the future of the 3D structure of the coronary arterial tree by image analysis techniques.

Development of an electronic prescription processing option: an aid for general practice.

An interactive computer-supported prescription processing system has been developed as an add-on to existing general practitioner information systems. The aim of the system is to improve the clarity, efficiency and economy of drug treatment choices and prescription writing. It enables the doctor to choose the best treatment from the system's formulary according to the patient's complaint, symptom or diagnosis. The selections are based on complaints and diagnoses from the International classification of primary care (ICPC). A prescription is printed and the potential exists for individualized patient instruction leaflets to be printed. Furthermore, the system may prove useful for retrospective and prospective statistical and epidemiological studies. This implies continuous adaptation, which is also necessary to keep the system updated. As well as an aid in daily general practice, the system is also designed to serve the needs of graduate and postgraduate training programmes.