Three-dimensional densitometric reconstruction and visualization of stenosed coronary artery segments.

In this paper we report results from an ongoing study about the diagnostic benefits of three-dimensional (3D) visualization and quantification of stenosed coronary artery segments. Biplane angiographic images do not provide enough information for the exact reconstruction of the coronary arteries. Therefore, a priori information about the 3D shape to be reconstructed must be incorporated into the reconstruction algorithm. One approach is to assume a circular cross-section of the coronary artery. Hence, the diameter is estimated from the contours of the vessel in both projections. Another approach is based on densitometry and searches for a solution of the reconstruction problem close to the previously reconstructed adjacent slice. In this paper we apply contour information as well as the densitometrical profiles of the two orthogonal vessel projections. We present a new probabilistic densitometric reconstruction algorithm, which extends the correct handling of the stochastic properties of the density profiles into the network flow based reconstruction algorithm. The reconstructed coronary segment is visualized in three dimensions. In order to assess the accuracy of the reconstruction, the method is applied to tubes with artificial obstruction of known geometry, modeling coronary artery stenoses. These catheter tubes are filled with normal iodine contrast material. The results of the reconstruction and visualization are discussed with respect to clinical usefulness.

Re-evaluation of a radiation protection cost benefit analysis study in brachytherapy.

Cost benefit analysis has been in use for many years as a method for making a comparison between the costs of radiation protection and the benefits of reduced radiation exposure. It is advocated by the International Commission on Radiological Protection (ICRP) and the National Radiological Protection Board (NRPB) has given more specific advice relating to the value of the man Sv to be used in the calculation of cost benefit. The purpose of this study is to investigate the changes in the NRPB advice over the last 10 years by correcting all figures for inflation and applying them to a particular radiation protection example. The example employed is a previously published case of the introduction of afterloading brachytherapy equipment at the Christie Hospital, Manchester. It has been shown that for this specific example the NRPB advice at one time led to a large cost benefit, at another time it led to a large cost deficit and later still it again gives a large cost benefit. Application of cost benefit analysis to decision making in radiation protection is therefore shown to be in need of further investigation and clarification before it can be used with confidence.