Image Display Techniques
A major advantage of magnetic resonance angiography (MRA) is the ability to acquire a three-dimensional (3D) data set of the vessel tree. Any technique, be it time-of-flight (TOF) or phase contrast, is usually applied in 3D format to obtain a series of sl
- PDF / 1,706,776 Bytes
- 9 Pages / 547.08 x 765.36 pts Page_size
- 36 Downloads / 253 Views
Image Display Techniques JOHAN VAN CLEYNENBREUGEL and GERHARD LAUB
to display. Therefore, this matter is fairly technical. To the radiologist reading the images, differences in dis9.1 Surface-Based and Volume-Based Methods 129 play results obtained by either technique may even be 9.2 Exoscopic Techniques: MIP, Volume Opacity unnoticeable in some cases. Rendering, and Surface-Based Rendering 131 Surface-based methods, such as shaded surface 9.3 Reformatted Techniques 133 display (SSD) or isosurface generation (e.g., based 9.4 Virtual Endoscopy 136 References 136 on "marching cubes:' LORENSEN and KLINE 1987) hinge on thresholding the image volume in order to obtain a binary classification in the vascular object and background. Therefore such techniques are more 9.1 appropriate for image volumes with a relatively high Surface-Based and signal-to-noise ratio. For example, in X-ray based Volume-Based Methods CT angiography, SSD is reported to be the preferred method (KALENDER and PROKOP 2000). In MRA A major advantage of magnetic resonance angiogra- imaging, contrast-enhanced MRA is a typical candiphy (MRA) is the ability to acquire a three-dimen- date for applying surface-based methods. An examsional (3D) data set of the vessel tree. Any technique, ple is shown in Fig. 9.1. Additionally, this figure also be it time-of-flight (TOF) or phase contrast, is usually demonstrates the functionalities to be expected from applied in 3D format to obtain a series of slices or current image reading systems. Indeed, by reprea volume data set which is interpreted as a series senting the 3D MRA volume as a 3D scene (VAN of thin contiguous slices or partitions. One can look CLEYNENBREUGEL et al. 1996), the vascular structhrough such individual slices or calculate multipla- tures are useful to interactively access (re)slices at nar reconstructions from interesting vessel regions. appropriate locations. For example, in a presumably While this approach is straightforward and simple to stenotic region, a reslice perpendicular to the vesuse, it is very difficult for the observer to obtain a sel's centerline can be included in the 3D scene whencorrect spatial perception of the vascular structure. ever needed. In analogy to the term MPR (multiplaDuring the period 1990-2000, methods developed nar reformatting), this reslicing facility is sometimes from image processing and computer graphics called CPR (curved planar reformatting). matured into so-called "visualization techniques". As Contrary to surface-based methods, volume-based a result, interactive real-time 3D reading of an image methods do not require a binary decision with respect volume has become common practice. In particular, to object and background. Volume-based methods spatial perception of vascular structures can be read- produce a 3D scene visualization by shooting rays ily obtained. Visualization techniques are usually from a given viewpoint (the center of a virtual classified as either surface-based or volume-based. camera) through the 3D image volume in order to This distin
Data Loading...
