Three-dimensional (3D) digital subtraction angiography (DSA) is the latest development in the neurovascular imaging armamentarium. 3D-DSA combines the anatomic resolution of DSA with 3D visualization abilities previously offered by only CT or MR angiography. 3D-DSA provides more detailed information than does DSA alone in the evaluation of neurovascular lesions, such as cerebral aneurysms. However, the inability of 3D-DSA to simultaneously image osseous and vascular structures is noted as a weakness of this technique compared with CT angiography. We describe a new 3D digital angiography reconstruction algorithm that allows the concurrent display of the cerebral vasculature and the osseous landmarks.

http://www.ajnr.org/content/ajnr/25/4/571.full.pdf

Three-Dimensional Digital Angiography: New Tool for Simultaneous Three-Dimensional Rendering of Vascular and Osseous Information during Rotational Angiography

Distance measurements of the vascular system of the brain can be derived from biplanar digital subtraction angiography (2p-DSA). The measurements are used for planning of minimal invasive surgical procedures. Our 90 degree-fixed-angle G- ring angiography system has the potential of acquiring pairs of such images with high geometric accuracy. The sizes of vessels and aneurysms are estimated applying a fast and accurate extraction method in order to select an appropriate surgical strategy. Distance computation from 2p-DSA is carried out in three steps. First, the boundary of the structure to be measured is detected based on zero-crossings and closeness to user-specified end points. Subsequently, the 3D location of the center of the structure is computed from the centers of gravity of its two projections. This location is used to reverse the magnification factor caused by the cone-shaped projection of the x-rays. Since exact measurements of possibly very small structures are crucial to the usefulness in surgical planning, we identified mechanical and computational influences on the geometry which may have an impact on the measurement accuracy. A study with phantoms is presented distinguishing between the different effects and enabling the computation of an optimal overall exactness. Comparing this optimum with results of distance measurements on phantoms whose exact size and shape is known, we found, that the measurement error for structures of size of 20 mm was less than 0.05 mm on average and 0.50 mm at maximum. The maximum achievable accuracy of 0.15 mm was in most cases exceeded by less than 0.15 mm. This accuracy surpasses by far the requirements for the above mentioned surgery application. The mechanic accuracy of the fixed-angle biplanar system meets the requirements for computing a 3D reconstruction of the small vessels of the brain. It also indicates, that simple measurements will be possible on systems being less accurate.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

/pdf/accuracy-of-distance-measurements-in-biplane-angiography-4ii3qwb1uk.pdf

Accuracy of distance measurements in biplane angiography

Method of image processing, the method comprises providing a sequence (2) of images (F) which have contrast modulation (100) along said sequence (2); providing a reference frequency (fm, 10) related to said contrast modulations (100) along said sequence (2); and filtering said sequence of images depending on said reference frequency (fm, 10). According to an embodiment, a windowed harmonic filtering is applied to the sequence of input images to extract fundamental in-phase (122) and quadrature (124) components at a heart beat frequency (fm). The resultant time- signal phase is displayed (34) as image sequence.

Filtering of image sequences

A first method for processing of a radiological image to be used as a mask image in subtracted angiography wherein processing for reduction of noise present in the mask image adapted to preserve the aspect of the noise in the mask image. A second method for processing of a sequence of subtracted images (Jn) obtained by subtraction of a mask image from each of the images in a sequence of images (In) acquired during angiography of blood vessels in an area of interest (104) of a patient (200), wherein processing for reduction of noise present in the subtracted images (Jn) adapted to preserve the aspect of vessels (80) in the subtracted images. A radiography apparatus for implementing a method according to one and/or the other of the first and second methods.

Method and apparatus for processing images for subtracted angiography

Application of hybrid systems for the visualization of 3d volume data

Extraction of blood vessel through new temporal filtering in angiographic sequence

Three-dimensional Computed Tomography (CT) with cone-beam geometry will take the place of a conventional CT because 3-D CT is superior to conventional CTs in terms of both data acquisition time and spatial resolution, particularly along the rotation axis. The small bone structures are reconstructed using magnified projections of the region of interest. This paper describes the solution for some problems in practical use. Experimental results show 3-D CT will be feasible.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Three-dimensional reconstruction from cone beam projections

We propose a high-speed surface reconstruction from three-dimensional data through optical–digital hybrid processing. Surface images are currently reconstructed through digital processing, which takes a long time mainly because of the rotation and interpolation of the volume data. In the proposed system, slice images of three-dimensional volume data are optically rotated and interpolated. In principle, one surface image can be obtained in the video rate when we use the same number of sets of optical processors as slices to be processed. Furthermore, this system could lead to a hybrid three-dimensional simulator; most operations such as rotation, cutting, digging holes, and peeling skins are interactively achieved at the video speed. Fundamental experiments are described that confirm the effectiveness of this method.

Satoru Ohishi

Papers

Extraction of blood vessel through new temporal filtering in angiographic sequence

Three-dimensional reconstruction from cone beam projections

High-speed surface display through hybrid processing

Visualization of 3D volume data using an optical model

Reconstruction of blood vessels from an insufficient number of projections obtained from venography