<title>Accuracy of distance measurements in biplane angiography</title>

Abstract

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°-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 3-d location of the centre of the structure is computed from the centres 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 (the maximum size for structures to be measured) 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 3-d reconstruction of the small vessels of the brain. It also indicates, that simple measurements will be possible on systems being less accurate.

From 2D to 4D in quantitative left ventricle wall motion analysis of biplanar X-ray angiograms

“…Accuracy of X-ray image acquisition is affected by pincushion distortion and spiral distortion [4]. Thus, distortion correction is performed prior to segmentation and reconstruction, based on an approach using control points obtained from a reference image.…”

Non-traumatic neurological emergencies: emergency neuroradiological interventions

“…Using 3D and/or high-resolution rapid sequences, the location of the acute aneurysm, its size, the anatomic location and the relation to the parent vessel have to be visualized, as well as the presence of an anatomical neck, additional aneurysms and the presence and severity of associated vasospasm. Exact measurements of the neck, body and dome of the aneurysm are performed before the intervention [15]. Depending on these measurements as well as on the clinical situation, the neurosurgical/neuroradiological interdisciplinary decision between early or late operation and endovascular treatment is made in the neuroangiographic suite [16].…”

Geometry of coplanar stereoscopic radiographic pairs for analysis of the lateral cervical radiograph: a study using mathematical models

“…The goal of this method, as is the case in medicine, dentistry, and other disciplines, is to display the true anatomical structures and their positions relative to the actual positions of other structures observed in the radiograph. [15][16][17][18] From a historical perspective, in 1838, the theory of stereoscopic vision was first introduced by an English physicist, Sir Charles Wheatstone, 19 paving the way for many other stereoscopic advances down through the years. The use of stereoscopic radiographic analysis in chiropractic is hallmarked by the work of Remier 20 (1938) at Palmer College of Chiropractic and in the 1960s by Dr WG Blair.…”