Babak Movassaghi

A quantitative analysis of 3-D coronary modeling from two or more projection images

A method is introduced to examine the geometrical accuracy of the three-dimensional (3-D) representation of coronary arteries from multiple (two and more) calibrated two-dimensional (2-D) angiographic projections. When involving more then two projections, (multiprojection modeling) a novel procedure is presented that consists of fully automated centerline and width determination in all available projections based on the information provided by the semi-automated centerline detection in two initial calibrated projections. The accuracy of the 3-D coronary modeling approach is determined by a quantitative examination of the 3-D centerline point position and the 3-D cross sectional area of the reconstructed objects. The measurements are based on the analysis of calibrated phantom and calibrated coronary 2-D projection data. From this analysis a confidence region (/spl alpha//spl deg//spl ap/[35/spl deg/-145/spl deg/]) for the angular distance of two initial projection images is determined for which the modeling procedure is sufficiently accurate for the applied system. Within this angular border range the centerline position error is less then 0.8 mm, in terms of the Euclidean distance to a predefined ground truth. When involving more projections using our new procedure, experiments show that when the initial pair of projection images has an angular distance in the range /spl alpha//spl deg//spl ap/[35/spl deg/-145/spl deg/], the centerlines in all other projections (/spl gamma/=0/spl deg/-180/spl deg/) were indicated very precisely without any additional centering procedure. When involving additional projection images in the modeling procedure a more realistic shape of the structure can be provided. In case of the concave segment, however, the involvement of multiple projections does not necessarily provide a more realistic shape of the reconstructed structure.

Initial clinical experience of selective coronary angiography using one prolonged injection and a 180° rotational trajectory

Evaluate the safety of prolonged coronary injections during a rotational acquisition covering 180°.

Rotational vs. standard coronary angiography: An image content analysis

Objective: To evaluate the clinical utility of images acquired from rotational coronary angiographic (RA) acquisitions compared to standard “fixed” coronary angiography (SA). Background: RA is a novel angiographic modality that has been enabled by new gantry systems that allow calibrated automatic angiographic rotations and has been shown to reduce radiation and contrast exposure compared to SA. RA provides a dynamic multiple‐angle perspective of the coronaries during a single contrast injection. Methods: The screening adequacy, lesion assessment, and a quantitative coronary analysis (QCA) of both SA and RA were compared by independent blinded review in 100 patients with coronary artery disease (CAD). Results: SA and RA recognize a similar total number of lesions (P = 0.61). The qualitative assessment of lesion characteristics and severity between modalities was comparable and lead to similar clinical decisions. Visualization of several vessel segments (diagonal, distal RCA, postero‐lateral branches and posterior‐descending) was superior with RA when compared to SA (P < 0.05). A QCA comparison (MLD, MLA, LL, % DS) revealed no difference between SA and RA. The volume of contrast (23.5 ± 3.1 mL vs. 39.4 ± 4.1; P = 0.0001), total radiation exposure (27.1 ± 4 vs. 32.1 ± 3.8 Gycm2; P = 0.002) and image acquisition time (54.3 ± 36.8 vs. 77.67 ± 49.64 sec; P = 0.003) all favored RA. Conclusion: Coronary lesion assessment, coronary screening adequacy, and QCA evaluations are comparable in SA and RA acquisition modalities in the diagnosis of CAD however RA decreases contrast volume, image acquisition time, and radiation exposure.

3D reconstruction of coronary stents in vivo based on motion compensated x-ray angiograms

A new method is introduce for the three-dimensional (3D) reconstruction of the coronary stents in-vivo utilizing two-dimensional projection images acquired during rotational angiography (RA). The method is based on the application of motion compensated techniques to the acquired angiograms resulting in a temporal snapshot of the stent within the cardiac cycle. For the first time results of 3D reconstructed coronary stents in vivo, with high spatial resolution are presented. The proposed method allows for a comprehensive and unique quantitative 3D assessment of stent expansion that rivals current x-ray and intravascular ultrasound techniques.

3D coronary reconstruction from calibrated motion-compensated 2D projections based on semi-automated feature point detection

3D rotational coronary angiography (3DRCA) is one of the application areas of 3D rotational X-Ray imaging. In this application a sequence of projection images is acquired when the C-arm is rotated around the patient. Since the heart is a moving object, only projections can be used which correspond to the same phase of the cardiac cycle. This significantly limits the number of projections available for reconstruction causing streaking artefacts in the reconstructed image due to angular undersampling. The involvement of additional projections in the reconstruction procedure from different viewing angles would increase the quality of the volume data. Each successive acquired projection is slightly different compared with the previous one due to two reasons: First, there is a motion to the deformation of the heart, second there is an induced deformation owing to the change in the projection angle. The purpose of this work is to determine the motion owing to the heart deformation, so as to compensate for this motion in projection images in a different heart phase. Hereto we propose to use concepts from coronary modeling in combination of conventional reconstruction procedures. The proposed method facilitates the use of additional projections in the reconstruction. Motion-compensated reconstructed volume data are presented for coronary arteries in an animal (pig) model.

4D coronary artery reconstruction based on retrospectively gated rotational angiography: first in-human results

A method is proposed that allows for a fully automated computation of a series of high-resolution volumetric reconstructions of a patients coronary arteries based on a single rotational acquisition. During the 7.2 second acquisition the coronary arteries are injected with contrast material while the imaging system rotates around the patient to obtain a series of X-ray projection images over an angular range of 180 degrees. Based on the simultaneously recorded ECG-signal the projection images corresponding to the same cardiac cycle can be utilized to reconstruct three-dimensional (3D) high-spatial-resolution angiograms of the coronary arteries in multiple (3D+t) cardiac phases within the cardiac cycle. The proposed acquisition protocol has been applied to 22 patients and the tomograpic reconstructions depicted the main arteries as well as the main bifurcations in multiple cardiac phases in all enrolled patients. For the first time, this feasibility study shows that a three-dimensional description of the coronary arteries can be obtained intraprocedurally in a conventional interventional suite by means of tomographic reconstruction from projection images without any user interaction.

3D vessel axis extraction using 2D calibrated x-ray projections for coronary modeling

A new approach for 3D vessel centreline extraction using multiple, ECG-gated, calibrated X-ray angiographic projections of the coronary arteries is described. The proposed method performs direct extraction of 3D vessel centrelines, without the requirement to either first compute prior 2D centreline estimates, or perform a complete volume reconstruction. A front propagation-based algorithm, initialised with one or more 3D seed points, is used to explore a volume of interest centred on the projection geometrys isocentre. The expansion of a 3D region is controlled by forward projecting boundary points into all projection images to compute vessel response measurements, which are combined into a 3D propagation speed so that the front expands rapidly when all projection images yield high vessel responses. Vessel centrelines are obtained by reconstructing the paths of fastest propagation. Based on these axes, a volume model of the coronaries can be constructed by forward projecting axis points into the 2D images where the borders are detected. The accuracy of the method was demonstrated via a comparison of automatically extracted centrelines with 3D centrelines derived from manually segmented projection data.

Three-dimensional reconstruction of coronary stents in vivo based on motion compensated x-ray angiography

The complete expansion of the stent during a percutaneous transluminal coronary angioplasty (PTCA) procedure is essential for treatment of a stenotic segment of a coronary artery. Inadequate expansion of the stent is a major predisposing factor to in-stent restenosis and acute thrombosis. Stents are positioned and deployed by fluoroscopic guidance. Although the current generation of stents are made of materials with some degree of radio-opacity to detect their location after deployment, proper stent expansion is hard to asses. In this work, we introduce a new method for the three-dimensional (3D) reconstruction of the coronary stents in-vivo utilizing two-dimensional projection images acquired during rotational angiography (RA). The acquisition protocol consist of a propeller rotation of the X-ray C-arm system of 180°, which ensures sufficient angular coverage for volume reconstruction. The angiographic projections were acquired at 30 frames per second resulting in 180 projections during a 7 second rotational run. The motion of the stent is estimated from the automatically tracked 2D coordinates of the markers on the balloon catheter. This information is used within a motion-compensated reconstruction algorithm. Therefore, projections from different cardiac phases and motion states can be used, resulting in improved signal-to-noise ratio of the stent. Results of 3D reconstructed coronary stents in vivo, with high spatial resolution are presented. The proposed method allows for a comprehensive and unique quantitative 3D assessment of stent expansion that rivals current X-ray and intravascular ultrasound techniques.

3D coronary reconstruction from calibrated motion-compensated 2D projections

Abstract One of the application areas of three-dimensional rotational X-ray imaging (3D-RX) techniques is focused on the 3D visualization of coronary vessel structures (3D rotational coronary angiography, 3DRCA). Since the heart is a moving object, only projections can be used, which correspond to the same acquisition time (e.g. end diastole) in the cardiac cycle. This significantly limits the number of projections available for reconstruction causing streaking artefacts in the reconstructed image due to the angular undersampling. The involvement of additional projections in the reconstruction procedure from different viewing angles would increase the quality of the volume data. However, each successive acquired projection is slightly different compared with the previous one due to two reasons: First, a nonlinear movement owing to the heart beat and, second, a linear movement owing to a different viewing angle. In order to use additional projections, the movement due to the different heart phase has to be transformed in the desired prior heart phase and the transformation (motion compensation) must take into account the geometrical rotation of the gantry. Therefore, considering two successive acquired projections and calculating the transformation matrix that transforms one projection into another must include both components. The purpose of this work is to determine and to separate the two mentioned movements and to involve additional projections (acquired at different acquisition geometry and in different motion state) in the reconstruction procedure. Motion-compensated reconstructed volume data will be presented for coronary arteries in an animal (pig) model.

Automatic gaiting window positioning for 3D rotational coronary angiography (3DRCA)

Three-dimensional rotational coronary angiography (3DRCA) is a new technique for imaging coronary vessels in the human body. Due to the residual cardiac motion, projections being in the same cardiac motion state are extracted from the acquired series using electrocardiogram (ECG) information. A gating window is determined at a pre-defined trigger delay relative to the R-peaks with a constant width. In order to achieve the best possible image quality, cardiac phases must be found during which the heart is nearly stationary. However, the (ECG) signal represents the electrical activity of the heart and corresponds to the heart movement only approximately. Currently, the optimum gating window positioning is based on values derived by experience. It is difficult to determine where the heart is most stable in the cycle due to a high patient variability. Furthermore, the optimal gating window position is depending on the coronary vessel segment. The purpose of this work is to introduce a simple and efficient image based technique, which is able to determine the optimal gating window position fully automatically. The measurements in this paper are based on the analysis of two-dimensional X-ray projection data of the coronary arteries in an animal (pig) model.