The International Journal of Cardiovascular Imaging 19: 255–256, 2003. Ó 2003 Kluwer Academic Publishers. Printed in the Netherlands.
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Editorial comment
Three- and four-dimensional reconstruction of intra-cardiac anatomy from two-dimensional magnetic resonance images Paul Steendijk, Ph.D. Department of Cardiology, Leiden University Medical Center, E-mail: p.steendijk@lumc.nl In response to the article by M.E. Miquel et al. (Int J Cardiovascular Imaging 19: 239–254) Evaluation of the complex cardiac anatomy based on 2D images requires a mental 3D reconstruction. Although for the experienced observer this method is adequate for clinical decision making in most instances, 3D visualization may provide potentially important advantages. These advantages are probably most obvious in patients with complex congenital heart disease where accurate evaluation of their morphological conditions may be critical for clinical management [1, 2]. In addition, planning of cardiac surgery or catheter-based interventions in these patients may benefit from a better pre-operative 3D understanding of the intra-cardiac anatomy [3–5]. Another example of an intervention in which detailed 3D visualization is likely to be of high clinical value is radio-frequency ablation of atrial arrhythmias. Recent studies indicate that the arrhythmogenic substrate responsible for initiation and perpetuation of idiopathic atrial fibrillation in many cases resides in the pulmonary veins and either focal ablation or electrical isolation of the pulmonary veins by creating circumferential lesions have shown to be an effective therapy [6–8]. However, the anatomy is highly variable between patients and thus accurate pre-operative visualization is likely to limit the procedure time and may increase the success rate [9]. In addition, complications of the radiofrequency catheter ablation technique have been reported, including pulmonary vein stenosis, which warrants long-term follow-up studies to evaluate lumen reduction over time. Non-invasive, 3D imaging would be an ideal modality for this purpose [10]. Currently several 3D imaging modalities are available including 3D echocardiography [11], 3D spiral computed tomography [12], 3D mag-
netic resonance imaging [13] and 3D magnetic resonance angiography [14]. In general, 3D imaging techniques in cardiology are aimed both at visualization and quantitative analysis. Improved and more effective visualization may lead to a more comprehensive insight in the anatomy, and may allow clinicians to obtain more objective and quantitative information. The study by Miquel et al. evaluates the feasibility and usefulness of 3D reconstruction of intracardiac anatomy from 2D MR images for the planning and guiding of trans-catheter closure of atrial septal defects and for radiofrequency catheter ablation of atrial tachyarrhythmias. The MR technique was compared against 3D images acquired by transesophageal echocardiography (TEE) and intra-cardiac echocardiography (ICE). ECG-gated, four-chamber MR images were obtained during breath-holding, and depending on image quality, T1- or T2-weighted spin echo images or gradient echo cine images were used. 3D reconstruction by commercially available software was performed off-line and was completed within 2 hours. The study demonstrates the feasibility of 3D visualization of intra-cardiac anatomy based on 2D MR images by creating insightful displays and suggests the usefulness of the 3D reconstruction in planning interventions in these patients. The quantitative information derived from the 3D MR images correlates reasonably well with 3D ICE and 3D TEE although some discrepancies were noted. The inter-observer variability was clearly more limited in the measurements based on 3D MRI as compared to the other techniques. As a drawback of the 3D MRI technique the authors mention a relatively long acquisition and processing time, but
256 improved segmentation algorithms and already available faster imaging techniques [15–17] are likely to solve this problem. The clinical usefulness as compared to alternative methods is difficult to judge based on the present study and ideally would require prospective randomized studies and objective end-points in terms of, e.g., procedure times, intervention success rate and ultimately clinical outcome. However, the study certainly indicates that 3D and 4D visualization of cardiac anatomy based on 2D MR images is a promising field. References 1. Balestrini L, Fleishman C, Lanzoni L, et al. Real-time 3dimensional echocardiography evaluation of congenital heart disease. J Am Soc Echocardiogr 2000; 13: 171–176. 2. Kawano T, Ishii M, Takagi J, et al. Three-dimensional helical computed tomographic angiography in neonates and infants with complex congenital heart disease. Am Heart J 2000; 139: 654–660. 3. Geva T, Greil GF, Marshall AC, Landzberg M, Powell AJ. Gadolinium-enhanced 3-dimensional magnetic resonance angiography of pulmonary blood supply in patients with complex pulmonary stenosis or atresia: comparison with Xray angiography. Circulation 2002; 106: 473–478. 4. Taguchi S, Niibori T, Moro K. Use of three-dimensional computed tomography images in deciding the approach for ministernotomy operations. Ann Thorac Surg 2000; 70: 1090–1093. 5. Tantengco MV, Bates JR, Ryan T, Caldwell R, Darragh R, Ensing GJ. Dynamic three-dimensional echocardiographic reconstruction of congenital cardiac septation defects. Pediatr Cardiol 1997; 18: 184–190. 6. Jais P, Weerasooriya R, Shah DC, et al. Ablation therapy for atrial fibrillation (AF): past, present and future. Cardiovasc Res 2002; 54: 337–346.
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