assessing the heart. However, 2D tomographic imaging with 1 or 2 image planes, as is current practice, is not opti- mal for accurate determinations of LV volume and EF because it requires the ventricle to conform to a particular geometry with uniform function for quantitative estimates that must be made with standardized views. 4 If heart shape or function deviates from the assumed model, or the required views are not obtainable, 5 the accuracy of 2DE can be dramatically reduced. In contrast, recent efforts in developing 3-dimensional echocardiography (3DE) have demonstrated that 3DE can provide superior accuracy to 2DE and perform comparably with radionu- clide or magnetic resonance imaging (MRI) for measure- ments of ventricular volume and function. 6-8 Previously described 3DE systems have not been rou- tinely adopted in clinical or research medicine for several reasons. They may be cumbersome and impractical in clinical settings, have long data acquisition and analysis times, and not allow the sonographer freedom to select acoustic imaging windows where image quality is optimal. Left ventricular (LV) volume and ejection fraction (EF) are important predictors of cardiac morbidity and mortal- ity. 1-3 Transthoracic 2-dimensional echocardiography (2DE) is the most widely used noninvasive method for From the a Cardiovascular Division, Charles A. Dana Research Institute and the Har- vard-Thorndike Laboratory of Medicine, Boston; b Department of Radiology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston; and c The Hewlett Packard Company, Andover. Supported in part by National Institutes of Health grant MO1-RR01032 to the Gen- eral Clinical Research Center of the Beth Israel Deaconess Medical Center. Drs Hib- berd, Chuang, and Douglas were supported in part by a research grant from the Hewlett Packard Company. Dr Manning was supported in part by an American Heart Association Established Investigator Grant (AHA 9740003N, Dallas, Tex). MRI facilities were supported in part by Philips Medical Systems and by an equip- ment grant from the Hewlett Packard Company. Submitted June 7, 1999; accepted May 4, 2000. Reprint requests: Pamela S. Douglas, MD, Cardiovascular Division, H6/352 Clini- cal Science Center, 600 Highland Ave, Madison, WI 53792-3248. E-mail: psd@medicine.wisc.edu Copyright © 2000 by Mosby, Inc. 0002-8703/2000/$12.00 + 0 4/1/108513 doi:10.1067/mhj.2000.108513 Accuracy of three-dimensional echocardiography with unrestricted selection of imaging planes for measurement of left ventricular volumes and ejection fraction Mark G. Hibberd, MD, PhD, a Michael L. Chuang, MS, a Raymond A. Beaudin, MS, c Marilyn F. Riley, BS, a Matthew G. Mooney, MS, c James T. Fearnside, MSEE, c Warren J. Manning, MD, a,b and Pamela S. Douglas, MD a Boston and Andover, Mass Background Accurate, reproducible, noninvasive determination of left ventricular (LV) volumes and ejection f (EF) is important for clinical assessment, risk stratification, selection of therapy, and serial monitoring of patient vascular disease. Three-dimensional echocardiography (3DE) approaches have demonstrated significantly great than current clinical 2DE, but the clinical utility of 3DE has been limited because of the need for substantial mod scanning technique (eg, all image acquisition from a single acoustic window) or cumbersome additional hardwar describe a novel 3DE system without these limitations and its application to patients. Methods and Results Twenty-five patients were examined by 3DE, 2DE, and magnetic resonance imaging (MRI). The 3DE system used a magnetic scanhead tracking device, and volumes were computed with a novel de shell model. End-diastolic volumes and EF by MRI ranged from 96 to 375 mL and 18% to 73%, respectively. Ther excellent correlation, without statistically significant differences, between MRI and 3DE for end-systolic volume ( 2 = 0.99) and end-diastolic volume (EDV) (r 2 = 0.98), ventricular stroke volume (SV) (r 2 = 0.93), and EF (r 2 = 0.97), with stan- dard error estimates less than 10 mL for volumes and 3% for EF. Conventional 2DE consistently underestimated (EDV, P < .01; ESV, P < .01; SV, P < .05); correlations with MRI were r 2 = 0.91 for ESV, r 2 = 0.88 for EDV, r 2 = 0.62 for SV, and r 2 = 0.72 for EF. Standard error estimates ranged from 16 to 20 mL for ventricular volumes and 9% for EF server variability was reduced 3-fold with use of 3DE. Conclusions The novel 3DE system allows unrestricted selection and combination of acoustic windows in a sing tion, improves accuracy of estimates of LV volumes and EF 3-fold compared with 2DE, and is practical for routin ment of LV size and function in patients with a wide range of cardiac pathology. (Am Heart J 2000;140:469-75.)