Quantitative three-dimensional reconstruction of left ventricular volume with complete borders detected by acoustic quantification underestimates volume Leng Jiang, MD, Richard Morrissey, MD, Mark D. Handschumacher, BS, Jose Antonio Vazquez de Prada, MD, Jun He, BS, Michael H. Picard, MD, Arthur E. Weyman, MD, and Robert A. Levine, MD Boston, Mass. Recently a new acoustic-quantification (AQ) technique has been developed to provide on-line automated border detec- tion with an integrated backscatter analysis. Prior studies have largely correlated AQ areas with volumes without direct comparison of volumes for agreement. By using complete AQ-detected borders as the input to a validated method for three-dimensional echocardiographic (3DE) re- construction, we can compare a n entire cavity volume mea- sured with the aid of AQ against a directly measured volume. This would also explore the possibility of applying AQ to 3DE reconstruction to reduce tracing time and enhance routine applicability. To compare reconstructed volumes with actual values in a stable standard allowing direct volume measure- ment, the left ventricles of 13 excised animal hearts were studied with a 3DE system that automatically combines two-dimensional (2D) images and their locations. Intersect- ing 2D views were obtained with conventional scanning and AQ imaging, with gains optimized to permit 3D reconstruc- tion by detecting the most continuous AQ borders for each view, with maximal cavity size. Reconstruction was per- formed with manually traced central endocardial reflections and AQ-detected borders. 3DE reconstructions of both manually and AQ-detected borders visually reproduced the left ventricular shapes; the AQ reconstructions, however, were consistently smaller. The reconstructed left ventricular (LV) volumes correlated well with actual values by both manual and AQ techniques (r= 0.93 and 0.88, with standard elrrors of 2.3 cc and 2.0 cc, p = not significant [NS]). Agree- ment with actual values was relatively close for the manually traced borders (y = 0.93x + 0.68, mean difference = -0.8 ± 2.2 cc). AQ-derived reconstructions consistently underesti- mated LV volume by 39 ± 10% (y = 0.62x - 0.09, mean dif- ference = -7.8 ± 3.0 cc, different from manually traced and actual volumes by analysis of variance [ANOVA], F= 69, p< 0.00001). The AQ-detected threshold signal was dis- placed into the cavity, and volume between walls and false From the CardiacUltrasound Laboratory,Massachusetts GeneralHospi- tal, Harvard Medical School. Receivedfor publicationJuly 5, 1995; accepted Aug. 15, 1995. Reprint requests: Leng Jiang, MD, Cardiac Ultrasound Laboratory, Vin- cent-Burnham 5, Massachusetts General Hospital, Fruit Street, Boston, MA 02114. Copyright© 1996 by Mosby-Year Book,Inc. 0002-8703/96/$5.00 + 0 4/1/69512 tendons was excluded, leading to underestimation, which increased with increasing cavity volume (r= 0.76). The AQ technique can therefore be applied to 3DE reconstruction, providing volumes that correlate well with directly measured values in a stable in vitro standard, minimizing observer de- cisions regarding manual border placement after image ac- quisition. However, when the complete borders needed for 3D reconstruction are used, absolute volumes are underes- timated with current algorithms that integrate backscatter and displace the detected threshold into the ventricular cavity. (AM HEART J 1996;131:553-9.) Recently a new acoustic-quantification (AQ) tech- nique has been developed to provide on-line auto- mated border detection 1-25 with analysis of the integrated backscatter from myocardium. 26-33 Prior studies, however, have largely compared two-dimen- sional AQ cavity areas with manually traced areas, or correlated two-dimensional AQ areas with three- dimensional volumes, without direct comparison of volumes for agreement. The purpose of this study was to use complete AQ-detected borders as the in- put to a validated method for three-dimensional echocardiographic (3DE) reconstruction 34-44 to com- pare an entire cavity volume, reconstructed with the aid of AQ and without geometric assumptions, against a directly measured volume. This would also explore the possibility that AQ can be applied to 3DE reconstruction 34-56 to reduce manual border tracing time and enhance routine applicability. 56 METHODS Experimental protocol. Thirteen formalin-fixed sheep hearts were studied to compare reconstructed volumes with actual values in a stable standard allowing direct volume measurement. Each heart was imaged in a water bath with the 3.5 MHz transducer of a Hewlett-Packard Sonos 1500 phased-array sector scanner (Andover, Mass., 77020A). Hearts were scanned in intersecting long- and short-axis sweeps with conventional and AQ imaging. 553