New Three-Dimensional Echocardiographic System Using Digital Radiofrequency Data—Visualization and Quantitative Analysis of Aortic Valve Dynamics With High Resolution

Abstract

Background-Common 3D systems have only limited spatial and temporal resolution (frame rate of 25 Hz). Thin structures such as cardiac valves are not imaged exactly; rapid movement patterns cannot be precisely recorded. The objective of the present project was to achieve radiofrequency (RF) data transmission to the 3D workstation to improve image resolution. Methods and Results-A commercially available echocardiographic system (5-MHz transesophageal echocardiography probe) with an integrated raw data interface enables transmission of RF data (up to 40 megabytes per second). A 3D data set may contain up to 3 gigabytes, so that all of the high-resolution ultrasound information of the 2D image is available. Frame rates of up to 168 Hz result in temporal resolution 6 times that of standard 3D systems. The applicability of the system and the image quality were tested in 10 patients. The structure of the aortic valve and the dynamic changes were depicted by volume rendering. The changes in the orifice areas were measured in frame-by-frame planimetry. The mean number of frames recorded per cardiac cycle was 122Ϯ16. The improved structural resolution enabled a detailed imaging of the morphology of the aortic cusps. The rapid systolic movement patterns were recorded with up to 51 frames. The high number of frames enabled creation of precise area-time diagrams. Thus, the individual phases of aortic valve movement (rapid opening, slow valve closing, and rapid valve closing) could be analyzed quantitatively. Key Words: echocardiography, 3D Ⅲ valve, aortic Ⅲ imaging T he impetus for the technical development of 3D echocardiography was its greater diagnostic potential than that of 2D examinations. 1,2 The spatial imaging of cardiac structures is especially important in the planning and performance of surgical and catheter interventional procedures. 3,4 In addition, new possibilities of quantitative analysis, such as the determination of ventricular size and function, are also offered. 5,6 Establishing 3D echocardiography as a clinical routine procedure requires, however, further technical improvements in spatial and temporal image resolution. Conclusion-The rationale for the technical realization of radiofrequency (RF) data transmission from the ultrasound unit to the 3D workstation via a raw data interface is the attendant considerable improvement in spatial and temporal image resolution. In this article, we present a system in which the frame rate has been increased 6 times to 168 Hz. Practical applicability and image quality of the system were tested under clinical conditions. Methods Data Acquisition SetupThe investigations were performed using a PowerVision 6000 ultrasound system (Toshiba Corp) equipped with a 5-MHz multiplane transesophageal echocardiography (TEE) probe and a digital RF data output. A 3D system with modified Echo-Scan software (TomTec GmbH) was used as a control unit. RF data were acquired at a data rate of 40 megabytes per second using a parallel input/ output interface. RF data were directly transmitte...

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