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High speed 3D imaging with a two-dimensional array
ABSTRACW
ULTRASONIC
IMAGING
AND
TISSUE
CHAFLMTERIZATION
SYIvPOSIUM
Although due to the complexity of the relationship between the received signal and the B/A parameter, it is not simple to actually measure B/A at a particular point, we still can detect the variations of the nonlinear property over the image. DUAL FREQUENCY TRANSDUCER DESIGN FOR ULTRASONIC NONLINEAR IMAGING, Jin-Yuan Wu’ and K. Kirk Shun@, ‘Department of Physics and ‘Bioengineering Program, The Pennsylvania State University, University Park, PA 16802. To image the nonlinear properties of the tissue by using second harmonic or frequency mixing methods, a transducer set capable of operating simultaneously at two different frequency bands is needed. This application requires that: (1) the transducer set work at two or more frequency ranges with separation as large as one octave, and (2) the acoustic beams of the two frequencies he coaxial. The transducer set contains two single element transducers and a heam separator. The beam separator is a set of thin glass or fused quartz plates. The plates have very low reflection coefficients at a certain frequency f. Therefore, a large portion of the wave at frequency f sent by the input transducer will be transmitted into the detecting zone. For the reflected signal with a 2f component, the plate has a high reflection coefficient at 2f. Thus, nearly all the 2nd harmonic energy is reflected into the receiver. This is a pure acoustical phenomenon with no exact optical correspondence. If we use more plates, we can design a beam separator for the frequency mixing detection. The setup has been proved as a useful transducer set design. By using the combination of the transducer set and the electronic filter, very weak nonlinear frequency mixing signals have been detected. It is predictable that this kind of transducer set will also find its application in speckle imaging, ultrasound attenuation measurement and other ultrasound measurements. We shall discuss the design principle of the beam separator. Some practical designs which have been used in our experiment will he described. Some experiment results will also be shown. 3D IMAGING HIGH SPEED 3D IMAGING WITH A TWO-DIMENSIONAL ARRAY, SW. Smith’, ’ and O.T. von Ramm,2 ‘Food & Drug Administration, Center for Devices and Radiological Health, Rockville, MD 20857 and ‘Department of Biomedical Engineering, Duke University, Durham, NC 27706. Previously, we demonstrated two simultaneous real-time orthogonal mode sector scans, each at 30 frames/s, using a two-dimensional phased array and parallel processing. Now, we have further developed this technique to enable high speed 3-D scanning in multiple planes. The scan format is pyramidal and permits viewing of 3-D objects. A specialized 2-D phased array pennits steering in any desired azimuth or elevation direction. The current prototype operates at 2 MHz using a 14 mm x 14 mm array which includes 400 transducer elements. 3D volumes are scanned at the rate of 15 times per second. The vast amount of echo data can be displayed in real time in a variety of ways, including multiple simultaneous C-scans, multiple simultaneous B-scans, projection images from different directions, and stereoscopic images. When projection images are displayed, the system is analogous to an optical camera with perspective, i.e., more distant targets appear smaller in size. Images obtained from phantoms and preliminary in vivo scans will be shown. THREE-DIMENSIONAL ULTRASOUND IMAGING OF THE FEMALE BREAST AND HUMAN FETUS IN UTERO: PRELIMINARY RESULTS, J. M. Levaillant,’ D. Rotten,’ A. Collett Billon: Y. Le Gu&inelz and P. Rua,2 ’ Centre Hospitalier Intercommunal, 40 avenue de Verdun, 94010 Cmteil Cedex, and *LEP: Laboratoites d’Electronique et de Physique appliquee, 3 avenue Descartes, 94451 Lime&Brevannes Cedex, France. Preliminary data of three-dimensional ultrasonic imaging of the normal breast, histologically characterized breast tumors and human fetus in utero are presented. Image acquisition was made using a 2D transducer, fixed to a pantographic arm fitted with potentiometers. Signals received from the transducer and the potentiometers were recorded simultaneously and used to reconstruct a 3D image. The original 2D successive planes and the 3D reconstruction are shown. Once the reconstructed image is obtained, signal processing allows modifications of the projection planes
149
ULTRASONIC
IMAGING
AND
TISSUE
CHAFLMTERIZATION
SYIvPOSIUM
Although due to the complexity of the relationship between the received signal and the B/A parameter, it is not simple to actually measure B/A at a particular point, we still can detect the variations of the nonlinear property over the image. DUAL FREQUENCY TRANSDUCER DESIGN FOR ULTRASONIC NONLINEAR IMAGING, Jin-Yuan Wu’ and K. Kirk Shun@, ‘Department of Physics and ‘Bioengineering Program, The Pennsylvania State University, University Park, PA 16802. To image the nonlinear properties of the tissue by using second harmonic or frequency mixing methods, a transducer set capable of operating simultaneously at two different frequency bands is needed. This application requires that: (1) the transducer set work at two or more frequency ranges with separation as large as one octave, and (2) the acoustic beams of the two frequencies he coaxial. The transducer set contains two single element transducers and a heam separator. The beam separator is a set of thin glass or fused quartz plates. The plates have very low reflection coefficients at a certain frequency f. Therefore, a large portion of the wave at frequency f sent by the input transducer will be transmitted into the detecting zone. For the reflected signal with a 2f component, the plate has a high reflection coefficient at 2f. Thus, nearly all the 2nd harmonic energy is reflected into the receiver. This is a pure acoustical phenomenon with no exact optical correspondence. If we use more plates, we can design a beam separator for the frequency mixing detection. The setup has been proved as a useful transducer set design. By using the combination of the transducer set and the electronic filter, very weak nonlinear frequency mixing signals have been detected. It is predictable that this kind of transducer set will also find its application in speckle imaging, ultrasound attenuation measurement and other ultrasound measurements. We shall discuss the design principle of the beam separator. Some practical designs which have been used in our experiment will he described. Some experiment results will also be shown. 3D IMAGING HIGH SPEED 3D IMAGING WITH A TWO-DIMENSIONAL ARRAY, SW. Smith’, ’ and O.T. von Ramm,2 ‘Food & Drug Administration, Center for Devices and Radiological Health, Rockville, MD 20857 and ‘Department of Biomedical Engineering, Duke University, Durham, NC 27706. Previously, we demonstrated two simultaneous real-time orthogonal mode sector scans, each at 30 frames/s, using a two-dimensional phased array and parallel processing. Now, we have further developed this technique to enable high speed 3-D scanning in multiple planes. The scan format is pyramidal and permits viewing of 3-D objects. A specialized 2-D phased array pennits steering in any desired azimuth or elevation direction. The current prototype operates at 2 MHz using a 14 mm x 14 mm array which includes 400 transducer elements. 3D volumes are scanned at the rate of 15 times per second. The vast amount of echo data can be displayed in real time in a variety of ways, including multiple simultaneous C-scans, multiple simultaneous B-scans, projection images from different directions, and stereoscopic images. When projection images are displayed, the system is analogous to an optical camera with perspective, i.e., more distant targets appear smaller in size. Images obtained from phantoms and preliminary in vivo scans will be shown. THREE-DIMENSIONAL ULTRASOUND IMAGING OF THE FEMALE BREAST AND HUMAN FETUS IN UTERO: PRELIMINARY RESULTS, J. M. Levaillant,’ D. Rotten,’ A. Collett Billon: Y. Le Gu&inelz and P. Rua,2 ’ Centre Hospitalier Intercommunal, 40 avenue de Verdun, 94010 Cmteil Cedex, and *LEP: Laboratoites d’Electronique et de Physique appliquee, 3 avenue Descartes, 94451 Lime&Brevannes Cedex, France. Preliminary data of three-dimensional ultrasonic imaging of the normal breast, histologically characterized breast tumors and human fetus in utero are presented. Image acquisition was made using a 2D transducer, fixed to a pantographic arm fitted with potentiometers. Signals received from the transducer and the potentiometers were recorded simultaneously and used to reconstruct a 3D image. The original 2D successive planes and the 3D reconstruction are shown. Once the reconstructed image is obtained, signal processing allows modifications of the projection planes
149