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Standardization of in-vivo measurements for ultrasound tissue characterization
ABSTRACTS,
ULTRASONIC
IMAGING
AND TISSUE
CHARACTERIZATION
SYMPOSIUM
conventional B-mode imaging, diffraction tomography, reflectivity tomography, impedioimage estimation, and wave extrapolation methods are all subsets gr=phy > statistical of a more general scatter imaging method. Ultrasonic scatter imaging, in all its forms, may be described by the fundamental imaging equation, M = DP'RPF + N, where M is the scatter-image map, F is the incident field, P and P' are propagators, R is the reflector or scatterer, D represents the detection equipment, and N is the noise. Using this formalism, we make a detailed comparison between the various imaging methods, showing the merits and disadvantages of each. We explore in some detail the concepts of resolution, distortion, and "image fuzziness" as applied to the various scatter-image methods. Our analysis demonstrates the need for exact tissue models, even if the computations are exact. An emphasis on computational accuracy in the presence of inaccurate models leads to high resolution images which are badly distorted and often very fuzzy. MICROPARTICLE CHARACTERIZATION USING ACOUSTIC SCATTERING, Mark S. Roes, Department of Applied Mechanics, Yale University, New Haven, CT 06520. A technique is presented for measuring physical properties of particles with radii from one to five microns. Tone bursts of 30 MHz center frequency are scattered by single particles as they are carried by a coaxial jet flow past three focused acoustic transducers (one sender and two receivers). The scattered pressure is measured simultaneously at two angles, which allows the density and compressibility of the particles to be determined given the volume of the particles and the density and compressibility of the host liquid. Because the particles are measured one at a time, statistical distributions of their properties may be estimated. Less than ten thousand particles are required for a measurement. The device is calibrated using particles whose properties are known. A study was conducted on human red blood cells in hosts of different tonicity. Density and compressibility values obtained in these experiments are in good agreement with a model accounting for changes in red cell properties due to variations of the cell water content. This work was supported by NIH Grant ROl-GM30419. SESSION
7:
CLINICAL
SCIENCE
II
AN ANALYSIS OF PANCREATIC SONOGRAPKY IN CHRONIC PANCREATITIS, Thomas H. Shawkerl, and Van S. Hubbard', 'Clinical Center, National Institutes of Health, Melvin Linzer*, Bethesda, MD 20205, and *Center for Materials Science, National Bureau of Standards, Washington, DC 20234. the changes associated with pancreatic carcinoma and acute While in general, pancreatitis can be easily recognized with ultrasound imaging, the diffuse parenchymal alterations associated with the various types of chronic pancreatitis have presented more of a diagnostic challenge. In this study, pancreas size and echo amplitude were reviewed in order to determine their value for distinguishing chronic pancreatitis 16 adolescent patients with A prospective study was performed using from normal. Antero-posterior chronic pancreatitis due to cystic fibrosis compared to 16 normals. measurements of the pancreatic body and the ratio of pancreas size to vertebral body Pancreatic echo amplitude was measured directly from the width were determined. B-scan and also evaluated in a blind review by 7 independent observers. It was found did not differ significantly (P>O.2) from that pancreas size in diseased patients In contrast, the pancreas of cystic fibrosis could be distinguished from normals. with an accuracy of 96.8 percent for direct B-scan normals by echo amplitude alone, and an accuracy of 81 percent for the independent echo amplitude measurements observers. STANDARDIZATION OF IN-VIVO MEASUREMENTS FOR ULTRASOUND TISSUE CHARACTERIZATION, A. F. Fleischer, and A. E. J. J. Erickson, G. Horev, R. R. Price, G. A. Thieme, Department of Radiology and Radiological Sciences, Vanderbilt University James Jr., Medical Center, Nashville, TN 37232. We have been investigating methods for the --in viva quantitative characterization Our laboratory has reported results from of different tissue states using ultrasound. a method which was based on several measures of the spatial echo amplitude characterIn further extending this work istics from composite B-scan images of the liver [ll. to include the quantitative analysis of digitized A-mode records, we have become aware of the importance of standardization. In phantoms consisting of graphite and gelatin mixtures and in normal VOlWteers, we are investigating the effects of object parameters (intervening tissues, location in the beam and transducer contact) and system parameters (beam, frequency and control
182
ABSTRACTS,
ULTRASONIC
IMAGING
settings) on the A-mode echo pattern tainties introduced by these factors correct for these factors using reference [l] Goddard J., Price, R., aid James, Vol. 1, p. 107 (1978) (Abstract Only). [Z] Horev, G., Price, R., Erickson, 145, 773-775 (1982).
AND TISSUE
CHARACTERIZATION
SYMPOSIUM
and its related derived parameters. The uncerare significant. The results of attempts to reflectors will be uresented 121. A. E., Jr., in Proc.* of 23rd Ann: Heeting AIUM, J.,
Fleischer
A.,
and
James,
A. E.,
Radiology
QUANTITATIVE VOLUME BACKSCATTER IMAGING: PRELIMINARY CLINICAL RESULTS, M. O'Donnell1 and II. F. Reillyz, 'Corporate Research and Development Center, General Electric Company, Schenectady, NY 12301, and 2Radiology Department, Ellis Hospital, Schenectady, NY 12308. A conventional B-scan imaging system has been adapted for quantitative volume backscatter imaging. Using this system, we have initiated a clinical trial of the quantitative volume backscatter imaging method. Accordingly, we have generated quantitative images from conventional B-scans of the right lobe of the liver for three groups of subjects. Thirteen healthy volunteers comprised the first group of subjects. Analysis of the images from this group yields an average backscatter coefficient for normal liver of 3.5 x 10d4 cm-l R-r with a standard deviation of 1.5 dB, a result consistent with in vitro studies published elsewhere. At present, the second group consists of six subjezith documented cirrhosis of the liver, while the third group consists of six subjects with documented metastisis to the liver from adenocarcinoma of the colon. The average backscatter coeeficient measured in the cirrhotic livers of the second group is 8.7 x low4 cm-l R" with a standard deviation of 2.5 dB. Finally, the average backscatter coefficient measured in regions of metastatic adenocarcinoma of the liver in the third group of subjects is less than 1.0 x 10e4 cm-' s-2-l. REGIONAL DIFFERENCES IN THE CYCLIC VARIATION OF MYOCARDIAL BACKSCATTER AND MODIFICATION BY ISCREMIA, Jack G. Mottley, Robert M. Glueck, Julio E. Perez, Burton E. Sobel, and J. G. Miller, Department of Physics, Cardiovascular Division, and Biomedical Computer Laboratory, Washington University, St. Louis, MO 63130. We have previously reported systematic variation in ultrasonic backscatter throughout the cardiac cycle in canine myocardium. To determine whether the cyclic variation observed is related to contractile events in myocardium, which exhibit systematic local variation in magnitude and which are impaired by ischemia, we characterized regional differences in cyclic variation of backscatter in intact normal and ischemic hearts. After the left ventricle had been exposed surgically in ten dogs, simultaneous recordings of left ventricular pressure and ultrasonic backscatter were obtained. Backscatter (3 to 7 MHz) was measured from 5 sites in each of 3 regions of the heart: apex, midwall, and high base. Measurements were referenced to those from a steel reflector, and frequency averaged (integrated) backscatter was calculated. Cyclic variation of backscatter was greatest at the apex (peak to trough variation of 5.6 f 1.3 dB (mean ? s.e.m.)) with the maximum near end diastole and the minimum near Variation was intermediate at the midwall (3.9 ? 1.0 dB) and least at end systole. the base (0.5 f 1.1 dB.). Five to ten minutes after coronary occlusion in five animals, the pattern of apical variation was markedly blunted with an average peak to trough difference of only 0.8 f 1.5 dB. Thus, well-defined regional differences in the cyclic variation of backscatter occur in the intact canine heart. Furthermore, the variation is blunted by acute changes in the functional state of the myocardium induced by ischemia. These observations are potentially applicable to clinical utilization in approaches designed to characterize local contractile properties. This work was supported in part by NIH Grants RRO0396, RR01362, BL17646, and RL28998. ALTERATION OF LEFT VENTRICULAR WALL GRAY LEVEL IN TWO- DIMENSIONAL ECHOCARDIOGRAMS DUE TO CARDIAC CONTRACTION, Steve M. Collins, David J. Skorton, Brian Olshansky, N. V. Prasad, and Hewlett E. Melton, Jr., University of Iowa and Iowa City VA Medical Center, Iowa City, IA 52242. Integrated ultrasonic backscatter from normal myocardium has been shown to vary with the phase of cardiac contraction (decreasing from end-diastole to end-systole) in previous studies of open-chest dogs. If confirmed, this finding would have important implications for clinical application of ultrasonic tissue characterization. Our hypothesis was that a cardiac cycle-dependent variation in regional average gray level would be detected by analysis of digitized two-dimensional echocardiograms. We analyzed echo images from 16 subjects with normal, technically-good echo studies
183
ULTRASONIC
IMAGING
AND TISSUE
CHARACTERIZATION
SYMPOSIUM
conventional B-mode imaging, diffraction tomography, reflectivity tomography, impedioimage estimation, and wave extrapolation methods are all subsets gr=phy > statistical of a more general scatter imaging method. Ultrasonic scatter imaging, in all its forms, may be described by the fundamental imaging equation, M = DP'RPF + N, where M is the scatter-image map, F is the incident field, P and P' are propagators, R is the reflector or scatterer, D represents the detection equipment, and N is the noise. Using this formalism, we make a detailed comparison between the various imaging methods, showing the merits and disadvantages of each. We explore in some detail the concepts of resolution, distortion, and "image fuzziness" as applied to the various scatter-image methods. Our analysis demonstrates the need for exact tissue models, even if the computations are exact. An emphasis on computational accuracy in the presence of inaccurate models leads to high resolution images which are badly distorted and often very fuzzy. MICROPARTICLE CHARACTERIZATION USING ACOUSTIC SCATTERING, Mark S. Roes, Department of Applied Mechanics, Yale University, New Haven, CT 06520. A technique is presented for measuring physical properties of particles with radii from one to five microns. Tone bursts of 30 MHz center frequency are scattered by single particles as they are carried by a coaxial jet flow past three focused acoustic transducers (one sender and two receivers). The scattered pressure is measured simultaneously at two angles, which allows the density and compressibility of the particles to be determined given the volume of the particles and the density and compressibility of the host liquid. Because the particles are measured one at a time, statistical distributions of their properties may be estimated. Less than ten thousand particles are required for a measurement. The device is calibrated using particles whose properties are known. A study was conducted on human red blood cells in hosts of different tonicity. Density and compressibility values obtained in these experiments are in good agreement with a model accounting for changes in red cell properties due to variations of the cell water content. This work was supported by NIH Grant ROl-GM30419. SESSION
7:
CLINICAL
SCIENCE
II
AN ANALYSIS OF PANCREATIC SONOGRAPKY IN CHRONIC PANCREATITIS, Thomas H. Shawkerl, and Van S. Hubbard', 'Clinical Center, National Institutes of Health, Melvin Linzer*, Bethesda, MD 20205, and *Center for Materials Science, National Bureau of Standards, Washington, DC 20234. the changes associated with pancreatic carcinoma and acute While in general, pancreatitis can be easily recognized with ultrasound imaging, the diffuse parenchymal alterations associated with the various types of chronic pancreatitis have presented more of a diagnostic challenge. In this study, pancreas size and echo amplitude were reviewed in order to determine their value for distinguishing chronic pancreatitis 16 adolescent patients with A prospective study was performed using from normal. Antero-posterior chronic pancreatitis due to cystic fibrosis compared to 16 normals. measurements of the pancreatic body and the ratio of pancreas size to vertebral body Pancreatic echo amplitude was measured directly from the width were determined. B-scan and also evaluated in a blind review by 7 independent observers. It was found did not differ significantly (P>O.2) from that pancreas size in diseased patients In contrast, the pancreas of cystic fibrosis could be distinguished from normals. with an accuracy of 96.8 percent for direct B-scan normals by echo amplitude alone, and an accuracy of 81 percent for the independent echo amplitude measurements observers. STANDARDIZATION OF IN-VIVO MEASUREMENTS FOR ULTRASOUND TISSUE CHARACTERIZATION, A. F. Fleischer, and A. E. J. J. Erickson, G. Horev, R. R. Price, G. A. Thieme, Department of Radiology and Radiological Sciences, Vanderbilt University James Jr., Medical Center, Nashville, TN 37232. We have been investigating methods for the --in viva quantitative characterization Our laboratory has reported results from of different tissue states using ultrasound. a method which was based on several measures of the spatial echo amplitude characterIn further extending this work istics from composite B-scan images of the liver [ll. to include the quantitative analysis of digitized A-mode records, we have become aware of the importance of standardization. In phantoms consisting of graphite and gelatin mixtures and in normal VOlWteers, we are investigating the effects of object parameters (intervening tissues, location in the beam and transducer contact) and system parameters (beam, frequency and control
182
ABSTRACTS,
ULTRASONIC
IMAGING
settings) on the A-mode echo pattern tainties introduced by these factors correct for these factors using reference [l] Goddard J., Price, R., aid James, Vol. 1, p. 107 (1978) (Abstract Only). [Z] Horev, G., Price, R., Erickson, 145, 773-775 (1982).
AND TISSUE
CHARACTERIZATION
SYMPOSIUM
and its related derived parameters. The uncerare significant. The results of attempts to reflectors will be uresented 121. A. E., Jr., in Proc.* of 23rd Ann: Heeting AIUM, J.,
Fleischer
A.,
and
James,
A. E.,
Radiology
QUANTITATIVE VOLUME BACKSCATTER IMAGING: PRELIMINARY CLINICAL RESULTS, M. O'Donnell1 and II. F. Reillyz, 'Corporate Research and Development Center, General Electric Company, Schenectady, NY 12301, and 2Radiology Department, Ellis Hospital, Schenectady, NY 12308. A conventional B-scan imaging system has been adapted for quantitative volume backscatter imaging. Using this system, we have initiated a clinical trial of the quantitative volume backscatter imaging method. Accordingly, we have generated quantitative images from conventional B-scans of the right lobe of the liver for three groups of subjects. Thirteen healthy volunteers comprised the first group of subjects. Analysis of the images from this group yields an average backscatter coefficient for normal liver of 3.5 x 10d4 cm-l R-r with a standard deviation of 1.5 dB, a result consistent with in vitro studies published elsewhere. At present, the second group consists of six subjezith documented cirrhosis of the liver, while the third group consists of six subjects with documented metastisis to the liver from adenocarcinoma of the colon. The average backscatter coeeficient measured in the cirrhotic livers of the second group is 8.7 x low4 cm-l R" with a standard deviation of 2.5 dB. Finally, the average backscatter coefficient measured in regions of metastatic adenocarcinoma of the liver in the third group of subjects is less than 1.0 x 10e4 cm-' s-2-l. REGIONAL DIFFERENCES IN THE CYCLIC VARIATION OF MYOCARDIAL BACKSCATTER AND MODIFICATION BY ISCREMIA, Jack G. Mottley, Robert M. Glueck, Julio E. Perez, Burton E. Sobel, and J. G. Miller, Department of Physics, Cardiovascular Division, and Biomedical Computer Laboratory, Washington University, St. Louis, MO 63130. We have previously reported systematic variation in ultrasonic backscatter throughout the cardiac cycle in canine myocardium. To determine whether the cyclic variation observed is related to contractile events in myocardium, which exhibit systematic local variation in magnitude and which are impaired by ischemia, we characterized regional differences in cyclic variation of backscatter in intact normal and ischemic hearts. After the left ventricle had been exposed surgically in ten dogs, simultaneous recordings of left ventricular pressure and ultrasonic backscatter were obtained. Backscatter (3 to 7 MHz) was measured from 5 sites in each of 3 regions of the heart: apex, midwall, and high base. Measurements were referenced to those from a steel reflector, and frequency averaged (integrated) backscatter was calculated. Cyclic variation of backscatter was greatest at the apex (peak to trough variation of 5.6 f 1.3 dB (mean ? s.e.m.)) with the maximum near end diastole and the minimum near Variation was intermediate at the midwall (3.9 ? 1.0 dB) and least at end systole. the base (0.5 f 1.1 dB.). Five to ten minutes after coronary occlusion in five animals, the pattern of apical variation was markedly blunted with an average peak to trough difference of only 0.8 f 1.5 dB. Thus, well-defined regional differences in the cyclic variation of backscatter occur in the intact canine heart. Furthermore, the variation is blunted by acute changes in the functional state of the myocardium induced by ischemia. These observations are potentially applicable to clinical utilization in approaches designed to characterize local contractile properties. This work was supported in part by NIH Grants RRO0396, RR01362, BL17646, and RL28998. ALTERATION OF LEFT VENTRICULAR WALL GRAY LEVEL IN TWO- DIMENSIONAL ECHOCARDIOGRAMS DUE TO CARDIAC CONTRACTION, Steve M. Collins, David J. Skorton, Brian Olshansky, N. V. Prasad, and Hewlett E. Melton, Jr., University of Iowa and Iowa City VA Medical Center, Iowa City, IA 52242. Integrated ultrasonic backscatter from normal myocardium has been shown to vary with the phase of cardiac contraction (decreasing from end-diastole to end-systole) in previous studies of open-chest dogs. If confirmed, this finding would have important implications for clinical application of ultrasonic tissue characterization. Our hypothesis was that a cardiac cycle-dependent variation in regional average gray level would be detected by analysis of digitized two-dimensional echocardiograms. We analyzed echo images from 16 subjects with normal, technically-good echo studies
183