- Email: [email protected]
A clinical evaluation of Contrast-Detail analysis of ultrasound images
ABSTRACTS, ULTRASONIC IMAGING AND TISSUE CHARACTERIZATION SYMPOSIUM
the superimposing on the original points the original image component tangential level value; 3) by the average radial function of time. sector by sector; or
local
velocity vector at even1 y-spaced image; 2) by replacing each point of by its velocity magnitude, its radial or velocity component represented by a grey plotting the average velocity magnitude or and tangential velocity components as a This can be done for the whole myocardium and 4) by building functional i mages level of each point the time of where the grey indicates occurence or magnitude of its maximum velocity. This work was supported in part by the National Sciences and Engineering Research Council of Canada and the Canadian Heart Foundat i on through a Research Scholarship to Guy E. Mailloux. 2:
SESSION
STATISTICAL
FUNDAMENTAL Wagner+, R. F. ‘Office of
M. F.
Science
Radiological
Health, Duke
of Radiology, 27706. There backscattered is contained
is
in displayed
typically statistical not readi The lower the size carry
moments
shape
information
video
or
scatterers.
depends
the
1 y accessed frequencies of diffuse
envelope contributions signatures samp 1 es density
a signals
avai of on
the
incoherently determination, samp 1 es available
II
PHYSICS OF MEDICCIL ULTRASONIC IMCIGES, Smithzv2, Insanal, D. G. Brown* and S.W. and Technol ogy , Center for Devices & FD&, Rockville, MD 20857 and =Department University Medical Center, Durham, NC wealth of physical i nf ormat i on in in medical ultrasound. This information radi of requency spectrum--which is not the viewer--as to well as in the higher of the envelope or video signal--which are human viewer of typical B-scans. by the of the rf spectrum carry information on scatterers and the higher frequencies on these small-scale scatterers. The carries information on the relative
of coherent The density is determined 1 able and
speckle
IMAGING
or
system compounded. there are
and
diffuse
information
of by
the
in
number
this is determined correlation cells. resol ut i on and the For a typical
of
incoherent) these tissue independent data in turn by the The latter density number of i Rages liver structure
all
of
about a thousand correlation cells or 5 cm= region. In conventional radiography, there are about forty thousand samples avai 1 able over 1 mm’. Thcrs, the ultrasound inverse scattering problem is relatively ill-posed and tissue characterization techniques must be based on statistical methods working at low
over
a
resolution.
A
CLINIC&L
EVCILUATION OF CONTRAST-DETAIL CIN&LYSIS OF H. Lopezl**, M.H. Loew” , P.F. Butler" and =Center for Devices and Radiological Health, FDA, Rockville, MD 20895 “Gear ge Washington and University, Washington, DC 20520. A major advantage of Contrast-Detail (C/D) analysis of ultrasound imaging systems is the quantitative information obtained, in the form of a Contrast-Detail plot, of the imaging system's ability to display a range of varying-size targets as a function of contrast. The C/D plot, however, is obtained by using human observer readings. Our study shows that data obtained from human observers is difficult to match ULTRASOUND t-l. H. Hill=,
IMAGES,
49
ABSTRACTS,
ULTRASONIC
IMAGING AND TISSUE
CHARACTERIZATION
SYMPOSIUM
with that of other observers in test that the and wow neither a larger test group nor repeated readings reduce the overall reading error as predicted by theory. Other investigators postulated that overall error should Cl,21 have decrease with the number of observers, number of observations, and with the independent images, based on number of simplifying assumptions about the statistics of the observations, and the reliability of the observers. Our results indicate that the determination of absolute threshold diameter values for targets of differing contrast in C/D analysis by human observers yields a high degree of error, which is not predicted by this theoretical relationship. We find that systematic the process of error is introduced by learning during the experiment and by variables other not included in the error prediction. These results suggest that C/D analysis may be impractical in the clinical environment, especially for observers without extensive training in a specific task. We suggest that a computer-based observer may be more reliable image quality for objective measurement of for evaluating ultrasound images, and propose a model of such an observer. Cl1 Swets, J.A. and Pickett, R-M. (Academic Press, NY, 1982). C21 Loo, L-D., Doi, K,, et al, Proc. SPIE XI,, (April, 1983). REAL-TIME ENHANCEMENT OF MEDICAL ULTRASOUND IMAGES, Tim Electrical Engineering, University Blankenship, Department of of Missouri-Rolla, Rolla, MO 65401. two techniques are discussed that produce In this paper, real-time or real-time improvements in the image near sharpness and contrast of a microprocessor-based medical ultrasound instrument. The first technique is histogram hyperbolization. This simply improves contrast by producing with a grey images level distribution that appears uniform (equal ired) to the human eye. The second technique, statistical differencing , primarily enhances (sharpens) edges. This locally-varying operation divides the image into subregions and applies a gain and bias to the center pixel of each subregion. The gain and bias are functions of the subregion's standard deviation and mean. These processes are evaluated by varying their respective parameters and comparing original image. A number of the resulting images with the comparisons are Image quality resulting from these made. histogram hyberbolization is examined when performed combination with statistical differencing. separately, and in possible hardware Also considered are some of the implementations. the Missouri Research This work was supported by Assistance Act and Linscan Systems, Inc., Rolla, MO. BY NARROWBAND FILTERING, F.G. IMAGES CREATED ULTRASONIC Departments of Radiology and Sommer, R.A. Stern and H.S. Chen, Stanford, CA Engineering, Stanford University, Electrical 94305. commercial scanner, unfiltered Using a specially-adapted were from region5 of interest ultrasonic waveform data from ultrasonic digitized to a standardized dynamic range and cirrhotic human livers. phantoms and from normal filtering the then created by first Ultrasonic images were filter, of 3.4 MHZ center digitized data with a narrowband and El00 kl-lz bandwidth, prior to thresholding on the frequency
50
the superimposing on the original points the original image component tangential level value; 3) by the average radial function of time. sector by sector; or
local
velocity vector at even1 y-spaced image; 2) by replacing each point of by its velocity magnitude, its radial or velocity component represented by a grey plotting the average velocity magnitude or and tangential velocity components as a This can be done for the whole myocardium and 4) by building functional i mages level of each point the time of where the grey indicates occurence or magnitude of its maximum velocity. This work was supported in part by the National Sciences and Engineering Research Council of Canada and the Canadian Heart Foundat i on through a Research Scholarship to Guy E. Mailloux. 2:
SESSION
STATISTICAL
FUNDAMENTAL Wagner+, R. F. ‘Office of
M. F.
Science
Radiological
Health, Duke
of Radiology, 27706. There backscattered is contained
is
in displayed
typically statistical not readi The lower the size carry
moments
shape
information
video
or
scatterers.
depends
the
1 y accessed frequencies of diffuse
envelope contributions signatures samp 1 es density
a signals
avai of on
the
incoherently determination, samp 1 es available
II
PHYSICS OF MEDICCIL ULTRASONIC IMCIGES, Smithzv2, Insanal, D. G. Brown* and S.W. and Technol ogy , Center for Devices & FD&, Rockville, MD 20857 and =Department University Medical Center, Durham, NC wealth of physical i nf ormat i on in in medical ultrasound. This information radi of requency spectrum--which is not the viewer--as to well as in the higher of the envelope or video signal--which are human viewer of typical B-scans. by the of the rf spectrum carry information on scatterers and the higher frequencies on these small-scale scatterers. The carries information on the relative
of coherent The density is determined 1 able and
speckle
IMAGING
or
system compounded. there are
and
diffuse
information
of by
the
in
number
this is determined correlation cells. resol ut i on and the For a typical
of
incoherent) these tissue independent data in turn by the The latter density number of i Rages liver structure
all
of
about a thousand correlation cells or 5 cm= region. In conventional radiography, there are about forty thousand samples avai 1 able over 1 mm’. Thcrs, the ultrasound inverse scattering problem is relatively ill-posed and tissue characterization techniques must be based on statistical methods working at low
over
a
resolution.
A
CLINIC&L
EVCILUATION OF CONTRAST-DETAIL CIN&LYSIS OF H. Lopezl**, M.H. Loew” , P.F. Butler" and =Center for Devices and Radiological Health, FDA, Rockville, MD 20895 “Gear ge Washington and University, Washington, DC 20520. A major advantage of Contrast-Detail (C/D) analysis of ultrasound imaging systems is the quantitative information obtained, in the form of a Contrast-Detail plot, of the imaging system's ability to display a range of varying-size targets as a function of contrast. The C/D plot, however, is obtained by using human observer readings. Our study shows that data obtained from human observers is difficult to match ULTRASOUND t-l. H. Hill=,
IMAGES,
49
ABSTRACTS,
ULTRASONIC
IMAGING AND TISSUE
CHARACTERIZATION
SYMPOSIUM
with that of other observers in test that the and wow neither a larger test group nor repeated readings reduce the overall reading error as predicted by theory. Other investigators postulated that overall error should Cl,21 have decrease with the number of observers, number of observations, and with the independent images, based on number of simplifying assumptions about the statistics of the observations, and the reliability of the observers. Our results indicate that the determination of absolute threshold diameter values for targets of differing contrast in C/D analysis by human observers yields a high degree of error, which is not predicted by this theoretical relationship. We find that systematic the process of error is introduced by learning during the experiment and by variables other not included in the error prediction. These results suggest that C/D analysis may be impractical in the clinical environment, especially for observers without extensive training in a specific task. We suggest that a computer-based observer may be more reliable image quality for objective measurement of for evaluating ultrasound images, and propose a model of such an observer. Cl1 Swets, J.A. and Pickett, R-M. (Academic Press, NY, 1982). C21 Loo, L-D., Doi, K,, et al, Proc. SPIE XI,, (April, 1983). REAL-TIME ENHANCEMENT OF MEDICAL ULTRASOUND IMAGES, Tim Electrical Engineering, University Blankenship, Department of of Missouri-Rolla, Rolla, MO 65401. two techniques are discussed that produce In this paper, real-time or real-time improvements in the image near sharpness and contrast of a microprocessor-based medical ultrasound instrument. The first technique is histogram hyperbolization. This simply improves contrast by producing with a grey images level distribution that appears uniform (equal ired) to the human eye. The second technique, statistical differencing , primarily enhances (sharpens) edges. This locally-varying operation divides the image into subregions and applies a gain and bias to the center pixel of each subregion. The gain and bias are functions of the subregion's standard deviation and mean. These processes are evaluated by varying their respective parameters and comparing original image. A number of the resulting images with the comparisons are Image quality resulting from these made. histogram hyberbolization is examined when performed combination with statistical differencing. separately, and in possible hardware Also considered are some of the implementations. the Missouri Research This work was supported by Assistance Act and Linscan Systems, Inc., Rolla, MO. BY NARROWBAND FILTERING, F.G. IMAGES CREATED ULTRASONIC Departments of Radiology and Sommer, R.A. Stern and H.S. Chen, Stanford, CA Engineering, Stanford University, Electrical 94305. commercial scanner, unfiltered Using a specially-adapted were from region5 of interest ultrasonic waveform data from ultrasonic digitized to a standardized dynamic range and cirrhotic human livers. phantoms and from normal filtering the then created by first Ultrasonic images were filter, of 3.4 MHZ center digitized data with a narrowband and El00 kl-lz bandwidth, prior to thresholding on the frequency
50