Ultrasonic diagnostic equipment

This invention relates to an ultrasonic diagnostic equipment usable to measure small vibrations in myocardial tissues superimposed on a large amplitude vibration of heartbeat. And it comprises a large amplitude motion analyzing means for deciding the an instantaneous position of the object by using the amplitude and phase of the detected signal and tracking a large amplitude of motion of the object, and a small vibration analyzing means for detecting a small vibration superimposed on the large amplitude motion by analyzing, succeeding positions of the large amplitude motion obtained from the large amplitude motion analyzing means. By using this invention, a local elasticity of width of 1-2 mm in myocardium and arterial wall can be evaluated noninvasively.

BACKGROUND OF THE PRESENT INVENTION 
This invention relates to an ultrasonic diagnostic equipment which is 
possible to measure noninvasively the movement velocity signal of a part 
of heart, artery and the other organs by using ultrasonic wave, especially 
relates to an ultrasonic diagnostic equipment usable to measure small 
vibrations in myocardial tissues superimposed on a large amplitude 
vibration of heartbeat. 
EXPLANATION OF PRIOR ART 
The techniques for ultrasonic diagnostic equipment are progressed highly in 
Japan, and there is not in the world a precedent study on "measurement of 
a small amplitude vibration of myocardial tissues superimposed on a large 
amplitude vibration of heartbeat" and the diagnostic equipment using the 
vibration measuring methods. 
On the other hand, the electrocardiogram and the phonocardiogram analysis 
have their history over a hundred year, and their various measurement 
methods and analysis have been developed. But they have some problems that 
(a) only signals of low frequency less than several tens Hz of frequency 
are contained in detected signals, (b) regional information in a 
myocardium is not contained and (c) a range possible to obtain signals in 
one cardiac cycle is restricted. 
The other principal prior arts are explained in the following. 
Zero Cross Point Detection of RF Signal Method 
A measuring method of vibration in heart wall or internal tissues by using 
ultrasonic pulse transmitted from external of a body has been reported. It 
measures the displacement of an objects based on the zero cross timing of 
RF (Radio frequency) signal of the reflected ultrasonic wave from the 
object. In this method, quantization error depending on the clock 
frequency f.sub.CLK of circuit is caused. The displacement signal is 
obtained by integrating the velocity signal, therefore the displacement 
signal can be measured with small error, but when the velocity signal is 
obtained by differentiation of the displacement, it causes a significant 
error. Only from a few Hz to ten Hz of frequency components are contained 
in the displacement signal of heartbeat, therefore the meaning result 
cannot be obtained from the spectrum analysis of the displacement signal. 
Tissue Doppler Method 
As a reference on this technique, "Japanese published patent specification, 
Tokkaisho No. 62-266040" (applicant of Toshiba LTD) is cited. It discloses 
an ultrasonic diagnostic equipment that receives reflected waves of 
ultrasonic pulse transmitted to an object and displays its ultrasonic 
images based on the reflected waves. It comprises a phase detecting means 
for detecting phase of reflected waves at any time, and sampling point 
designating means for designating sample points of any positions of 
reflecting waves, sample shifting means for detecting the phase deference 
at sampling points of the reflecting waves and shifting the sampling 
points by the distance accordingly to the phase difference, and dynamic 
measuring and displaying means for automatically measuring the object 
movement by tracing the translation of sample points and displaying the 
movement of the target on a display. 
This equipment detects the phase deference of sampling points of the 
reflected waves, and moves the sample points by the distance depending on 
the phase deference. On the other hand, the distances of sampling points 
are several hundreds .mu.m and the invivo wave length of ultrasonic wave 
of 3.5 MHz is about 500 .mu.m, therefore, if sample points are close, only 
same signals can be obtained, so it is ineffective to make the distance 
between succeeding sampling points more close. In either case, as the 
distance between sample points is several hundreds .mu.m, its accuracy on 
measuring the displacement is same as this order, therefore the accuracy 
of the prior art is very rough. 
The displacement signals are obtained by integrating velocity signals on 
the displacement measurement. The displacement signals can be measured by 
using the prior art, but when they are converted to velocity signals by 
differentiation, the measuring error becomes large. Only from a few Hz to 
ten Hz of frequency components are contained in the displacement signal of 
heartbeat, therefore, the meaning result cannot be obtained from the 
spectrum analysis of the displacement signal. 
Further, the equipment gathers reflected waves obtained from the 
transmitted ultrasonic pulses of a few or over ten Hz of frequency (let us 
suppose that it is N), and calculates their average Doppler shift by 
averaging them. Therefore, the time resolution on the obtained velocity 
signal is bad and the velocity signal is sampled with sampling frequency 
of one Nth of pulse transmission frequency PRF. 
In the prior art Doppler measurement of blood flow velocity, the distance 
from a ultrasonic probe to an object reflecting the ultrasonic wave is 
constant, but, in the case of measurement of heart wall vibrations, a wall 
position moves more than 10 mm according to the heartbeat motion, 
therefore the distance from the ultrasonic probe to the object changes 
largely with time passing. This influences the measurement of the 
myocardial wall vibrations, and it has been cause of errors. 
SUMMARY OF THE PRESENT INVENTION 
The present invention resolves the prior art problems by tracking highly 
accurately the object positions which moves with its vibrations. 
This invention is that the ultrasonic diagnostic equipment for measuring 
the position and movement of an object by transmitting ultrasonic wave 
into an inner body and detecting reflected ultrasonic wave from the object 
and analyzing it. And it comprises the following means. 
A large amplitude motion analyzing means for deciding an instantaneous 
position of the object by using the amplitude and phase of the detected 
signal and tracking a large amplitude of motion of the object, and a small 
vibration analyzing means for detecting a small vibration superimposed on 
the large amplitude motion by analyzing succeeding positions of the large 
amplitude motion obtained from said large amplitude motion analyzing 
means. 
FIG. 1 shows a drawing of principle of the present invention. 
In FIG. 1, an ultrasonic transducer 1, a chest wall surface 2, a myocardial 
wall 3, an amplifier 4, a quadrature demodulator 5, an A/D converter 6, a 
data analysis processing part 7 are shown. 
The transducer 1 is driven by ultrasonic wave pulse of frequency .DELTA.T 
and transmits ultrasonic pulse for the inner body from the chest wall 
surface 2. The transmitted ultrasonic wave is reflected from a vibrating 
heart wall of velocity v(t) and the reflected waves are received by the 
transducer 1. The ultrasonic signal of the received wave is amplified with 
the amplifier 4 and detected with the quadrature demodulator 5, and output 
signals from it are converted to digital data sampled with the sampling 
frequency of Ts in the A/D converter 6 and they are input into the data 
analysis processing part 7. 
The data analysis processing part 7 detects phase shift 
.angle..beta.(t+.DELTA.T/2) during .DELTA.T second by the detected 
reflected signal y(x;t) from the object at time t and the detect reflected 
signal y(x;t+.DELTA.T) at time t+.DELTA.T, and calculates the movement 
distance of the object during .DELTA.T second. In this calculation, for 
suppressing noise, it obtains the phase shift .angle..beta.(t+.DELTA.T/2) 
during the .DELTA.T second by using minimizing the squared difference 
between the signal y(x;t) at time t and the signal y(x;t+.DELTA.T) at time 
t+.DELTA.T under a constraint condition that the amplitudes do not change 
and only the phase and reflection positions change between signals of time 
t and time (t+.DELTA.T) and further calculates the vibration velocity 
v(t). 
(2-1) Method Increasing the Accuracy of Phase Deference Calculation 
FIG. 2 shows a model of waveform of the detected signals of the reflected 
signals (complex signal), and signal y(x;t) at time t is shown in figure 
(a), and the next signal y(x;t+.DELTA.T) is shown in figure (b). The mark 
of .quadrature. shows real component and mark of X shows imaginary 
component. 
When the object moves .delta.x after .DELTA.T second for the detected 
signal y(x;t), an error .alpha.(.DELTA..theta.(.delta.x);.delta.x) between 
the detected signals y(x;t) and y (x+.delta.x,t+.DELTA.T) under the 
constraint that amplitude does not change and only phase of 
.DELTA..theta.(.delta.x) change is denoted as a following equation 
##EQU1## 
where x.di-elect cons.R means that the sum is calculated for x in a rage R. 
It is necessary for finding .delta.x which minimizes the error 
.alpha.(.DELTA..theta.(.delta.x); .delta.x). It may be happen for the 
signal power in the range R to change by the movement .delta.x of signal 
y(x;t+.DELTA.t), therefore, for normalizing the power, the right-hand side 
of the equation (1) is divided by the denominator which is the average 
power of two signals. 
FIG. 3 shows the change of the error 
.alpha.(.DELTA..theta.(.delta.x);.delta.x) for .delta.x. A case that 
permits both of phase and amplitude to change is shown in FIG. 3 (a), and 
as shown from it, it takes minimum in all region for larger than true 
value .delta.x=-5. The other case that permits only phase to change is 
shown in FIG. 3(b), as shown in (b), only one minimum value can be 
obtained at true value .delta.x=-5. 
For obtaining .DELTA..theta.(.delta.x) which minimizes the equation (1) for 
.delta.x, taking account of a partial differential equation of 
.alpha.(.DELTA..theta.(.delta.x);.delta.x) by .DELTA..theta.(.delta.x) and 
making the equation equal to zero, by resolving the equation the suitable 
.DELTA..theta.(.delta.x) minimizing 
.alpha.(.DELTA..theta.(.delta.x);.delta.x) is obtained as following. 
EQU exp {j.DELTA..theta.(.delta.x)=exp (j.angle.C(.delta.x)) (2) 
where C(.delta.x) is following 
EQU C(.delta.x)=.SIGMA..sub.X.right brkt-top.R 
y*(x;t).multidot.y(x+.delta.x;t+.DELTA.T) (3) 
And .angle.C(.delta.x) is phase of complex number C(.delta.x). Mark "*" 
shows conjugate complex. And further, changing .delta.x in a range, the 
above equation is calculated for each .delta.x. From the results, .delta.x 
and .DELTA..theta.(.delta.x) which make the error minimum are obtained. By 
using such obtained .DELTA..theta.(.delta.x), an average velocity 
v(t+.DELTA.T/2) in this range can be calculated with following equation. 
##EQU2## 
Where .DELTA.T is a pulse transmission interval, .omega..sub.0 
=2.pi.f.sub.0 is angle frequency of ultrasound the ultrasonic wave and 
c.sub.0 is propagation velocity of the ultrasound. 
(2--2) Method of Increasing the Tracking Accuracy 
Moreover the object displacement .DELTA.x(t+.DELTA.T/2) during .DELTA.T is 
obtained multiplying to v(t+.DELTA.T/2) by .DELTA.T. 
EQU .DELTA.x(t+.DELTA.T/2)=v(t+.DELTA.T/2).times..DELTA.T (5) 
The object position of the next time can be estimated by adding the 
displacement .DELTA.x(t+.DELTA.T/2) to the object position x(t) of the 
former time t. 
EQU x(t+.DELTA.T/2)=x(t)+x(t+.DELTA.T/2) (6) 
The tracking trace x(t) can be obtained from this. 
When velocity is 0.01 m/s, .DELTA.T=250 .mu.s, the displacement is 2.5 
.mu.m. The spatial resolution is made better more than several times than 
that of prior art, and it is apparent from comparing zero-cross point 
method based on PLL shown in FIG. 4(A) with the method of this invention 
shown in FIG. 4(B). 
FIG. 5 is a drawing of explanation of a measuring accuracy and a measuring 
limit of velocity measurement of reflection waves based on a prior art 
method shown in FIG. 4(A) and the present invention method shown in FIG. 
4(B). It is apparent that the spatial resolution is 1/fclk.times.c0/2 and 
quantization error is large in case of the prior art method based on PLL 
which detects the displacement of object during .DELTA.T with a circuit of 
inner clock fclk. 
(2-3) Merits of the Present Invention 
The small vibration in myocardium can be obtained by the present invention, 
and the present invention has an excellent features as followings, 
(a) The small vibration of myocardium of a high frequency until several 
hundreds Hz can be measured with a sufficient reproducibility. 
(b) A local elasticity of width of 1-2 mm in myocardium and arterial wall 
can be evaluated noninvasively. 
(c) Signal components can be obtained at any timing of one cardiac cycle. 
(d) Frequency spectrum analysis is applicable.

EXPLANATION OF PREFERRED EMBODIMENT 
By this invention, quite new information for finding a myocardial 
infarction part and range, a quantitative diagnostic information on these 
degrees, can be observed with a real-time non-invasive observation from a 
body surface. Therefore the study on the measurement of myocardial small 
vibration and analysis developed by inventors of the present invention 
will be a pioneer in this region, and it will be a new learning region and 
replaced with many prior art on electrocardiogram and phonocardiogram. 
Further it has a possibility of application to organs like a liver and 
histological diagnostics of arterial wall in combination with applying a 
external forced vibration, for example by using a mechanical vibrator. 
Therefore the contribution of the present invention for non-invasive 
histological examination is very great. 
The end-diastolic period pressure is an important factor of diagnostics for 
heart diseases, and there was only an invasive observation method like 
cardiac catheter method. As an example of application of the small 
vibrations of myocardial wall observed non-invasively by using this 
invention for the diagnostics, inventors of the present invention have 
proposed an epoch-making method which is possible to measure the 
end-diastolic pressure non-invasively by deciding eigenfrequency of the 
object obtained from a detailed spectrum analysis. The propriety of this 
invention method is confirmed experimentally, and it is a great important 
result in a domain of medical engineering. 
Moreover a simultaneous measurement and analysis of the small vibrations of 
two points at distance of a few milli-meter on arterial wall is possible 
by using the above mentioned method. And by calculating the delay time of 
the pressure wave propagating on the vessel wall, the state of arterial 
wall can be evaluated non-invasively. These will be an effective method 
for diagnostics for an early stage of arterial sclerosis. 
Therefore these diagnostic methods developed by inventors of this invention 
are original in both domains of engineering and medical science, and they 
are hoped a great development in near future. Further they are possible to 
diagnose an early stage of myocardial infarction of which patients are 
increasing rapidly, for reasons of it, The proposed ultrasonic diagnostic 
equipment will contribute to prevent and overcome it. Therefore this 
invention has a great social significance. 
(3-1) Measurement of Myocardial Vibration and Macro Analysis of Cardiac 
Functions 
Subjects are three normal males in their twenties years old and three 
patients in their twenties years old who are prescribed anticancer drugs 
of anthracyclines series. The anthracyclines series anticancer drugs has 
the strongest anticancer action and have a high complete remission. For 
this reason, they are used frequently, but they have a nature causing a 
myocardial damage, and in case prescribing more than a fixed quantity of 
dosage it causes an irreversible cardiac insufficiency. Therefore, it is 
necessary to hold an exact information whether the myocardial damage is 
caused or not. Thus it is desired to develop an easy method to possible to 
diagnose it and hold its degree from the start of prescription. In this 
specification, it is discussed and confirmed that the myocardial damage 
caused by the prescription on anticancer drugs can be detected from the 
small vibrations of ventricular wall by using the present invention. 
FIG. 6 shows a standard B-mode cross-sectional image of the male patient of 
23 years old having myocardial damage. In FIG. 6, ultrasonic 
cross-sectional images of the right ventricular side (A point) of 
interventricular septum (RV) and the left ventricular side (B point) of 
interventricular septum (LV) are shown under a condition that the 
ultrasonic beam is almost perpendicular to the septum. 
FIG. 7 and FIG. 8 show vibration waveforms v.sub.A (t), v.sub.B (t), an 
electrocardiogram (ECG), a phonocardiogram (PCG) sound chart of the right 
ventricular side (A point) of interventricular septum and the left 
ventricular side (B point) of interventricular septum. In each figure, the 
ultrasonic wave is almost perpendicular to the septum. FIG. 7 (a) shows M 
mode, wherein a result of tracking x.sub.A (t) and x.sub.B (t) are 
overlaid, FIG. 7 (b) shows electrocardiogram, FIG. 7 (c) shows a 
phonocardiogram (PCG), FIGS. 7 (d), (e) show the velocity waveform v.sub.A 
(t) of the right ventricular side (A point) of interventricular septum and 
the velocity waveform v.sub.B (t) of the left ventricular side (B point) 
of interventricular septum. FIG. 7 (f) shows change of the septum 
thickness hAB(t). 
And FIG. 8(a) shows an electrocardiogram (ECG), FIG. 8 (b) shows a 
phonocardiogram (PCG), FIGS. 8 (c), (d) show the velocity wave v.sub.A (t) 
of the right ventricular side (A point) of interventricular septum and 
velocity wave v.sub.B (t) of the left ventricular side (B point) of 
interventricular septum. 
Those for five heartbeats corresponding to R wave of the electrocardiogram 
are displayed. 
FIG. 9 and FIG. 10 show velocity waveform on a surface of the left 
ventricular side of interventricular septum of the six subjects at timings 
of end ejection period--isovolumic relaxation period--rapid filling period 
centered to the second sound, and their mean power spectra. 
In the left side of FIG. 9, waves around the second heart sound of the 
small vibrations of the left ventricular side of interventricular septum 
of three normal males of their twenties years old for several heartbeat. 
At the right side of FIG. 9, the average power spectrum of velocity 
waveform are shown. Vertical bars (showing power spectrum) show a range 
between the maximum and minimum power during several heartbeats. The 
reproducibility is quantitatively confirmed up to 100 Hz. 
In the left side of FIG. 10, waveforms around the second heart sound of the 
small vibrations of the left ventricular side of interventricular septum 
of three patients having myocardial disease are overlaid for a few 
heartbeats and in the right side of the FIG. 10, the average power 
spectrum of each velocity signal is shown. Those for 8 heartbeats of the 
male of 32 years old measured two months before his dead are shown in the 
figure (a-1,a-2). Those for 8 heartbeats of same patient with FIG. 8 
(a-1,a-2) measured three months before the measurement of FIG. 10 
(a-1,a-2) are shown in FIG. 10 (b-1,b-2). And in figure (c-1,c-2) those 
for 5 heartbeats of the male of 23 years old are shown and in FIG. 
10(d-1,d-2) those for 6 heartbeats of females of 25 years old are shown. 
As shown in FIG. 9, the waveform of normal subjects are similar and the 
power spectrum distribution is also mutually similar. In contrast to 
these, the amplitude of the patients are clearly small as shown in FIG. 
10, and all power spectra, especially up to the 100 Hz, are decreased a 
few .about.10 dB. It is considered that the decrease of the power is 
caused by the decrease of myocardial functions. 
(3-2) Measurement of Change of Myocardial Thickness and Macro Analysis of 
Myocardial Functions 
Measurement results of the change of local myocardial thickness at 
myocardial interventricular septum are shown in FIG. 11. In FIG. 11, an 
electrocardiogram (ECG) is shown in figure (a), a phonocardiogram (PCG) is 
shown in figure (b), M-mode image is shown in figure (c), M mode chart and 
tracking results xi(t), i={1, 2, . . . , 13} of at interval of about 0.75 
mm are overlaid in figure (d), the movement velocity signals vi(t) on each 
tracking trajectory are shown in figure (e), the waveforms of change in 
local thickness of the interventricular septum xi(t)-x1(t), i={1, 2, . . . 
, 13} calculated from the diference between xi(t) and the tracking x1(t) 
at right ventriculer side are shown in figure (f). The absolute value of 
the spatial difference .vertline.vi+1(t)-vi(t).vertline. between the 
movement velocities for the result of tracking (d) x1(t) are shown in 
figure (g) in which the value is indicated by shading. In such a way, the 
change in thickness caused in each regional myocardium can be estimated. 
FIG. 12 shows a magnified of measurement result of the change in thickness 
of the local myocardium of interventricular septum in FIG. 11, and it 
shows that of one heartbeat. 
In FIG. 12, an electrocardiogram (ECG) is shown in figure (a), a 
phonocardiogram (PCG) is shown in figure (b), M-mode image is shown in 
figure (c), the movement velocity v(t) on each tracking trajectory xi(t) 
is shown, the change in thickness caused in each regional myocardium of 
the interventricular septum xi(t)-x1(t) calculated by the difference 
between the tracking result xi(t) and x1(t) at the right ventricular side 
is shown in figure (e), the absolute value of the difference of the 
movement velocity for tracking results .vertline.vi+1(t)-vi(t).vertline. 
in figure (g) is shown in figure (f) in which the value is indicated by 
shading. 
(3--3) Estimation of Kinetic Energy Consumed at each Regional Myocardium 
In FIG. 13, the movement velocity waveforms of interventricular septum of 
myocardium of R wave of electrocardiogram for 5 heartbeats are overlaid. 
In FIG. 13, a phonocardialgram is shown in figure (a), an electrocadiogram 
is shown in figure (b), movement velocity waves vi(t) on each tracking 
trajectory xi(t), i={1, 3, 5, 7, 9, 11} same with FIG. 11 (d) is shown 
again in FIG. 13 (c). These trackings are measured at intervals of about 
1.5 mm. The velocity waveform showing the change in myocardial thickness 
can be obtained by the spatial difference of these movement velocity waves 
vi(t)-vi+1(t). A kinetic energy of myocardium can be calculated by 
multiplying the myocardial density or mass of the objective region by the 
square of the velocity and dividing them by two. They are corresponding to 
the chemical energy of oxygen and nourishment sent to the myocardial 
tissue from coronary arteries. Therefore, the non-invasive histological 
estimation of myocardial activity can be possible by this kinetic energy. 
(4) Measurement of Change of Arterial Wall Thickness and Non-Invasive 
Measurement of Elasticity of Arterial Radial Direction 
The movement velocity wave of arterial wall can be also measured more 
precisely than by prior art. FIG. 14 shows calculated small vibration 
velocities v1,v2 at two points on wall of the abdominal aorta of a healthy 
male of 22 years old. The thickness changes h(t) can be obtained by 
calculating the difference between v1(t) and v2(t) of two waves and 
integrating regarding to time. 
Further as shown in FIG. 15, by combination of the change of arterial wall 
thickness h(t) with intraventricular pressure p(t) measured with a blood 
pressure meter, the modulus of elasticity of radial direction of arterial 
wall can be calculated. By the time change of vessel lumen d(t) and the 
wall thickness h(t) at one heartbeat, young's modulus Er of radial 
direction may be calculated as following. 
distortion rate; 
EQU .epsilon.=.DELTA.h/h (7) 
EQU Young's modulus Er=p(t)/.epsilon. (8) 
(p: intraventricular pressure) 
This is a new index for diagnosing arterial sclerosis which is different 
from an index E .theta. of prior art. 
(5) Non-Invasive Measurement of Intraventricular Pressure by Analyzing the 
Cardiac Vibration 
The intraventrcular pressure is a very important measure of heart 
diagnostic. Especially the end-diagnostic period pressure of left 
ventricle is necessary and indispensable for the estimation and 
observation of cardiac functions, but it is normally 10-20 mmHg, therefore 
it can not be measured at the artery of upper arm. Therefore, a cardiac 
catheter is used for the measurement of the end-diastolic period pressure, 
namely, a part of arterial of upper arm or under limb is cut open and a 
small pressure sensor is inserted to the ventricle through the artery for 
measuring the pressure. This method can measure a precise intraventricular 
pressure, but for the reason of an invasive observation, it cannot be 
executed easily and repeatedly at a place like an outpatient hospital or a 
bed side. 
Therefore, the present invention proposes a new method for the measurement 
of small vibration of myocardial. It is a non-invasive observation method 
that observes the small vibration of myocardial wall and is possible to 
decide the eigenfrequency of ventricle by analyzing the spectrum of the 
small vibration, and further by combination with a geographical 
measurement of myocardial wall thickness and radius etc. decides the 
end-diastolic period pressure of left ventricle non-invasively. It has 
been resulted by a quantitative estimation based on an application of in 
vitro experimental data to be possible to measure the end-diastolic period 
pressure of left ventricle non-invasively within error of 2-3 mmHg. It is 
not too much to say that it is a great epoch making result on domains of 
medical engineering, acoustic engineering and circulatory internal 
medicine. 
Theory of Non-Invasive Measurement of Intraventricular Pressure 
According to Mirsky method for a left ventricle elasticity, when the left 
ventricle is supposed as an elastic shell of radius r m! and thickness h 
m!, where the thickness corresponds to the ventricular wall thickness, a 
relation of left ventricular stiffness Eq Pa! and the pressure p(t) Pa! 
of left ventricular cavity at time t are the following. 
##EQU3## 
Where V is the volume of left ventricular cavity, Vw is the volume of left 
ventricular wall and .sigma.m is the left ventricular wall stress Pa! at 
the wall center of thickness direction. And .alpha. and .beta. are the 
coefficients when dp(t)/dV is expressed as dp(t)/dV=.alpha.p(t)+.beta.. 
Experimentally, is calculated from .alpha.V=1n(p(t)/57.32), .beta. can be 
neglected. 
On the other hand, Honda, Koiwa etc. of Tohoku University have shown 
experimentally that the myocardial elasticity E can be approximated by a 
following equation, when the left ventricle is supposed as an elastic 
shell. 
EQU E=8.7.times.10.sup.4 r.sup.2 f(t).sup.2 (10) 
where f(t) is eigenfrequency Hz! of left ventricular mode 2. When the left 
ventricular radius r, the left ventricular wall thickness h, the 
eigenfrequency f(t) are given, the left ventricular cavity pressure p(t) 
can be calculated by resolving an equation that the myocardial elasticity 
Eq of the left ventricle denoted by formula (9) and elasticity E denoted 
by formula (10) are equal. 
Spectrum Analysis for Deciding the Eigenfrequency 
The left ventricular radius r and wall thickness necessary for calculating 
the left ventricular pressure p(t) at time t can be easily measured with 
the ultrasonic diagnostic equipment. On the other hand, because of the 
nonstationaryty of cardiac wall vibration, the time frequency analysis is 
necessary for the estimation of instantaneous eigenfrequency f(t). 
Therefore, in this invention, the spectrum analysis of the nonstationary 
cardiac wall vibration is done by using wavelet conversion. 
The eigenfrequency f(t) must be decided carefully by considering the 
following. 
(1) The time-frequency distribution obtained from the small vibration 
analysis on the cardiac wall with the wavelet transformation contains 
various frequency components beside components of mode 2 of the left 
ventricle. 
(2) Signal analysis accuracy depends on each spectrum analysis method or an 
adapted window function. 
Therefore, considering that the frequency range of mode 2 of the small 
vibration of cardiac wall is more than 20 Hz, the frequency having the 
largest value of (maximum) power spectrum .vertline.T'.sub..PSI. 
(t,f).vertline..sup.2 in range of 20-80 Hz in each distribution obtained 
at each time t is decided as an instantaneous eigenfrequency f(t) of mode 
2 of cardiac wall. 
Estimation of Intraventricular Pressure Measurement by In Vitro Experiment 
The estimation of intraventricular pressure of the left ventricle are done 
by using the small vibration s(t) of back center of left ventricle of an 
excised and isolated heart of canine measured by acceleration meter. FIG. 
1 shows the result of the estimation of intraventricular pressure. 
In FIG. 16, an electrocardiograph (ECG) is shown in figure (a), the cardiac 
vibration s(t) is shown in figure (b), the time-frequency component 
distribution .vertline.T'.sub..PSI. (ti).vertline..sup.2 is shown in 
figure (c) and eigenfrequency {f(ti)} is overlaid in figure (c), the 
intraventricular pressure p(t) of an actual measurement with catheter is 
shown in figure (d), in figure (d) mark of .quadrature. shows the 
estimated intraventricular pressure {p(ti)} of end-diastolic period. 
The experiment for estimation is done by using Modulated Gaussian function 
.PSI.M(t), Hanning function .PSI.H(t), the second derivative of a Gaussian 
.PSI.SG(t) as the basic wavelet. 
FIG. 16 (c) shows a time-frequency distribution .vertline.T'.sub..PSI. 
(t,f).vertline..sup.2 which is obtained by applying .PSI..sub.M (t) (m=6) 
to the myocardial vibration s(t) and eigenfrequency {f(ti)}(i=1, 2, . . . 
, 15) over 75 ms at each interval of 5 ms before 15 ms of R wave are 
decided. 
Also FIG. 16 (d) shows an actual measurement result of the left ventricular 
pressure p(t) by using catheter and estimated values {p(ti)} (i=1, 2, . . 
. 15) around the end-diastolic period obtained by this invention. 
From these consequence, the left ventricular pressure can be estimated 
exactly in a case of using the modulated Gaussian .PSI.M (t) as a basic 
wavelet function. 
Furthermore, for estimating the intraventricular pressure at timing of a 
good S/N in end-diastolic period on eigenfrequency of mode 2, while 
changing the variable of the basic wavelet function, an average of 
.DELTA.pmax of difference between an actual measured value p(tmax) and an 
estimated value p(tmax), and a standard deviation .sigma.max for 16 
heartbeats are obtained, where the actual measured value p(tmax) at time 
tmax that the power of the eigenfrequwncy {f(ti)} is the maximum of 15 
points in one heartbeat. The result is shown in FIG. 17. As shown in FIG. 
17, both of .DELTA.pmax and .sigma.max are very small as under a few mmHg. 
This shows that the intraventricular pressure of left ventricle is 
estimated very accurately in this invention.