Background technology
Skeleton is the human body important component part, and it plays a part indispensable to motion, growth, the growth of human body.But all can cause the change of bone mass because of factors such as aging, external force damage, tumors.Therefore measuring the skeleton mineral density is important monitoring index in the clinical medicine.
Ultrasound wave is to exceed people's ear audition, the sound wave of frequency more than 20KHz.When ultrasound wave is propagated in different media, have the different velocities of sound because of the physical characteristic of medium is different, in other words, it has different spread speeds in normal bone and improper skeleton, can distinguish osteoporosis thus, fracture patient or normal population.
1989, R.P.Heaney proposed in one piece of paper: have following relation between the speed that sound wave is longitudinally propagated in bone and the density of bone:
D=KV
L (1)
D is a bone density in the formula, V
LThe vertical transmission speed of sound wave, K is a constant.
Measuring vertical bone velocity of sound this shows that between the spread speed, there are a functional relationship in bone density and sound wave in bone, as long as therefore just can calculate bone density.
When adopting ultrasonic measurement, generally be measuring object with the long bone, this mainly is the operation because tibia and radius are more convenient for.But find in measuring that the peripheral soft tissue of skeleton has interference to measurement result, the soft tissue velocity of sound is slower than the bone velocity of sound, and its thickness has uncertainty, more because the flexibility of soft tissue causes probe and tested bone plane to be difficult to keeping parallelism, thereby brings measurement error.
In order to solve the influence of soft tissue to measuring, russian patent SU1,342,479 utilize an emitter and two accepters, receive the time difference of same ultrasonic signal by the receptor that calculates two diverse locations (at a distance of being d), with the influence of counteracting soft tissue, and calculate bone velocity of sound V=d/ Δ t.This method only when three ultrasonic devices are parallel with tested skeleton measurement result just can reflect the velocity of sound of tested bone section, but when actual measurement, cause probe swing at any time because of the flexibility of soft tissue, require probe and bone surface keeping parallelism to be difficult to accomplish.
For this reason, people such as Israel scientist Edward Kantorovich proposed one in 1998 and contains four independent variable V
S(the soft tissue velocity of sound), V
BThe quaternary Simultaneous Equations of (the bone velocity of sound), φ (angle of probe and tested bone) and h (probe and skeleton average distance) is found the solution this equation group, can try to achieve the bone velocity of sound.But the problem of thereupon bringing is, it is what complicated again to separate a quaternary Simultaneous Equations that comprises three kinds of trigonometric functions, even the author is with one of them variable V
SCome generation to dive with an experience constant, go still to can't resolve the complexity of its solution procedure, correspondingly, also just influenced the practicality of this measuring method.
Summary of the invention
Problem to be solved by this invention is to propose a kind of easylier, faster, just can accurately measure the measuring method of sound spread speed in tested skeleton without estimated data and complicated calculations.
The technical scheme that addresses the above problem is:
A kind of method of measuring the velocity of sound in the skeleton, it comprises the steps:
A. the outer surface at the soft tissue that covers one section skeleton is provided with ultrasonic transmitter and ultrasonic receiver, and described emitter and receptor are arranged and are arranged on the straight line along the y direction of above-mentioned skeleton;
B. launch ultrasound wave by ultrasonic transmitter to skeleton, receive ultrasound wave by ultrasonic receiver;
C. described ultrasonic transmitter is two, is respectively emitter R, A1, and ultrasonic receiver is two, is respectively receptor B1, B2;
D. above-mentioned emitter and receptor are arranged continuously according to the order of R, A1, B1, B2, are arranged in a probe, and are arranged on the straight line, and the distance between two emitters equates with the distance between two receptors; And be L.
E. determine that the time that receptor B1 receives emitter R ultrasonic waves transmitted is T1, determine that the time that receptor B2 receives emitter A1 ultrasonic waves transmitted is T2, determine that the time that receptor B1 receives emitter A1 ultrasonic waves transmitted is T3;
F. compare T1, T2, when T1=T2, the spread speed of sound wave in this section skeleton can be calculated with following formula:
V=L/ΔT
Wherein L is two distances between ultrasonic receiver B1, the B2, and Δ T=T2-T3 is the time difference that two ultrasonic receiver B1, B2 receive the same ultrasonic pulse of ultrasonic transmitter A1 emission.
The method of the velocity of sound in the said determination skeleton, probe can be slightly mobile at the outer surface of the soft tissue that covers measured skeleton during measurement, when Measuring Time T1 is identical with T2, stops to move and keeping the position of probe, record parameter T2, T3 at this moment.
The method of the velocity of sound in the said determination skeleton, the ultrasound waves appearance that described ultrasonic transmitter R and A1 send are together.
The method of the velocity of sound in the said determination skeleton, described angle of incidence γ selects between 10~25 degree.
The method of the velocity of sound in the said determination skeleton, the time data that the ultrasound wave that described ultrasonic transmitter R, A1 are sent arrives ultrasonic receiver B1, B2 is transported in the microprocessor, the time T 2 that the ultrasound wave that the time T 1 that the ultrasound wave that R is sent by microprocessor arrives B1 and A1 send arrives B2 compares, when T1, T2 equate, microprocessor sends the measurement commencing signal according to the condition that is provided with in advance, note the time that ultrasound wave is advanced, calculate the bone velocity of sound.
Adopt method provided by the invention, eliminated the interference of the soft tissue that covers measured skeleton, the variate-value that does not have hypothesis in the computational methods, the selection critical angle of science can make measure ultrasonic propagation in the skeleton speed more accurately, more easy, more quick, also be easier to extrapolate the bone density of being asked.
The specific embodiment
From background technology as can be known, when ultrasonic emitting after bone surface, the same with the ripple of other type, the refraction effect of similar light when dredging the property material to the close property of sound material, sound can take place, can be scattered through the most of sound wave in bone surface refraction back, has only the sound wave that is transmitted into bone surface along a certain angle [alpha], its refractive direction is just in time parallel with bone surface, and after bone surface advances the stretch journey, reflect from bone surface with identical angle of emergence α again, what we can utilize is exactly this part, and its angle of incidence α just is called critical angle.People's firing angle α (or γ) also is the angle of inclination of transducer work surface in the ultrasonic transmitter-receiver.Because this bundle ultrasound wave is vertically being advanced along bone surface,, we just can be regarded as out the velocity of sound of ultrasound wave in bone in time and distance that bone surface is advanced as long as measuring it.But at the same time, ultrasound wave will consume the time through two sections distances equally in the soft tissue around the bone when arriving bone surface and reflexing to skin surface.Because because of firmly uneven, can produce an inclination angle usually when probe is pressed on the skin, promptly the plane at ultrasonic element place is uneven on the surface of skeleton and the instrument probe.When the ultrasound wave transdermal, its emission distance is different with turning back to the receptor distance, has increased the time of advancing in soft tissue, thereby has influenced the degree of accuracy of measurement result.When calculating the spread speed of ultrasound wave in skeleton, remove of the influence of skeleton surrounding soft tissue to measurement result, just must guarantee that the transmission path of ultrasound wave in soft tissue is identical with RX path length, could guarantee that detecting head surface is parallel with bone surface, accurately calculate the spread speed of ultrasound wave in skeleton.
Fig. 2 is presented at two ultrasonic transmitter R, A1 and two ultrasonic receiver B1, B2 (also can adopt more emission to accept device) has been installed in the probe, and they are arranged along parallel bottom surface one straight line in probe continuously according to the order of R, A1, B1, B2.Distance between distance between two emitter R, the A1 and two receptor B1, the B2 equates that be L, the distance between emitter A1 and the receptor B1 is X.
The time that receptor B1 receives emitter R ultrasonic waves transmitted is:
T1=t1+t1 '+t1 ", wherein t1 ' and t1 " be respectively time of the soft tissue that emitter R ultrasonic waves transmitted enters and reflect, t1 is this ultrasound wave elapsed time in skeleton.
The time that receptor B2 receives emitter A1 ultrasonic waves transmitted is:
T2=t2+t2 '+t2 ", wherein t2 ' and t2 " be respectively time of the soft tissue that emitter A1 ultrasonic waves transmitted enters and reflect, t2 is this ultrasound wave elapsed time in skeleton.
The time that receptor B1 receives emitter A1 ultrasonic waves transmitted is:
T3=t3+t3 '+t3 "; wherein t3 ' and t3 " be respectively time of the soft tissue that emitter A1 ultrasonic waves transmitted enters and reflect, t3 is this ultrasound wave elapsed time in skeleton, t3=X/V, X is the distance that ultrasound wave is propagated in skeleton, and V is the speed that ultrasound wave is propagated in skeleton.
The time of the ultrasound wave arrival ultrasonic receiver B1 that ultrasonic transmitter R in above-mentioned probe sends is identical with the time that the ultrasound wave that ultrasonic transmitter A1 sends arrives ultrasonic receiver B2, promptly two emitter ultrasonic waves transmitted arrive two receptors the distance of the soft tissue around the skeleton of process identical, its time also just equates, be t1 '=t1 "=t2 '=t2 "=t3 '=t3 ", at this moment just can utilize above formula to calculate the transmission speed of ultrasound wave in skeleton.In above-mentioned formula, because probe this moment is parallel with bone surface, be respectively L+X to B1 with by A1 to ultrasound wave distance of process in skeleton of B2 by R, the elapsed time t1 of institute, t2 equals (L+X)/V respectively.
As can be seen from Figure 1, time T 2, T3 that two ultrasonic receiver B1, B2 receive the same ultrasonic pulse of ultrasonic transmitter A1 emission are different, and free poor Δ T between them according to above-mentioned formula, can calculate:
ΔT=T2-T3=(t2+t2’+t2”)-(t3+t3’+t3”)
=t2-t3
=(X+L)/V-X/V
=L/V
So V=L/ Δ T
In this formula, L is the distance between known two receptor B1, the B2, Δ T is the time difference that two receptor B1, B2 measuring receive the same ultrasonic pulse of ultrasonic transmitter A1 emission, so the transmission speed V of ultrasound wave in skeleton can be easy to calculate.
In order to explain its derivation in more detail, do further to discuss below in conjunction with accompanying drawing.
In the sonic propagation figure that Fig. 1 represents, just can be regarded as out the velocity of sound of ultrasound wave in bone in time and the distance that bone surface is advanced as long as measure sound wave:
V
B=L
B/T
B (2)
Wherein: L
BThe distance of in bone, being walked for sound wave;
T
BThe time that sound wave is walked in bone.
As we can see from the figure, ultrasound wave has also transmitted AO and O in the soft tissue around the bone
1B
1Two sections distances have consumed the time equally.Because the density and the bone density of integumentary musculature and fat have very big difference in the soft tissue, and because of crowd and health status individual variation are bigger, it almost is impossible wanting to calculate sound wave spread speed therein.
For this reason, the present invention sets up a plurality of receptors, as B
2B
3Deng, and the distance between them is pre-determined, is assumed to L
1
Sound wave by emitter A to receptor B
1Time be:
T
A1=AO/V
S+OO
1/V
B+O
1B
1/V
S (3)
Sound wave by emitter A to receptor B
2Time be
T
A2=AO/V
S+OO
1/V
B+L
1/V
B+O
2B
2/V
S (4)
Because O
1B
1=O
2B
2(4) formula and (3) formula are subtracted each other
T
A2-T
A1=AO/V
S+OO
1/V
B+L
1/V
B+O
2B
2/V
S-(AO/V
S+OO
1/V
B+O
1B
1/V
S)=L
1/V
B
Our the desired bone velocity of sound is like this
V
B=L
1/(T
A2-T
A1) (5)
Arrive receptor B as long as record ultrasound wave
1B
2Time difference just can calculate V
B
In order to improve the degree of accuracy of time difference measurements, we can install two or more a plurality of ultrasonic receivers, calculate the meansigma methods of its time difference.
In addition, because skin is a soft tissue, because of firmly uneven, can produce an inclination angle usually when being pressed in probe on the skin, promptly the plane at ultrasonic element place is uneven (see figure 2) on the surface of skeleton and the instrument probe.When the ultrasound wave transdermal, its emission distance AO is identical, but it turns back to receptor B
1B
2The time distance O
1B
1And O
2B
2Be different, increased by one section B that in soft tissue, advances
2The distance of M has increased the time Δ T=B that advances simultaneously in soft tissue
2M/V
SThereby, influenced the degree of accuracy of measurement result.
In order to address this problem, in probe, can increase by one group of reference ultrasonic transmitter R, and the distance between R and the main emission A1 is pre-determined, also be L, the ultrasound wave arrival receptor B that sends when the reference emitter
1Time and the ultrasound wave that sends of main emitter arrive receptor B
2Time when identical, when promptly their paths of walking equate, the declination angle of detecting head surface and bone surface=0 at this moment, promptly detecting head surface and bone surface are in completely parallel position.
In practical operation, a data microprocessor can be installed in probe or instrument, it is comparing the time that the ultrasound wave that is sent by reference emitter and main emitter arrives corresponding receptor constantly, when both times equate, be that detecting head surface and bone surface are when being in parallel position, also show in the display this moment, represent the colour band of used time of two paths isometric, note the used time of ultrasound wave, and calculate the bone velocity of sound, and extrapolate bone density by (1) formula with (5) formula.And go out the result by printer prints.This result has eliminated because of the caused error of probe inclination, has guaranteed the degree of accuracy of measurement result.
This method principle is simple, does not need complicated calculating, and date processing is undertaken by computer, has avoided artificial disturbance, and the certainty of measurement height has been received good effect in implementing practical operation.
Use and adopt the instrument of the principle of the invention to randomly draw 30 routine prescription on individual diagnosis patients (male's 15 examples, women's 15 examples), carry out the bone density inspection.And compare experiment with X line dual energy bone densitometry instrument (DEXA) testing result produced in USA, and will measure actual result and carry out statistical procedures, to analyze its dependency, see the following form 1.
Wherein use dual energy X line and make a definite diagnosis osteoporosis person's 11 examples, and using ultrasound sclerotin analyser diagnosis osteoporosis 13 examples wherein there are two example diagnosis not to be inconsistent.
Diagnostic accordance rate 28/30=93.3% illustrates that the accuracy of instrument of the present invention meets the requirements (>90%).
Because the ultimate principle difference of two kinds of detection methods, its range of normal value and diagnostic criteria are also just different, in the SPSS statistical software, two groups of data are carried out the rectilinear correlation analysis
Show through SPSS 11.5 statistic analysis result:
Correlation coefficient r=0.697 p=0.000 p<0.01
Therefore two kinds of sclerotin indexs that analyser is surveyed are dependency relation, illustrate that testing result of the present invention is true and reliable.
Another group test data sees the following form 2:
Wherein only have 1 example diagnosis not to be inconsistent with matched group, diagnostic accordance rate 96.67% greater than 90%, illustrates that the accuracy of sclerotin analyser of the present invention meets the requirements.SD-1000C type in the table is the model of the single photon bone mineral analyser that generally uses of medical industry.