230

U L T R A S O N I C I N S f R U t f E N f S FOR 1 I V E A N I M A L E V A L U A T I O N

JAMES K o D A V I S

To prepare a t a l k from a topic of "Ultrasonic Lnstrumentation" would be a b i t d i f f i c u l t without the cooperation of those involved with the designing and engineering of the equipment. So, before delving in to the topic a t hand, I would l i k e t o express my appreciation t o Branson Instru- ments, Sonomedic Corporation, Hoffrel Instruments and the Meats Research Division of the U. S. Department of Agriculture fo r supplying me with additional information i n preparing t h i s presentation. Furthermore, I consider it a r e a l honor and privilege t o have the opportunity t o share some of miy ideas and thoughts before t h i s group f o r such a matter.

'

In sp i t e of considerable advancement in beef production technology, accurate and precise methods of predicting carcass value i n the l i v e animal have yet t o be developed. beef, the producer i s i n need of some re l iab le method of determining the proportions of f a t and lean. Beef carcasSes a re composed of three maJor t issues: the proportion of these t i s sues within a carcass consists of the pbJrsical separation of bone and chemical analysis of the remaining material. How- ever, t h i s method is prohibit ive because of the expense and time involved and obviously is impossible in the case of the live animal and cannot be used in breeding programs except by way of progeny or sib tests.

With the increasing demand for high yielding

muscle, f a t and bone. Probably the most accurate measurement of

For the past decade, researchers have used ultrasonics t o remove sone Of the subject ivi ty from selection of livestock, but s t i l l , we have not f u l l y developed t h i s method. precision is the differences in instruments and techniques.

Perhaps one of the reasons f o r this lack of

21 order t o fu l ly appreciate ultrasonic instrumentatian, I th ink the place t o s t a r t is a t the very beginning and make a brief review of pr inciples and fundamentals of sound, even though it may be elementary t o some in the audience.

Ultrasonics i s a branch of science dealing with the principles

Ultrasonics deal both with the e f fec ts governing ultrasound, the equipment used t o generate the sound, and the prac t ica l applications of sound. of mechanical vibrations of ul t rasoaic waves and with the apparatus used t o produce these waves, high t o be audible by the human ear, which, generally speaking, is above 16,000 cycles per second. Sound waves can be propagated through solids, liquids and gases. the velocity of sound in it, and the less power required t o transmit sound energy a given distance. No homogeneous material is an insulator against sound energy.

Ultrasonic waves a r e sound waves a t a frequency too

In general, the more so l id the med ium, the greater

Ultrasonic waves can be u t i l i zed i n evaluating l i v e animals because of two primary reasms: tes t ing and;

1) it is a method of non-destructive- 2) t he waves provide a directionalbeam. When an ultrasonic

231

beam passing through one medium reaches the boundary of t ha t medium and strikes a dissimilar medium, par t of the energy is transmitted in to the second medium while the r e s t is ref lected back through the or iginal medium t o the source. The amount of ref lect ion is determined by the nature of t h e two media or the acoustical impedance of the material, which is the product of the densit;r of the material and the velocity of sound through it. Echo-ranging, the type of ultrasonics applied t o l i v e animal evaluation, is the transmission of sound energy through a medium and the reception O f an echo caused by a medium of different make-up. These echoes a re generally displayed on a cathode -ray-tube .

The source of ultrasonic energy used in l i v e animal evaluation is Once the energy is propagated, it i s transmitted t o an e l e c t r i c generator.

acoustical energy by a transducer.

Because of the var iab i l i ty in l i v e t issue, the transducer i s a major factor i n evaluation. used i n ultrasonics. piezoelectric. bioacoustical studies. insofar a s it transmits e l e c t r i c a l energy, through a crystal , t o sound energy.

There a r e three main categories of transducers They a re magnetostrictive, electromagnetic and

The l a t t e r , piezoelectric, i s the type primarily used for It functions much the same as a phonograph needle,

The precise reasons f o r the piezoelectric e f fec t a r e not &own In de ta i l , but apparently, with no pressure applied, the e l e c t r i c a l charges i n the c rys t a l domains of the material a r e spaced so tha t no net e l ec t r i c charge appears on e i ther surface. Under pressure, t h e c rys t a l domains a re realigned so tha t opposite e l ec t r i c charges appear on the t w o surfaces. a voltage applied across the material causes a physical realignment of c rys t a l domains, producing a change i n shape. Barium t i t ana te and other t i t ana te s a r e currently t h e most commonly used piezoelectric materials fo r ultrasonic applications. Quartz and Rochelle s a l t a r e a l so used. Each material i s better sui ted fo r par t icular applications, i s hard, impervious t o moisture and can be used i n higher frequencies; how- ever, a larger amount of voltage i s required for proper transducer action.

Similarly,

For instance, quartz

In our work, we have found tha t with the present transducers, frequencies of 1.6 t o 2,25 Mc/sec. deliver the best results. t h i s frequency range there a r e great differences. quencies near 2.25 Mc/sec . w i l l give greater def ini t ion of interfaces, but w i l l not penetrate t i s sue a s well a s transducers near 1.6 Mc/sec. type transducer, not ye t available on t he market, has a transmitter and a receiver mounted separately i n the head. def ini t ion a t shallow depths, without the confusion of other signals. This should improve f a t thickness measurements.

Even within Transducers with fre-

A new dual

They function t o give maximum

Not only i s the transducer of major consideration i n ultrasonic evaluation, but a l so the consistency and character is t ic of the t issues . a p i l o t study conducted while I was a t Cornell, sound transmitting time, or the apparent velocity, was measured by using a set of Germany-made cal ipers with a transmitter and a receiver mounted i n the t i p s of t h e probes. An ident ica l s e t of calipers, except without the transducers, was mounted on the face of the oscilloscope t o accurately measure the t ransmit ta l time in various t issues . The caliper-transducers were calibrated i n d i s t i l l ed water a t room temperature using 1490 M/sec. a s the standard, We studied the sound

In

232.

t ransmit ta l time, with varying temperature, in the first and second layer of pork f a t removed from the shoulder region opposite the first rib, i n beef muscle t issue, in d i s t i l l e d water and in paraffin o i l , which, in application, is used a s an acoustic coupling, Specific gravi t ies of these materials were a l s o studied, but the data were inconclusive, presents the results of t h i s preliminary study. You w i l l notice t h a t a t 32 F., the t ransmi t ta l time i n the first layer of pork f a t i s 1725 M/sec. and the apparent velocity of sound in the second layer a t 3Z0 F. is 1665 M/sec. These apparent veloci t ies paralleled each other a s the temperature was in- creased t o the boiling point a t which the transmission time had decreased t o 1230 M/sec. T U s slowing of t ransmit ta l time can par t ly be explained by the f a c t t ha t increasing temperature causes an increase in volume and number of vapor deposits and a i r spaces, causing the d i r ec t iv i ty of wave transmission t o be defrayed, resulting in a greater time lapse for the returned pulse echo. In the case of beef muscle, the reverse action takes place. Because of i t s structure, muscle tlssue appears more dense a t lowest temperatures and becomes less dense a s t he temperature increases unt i l a point around 170' F., when the muscle beglns t o decompose and defray the wave transmission, resulting in a slarer apparent velocity. The same general action occurs with d i s t i l l e d water, suggesting that the pa r t i c l e s a r e more closely adhered t o each other a t approximately looo F.; then, the inter-molecular space increases a t temperatures about 100' F,, due t o the vapor produced, again defraying sound waves. The speed of sound in paraff in oil i s much slower than i n the other materials studied. Perhaps t h i s is due t o i t s viscosity; nevertheless, t he t ransmit ta l time paralleled t h a t of pork fa t . h e precaution must be taken in a study such a s th i s , and that is t o maintain a constant pressure. These data were collected under normal atmospheric pressure.

Figure 1 graphical %

Assuming t h a t the speed of sound in beef f a t i s nearly the same a s in pork f a t , and the speed of sound in pork muscle is the same a s i n beef muscle, some of the problems of cal ibrat ion a re a l leviated by the fac t t ha t the r e l a t ive speed OP sound in f a t and muscle is nearly the same a t body teaperature. Since the greatest mass of t i s sue being measured in l i v e animals is f a t and muscle, with the blood in it, we collected some blood from hogs immediately a f t e r st icking and the velocity appeared t o be approximately 1500 M/sec., nearly the same a s tha t of f a t and muscle a t body temperature. This, again, presents l i t t l e problem in cal ibrat ing fo r l i v e animal evaluation,

A l l of these data were collected by using a standard A-scan pre- sentation on the cathode-ray-tube. A cathode-ray-tube is basical ly a large vacuum tube which projects a t high speeds a fine stream of invis ible electrons from the cathode a t one end t o the face of t h e tube a t the other end, The face is coated with a fluorescent screen, which glows when struck by electrons, and results in a visible signal. The standard A-scan presentation is one where the t race appears i n a s t ra ight line with the i n i t i a l pulse, and the pulse of the echo appears a s a b l i p a t right angles t o the trace. This type scan is used for velocity studies and depth measurements.

The B-scan, which i s used t o record area, i s a series of s ignals wtth the in tens i ty modulated so t h a t the b l ips or signals appear as a single point, t h a t sweeps across the cathode-ray-tube i n d i rec t r a t i o t o the movement of a scanning potent imeter . This potent imeter i s mounted in the t i s sue scanner and i s in

233

accordance with the time axis of the cathode-ray-tube. In some new equip- ment not yet on the market, a J-scan, i s used fo r l inear measurements. It i s a c i rcu lar sweep near the edge of the cathode-ray-tube. of the oscilloscope calibrated i n a l inear fashion, depth measurements a re eas i ly and quickly obtained.

With the face

Perhaps one of the best ways t o test the va l id i ty of ultrasonics This type of work has been done in a i s t o test one uni t against another.

couple of instances. Four Branson Sonoray animal scanner uni ts were used t o evaluate rib-eye area and f a t thickness of a l l Junior Yearling s teers and the senior calf classes of Shorthorns and other breeds i n the Quality Beef Contest a t the Lnternational Live Stock Show l a s t year. were similar, except f o r the operators. t i s sue scanner containing a 1.6 Mc/sec. transducer mounted on a f loa t ing skid. interpretat ion of the resul t ing pictures was done by Dr. 3. R. Stouffer. The units represented were frcm Cornell University, University of Kentucky, V. P. I., Southeastern U.S.D.A. post a t KnoxvIUe and a spare uni t from Branson Instruments .

The uni ts Each unit was equipped with a

I, personally, calibrated a l l units a s closely as possible and the

As the steers came out of the photography chute, they were gate sorted t o one of the four units. Herefords were subjected t o a l l four units.

However, a l l of the Junior Yearling

Simple correlation coefficients between ultrasonic and carcass measurements f o r f a t thickness and rib-eye area, t o t a l l y and within breeds, a re shown in tab le 1.

Ultrasonic measurements of f a t thickness were highly correlated with the ac tua l f a t thickness within the Angus (r = 0.50) , Shorthorn and other breeds (r = 0.80), and the t o t a l (pooled) of 69 s teers (r = 0.67). The f a t thickness was signif icant ly re la ted within the Hereford breed (r = 0.51).

For rib-eye area, only the Herefords showed a highly s ignif icant relationship (r = 0.70) between the ultrasonic and carcass values. Short- horn and other breeds showed a s ignif icant relationship (r = 0.40), a s was revealed when the data were pooled; while a non-significant association was found between ultrasonic and carcass rib-eye value in the Angus breed.

These data, coupled with the means and standard deviations a re shown i n tab le I1 and suggest t ha t a breed difference l ike ly exis ts . It i s suggested tha t the breed differences may be due t o the differences in: 1) hide thickness; 2) properties and character is t ics of f a t t issues; 3) marbling and other muscling characterist ics; 4) temperament i n re la t ion t o muscle tension a t time of evaluation; and 5) changes i n muscle and f a t character is t ics during and a f t e r slaughter. A l l of t h e factors, except the l a t t e r , can a f fec t the properties of sound waves.

Table I n shows the correlation coefficients among four u l t r a - sonic units tha t evaluated the same Junior Yearling Hereford s t ee r s and the carcass values. Tables N and V show the correlation coefficients between the various uni ts for f a t thickness and rib-eye area, respectively.

234.

It is noted that uni t s 1 and 4 were reasonably close i n predicting f a t thickness, while the other units were not s i m f i c a n t l y related.

In the case of rib-eye area, units 1, 2 and 4 were s ignif icant ly re la ted when used fo r predicting r i b eye area values. only 5 steers, rendering it not feasible t o base any valid conclusions on the results of t ha t unit.

Unit 3 evaluated

The first and second place steers of each class, within each breed, were ultrasonically evaluated by the Cornell and Kentucky units. Each steer was evaluated by both units. study are present i n tab le V I . These re su l t s would indicate tha t , with more time allowed t o evaluate each steer, greater accuracy was obtained for rib-eye area. Fat thickness values fo r this group of c a t t l e were f a i r l y uniform, which resulted in a lower correlat ion ( r = 0.31), than f o r a l l c a t t l e (r = 0.67).

Data sharlng t h e r e su l t s of t h i s

Table VI1 shows a comrparison of two uni ts a t the Georgia Coastal P l a i n s Experiment Station. The correlation between uni t 1 and carcass values f o r heifers was 0.72. Unit 2 was correlated with the heifer r i b - eye area values t o the extent of 0.68. On bulls, unit 1 had a correlation of 0.71 and uni t 2, a correlation of 0.46. The correlation between uni t 1 and uni t 2 f o r bu l l s was 0.62 and heifers 0.74. On bu l l s not slaughtered, the uni ts were correlated t o the extent of 0.78.

In a study in conjunction with a Meat Animal Evaluation Clinic a t Georgia, rib-eye area and f a t thickness were estimated on t en steers. Table V I I I shows the correlation coeff ic ients between a committee estimate and carcass value, and ultrasonic estimates and carcass value. Committee estimates were correlated t o the extent of 0.70 with carcass rib-eye area, while ultrasonic estimates were more highly correlated t o the extent of 0.83, For f a t thickness, t he cammittee estimates were a l i t t l e more closely correlated t o carcass f a t thickness than were the ultrasonic estimates,

Appa rent Velocity

of

Sound

(M/sec .)

17 40 1720 1700 1680 1660 1640 1620 1600 1580 15 60 15 40 1520 1500 1480 1460 1440 1420 1400 1380 13 60 1340 1320 1300 1280 12 60 1240 1220 1200 1180 11 60 1140 1120 1100 1080 10 60 1040

N M

‘. . . . ... .. , .... ... _..- ..... .:.., , , . . .I .. , ~ _... .... ‘ ._..

. ’. \ \ \

\ .\

Temperature (FO.)

. - , - .Dis t i l l ed llater . . Beef Muscle

,- -, - 2nd Layer Pork Fat - 1st Layer Pork Fat

- - - - - Paraffin O i l

Velocity of Blood of swine a t bow temp. = 1500 M/sec.

Figure 1. Apparent Velocity of Sound i n Various Materials;

236.

TABU I

Correlation Coefficients Between Ultrasonic Live Animal Measurements and Carcass Values .

Breed NO. ObS. Fat thickness Rib-eye Area

Angus 22 Hereford 14 Shorthorn & Others 33

Total (Pooled) 69

.58* .22 51* . ? O w . 80* 40

.67* 40*

* P e .01 * P < 005 TABU I1

Means and Standard Deviations Por Ultrasonic and Actual Measurements.

-~ __ -

Ultrasonic Actual Fat Thick. Rib-eye Fat Thick. Rib-eye

m 3 u s 1.2 (0.3) 14.6 (1.6) 0.9 (0.2) ll.7 (1.0)

Hereford 1.1 (0.1) 12.5 (1.4) 0.8 (0.2) 12.1 (1.1) Shorthorn & Others 0.8 (0.3) 11.8 (1.5) 0-6 (0.2) 11.2 (1.6)

TABLE Irr Correlation Coefficients Between Four Ultrasonic Units and the Carcass

Values on the same Junior Yearling Hereford Steers.

mit NO. ObSo Fat Thickness Rib-Eye Area ___ _ _ _ ~ ~

1 (Cornell) 10 2 (univ. of IQ.) 10 3 (V.P.I.) 5

4 ( U m S . D d . ) 10

0 88* .55

67

66*

053

.58

38

052

W P C.01

* P < .05

237 e

TABLE N

Simple Correlation Coefficients Among Ultrasonic Units (Fat Thickness)

UNITS 2 3 4

1

2

3

50 .40

.43

68*

.49

52

TABLE V

Simple Correlation Coefficients Among Ultrasonic Units (Rib-Eye)

UNITS 2 3 4

1 e 63* 75 70*

2 e 5 7 a38

3 70

* P < e05

TABLE VI

Correlation Coefficients Between Ultrasonic Measurements and the Carcass Values on the F i r s t and Second Place Steers of Each Class.

Carcass Fat Thickness Rib -Eye Area

Ultrasonic

Fat Thick 31

Rib-Eye Area e 6 7 w

238

Simple Correlation Coefficients Between Two Different Ultrasonic Rib-Eye Estimates and Carcass Measurements, and Correlation Coefficients Between the Two Ultrasonic Units for Rib-Eye Area.

-- v n i t 1 Unit 2

Heifers Bulls

Correlation Between Units:

Heifers 0.74* Bulls 0.62*

Bulls (not slaughtered) 0 78*w

0.72w 0.68*

0 71* 0.46

* P < .01 * P < 405

TABLE V I 1 1

Simple Correlation Coefficients Between Rib-Eye Area and Fat Thickness Esti- mates by Ultrasonics and by a Cammittee of Three, and the Carcass Values.

Carcass

Rib Eye Ares Fat Thickness

Ultrasonics 0.82H 0 83*

C oxnittee 0,70+ 0 92H *

M- P < 001 * P < .os

DR. €UUISEy: Thank you very much, Jim.

Now t ha t we have learned something about instrumentation, l e t ' s c a l l upon tha t t a l l gentleman who originally hailed from the deep south, Dr. R. H. Alsmeyer. ultrasonic research on beef c a t t l e in the United States and give us an idea of the research that is now i n progress. We asked Dick t o devote a large portion of h is time t o h i s own work and tha t of h i s associates a t t he Meat Quality laboratory a t Beltsville.

He i s going t o t e l l us some of the resu l t s of

# # # # # i f # # # # # #