of the
and
18—20 September, 1984
of the papers and posters
of the
and
Medicine
Scientific, grammatical or typographical inaccuracies have
not been corrected.
may be purchased.
TABLE OF CONTESTS
Myography 35
Ultrasonic 45
Nuclear a.adiulosy CAfcCnSt-O £\\) 75
Intensive therapy 119
Respiratory measurements 14-5
Clinical engineering and education 251
Different instruments on posters 277
Evening workshop 293
Free discussions 297
Authors' index 305
is the sixth international programme within a series of
organizations which were started 20 years ago. It was
often asked during this 20 years whether it was worthy
for a small country to organize great overall conferences.
This question seems to be justified, but the answer can
be only that it is worthy. This opinion has hardly to be
asserted to the readers of this volume containing the
abstracts of all free papers and posters.
We are proud of it that this series of conferences
is accepted, kept in evidence and visited by many experts.
The conference cannot be even imagined without their
participation by now. It is very pleasing that the experts
of IMEKO TC-13 will be also present this year because of
the common organization of the two conferences.
The conference has a good reputation because there
is a medical industry of European level in the background
which is helped by high level medicine on the other hand.
Nevertheless public health is provided only moderately
with experts and equipments of bioengineering.
It also means a classification that the Hungarian
section of medical engineering will be supported by the
International Federation of Medical and Biological Engin-
eering as its member and further on that the Federation
is counting on the work of our experts. It is a further
sign of recognition of the Hungarian section's activity
that the Federation's Administrative Council is holding
its meeting joining to the conference.
It has to be mentioned that Hungary was among the
first socialist countries organizing overall conferences.
Therefore we were endeavoured to draw the representatives
of the socialist countries into this work to help them
to widen out their connections with the other members
of the Federation.
namely that several "rival" conferences will be organized
nearly on the same topics and at the same time. The
consequence is that the active specialists having papers
at these conferences and the other participants as well
will be divided among these conferences. Therefore mutual
information and coordination, the main functions of the
great conferences, cannot be fulfilled. It is unimagin-
able on the other hand that experts and all interested
people will take part in all conferences. The Federation
seems to be the best authority in solving this problem.
It would be nice to find a real compromise between
healthy local patriotism, national prestige, professional
interests and increasing conference costs. Perhaps it
would be possible not to set only place and time of a
conference, but the main topics, too. If methods for
cooperation could be worked out, a common conference
could be more effective than two different ones.
Another personal remark of the editors. Preliminary
works of a conference are not very spectacular, but it
is a fine feeling to order the different abstracts and
to see how the future conference gets more unified and
convincing. The conference to-be becomes alive and real
on the editors' tables: many personal contributions,
personal results form an effective and active power
showing the results of the past and determining the plans,
marks and ways of near and far future. If this conference
will be able to realize all this, success will attend
our tireful but well-meaat efforts in organizing work.
The Editors
Oslo/:
Information in Medicine, City University,
London/
Model-based measurement in physiology
AMD
IMA.SE
THE METHOD OF RECEIVER OPERATING CHARACTERISTIC (ROC) APPLIED TO CARDIOVASCULAR DIAGNOSTICS
by
W. Steinbach, K. Richter, H. Cobet, H. Gerst
Academy of Science of the GDR Central Institut of Heart Disease Research Department of Radiology Wiltbergstrasse 50, DDR-1115 Berlin German Democratic Republic
1. Introduction
Receiver operating characteristic (ROC) has become a valuable tool in measuring the observer's performance also in medicine diagnostics. But there is still to find out whether the concept holds also in more complicated differential-diagnostic tasks.
2. l-.ethod and Material
ROC describes the detection performance by the relationships among the various possible decision frequencies which are gene- rated as different confidence thresholds that are adopted by the observer whereby discriminability is almost independent on the observer's bias.
Two large probes of fluorographs and full size radiographs had been preo.-rr.c: tc be classified for recognition of four type?- of Cr ro'iovascular diseases against the non-diseased cases. The classes were defined according to changes in the heart contour and the great vessels in the following wry: • f-ss 0: normal, no heart disease
class 1: leit vent riculsr i.r.\-c'..vr " "~ " class 2: left ^trio-ventricular involvement cJass 3: bilateral involvement with left prevalence class 4: right-side involvement or bilateral involvement with
richt-side prevalence. Everv clasr is a combination of the h e m contour structure ele- ments sno surroundings to be judged by a detection and/or a dis- crimination criterion. The observers had to make their decisions not in a yes-no answer but by using a ten-point rating scale to overt their degree of confidence.
3. Results
The observer's ability to distinguish between class o and class 1 W E S compared with the results yielded! with a hardware classification device that had been introduced into the algorithm by a learning sample. The classificator's performance was found comparable with the lowest accuracy achieved by the observers. However,the points on the clessificetor1s ROC-curve were spotted almost equitiistantly due to a Gausc'ian probability density function underlied rather than on the observer's ROC.
Diagnostic performance in an alternative classification of class O agsinst class 1 was studied in dependence of the probe dimensions of n = 16, 50, 100, 200, 300 and 374 films of each class. Using the srea bener.th the RCC-curve, F(F), as an accuracy measure it
II
2.1 0
could be demonstrated that at sample dimensions higher than n * 200 (400 in total) performance index tends to constancy. ROC-curves derived from lower dimension probes showed high deviations in the detectrability measure P(F) depending on the observer's performance.
A comparison -"of the decision-maker's attitude was performed at hand of ROC-curves from observers who had evaluated two different samples. The second sample was evaluated about one year after the first. It was found that the positions of the points on the ROC- curves as a reflection of the evaluator's bias form a typical pattern. This pattern was reproduced by the evaluator rather than his discrimination index.
12
GERST,H.Í RICHTERJK.Í STEINBACHJW.
ENHANCEMENT OF LOM CONTRAST DETAILS IN RADIOGRAPHS BY MEANS OF ANALYTICALLY CALCULATED AND CORRECTED BACKGROUND
DETECTION OF LOW CONTRAST TWO DIMENSIONAL (X-Y-) OBJECT DETAILS CAN BE EASILY AND SOMETIMES CONSIDERABLY IMPROVED IF BACK- GROUND INFORMATIONS ."iRE NOT MERELY STATISTICAL BUT FOLLOW SOME ANALYTIC FUNCTION GIVEN BY
2 2 2 2 D U/DX + D U/DY = Of
UHICH IN TERMS OF THE POTENTIAL FIELD THEORY DESCRIBES A SOURCE FREE AREA WITHIN A GIVEN BOUNDARY G(X»Y) OF THE SCALAR POTENTIAL FIELD U(XrY). SUBTRACTION OF THE CALCULATED POTENTIAL AREA IN A STANDARD REGULAR REGION OR IN A REGION BOUNDED BY SOME DIPLAY-AND-CURSOR METHOD YIELDS AN ENHANCEMENT ÜF ALL SOURCES SPOTTED OVER A FLATTENED SOURCE FREE BACKGROUND. RESTRICTING FACTORS ARE? OF COURSE, DEVIATIONS FROM THAT PRIMARY ASSUMPTION OK A POTENTIAL FIELD BACKGROUND ANB» AS USUAL* A GIVEN SIGNAL-TO-NOISE RATIO OF THE CONSIDERED A/O CONVERTED PICTURE -,
CALCULATION OF THE POTENTIAL FIELD UITHlN A SELECTED RECTANGULAR SURROUNDING REOUIRES CONSIDERABLY SMALLER CALCULATION EFFORT THAN AN IRREGULARLY BOUNDED AREA. SINCE THE REGULAR CASE REQUIRES MERELY ONE STANDARD SET OF DISK STORED GREEN'S FUNCTIONS UHICH ARE USED TO SÜLVE (HE POTENTIAL EQUATION RECURSIVELY FOR ANY GIVEN SET OF BOUNDARY VECTORS G<lrY). (3<NfY)r G<X,1>» AND G(XJM) <N,M MAXIMUM INDICES IN X AND Y DIRECTIONS) INSTEAD OF SEVERAL SETS OF GREENS FUNCTIONS IN A MUCH MORE COMPLEX WAY* THE IRREGULAR BOUNDARY IS PROJECTED UPON A REGULAR BOUNDARY. DEVIATIONS OF THE POTENTIAL FIELD CUTTING THE IRREGULAR BOUND- ARY FROM EXACT BOUNDARY VALUES ARE CALCULATED AND USED FOP AN ITERATIVELY IMPROVING RECTANGULAR ENCLOSURE. UNNECESSARY TO EXPLAINf ALL POINTS ON THE IRREGULAR BOUNDARY SEEN FROM A PROPERLY SELECTED PROJECTION CENTER MUST BE SEEN ONLY ONCE? I.E. EACH POINT WITHIN THE RECTANGULAR ENCLOSURE BELONGS TO ONLY ONE POINT ON THE IRREGULAR BOUNDARY. THE WHOLE ITERATION PROCESS IS STABLE AMD SUFFICIENTLY FAST EVEN IF THE IRREGULAR REGION HAS SOME RAPID CHANGING COORDINATE VALUES. CALCULATION TIME DEPENDS UN SELECTED PROJECTION PARAMENTERS AS WELL AS REQUIRED ACCURACY (I.E. REST DEVIATIONS). THE METHOD WAS APPLIED TO SHALL ÜRUAN DETAILS IMBEDDED IN LARGER ORGANS WHICH TOTALLY OVERLAP I HE REGION OF INTEREST. IT Ct-'iN BE APPLIED AS WELL TU COMPOSED PICTURES WITH DETAIL fTC CURES NOT FITTING TOGETHER BECAUSE OF INDIVIDUAL COORDINATE DEPENDING SHADING OF EACH DETAIL PICTURE AS CAN BE OBSERVED OFTEN ON COMPOSED PICTURES OBTAINED FROM SATELLITES.
13
by
1. INTRODUCTION
Two-dimensional (2-D) data processing methods and techniques are of increasing interest in biology and medicine due to several rea- sons: high efficiency which is obtainable permitting a better bio- medical image processing and analysis; great application flexibili- ty and adaptivity; large expansion of standard computers, minicom- puters, array processors and microprocessors or special type digital processors (VLSI chips) at decreasing cost.
Among the different methods of 2-D data processing, digital filte- ring operations are here mainly considered, outlining their impor- tance for biomedical image processing. At first some finite im- pulse response (FIR) and infinite impulse response (IIR) 2-D digi- tal filters are described, pointing out their efficiency and cor- responding complexity for biomedical image processing. After,some applications to the processing of 2-D biomedical data are shown: in nuclear medicine, in ECG-EEG mapping, in computer tomography.
2. SOME EFFICIENT 2-D DIGITAL FILTERS
Many types of 2-D digital filters with finite or infinite impulse response (FIR, IIR), having a non-recursive or a recursive structu- re, have been studied, developed and applied [1] .
A 2-D digital filter can be in general defined by the following re- lation
N,-l N.,-1
- 2— 2— bOiu,m7)g(n1-m1,n--m2) (1) 1 =0 m=0 1 l l l l L2—
m2=0311^+1712*0
where f(n,,n_) are the input data (samples of the input image),
14
2.3 0
gin^.n,) are the output data (samples of the output image), a(kpk2) and b(m,,m_) are the coefficients defining the 2-D frequency respon- se of the digital filter, NpN-.M^.M, are suitable integers [l] . If in the relation (1) all b(m,,m-) coefficients are zero, the 2-D digi- tal filter is of FIR type, otherwise it is of IIR type. FIR filters have in general non-recursive structure, while IIR filters have recur sive structure.
Of particular interest for biomedical image processing are linear pha se filters (for instance filters having a symnetric impulse respon- se), which don't introduce phase distortion in the processed images.
The problem of designing the digital filter in the 2-D frequency do- main appears clearly connected to the evaluation of the coefficient matrix a(k, ,k2) and matrix bOiu^m,), in such a way that the obtained
frequency response satisfies the required characteristics. Several design methods have been defined for 2-D FIR or IIR digital filters, some of which are a direct generalization of their 1-D counterpart [1]. For what regards 2-D FIR digital filters, three interesting and useful methods are: methods using suitable correction functions or windows; frequency sampling methods; approximation methods (optimum filter design). Filters of IIR type can be designed through some me- thods as: differential correction methods; factorization methods; ro tation methods or transformations from 1-D to 2-D filters.
Digital filters of FIR type can present adequate efficiency (in parti cular linear phase characteristics) and relatively simple hardware and software implementation: they are useful for many actual digital processing applications to biomedical area, assuring in particular no phase distortion. Digital filters of IIR type require in general a lower nunber of coefficients and therefore are useful for faster inplementations, but can present phase non-linearity.
3. SOME APPLICATIONS TO THE PROCESSING OF 2-D BIOMEDICAL DATA
2-D digital filters can be applied to the processing of 2-D biomedi- cal data, to perform smoothing (noise reduction), enhancement, edge extraction and restoration.
2-D digital filters have been applied to nuclear medicine maps, to reduce noise and improve image quality: in particular low-pass cir- cular symmetry filters and restoration filters have been used [11 [2] .
For what regards ECG-EEG signals, a two-step digital processing has been applied: at first 1-D digital filtering is performed on single ECG-EEG signals to reduce noise or extract significant frequency com ponents (as ot component in EEG); after 2-D digital filtering is used to process 2-D signal groups (taken at regular space sampling) in particular to perform interpolation or pattern extraction.
IS
2.3 0
2-D digital filters can be applied to X-ray images, in particular to obtain image enhancement of particular regions ot tissues, per mitting a better investigation and diagnosis by the physicians.
For what regards computer tomography images, 2-D digital filters can be applied to improve the image quality, especially if no spe cific 2-D digital filtering is already enclosed in the image recqn struction process. In particular 2-D low-pass filters can reduce noise components, while high-pass filters can enhance the images. A special 2-D digital filter of parabolic type was implemented at Dipartimento di Ingegneria Elettronica in Florence with the purpo- se to perform a controlled image enhancement: the filter perfor- mance (as trade-off between smoothing and enhancement) is defined through two very simple parameters,.the origin and slope of the parabola. This last filter can be very useful also for processing other biomedical images as above considered or of other type (for instance ultrasonics images).
In conclusion 2-D digital filters, having linear phase properties, can be applied to the processing of biomedical images for obtai- ning several useful results: noise reduction (through smoothing or special frequency components extraction), increase of image contrast (through enhancement), pattern extraction (through deri- vative filtering or restoration), reduction of the amount of da- ta for local storage or "telemedicine" (through low-pass filte- ring and data decimation).
REFERENCES
[1] V. Cappellini, A. G. Constantinides and P. Emiliani, "Digital Filters and Their Applications", Academic Press, London - New York, 1978.
[2] V. Cappellini and A. G. Constantinides Eds., "Digital Signal Processing", Academic Press, London - New York, 1980.
16
CALCULATION OP RADIATION QUAHTUT, QUALITT AND CONEtASI FOR PULSATING POTENTIAL X-RAT GENERATORS
by
T.'. PORUBSZKZ" X-ray Division Medicor Works R&D I n s t i t u t e S-1475 Budapest, P . 0 . Box 90 HUNGARY
1 . INTRODUCTION
As c o n v e n t i o n a l and newer types of r a d i o g r a p h i c X-ray generators are expected to operate for several decades i t i s very important to qualify them front the point of view of actual radiation quantity and quality perfor- mance. We present a method for this qualificatiort with some resul ts and application poss ib i l i t i e s ,
2. BASES
Taking into account some known expressions (i. e. ab- sorbed dose of a heterogeneous beam, attenuation, weighted averaging of time dependent quantities); we have derived a complex formula for the absorbed dose from narrow X-ray beams generated by pulsating potential X-ray generators having any waveform, passed through any attenuating medium (Porubszky 1983, 1984>. A com- puter program was elaborated for the calculations, com- pleted with the calculation of fluence, energy fluence, as well as effective energies weighted by fluence, en- ergy fluence and exposure, respectively. A3 the power factors f of ISC(l979) as well a3 some other attempts Ce. g. O'Foghludha-Jbhnson 1981) are not adequate for qualification of newer (e. g. inverter-type I1 X-ray ge- nerators we have defined a new ripple correction, factor which characterizes the actual radiation energy perfor- mance of a generator. The computer program contains the calculation of this quantity, too.
3. METHODS
The data needed for the calculations are the following: - X-ray spectra of constant potential, minimum inherent filtration machines were taken from the catalogue of Birch et al(l979) and own measurements (Porubszky et al, 1984). » - Interaction coefficients were taken from Plechaty et al(1981) and Hubbell(l977K - Voltage and current waveforms were analytically app-
17
2.4 0
roximated. For current a power function fitted to the X-ray tube emission characteristics proved to he" the best approximation. Inverter-type waveforms were model- led by negative pulses having a width of 25 9J of the pe- riodic time superimposed to a constant value. Pulse depths were 40, 20, 10 and 5 % for voltage, the corres- ponding values for current were 75 % of the former.
Input data of the program are: generator type, peak ki- lovoltage, focus-to-object distance (=thickness of air), Al filter (including inherent filtration) and thickness of some other attenuating media (water, tissues, lead etc.) Input signal values of image transmission system (atte- nuation in scintillators) were also calculated. Prom input signal values A and B for different attenuating media the c=(A-B)/(A+B) contrast was calculated.
4. K3SUMS
Some typical results are shown in Table I. All data re- fer to IKL00 kVp, 2 mm Al and 1 m focus-to-object dis- tance. The fluence, energy fluence, dose in air and in water (yuGy/mAs) are for current maxima. Values for cur- rent means can be got by dividing them by imean/imax. Types: 0=2pulse, l=6pulse, 2=l2pulse, 3=40 %, 4=20 %. 5=10 %, 6=5 %, 7=constant. Suffixes: l=analytic, 2=po- wer function, 3=constant current approximation.
5. SOME APPLICATION POSSIBILITIES
1) Development of X-ray generators (choice of smoothing etc.) - 2) Development of less attenuating radiographic table materials. - 3) Evaluation and planning of radi- ation protection shieldings. - 4) Estimation of patient dose ratios for different types of machines. - 5) Deter- mination of visibility of tissue differences for given radiographic parameter settings. - 6) Choice of better image detectors with dose-contrast optimization.
6. R3FBR3NCES
Birch, R., Marshall, II., Ardran, G. Iff,, 1979, Catalogue of Spectral Data for Diagnostic X-rays IHPA, London)
IEC, 1979, High Voltage Generators of Diagnostic X-ray Generators, IEC Draft, p. 13.
Hubbell, J. H., 1977, Radiat. Res. 70, 58-81. O'Foghludha, P., Johnson, G. A., 1981, Phys. lied. Biol. :
26, 291-303. : Plechaty, E. P., Cullen, D. S., Howerton, R. J., 1981,
Tables and Graphs of Photon Interaction Cross Sec- tions, Report UCRL-50400, Vol. 6., Rev. 3.
Porubszky, T.f 1983, Proc. XI. IRPA Reg. Congr., Vienna, 20-24 Sept 1983.
Porubszky, T., 1984, to be published. Porubszky, T., Végh, A., Török, Sz., 1984, to be published.
18
CO IfN O O O vo
UN ON fcfN K\ o o o & 8 H C f t C O O O C O C O O r i V O CO
O M in in in in
tr\ o CM t*\ K\ •<*• in in in in UN vo
H O t> c^ c-
•<*• t ~ t ~ c>- c ^
o o 3 o
in • * cvi in (fN VO CO VO ON ON ON ON
o o
m u
VO
CM
VO
CM CM
in ii
8 ifN ' CO UN tfN CM H rH C - ON VO CO ON
00 ON ON ON ON ON ON • o o a o • ,
O O O O H O O O rí rí
I I
19
2.5.0
20
2.6.0
Tosser
electrophoretic gels.
21
by J. Barsai MS 32 M3DIC0R BUDAPEST HUNGARY
and 3. Ditrói M.D. CITY HOSPITAL MISKOLC HUNGARY
Stereoscopic vision and photography had been known and
used by the time of the discovery of X-rays, both in
theory and practice. The term stereoradiography itself
ia a contradictio in adjecto; with X-ray radiation no
stereoscopic vision can possibly be brought about, since
X-rays do not produce any image on the retina. A method
analogous to that of Wheatstone 's experiments, can
yield two adequate radiographs which viewed in a stere-
scope can form a three-dimensional image. In spite of
promising openings the acceptance os stereoradiography
was delayed by technical and subjective handicaps. The
shifting method i.e. to shift either the patient or
the X-ray tube a given basic distance, was cumbersome
• and resulted in much inaccuracy. Jtereoradiographs were
evaluated by subjective assessment instead of objective
methods. Another difficulty was that many people have
the faculty of stereoscopic vision insufficiently
developed.
After those said above, the question may be raised:
why bring forward this subject again and why to take the
trouble ' to v/restle with a problem which has proved to
be too cumbersome for the radiologist. The an sv/er is
simple, otereoradiography does no belong to routine
radiographic methods, be cause it is still in statu
nascandi. Technical conditions for the implementation
the fundamental idea3 of classical stGreoradiography
were lacking. The latest technical progress helps to
overcome the difficulties. As regards subjective
obstacle viewing and evaluating devices i.e. photo-
grammetric apparatus have been developed by wich persona
with no aterescopic vision or even one-eyed persons can
22
tion that by the faculty of terescopic vision of the
individual or through the viewing and evaluating devices
mentioned above, some results that could not be obtained
by other techniques become available through stereoradio-
graphy. Stereoradiography is of parti cular importance in
cases i.lien inc order to ascertain the right diagnosis to
perfonr operation, the physician cannot content him self
with the location Í21 depth of a points only, but he needs
reliable information on the location of a grat number of
points. As mentioned above, the problems of stereography
fall into tv.'o groups:
- Problems with radiographic techniques
Luce stereographs fit for i
photogrctmr-etry, three data mist be l:r:own:
- f oID Jource-Ime.gc Die to:.'."••;- / Pocus-Pilm /
- b Basic / Focus-Focus / Distance
Unless these distances e.ro vrecisely determined and properly r.a.vl:ed out, evclustio:: cannot he reliable.
In case of photography, stereoscopic images analogous to actual eyesight ere obtf.i~&d '..he:: the dists^ice bet'.."ec-"i the t\:o obJe-ct-leneGc / bseic-distance / is theeecu:: as ühe interocular distance / 65-7C un / . i i sterecrcdiogrcpliy '.."ith a single ]>ray tube this ".issz'S ~úhc:'; the tube has to be shiftod by theseame distance, .'oothc:- D-2thc£ is to leave the ">r:_y tube lumoved and
heve the patient or the fil::: ciiifted by the basic
distai.ee; o:.- the patient sliglrily turned. JL t'..in-tube
.l-;-L.i c.ppc.rctus dcies a"..ay v:itli the cumbersome shifting
arid lo::ds itself to serial Etcreoradicgraphy, sterec-'Z'V
i;tc. The dnv.."bi.r:":: of sue;: arrazi.jements is
23
distance. This effects vision in depth and narrov;s its
range. Tadiographs can be inspected only through, stereo-
scopes with a prism or mirror system, where the pictures
are placed at distances considerably larger than the
interocular distance, while the eyepieces conform to the
interoculardistance. Stereoscopes need to be equipped
with photogrammetric evaluators. It permits the measure-
ment of the stereoscopic parallax and the distance of the
point under observation to the basic plane can be calcu-
lated.
radiograph pairs is presented in PÍQ.1. Oar idea in de-
•signing the device was to relieve the radiologist fron
calculations. Our solution by mechanical means actually
makes use of a complex hyperbolic function of four vari-
ables. The equation is t = p.f:b+p, where t is the dis-
tance of the point under examination to the basic plane,
where f, b, p are mentioned above. The pair of stereo-
radiographs viewed in the device through a binocular
eyepiece give a stereoscopic effect. The problem is to
determine the distance of the point under examination
to the basic plane indicated. The device solves this
problem fully. The device can be handled by persons v:ith
no faculty of stereoscopic vision too.
24
2.8.0
imaging
25
Prof. A. NASZLADY M.D., I.Rodek Dipl.Math. and Irene Szabo Dipl.Org. Cardiopulmonary Department in Mtl. Inst. of Pulm. Budapest 1529 HUNGARY
An Image Processor System Electronics /IPüii/ were developed for digitaliaing pictures. 16-level of densities can be distinguished on the gray-scale of IP3E. Each pixel is represented by 4 bits, different levels of densities can be converted to pseudocolo- red pictures. Minute alterations are to be detected on medical chest roentgenograms quantitatively, oo various parts of lungs become'comparable quantitati- vely to each other relating to its blood perfusion intensity and or differences in densities of the tex- ture of lung and/or heart tissues.
26
2.10.0
27
28
by
BARABÁS, GY., SZÁNTÓ, A S Department of Radiology District Hospital of Veszprém Province H-8201 Veszprém, Marx tér 8. HUNGARY
INTRODUCTION
The low overall 5-year survival rate of breast cancer patients, namely cca 35 /»t as compared to the nearly 100 i» survival of those treated with tumors less than 1 cm in diameter, necessitates the broader use of deli- cate examination techniques. Kammographie screening is widely acknowledged as the most efficient means to the timely detection of small mammary cancers.
The most disturbing difficulty at mammographic work, es- pecially at mass screening, and at repeated and serial examinations is the high radiation exposure to the femal breast. Considering the summation of dose, after 20 rep- eated mainmographic studies during one woman's gestatio- nal age, one must count with the risk of a radiation-in- duced cancer. Every effort toward reducing radiation burden at marnmography should be honoured with interest.
MATERIAL
Authors carried out 15.000 breast examinations the last 10 years through, in clinical patients. Nearly I400 of them have been subsequently operated, and "J1Z had a pro- ven carcinoma. Besides that, a symptomless group of 658 women were screened, one had her non-palpable cancer rem- oved, 1 had a praecancerotic focus.
PHYSICAL BASIS
Due to the minimal difference in density between normal breast tissue and cancer, and to the delicacy of texture to be radiographed, the resolving capacity of the imaging system should approach that of the human eye, i.e. the visibility of less than 100 urn shadows at the 10 ,i contrast level. It means 6-8 line pairs pro cm, what can be easily assured with industrial-type non-screen films. In order to avoid the above mentioned radiation risk however, the use of a more sensitive system is mandatory.
Authors compared the sensitivity of the various maamo- graphic systems at 3° kVp, s nd found a 6-fold dose reduc- tion by xerographic / X / and LaOBr / DP-/ systems, whereas
29
a sixteen-fold gain is achieved by the GdOS-conteining screens / KIN / , against the non-screen films. As the gadolinium s61t exaits green l ight , a specially sensi t - ized film, single-coated i s used in the Kodak kin-H sys- tem, introduced by the autnors in Hungary. The relevant sensit ivity curves are shown on Fig. 1.
2.12 P
3 i log. megvilágítás
The e ehievenent is enhanced b;,: tiie introduction ol" s. speci- a l Lolibdenium-anode, be-v.indov: X-r&j tube /óiei^ens Lo 12/30/. ihe relevant xiioduletion transfer function values or tnese e:;Eteir.E i.;ere checiced f i r s t and found to l ie reesoncDly cl©- £f! to the best one, thct of the non-&crecn fiii ; / ?i£,»2./.
FFT 60cm FGT 55 cm GFT S cm Focus 0.3 mm
30
1000
The relative output of the rare-earth screen systems is even better than mentioned at , or around the most impor- tant 22-2p kVp range, since the silver-haloid granula of the non-screen film show their lowest sensitivity here. It is due to the increased photon-capturing threshold. The mi- nimus exposure needed to a mammogram as function of the av- erage photon energy can be seen in Fig. 3« / Modified after Brodie~& GutchecJc, 1932 / .
3y the use of such a sensitive imaging sys- tem, scalier focal spot and a longer focus-to- film distance was af- forded, íhe inherent benefit is the reduc- tion of penumbra, thus increased sharpness.
The dose reduction is however not endless, since the white noise of the system, as well as bacJjground radia- tion, quantum noise and quantum uottle altoge- ther limit our efforts.
Up-to-date rare earth intensifying systems closely approach the sensitivity of an ide- al SÍ'stem in the uost important 22-25 k~f range.
The rare-earth nar.xio- graphic /i'CLlAS/ sys- tems consist of one back screen and c-. sing- le-coated, green-sensi- tive film, facing its
emulsion downward. Tliese are placed into s snecial synthetic cassette, easy to handle. Thanks to a decreased access of ec&ttered radiation to the ri.ua, sharpness cud ijarmony are more excellent than we had anticipated theoretically.
aiace January 1 83 authors introduced also double-screen rare-earth dose-reducing systems for regular radiograohy, especially in their pediatric work.
Sxamplss and bibliography will be siiov,n on the poster.
Previous -.lorfc as preliminary article: iarabús £ Szántó: Radiológia i)ia:.;nostica / merlin / , 1^77, 12, 77".-
20 30 40 50 ATLAGENERGIA ( IHV)
31
2.1J.P
A custom-design integrated circuit
"Zain special circuit was realized by applying the so called
ULA / Uncommitted logical Array / semicustom circuit CGB / CMOS
Gate B version / developed by the Central Research Institute for
Physics, Budapest.
The chip is applied in aedical X-ray equipments produced by
MEDICOS factory. It drives a 1 digit display showing the time
/ minutes / passed by the pacient in the X-ray equipment. Besides,
it has prograaable inputs anabling the Physician to preset different
periodes / 0, ... 9 minutes /. Passing the preset period, the chip
produces a voltage level on one of the output pins, which switches
a bell to alarm the Physician. After passing. 10 or 5 minutes -
according to programing set by MEDICOR factory - an another output
signal shuts the X-ray equipment off.
Technical data:
Fan out: 3 TIL,
32
UV-type ezaaiaation devices of Medicor Works.
English abstract was not available.
?> 33
2.15.P
34
Section
3
MYOGRA.PHT
COMPARATIVE EXPERIMENTAL INVESTIGATIONS OF THE CORRELATION 5*1*0
BETWEEN ISOMETRIC LOWER LEG EXTENSION TORQUE AND SURFACE EMG- SIGNALS IN NORMAL AND PATHOLOGICAL KNEE JOINTS ;
G.O.Hofmann, M.Bergmann, K.H.Weinmann
Chirurgische Klinik und Poliklinik (Head: Prof.Dr.G.Heberer) und Labor für Biomechanik und Experimentelle Orthopadie der Orthopadicchen Klinik und Poliklinik (Head: Prof.Dr.M.Jiger) der Ludwig-Haximilians-Universitat München.
The bionechanics of the knee can be disturbed in its physio- logical concept by congenital (e.g. patella alta) and acquired alterations (e.g. meniscectomy, lesion of the cruciate ligaments). An altered direction of pull or a reduced lever ara demands a pathological increased expenditure of energy for a special muscle group generating a defined torque. The experimental device developed by our team enables the measurement of surface EMG-signals produced by the main com- ponents of the m.quadriceps (m. rectus fern., m.vastus med., m. vastus lat.) related to defined isometric extension torques and defined knee angles. The EMG-signals are derived with special bipolar electrodes with a defined distance between the two poles situated over the bellies of the three muscles. The force is measured by the help of a strain-gage-transducer. The three EMG-signals and the force signal are amplified and inte- grated simultaneously in a determined period of time. The presented method is reproducable, not invasive and simple in application.
In a population of young healthy adults curves were evaluated indicating the correlation between the lower leg extension tor- que and the surface EMG-signals of the activated muscles. Cases of altered biomechanics led to divergences of this correlation: to produce a defined torque an increased surface EMG-signal demonstrates the raised expenditure of energy. The comparative examination of normal probationers with patients suffering from defined knee Joint anomalies is possibly a con- tribution to the diagnosis of the knee arthropathies. Concerning reconstructive surgery of knee joint ligaments the presented method may help to evaluate a postoperative improvement of the biomechanics. 37
3.2.0
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- PL0TT3R TOO.
Sógor M. Bán Gy. - Medicor Budapest
Wide range biopotential amplifier
amplifier. This amplifier complies with the high
requirements on the field of electromyography and
electroneurography. The circuit system containing
special feedback networks assures with wide frequency
band high CMR and very low noise level. The results
getting by the new amplifier will be represented
during the lecture.
nerre-auscle stiaulator.
3.5.0
Comparative Studies on ATM-'l Automatic Thresholdmeter
and EMG in the Early Stages of Peripheral Neurogenic
Lesions
and reliability of ATM-1 Automatic Tresholdmeter in
determining chronaxy and rheobase as well as recording
int.ensity-duration curves in the diagnosis of deseases
of neurogenic origin. As established by them ATM-1 is
suitable to further the electrophysiological armoir.
In present investigations authors compared the electro-
physiological data gained by this method with the routine
EMG recording in early stages of peripheral neurogenic
lesions. The advantages of chronaxymetry and I-D curve
analysis are stressed, namely, its speed, reproduci-
bility and its simple managing. Due to these characteristics
this method is regarded useful mainly in screening
examinations.
Medicor Works Researc Institute Budapest
41
3.6.0
NBURAN.
+ + + ++ • lth Sz., Sólyom A., Tóth Z., Sógor M., Bán Gy.
Different type evoked potentilas were recorded both on deep structures and surface electrodes* Possibilities of NA-10 microprocessor system in the analysis of evoked potentials have been investigated* Peak latencies slope measurements and the stability of each component have been studied. Investigations have supported the opinion that KA-10 MEDICOR equipment has provided possibilities tu study the most important parameters. Results have given possibilities of development of fixed analysing program.
+ Országos Idegsebészeti Tudományos Intézet
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Section
4
ULTRASONICS
by
Prof. Or Ir N. BON Thoraxcenter Erasmus University Rotterdam P.O.Box 1738 3000 DR Rotterdam THE NETHERLANDS
1. INTRODUCTION
In order to describe the developments of ultrasound transducers as used for diagnostic ultrasound, and in particular transducers such a being used 1n cardiology. I t may be good to describe the rapid development of echo-equipment over the previous years. The f i rs t generation systems show M-mooi combined with linear array or mechanical sector scanners. As 1s shown in the table the transducer frequencies were around 2.25 MHz which resulted In limited imft quality. The N-mode was a separate hand-held transducer with a disc shaped format and i t was not Incorporated In the two- dimensional image. At the timt not only the two- dimensional real time caused a breakthrough but so did the Introduction of fiberoptic recorders for proper documentation of the M-mode.
Generation 1 M-mode L1n. array Sector
Display Frequency Beam control Manual Registration U.Y. paper Fr. frame Calculation Doppler
Oscilloscope T.V. monitor Oscilloscope 2.25 MHz 2.25 MHz 2.25 MHz
Electronic Mechanic V.T.R.
The second generation devices Include either phased array or mechanical sector scanner. Linear arrays have disappeared from cardiac use of ultrasound. It proved that the point entry facilitated by sector scanners was of major Importance for cardiac purposes. The linear array proved to be of excellent use in more abdominal or obstetrical oriented diagnostic applications. Transducer frequencies »rt around 3 MHz and registration capabilities have been added to all systems.
47
Generation 2 M-mode Ph. array Mech. sector
Display T.V. monitor T.V. monitor T.V. monitor Frequency 3 MHz 3 MHz 3 MHz Beam control Line select 32 el. Mechanic Registration U.V. paper V.T.R. V.T.R. Fr. frame T.V. monitor T.V. monitor T.V. monitor Calculation Limited Limited Limited Doppler - - Pulsed
The third generation table shows a tendency to further increase frequency and incorporate regi strational dry silver paper. Doppler and good registration on video have become standard. The third generation already sometimes includes a variety of routines for calculation of ejection fraction or other cardiac parameters.
Generation 3 M-mode Ph. array Mech. sector
Display Frequency Beam control Registration Fr. frame Calculation Doppler
T.V. monitor 3,5/5 MHz Line select Dry silver T.V. monitor Extended
T.V. monitor 3,5 MHz 32 el./64 el. V.T.R. T.V. monitor Extended Pulsed
T.V. monitor 3,5/5 MHz Mechanic V.T.R. T.V. monitor Extended Pulsed/cont.
2. PHASED ARRAY versus mechanical sector scanner
For present cardiogical systems one has to make a choice between the mechanical sector scanner or the electronic phased array system. Both are combined with M-mode. Image quality seems equivalent, however differences remain the transducer size and the possibilities to combine simultaneously with Doppler or M-mode. In our opinion the flexibility of electronic systems will eventually out date systems with mechanically driven transducers. Early Doppler applications were often vascular blood velocity measurements based on continuous Doppler with only poor registration capabilities. Present integration of pulsed Doppler in combined M-mode/to the real-time systems have brought Doppler into being widely used. The possibilities to integrate Doppler applications into various probes and the need for a combination of continuous wave together with pulsed Doppler will be discussed in relation with the requirements as to the ultrasound probe.
4.1 0
System costs Transducer size Image quality Sim. M-mode Sim. Ooppler Spurious lobes Focussing Frequency range
Mechanical Medium Large
Electronic High Small
3. TRANSDUCER EVOLUTION
Existing Possible High Dynamic Limited
Not only the focussing capability and in particular the beamshape do Influence the ultrasound image. Many practical points such as the dominant vibration modes of the individual elements Influence the image as well. Correct application of the matching layer and thereby establishing optimal bandwidth and thus short pulse length is necessary. The need to avoid the grating lobes will be explained and examples will be given. Presently various transducer sizes and shapes are being developed for special applications such as esophageal echo measurements and Intra-operative applications.
49
Benny Löfström, Nils-Gunnar Holmer, Goran Salomonsson, Itigvar Claesson Telecommunication Theory, university of Lund
S-220 07 LUND, SWEDEN,
1. Background. The applicability of the ultrasonic pulse echo method in medical diagnostic has gradually increased since the 1950 :s and still do so by improvements of the equipment and examination methods. The ultra- sonic pulse echo method is based on transmitting a sound burst from a transducer into the tissue being examined. Due to the inhomogeneities within the tissue, acoustical energy is backscattered to the transducer and registered as echoes. The reflected signal is presented either on an oscilloscope (A-mode) or as a 2-D-image (B-mode). In recent years the qua- lity and diagnostical value of ultrasound images have been considerably improved due to e.g. grey-scale technique and increased resolution. These images mainly outline the overall structure of the tissue, while detailed information (e.g. about the attenuation and scattering pattern) only can be aquired indirectly from the image. This indirect interpretation of an image is very much dependent on the skill and experience of the operator.
It is desirable to make visible in an image such features of an ultrasonic signal that would enable discrimination between healthy end diseased tissue. One feature of interest is the attenuation of the ultrasonic signal in the medium. Today there is quite a large knowledge about the values of the atte- nuation for different tissues, through contributions of many investigations. Among other things it is known that the attenuation increases with the amount of collagen and decreases with the amount of water. Studies of infarcts indi- cate an increase of collagen in the tissue. It is found that the attenuation of infarcted tissue is larger than in the surrounding tissue, while a cyst ' with a large percentage of water has a lower attenuation than the surroun- ding tissue.
2. Estimation methods. The methods for estimating the attenuation may be divi- ded into two classes, the frequency domain methods (FDMs) and the time domain methods (TDMs). In the FDMs the power spectra of two segments at different distances from the transducer are compared to estimate the attenuation be- tween the segments. In the TDMs the decay with depth of the reflected sig- nal is the function to be estimated. Comparision between the TDMs and the FDMs has been done theoretically and on model signals, which shows that the TDMs are superior in detecting intervals of different attenuation in the tissue 111. For cur measurements we have used a TDM briefly described as follows:
The transmission properties of the tissue are assumed to conform to the
transfer function H(f,x) = exp(-A(x) - T(x)fe), where A(x) and T(x) de- scribes the attenuation between the transducer and the point x. The enve- lope of the reflected signal may be written as E(k) « exp(-B(k))«e(k),
where B(k) = A(k) + r(k)fQ B depends solely on the attenuation Oiile e(k)
is a function also of the scattering pattern of the tissue. The frequency ffjis within the pasaband of the transducer. Thus B(k) can be used as a
base for the estimation. By logarithming E(k) a signal y(k) = * B(k) + In e(k) is obtained. While e(k) changes faster than B(k) we regard 2ne(k) as noise, and we are facing a classical comunication theory problem: to estimate an unknown function B(k) that is disturbed by additive noise. This may be done by several efficient methods using linear and/or nonlinear filtering.
50
4.2 0
The equipment developed. Besides the attenuation there are two more basic acoustic parameters that characterize the tissue, namely the sound velo- city and the impedance. To be able to estimate these and other parameters from the backscattered signal and display them as fast as possible vge have developed a new equipment, the Digital Ultrasonic Processor. It has faci- lities to transmit and receive ultrasonic signals, and after digitalization the parameters are estimated by means of digital signal processing. The processed data Is then displayed on a video 9creen. The block diagram be- low shows the system configuration of the Ultrasonic Processor:
VIDEO
Fig. 1. Digital Ultrasonic Processor - block diagram.
The transducer acts as both transmitter and receiver of the ultrasound, and may be either a single transducer or a linear array transducer depending on the application. The input amplifier can be equipped with time gain control (TCC) to compensate for the progressive attenuation. (The signal amplitude may decrease 80 dB from the start to the end of the signal). The amplified and antialiasing filtered KF-signal is sampled with the sampling frequency 15.4 MHz and A/D-ccnverted with a resolution of 8 bits. This makes it pos- sible to use up to 5 MHz transducers. With a special technique it will be possible to use transducers with even higher frequencies. The high sampling frequency requires a fast memory after the A/D-converter. To meet this de- mand the converted data is temporarily stored in a doubled fast buffer memory of 4k x 8 bits size (each half). From this buffer the data is transfered to a larger memory by DMA (2-10 i*»yte/s) • Thus, the recording depth will be approximately 20 cm in human soft tissue (v ~ 0.15 cm/ps) and a maximum pulse repetition rate of 2 kHz is achieved.
When only one line is of interest (A-raode) a single transducer is used. To differentiate between randan and non-random components of the signals, the algorithms uses averaging over a number of shots (8-16) along the sane line. The time required to sample 16 shots is 8 ms. By using a linear array instead of a single transducer it is possible to create a 2-D image of the tissue. The array nay consist of 16-400 transducers, with a total length of 5 to 20 cm. With an array of 128 transducers an image can be produced within 64 ms, which corresponds to 16 frames per second. A higher frame rate can be achieved by decreasing the recording depth.
SI
4.2 O
The digitized line or image is processed in a 16-bit microcomputer, Motorola M68000, where the characteristic parameters are estimated. Thereafter these parameters are displayed on the video screen. In 2-D investigations the es- timated parameters are used to modulate the grey scale. The image matrix consists of 512 x 512 picture elements with 12 bit resolution.
A further possibility with the ultrasonic processor is to digitize the TV video signan derived from existing clinical ultrasonic equipment. The vi- deo memory has hardware facilities to perform real time averaging of con- secutive images. This will suppress the randan noise, and the anatomy will appear clearer. The digitized image may also be processed in the micropro- cessor.
Results and conclusions. Measurements on a tissue equivalent has been done, from which an attenuation image has been estimated by use of the time domain method described above. In this picture the area with increased attenuation is clearly distinguishable, while an ordinary amplitude image of the same tissue equivalent does not show the shape of the area of interest.
Though the main interest has been in estimating and presenting an attenuation image, the equipment is flexible and a very useful tool in the development and testing of new methods and parameters in tissue characterization. Also, because of its portability the equipment may be used in later clinical eva- luation of the methods.
References
|l[ Claesson I., Holmer N-G., Salomonsson G., December 1963. "Estimation of Ultrasonic Attenuation in Soft Tissue. A Comparison of Frequency and Time Domain Estimation Methods", Technical Report TR-181, Telecommunication Theory, University of Lund.
52
Inst. Applied Biophysics, Univ. Halle/S..GDR - 4020 Halle
t. IMTRODUCTIOK
The spectrum of an ultrasonic pulse which has passed a biological tissue contains a lot of information about the properties of the material. Therefore ultrasound spectrum analysis allows us to combine the advantage of the ultrasonic imaging metnode with a noninvasive tissue characterization.
2. METHOD
In the following we report on a measuring equipment developed for studies to estimate the structure of simple models and for in-vitro-measurements to find empirically correlations between clinical statements and acoustic spectrograms. The unit consists of a common echoscope for the signal production. The received signals are selected by means of a linear gate, followed by an electronic Fourier trans- formation accomplished in a spectrum analyzer. After digitizing, data processing by means of a desk computer is performed to get the desired data presen- tation, e. g. the frequency dependent attenuation or certain structure data from back scattering experiments.
3. EXPERIMENTAL RESULTS
The performance of the method described above is to be demonstrated by means of some results obtained from investigations on human testes. Á re/narkable difference between the very low attenuation of the normal and the high attenuation of the patholo- gical specimen is to be seen. The neoplastical data differ from the chronical inflamed data.
S3
4.4 0
OPTIMIZING THK KSTIMATIOK OF MAXIMUM FREQUENCY OF DOPPLÍR SIGNALS BT MEANS OF SPECTRAL ANALYSERS
T. D'Ain—ir> ( * \ C- Di Giotto Ban* l*}, H. Sacco ( < )
(*) INFO CON Dpt- and Centro Esgegneria BJoaedLca - Onivexsita* di ROB a; ($) Biotronix Ltd. Horn*
1.PREMISE
The techniques com in only used in the analysis of ultrasound Doppler signal* exploit only partially their information content and leave wide margins to operator's subjective intervention. In the attempt of defining more "objective" procedures of analysis and of interpretation of these signals, real-time spectral analysis is used to estimate maximum frequency envelopes of Doppler signals, and thus the so-called spectral broadening. In fact, i t is claimed that this procedure enables to determine with greater sensitivity the occurrence of stenoses or other alterations in arteries. However, no rational procedures useful to estimate maximum frequency in presence of nodse are available.
In this paper, a procedure for the estimation of maximum spectrum frequency in spectral analysers is proposed. The procedure starts with the knowledge of the overall sensitivity and specificity required in the decision strategy, is based on the statistical characteristics of FFT (Fast Fourier Transform) spectral estimates and implements a two-threshold discriminator. The levels of the two thresholds have been optimized by means both of theoretical considerations and of simulations.
2.SPECTRAL ESTIMATOR CHARACTERISTICS
Doppler signal s(t) can be modelled as a zero mean gaussian.process [1] which is non-stationary because its power density spectrum varies as for amplitude and bandwidth during the cardiac cycle. The noise n(t) superimposed to this signal can be assumed as a white gaussian process i.e. with constant spectral density NQ over the bandwidth C°»B
ma3CJ/ where Bmax ** t h e o v e r a^- low-frequency system bandwidth which has been determined following the maximum frequency admissible for Doppler signals. Therefore, the signal to be dealt with is:
(U x(t) - s(t) + n(t)
and the spectral estimator is P ^ » lxtf^)!2 where X(fk> is the Fourier transform of x(t). Due to its variations the signal s(t) will in general have a bandwidth B_ considerably less than Bm • This means that during most of the cycle the samples in the bandwidth LBm - BgJ are due to noise only. Therefore a rational discrimination between signal and noise is necessary, for maximum frequency and spectral broadening evaluation.
To this end, we propose a two-atep procedure baaed on the specificity P ( (probability that a spectral bin could be correctly recognised as due only to ncdse, and therefore discarded) and on the sensitivity PD (probability of detecting a spectral bin when due to signal, plus noise) of the decision strategy. According to this approach, two successive thresholds must be jointly determined in order to attain the prefixed P • while maximizing PQ:
54
4.4 0
- the first threshold (Th) is compared with the amplitude of the spectral samples. Only when a sample crosses T^ a "one" is produced and sent to a running counter of length m, otherwise the counter is fed with a "zero"; - the second threshold, at the output of the running counter, is set at a level r * m such that at Least r "ones" out of a sequence of m consecutive samples (r/m) have a probability of occurrence of only (1-P ), if noise alone is present.
The detection probability PD is determined according to the values of r,m, the signal-to-noise ratio (SNR) and Pg (which determines (1 - PT) that is the probability that T, is depassed by noise alone).
The whole procedure starts by fixing a value pg (typically in the range 95-99%) for the overall specificity. As the spectral samples are incorrelated f2j and thus independent (being the process gaussian), the distribution of at least (ro/m) samples above Th is a Bernouilli, that is:
(2) P [ r ^ rol = 2 C> pk(1 " P)m"k
° k=ro
where P is the probability of crossing T . If we put P = 1 - PT» or P = P ^ / where Pd. is the probability that signal plus noise crosser T. , we respectively obtain P and P . ^
There are infinite combinations of ro, m, PT that give the desired Pfi but with different values of sensitivity and resolution in the maximum frequency estimation. Moreover, the levels (Th and r) of the two thresholds must be chosen according to the decision strategy and the statistical characteristics of signals, noise and spectral estimators used. In fact, a decision strategy can privilege either specificity or sensitivity because the two requirements are conflicting. In order to optimize threshold levels, from eq.(2), PD versus Ps, with the SN R as a parameter has been evaluated, for different ratios (r/m) [that is (2/2), (3/6), (4/6)]. It resulted that for low SNR,the three algorithms give nearly similar results, while for^higher SNR, (3/6) and (4/6) are better than (2/2). For instance, with P s = 0.99 and average SNR = 3 dB, a sensitivity of 0.53 (with ?T = 0.91) or of 0.21 (with PT= 0.9) is attained respectively with a 3/6 and a 2/2 algorithm. However, the 3/6 one can give a maximum error in resolution, with respect to the 2/2, up to 3if, where df is the resolution of the FFT. When the SN R is high, the 2/2 or the 3 /6 algorithm give similar results as for P_ together with high values for Pg . As the simplicity of the (2/2) procedure is appealing, we have preferably used these values.
p„ and P., can be obtained as: SNR/10 - T /N - T / [ N ( 1 + 10 K )1
(3) 1 - p = e h ° (4)P = e h °
T QfK
where: Psk(5) SNRk- 10 log1 ( ) — ^ (dB) o
with P v power density spectrum of s(t) alone. Eqs. (3) and (4) have been obtainea knowing that the distriubution of the spectral estimator used is a chi-square with two degrees of freedom f2].
Having fixed P , r and ra (and therefore P^) the steps are: 1 - Estim ate noise power density No, to be inserted in eq.(3) in order to 2 - evaluate the first threshold T^. Subsequently:
S5
4.4 0
3 - evaluate maximum doppler frequency in the following way: 3a - Starting from the upper end of the bandwidth B m a x , observe when the threshold rQ of the counter is reached JT so: 3b - Decide for the presence of signal (plus noise) and estimate f
m a x as the frequency of the first (or of the mean) bin of this sequence.
SOME EXPERIMENTAL RESULTS
He have recorded some Doppler signals, measured by means of a c W flow meter on the radial artery of young subjects. Signals have been sampled at a frequency of 12 kHz and sequences of samples 21 ms long have - been chosen. To each one of these sequences (obtained in good conditions as for the SN R) eight different white noise sequences have been added with a root mean square value such that the ratio
t signal power in the bandwidth (0 - B ) sSNR noise power in the bandwidth (0 - B )
maxcould assume the values - 5, 0, + 5, + 10 dB. Each sequence of signal plus noise has been transformed via software, using a standard FFT. The eight estimates of f m a x have been averaged in order to improve accuracy. In the Table these mean values are reported together with their standard deviations (in kHz) and the percent difference from the "true" value, for the following decision strategy: P - 0.99; m « 2; r « 2.
Seq. SNR -00 SNR «-5 SNR -0 SNR «S SNR -10 dB 1 1.27 1.20 (-6%) 1.40(+10%) 1.3S(+7%) 1.33(+5%) kHz
0-0 .12 CT.16 0.04 0.02
2 2.15 1.80(-17%) 1.90(-10%) 2.30(+7%) 2.20(+3%) kHz tf-0.20 0.17 0.10 0.09
In the first column the value of fmax estimated without noise (S N R» 00 ) is reported.
4.CONCLUSIONS
In this paper an algorithm, based on the specificity and sensitivity of the decision procedure, for maximum frequency estimation in Doppler spectrum analysers has been proposed. The algorithm has been tested by using some experimentally measured Doppler signals with different bandwidth and signal-to-noise ratios. The algorithm gives estimates of maximum frequency which are robust with respect to the noise added on the signal and independent of analyzer gain and subjective evaluation of the experLm enter.
References 1) Brody W.R., Meindl J.D.,(1974), Theoretical analysis of the CW doppler ultrasonic flow meter, IEEE Transactions on B ME, 21, 183-192 2) Jenkins G.M, Watts D.G., (1968), Spectral analysis and its applications. Holdén Day. 3) D'Alessio T., i n "objective" algorithm for maximum frequency estimation in doppltr spectral analysers, Med. and BioL, Eng. and Comp., in
56
FLUORIDE TRANSDUCER ARRAYS
University of Technology, Loughborough, Leics.
SUMMARY
constructed for monitoring spatial variations of pressure or intensity in
an acoustic field. Each array consisted of 16 strip elements of 45 ym thick •
PVF sheet. Real time acoustic field measurements were obtained using a
l-to-16 multiplexer circuit and 16 analogue switches. With this electronic
system, which can be extended for use with any number of elements, the
electrical output of each element was monitored sequentially. Hie acoustic
pressure distribution as seen by the array can be displayed on a conventional
cathode ray oscilloscope. By including a squaring circuit the corresponding
intensity profile can be displayed. Once the absolute intensity is aeasured
at a single field point, vertical deflections of the CRO beam can be _2
calibrated in Wm . The system is particularly useful for monitoring
the acoustic fields of directional sources, such as medical devices and
sonar arrays.
D1VE10PMEHT OP THE COCHLEAR HEUROPROSTHESES FOR THE DEAF III CZECHOSLOVAKIA
by
Dr. J« HRÜBÍ log. S. SEDLÍX Institute of- Radioengineering and Electronics of the Czechoslovak Academy of Sciences Lumumbova 1, 182 51 Praha 8
and
Ing. J. PICKA Department of Circuit Theory Faculty of Electroengineering Technical university of Prague Suchbátarova 2, 166 27 Praha 6 CZECHOSLOVAKIA
1. IHTRODOCTIOH
Untill the recent time there was no medical or technical help for the deaf patients without any residual hearing. During the last ten years great interest was attracted to the direct electric stimulation of the surviving acoustic nerve fibers by means of microelectrod.es surgically implan- ted into the cochlea. Some implantable electronic nerve stimulators (cochlear neuroprostheses) were introduced into experimental use throughout the world. The single channel neuroprostheses stimulate the acoustic nerve as a whole, while the multichannel devices attempt to put into use the cochlear tonotopy by the more or less selective stimulation of some nerve fibers groups.
The development of the Czechoslovak neuroprostheses began about two years ago in the cooperation of the Institute of Radioengineering and Electronics and the Institute of Expe- rimental Medicine, both of the Czechoslovak Academy of Sci» ences, together with the Faculty of Electroengineering
61
2. IMPLAHTABLB STIMULATOR POR EgBRMBHTAI ABIMALS
The first developed inplantable stimulators of the acoustic nerve were destinated for experimental guinea pigs. These stimulators delivered constant current pulses (about 300/uA) to the pair of Ftlr teflon coated electrodes. The pulse width and the repetition rate was adjustable front the ex- ternal part of the stimulator. The transcutaneous transfer of signal and energy was based on the inductive coupling between the external and internal coil. The "carrier" fre- quency of about 150 kHz was used. The diameter of the im- plantable part was about 10 mm and thickness about 7 mm.
3. COCHLEAE SEÜROPROSTHESIS TOR THE DEAF
Based on the experience with the experimental stimulators for animals the development of the neuroprosthesis for the human has begun. Our first cochlear neuroprosthesis is a single channel device. The active electrode may be placed either in the scala tympani or outside the cochlea on the round window. The signal from the wearable speech processor of the laboratory equipment is delivered to the implantable subcutaneous part of the neuroprosthesis again via induc- tive coupling. The stimulating signal is amplitude modulat- ed or keyed on the carrier frequency 2.64 MHz. The constant current pulses were abandoned, so even the intensity of the stimulating current may be controlled from the external stimulator. Because it is an experimental device, the maxi- mum signal transparency was one of the most important de- sign aims. The prosthesis is able to transfer a great va- riety of stimulating signals in order to evaluate the op- timal one for the individual patient. The implantable part of the diameter 30 am and thickness about 6 an is inside the epoxy-reain encapsulation. The encapsulation technology used for years in the Czechoslovak pacemakers was applied. The electrodes of the 0.1 mm Ptlr wire with ball endings
62
5.2 O
are again teflon coated by tbe Indigenous technology. Over the teflon layer is another biocompatible layer of medical grade Silastic.
4. RBHSREHCES
Hruby", J.: Otoproathetics for Deaf Patients (in Czech). Journal Xékaf a technika, Ho.4, 1983, pp.73-76
Hruby, J. - Sedlák, S. - Plcka, J.: Single channel cochlear
neuroprosthesea for the deaf, (in Czech)
Research report Ho. Z-1420/I, tfRE SAV, Praha
1984
Hruby, J.: Status of the technology and use of the cochlear neuroprostheaes for the deaf in the world in 1983* Survey of references, (in Czech) Research report Ho. Z-1419/A, IÍRE SAV, Praha 1984.
5.2 O
UP-TO-DATE FRC~LE:-:S I:; corner A:T>IC *IE7,ÍJ
5. -.lüXE-TlRITT ane G.
Motion ana lyses and extens ion measure-nfnts are frequent 7y
fxair.inati.ort metVodE of or thopaedic bjoaeo'^anicc. Vcr i:rtf-
g problfiTis posfiirTe app1 ications; ci ' D!-Qt;^ra.Ti!rir^t-"ic
rik ^!etv.o6i- are ÖÍEOUSFSÓ. An e r t j - a t i o n o í t f
cBps'.:-51ities j i B.ive". bv v ey of ezi*r,nTrs r>s y , ' l l «F cer.er.1"1.!":
e corrie t o ths r e s u l t t ' -at ex tens ion wsasursaej5ÍF v i t :
le . 'g th changes of more than 0.1 nro on t v e -notion sv£.t»-i
can be" perform* j photo; rs .~n!e t r ica l iy . Appl ics t icnf f-speci-sCj'
in th« region of t v e r^ ine »u££ftst t '-^mr«lvef. As
v i t b X-ray -nety-ocs p^.ti=nXE are not subjected to r s . ' i s t i o n
i o s e s , fo t1 -at c^rTanentiy rep^Ete- o o i i r c l - e e s u r f n ^ n i s iYi
e.rpepirr.entE wil l c i r t s j ^ v ":.e s ore-"•?tir:«c i'ie"1?. oi "p-'-'l:"-
oe t ion . <i.1fo v* - f ferj-i or p&^tiou'. s r ' v IOOF -r.-,-' re. 'íor.r d '
t're sniine c " ! f- re-ín-T!iüei r-irt t ' ^ . i r r í . - r f t T e c r u r f ' . (."-:•=
r.u"i , •'•ovevsr, ' e w i r e oi' f-<= fse* t v = t • ' • • s a r f M r t ? =rs
-sr . i cr; t ' e eu r i s ce ci"' the ".••oiy 6.',: t v s t conre.-u0*f 'v flr;".
di sp* 50=T.f ritf T.K'- i - " l u ' n c - . t v ? r«Fu-3t,
-he a rr. oi' t ' ? .i.-eEicaremS:'. IF v as to 'v;\e5tii::.í< :. V~€ J í">*íí"-'.~' ;:•
c; t i p F"3'i i t -r'-"1! v e r t e i . " 1 '• o: •." te Víír'e.-rs" r : . - u jv" r
{=•!= r r a r u ? ! ^-sr.uctjc.- c: 'o-- -; c •" t v ? rr-i-.e iv ' f Vi->-,-",
.-•"-•ir:;.. V? discus? t ' "tru'tr ••r ' v t - ' - r - ?-: -? •<-uT s-" ' ;r - '
64
spine. Compared with the :noire technique, digitization is
considerably more exact and more practicable.
3. PUI53 LIGHT PT*OTO?RA'" "STHY
The fundamentals of pulse light photogrammetry its applica-
tion in orthopaedics are presented. This Tiet^oí üiay be used
for the analysis of huaan "notion according to íine-natic *
parameters. Pulse light pt-otograireetry is believad to be
the -nost exact contactless measuring ttchninue. -Tusi an ">.oti ns
are frequently reoeated throughout tv9 year by the million.
It is also for this reason that parts of the bodv often
perform notions with mi lli.~:eter exactness. Hence, ascer-
taining differences also requires measuring -nethoás of t^is
accuracy. ?ilm qtialyses as an alternative; do consequently "'
^>iot lead to the íesired investíeation ÍÍTIS as is also
apparent from induviiiual papers and information issued
at the last Interactional Conaresnes for Bi /Mechanics.
Our Dara>netpr«'.vsyst«'n as result of -notion, analyses at
25 healthy adults and patients vith (iifferent motion system
diseases are presented.
during the evalution process, it should oe reserved fcrv,
selected mt^suring proRlems. In cornorev'e'if!iv9 and, if
possi.ole, highly exact analyses of si^Dle as «*T!. as
complicated •notions with unkriovin space-time-function
puls« liaht Dhotorframmetry is at t' a moment unexcelled
by nny ot'"-'!? method.
Ms. S Z Ü ^ T Í . Ann* Gera — larolT Saöréui
Application of microprocessor in audiometers
The electronic derices of auditory examination established
the base of quantitatiTe measuring* also in audiology, and
development of reproducible, exact measuring procedures
set off. In the practice coming into being in the years 70,
20-30 technics of audiometry are being performed, which are
suitable on base of differential diagnostics for determining
o the reason, place of hearing deterioration and offer an adequate
base for medical intervention. leverjtheless subjectivity of
patient and of the expert performing the examination affect
o the results.
Purposes of forthcoming development of proceedings and means
follow from above-said:
- reliability, objectivity of measuring results are to be
improved
first of all by automizing the examinations.
Availing ourselves of the mYT system, we elaborated those mo-
dules of hardware and software, by which audiometers satisfying
tie different requirements of application can be constructed.
Audiologic activity is directed at present to several routine-
o -proceedings when determining the auditory thre-shold, reap,
in case of measuring above threshold. We automized these methods,
such as ie. determination of threshold, method of Btfkésy, S.I.S.I.,
fowler, TOT, etc. - since methods applied in medical practice are
unified.
66
5.3.0
67
A MUSCLE USE DISORDER.
Department of Clinical Physics and Bioengineering. Guy's Hospital, London SE1 9RT, England.
The concept of misuse was developed by Alexander (i), who proposed that attention should be paid to general muscular coordination,, and not simply to the local site of the pain in the muscle or joint., 'use' means the characteristic and habitual way of using and moving the body, and the form and extent of movement of one part of the body to another part in response to circumstances and environment. As well as the specific problems for which the patient is being treated, it is observed also that there is a postural imbalance. In writer's cramp the whole arc may be affected, or even the whole of the shoulder, and chest on the same side. In neck muscle cases the imbalance includes the shoulders and sometimes extends to the back and affects breathing. This is because one pair of neck muscles can also be used as auxiliary breathing muscles. Curvatures of the spine are also found with neck muscle problems. |)
Writer's cramp is a relatively rare functional motor disorder in which the learned skill of writing- is impaired. The syndrome usually consists of muscle spasm, tremor, poor coordination and craap with discomfort, fatigue or weakness in the hand and forearm. For patients suffering from tension headache, who have rafjed resting levels, a progressive lowering of contraction in the muscles of the forehead with improved voluntary control, is the desired objective. A similar approach is tak^n with writer's cramp, with controlled and limited exerciser in ., writing. A more disabling condition is torticollis in which the patient experiences difficulty in turning the headland the head is deviated continuously to one side. When accompanied by involuntary movements it is called spasmodic torticollis. It is a progressive condition and within weeks of onset, there is inability to control the head position. The three pairs of muscles particularly affected arei^tlie sternomastoids, the trapezius, arid splenius capitis. íj
For effective motor learning the patient has to ble goal motivate? and be able to learn to produce a motor response. The parameter in bio- feedback technique displayed to the patient oust be indicated immediate- 1,: and be sufficiently accurate. Frequent repetition during a treatment session with display of the record of performance, reinforces motivation.
Basmajian (2) in his reviev of the use of biofeedback in rehabilit- ation, concluded that spasmodic torticollis has proved to be particularly suited for behavioural methods: of treatment including SVG feedback. Fe íicneereá the technique of single motor unit training. In E'íQ feedback, th-3 parameter of physiological activity or physical action is amplitude of th-= E\X obtained with surface electrodes. It can be disalayed as rat? sirnil on the C.R.O. or louflspeaker, or as: the movement of a visueZ indicator, or as a tone whose frequency rises fcitíí t".a siren^ti of contraction. Alternatively a seriec of clicks whose rate correspond? to the strength of the E.'G ::iay be used depandin?: on th-? preference of th° patient. Tnus the patisnt learns to relate conscious effort ani will to a simple indication of the immediate resjlt. At the beginning of a res-ion for a torticollis patient a record is tasen from the pair of muscles BSOF* affected, or those which will be the bac.iru of the therapy session. "*he first record is usually the worst for spans and tremor. Techniques include relaxation for overused muscles. a?i:3 strengthening for underused iriusoler with feedaacK. Head taming without feedback is us<?d to overcome the tendency to spa.E£. Fast and slow turning are tried. $'itb th<=> variable pitch tone, the shoulders are tensed for a specifieti period, short of
68
causing fatigue. During relaxation, the change in pitch gives the patient an immediate measure of achievement.
XMGs taken with surface electrodes show clear departures from the normal. The prime mover ana its antagonist contract simultaneously, thus preventing normal movement. The £116 waveforms often show an increase in low frequency rhythmicity or tremor. A narrower spectral distribution is inferred from the simpler waveshapes.
Tremor at rest is a fairly common observation in torticollis. It shows as distinct and discrete motor unit activity at a uniform rate ranging from about six to around fourteen per second. Most of the record- ings in all sessions show tremor at the same frequency in the neck muscles, recorded two or four at a time. The frequency varies during recording. It is higher at the beginning of each session, and shows an increase during turning effort. The frequency of tremor as interpreted from recordings ÍE the repetition rate of motor unit activity. In the early recordings of one case study, it appeared as a discrete diphasic action potential repeating at rates of ten to fourteen per second. In recordings tiro months later the waveshape was polyphasic, with similar repetition rates. The progressive change form simple to polyphasic is taken as an index of improvement of control of muscle function. The simple diphasic form fast component occupied 26 msec, whils the later fora occupied 50 msec. The polyphasic form approaches the normal full interference patternijtof an EMQ. In the full interference pattern single potentials summate and overlap or 'interfere' with one another, giving rise to the normal continuous pattern in which the baseline has dis- appeared .
Synchronization phenomena appear in two forms. The discrete motor unit potential, previously described had relatively high amplitudes of nearly a millivolt. Such high amplitudes detected with surface electrodes can only occur when many motor units fire simultaneously. Synchronization at the spinal level is the probable explanation. The other form of synchronization is tremor at the same frequency in two or more muscles controlling1 head posture and position. Small oscillatory movements or tremor can sometimes be felt by the therapist. The patient is some- times aware of a vibration or treacling in the muscle. The mechanism which causes there oscillations is likely to involve two muscles at least. One muscle will pull against the force exerted by another, and tremor Vill be tranrmitted to others by the common mechanical linkage; or if one muscle goer, into tremor, another will respond with the same tremor pattern. In one record of a head turn it was found that one muscle had twice the frequency of tremor SF its contralateral. Phase relationships seem to be r.teady. The sternomastoids show alternate tremor, but one side will be in step Kith the trapezius of the same side.
Brudny (k) puts forwar the vie* that the adult-onset condition of torticollis apparently occurs in patients with a genetic predisposition for a deficit in neuronal transn-ittal agent, most probably ea»aa-aa:ino- butyric acid, of inhibitory action relating to the extra-pyramidal system. It is resistant to various therapies, but doer often respond to behavioural treatment. " c,
In a review of the effects of increased demand on skeletal auscle it was concluded that the character of a muscle can be influenced considerably by its recent history of use (8). It has been demonstrated that during chronic low freouency stimulation of * fast twitch,Muscle, it undergoes an orderly sequence of changes which ultimately brings about a complete transformation to e slow twitch muscle. Ctae of the earliest changes IF an increase in capillary density and a significantly greater capillary to muscle fibre ratio, but with aiuscle fibre diameter decreased y. The authors noted that these changes were induced by low frequency
5.4-.O
stimulation only, and not by an overall increase in activity. Increased resistance to fatigue is observable after only four days.
Properties characteristic of slow muscle can be established and maintained by postural patterns of motor nerve activity. On removal of these patterns, or on removal of the slow rate electrical stimulus the muscle regains its former characteristics after six weeks: and after a further six weeks, oxidative enzymes have declined to normal levels, but capillary density is still somewhat elevated. Th« discharge frequency to slow motor units is 10 Hz (5).
It has been observed that some torticollis p*ti«nfts exhibit strong persistent tremor in the head turning muscles, as well as the other features of the condition. The frequency is often about 10 3z, bat can be as high as 14 or as low as 6 Hz.
Physiological tremor is a normal fluctuation in muscle contraction occurring at around 10 Ha (7). The strong tremor observed in torticollis may be indicative of a condition in which normal physiological tremor is so strong as to change the pathology of muscle, and interfere with normal function, conferring the property of fatigue resistance, and causing hypertrophy in one or more neck muscles.
Treatment in consequence of the ' 10 Ha hypothesis ' will include tremor amplitude-as a biofeedback parameter.
Analysis of spike trains of normal motor unit firing (6) showe-i statistically significant spectral peaks in the 8 to 12 Hz ranee, as well as the expected spectral peaks corresponding to the mean firing frequencies. The effect resulted from a tendency towards action potential grouping. Also observed was a double discharge firing pattern with intervals corresponding to the 8 to 12 Hz spectrum. This latter effect was believed to arise from Renshaw inhibition-rebound excitation.
References. (1) The Alexander Principle by W. Barlow. Gollancz, London 1973- (2) BaBMJian J.V. (1981) Biofeedback in Rehabilitation,
Arch phys Med Rehab 62:469-^75. (3) Brown M.D. et al (1976) Ffluegers Archiv 361:2^1-250. CO Brudny J (1981) Feedback of EMG in neuromuscular rehabilitation of
spasmodic torticollis. Int Behavioural Treatment of Disease. . PltnvM Publishing Corp., N«w Tork.
(5) Buchthal F & Schmalbruch H (1980) Motor Unit of Mammalian Muscle p.120 Phyaiol Rev 60:90-1^2.
(6) Bible R.J. & Randall J.E. (1976) Motor unit Activity and Tremor. J Neurophysiol. 39(2): 370-383.
(7) Marshall J (1962) Observations on Essential Tremor. J Neurol Neurosurg Psychiat 25:122-125-
(8) Salmons S & Htnriksson J (19^0) (Pre-publication connminication).
70
-afc
5.5.0
human motion analysis
71
5.6.0
A SIMULATION MODEL OF LOADS IN ARTIFICIAL HIP JOINTS by
Prof. D. Gebauer Department of System.Safety Sciences University of Wuppertal Gauflstr. 20, D-56OO Wuppertal 1 Federal Republik of Germany
INTRODUCTION
The problem of longterm function in total hip replacement is
not solved yet. Biomechanical forces and moments are consi-
dered as essential reasons for an aseptic loosening of the
endoprosthesis. The mechanical loads occuring in the joint
while walking were measured or calculated and used for mate-
rial investigations in simulating testing machines. All of
these hip simulators induce a single pressing force on the
replacement while relative movements take place. Therefore
the physiological situation of the pelvis as bending frame
is neglected in that simulation.
Other increased forces as impact loads during falling are
not investigated sufficiently. As tests in human beings can-
not performed in this field, mathematical methods can be
used to get more information about that.
MATERIAL AMD METHODS
The friction torque in the artificial joint, is often accused
to induce the loosening of the implant in the interface bet-
ween bone und the mainly for fixation used bone cement. To
find out the influence of these torques during walking they
were measured in the direction of extension/flexion and in
the direction of rotation by a new self-constructed hip
simulator. In the contrary to other simulators the physiolo-
gical bending of the pelvis is imitated by implanting the
cup in a bending frame. Ten explanted endoprostheses of
different materials were tested without any lubrication to
get the friction torque under the worst conditions in vivo.
72
5.6.0
The values can be transferred to shear stresses in the inter-
face.
As we saw several fractures of plastic and ceramic cups in
explanted prostheses, we tried to find out the influence of
impact loads as falling from a stair or curbstone by a bio-
mechanical model of the lower extremity. The simulation is
based on an one-mass-swinging model for one extended leg
which is falling down from a height of 5 cm and 20 cm to the
ground. As values of the damping factor of the leg under
physiological conditions are not known, self tests were per-
formed to find hints of the spectrum of the damping factor
by measuring the acceleration while falling from different
heights. The values of acceleration were transferred to for-
ces in the hip joint.
RESULTS
The friction torques measured under the circumstances of dry
friction is depending on the type of bending frame which is
used for simulating of the pelvis. The values of the longer
frames are lower than those of smaller frames in most cases.
Under walking conditions the maximum friction torques were
lower than 15 Nm. The transposition of these values to shear
stresses in the interface shows that the stresses don't
reach the level of critical values measured by Kölbel (1).
The comparison with experimental loosening torques of the
cup investigated by Andersson (2) as well as Jáger (3) also
demonstrated that only the friction by itself cannot induce
a loosening of the cup.
The mathematical calculation of the effect of impact load
shows the dependarice of the maximum force K „ „ on the dam- in&x
ping factor jt. In the interval of ft > 0.2 to 0.4 a decrease
can be determined. The forces increase linearly for higher
damping factors. For a falling from a height of 20 cm a
maximum force of 11 kN up to 25 kN can be seen in the inter-
val of * * 0.4 up to 1.0. In an endoprosthesis with a 38 mm
ball an average pressure of 0.96 up to 2.19 kN/cm2 and a
maximum area pressure of 1.51 up to 3.44 kN/cm1 is resulting
73
pressure of polyethylene is 1.3 kN/cm3, it can be presumed
that several parts of a polyethylene cup can be damaged under
the described circumstances.
calculated and compared to limit values experimentally in-
vestigated. This comparison shows that the described falling
can effect a destruction of the interface which consists of
cancellous bone and cement. The connection between cortical
bone and cement will probably not be destructed by those
i