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US 3344275 A
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p 6, 1967 H. M. MARCHAL ETAL 3,344,275
X-RAY APPARATUS FOR STUDYING PERIODIC BQDILY PROCESSES CHARACTERIZED BY AN OSCILLATION OR PULSATION OF SOME BODY PORTION Filed Dec. 21, 1964 2 Sheets-Sheet 1 p 26, 1957 H. M. MARCHAL ETAL 3,344,275
X-RAY APPARATUS FOR STUDYING PERIODIC BODILY PROCESSES CHARACTERIZED BY AN OSCILLATION OR PULSATION OF SOME BODY PORTION Filed Dec. 21, 1964 2 Sheets-Sheet 2 mom I V 55 a J, m l r l l 1 O *1 '1 l 3\5 Q1 R2 I sou/m 121 TC? TC;
, r6 I I 1i: *TAZ l i SOURCE FRO/1 L6. l :34 575p gy- 5TP 5 WITCH X-RAY APPARATUS FGR STUDYING PERIODIC PRUCESSES (ZHARACTERIZED BY AN (ESCELLATION R PULSATIGN 0F SGME BQDY PORTHUN Henri Maurice Marchai, Paris, France, and Marie-Therese Marchal, born Dupuy, laris, France, assignors to Centre National de la Recherche Scientifique, Paris, France, a French Government Administration Filed Dec. 21, 1964, Ser. No. 419,991 6 Claims. ((13. 250-415) ABSTRACT @E THE DISQLGSURE In a radiology apparatus for densigraphic examination there is effected a simultaneous recording on the one hand of relatively slow variations of density of the obstacle that is examined due to its ventilation, and on the other hand of small variations of density of the obstacle that is examined due to the circulation of blood therein by making use in two different channels of the intensity of the current delivered by a cell. Caculating means may be provided for directly combining together some of the informations thus simultaneously recorded for medical diagnostic purposes.
This invention relates to radiology apparatus, and particularly to apparatus for applying radiological techniques to the study of those periodic bodily processes which are characterized by an oscillation or pulsation of some body portion.
The present invention concerns novel radiographic devices for the performance of densigraphic examinations in which a record is made of the relatively low frequency (i.e., less than 3 c.p.s.) variations in the attenuation of a beam of X-rays, or other rays, modulated at its source by a relatively high frequency (i.e., 50 to 190 c.p.s.) and traversing a body under examination, said variations being a function of the variations in opacity which corresponds either to a variation in density or in thickness of the body under examination. The present invention is particularly intended, because this application seems to represent the most useful employ of the invention, for use in the diagnosis of the transparency of lungs by medical radiology.
This invention involves the provision, in combination with apparatus of the type discussed herein having means for converting, into variations of electrical current, the variations of intensity of an X-ray beam passing through a subject, of first means for recording these variations and/ or the average value thereof directly after amplification so as to obtain a measure of the relatively low-frequency variations in the opacity of the subject due to his breathing, and/or the average value thereof, and second means for recording the signal obtained by the removal of any carrier wave modulation applied to the X-ray beam followed by a substantially larger amplification than that produced by said first means, the resulting signal serving to indicate the variations in opacity due to the subjects blood circulation.
Such apparatus could also comprise a computing arrangement for combining these signals in various ways in order to yield medically useful relations, such as, for example, a quantity representing the quotient of the amplitudes of the impulsions of the output from said secnitcd States Patent 0 M 3,344,275 Patented Sept, 26, 1967 0nd means divided by the output (either instantaneous or averaged) of said first means, the value of which quotient is directly related to the blood flow rate in the subject.
These and other objects, features, and advantages of the present invention will become more readily apparent from the following detailed description when considered together with the attached drawings, in which:
FIG. 1 is a schematic block diagram of a device employing one embodiment of the present invention;
FIG. 2 is a schematic diagram of a portion of the electronic circuit of the device of FIG. 1;
FIG. 3 is a schematic diagram of another portion of said electronic circuit; and
FIG. 4 shows a pair of graphs which are useful in explaining the operation of said other portion.
Before proceeding with a detailed description of preferred embodiments of the invention, it would be well to review briefly the basic elements of a densigraphic examination of, say, a portion of a lung.
The performance of such an examination involves essentially the formtaion of an image 1 (see FIG. 1) of the lung upon a radioscope screen 2; a small fluorescent screen 26 (see (FIG. 2) is disposed in the path of the rays having traversed the lung in the region to be examined, the image of this small screen on screen 2 is indicated at 3 in FIG. 1; and the light which the rays cause small screen 26 to emit is directed towards a photo-cell 4 which transforms the received light energy into an electric current whose variations are recorded.
In the prior art, the recording was made either: directly, after a simple amplification, so that an examination of the envelope of the recorded curve revealed the large amplitude, relatively low frequency opacity variations caused by the ventilation or respiration of the lung portion being examined, and/or the average value of said opacity; or indirectly, after both a higher power amplification than in the preceding case and a suppression of the high frequency modulation, or carrier frequency, originally given to the rays, so that the final curve revealed the small opacity variations caused by the pulsating blood circulation occurring in the lung portion under examination.
If it were desired to investigate, both the respiratory operation and the state of blood circulation in a given lung portion-which would be of great value for certain diagnoses such as those of cancers of the lungs, emphysema, silicosis, etc.it was always necessary in the past to perform two successive examinations each requiring a different apparatus. This procedure caused the following major inconveniences:
One coud never be certain that the two examinations corresponded to a single set of examining conditions because it is difiicult to successively position two small fluorescent screens so that they will each be opposite the same lung portion, the subject has a tendency to move, and it is extremely diflicult to obtain the same respiration and blood circulation conditions for the two successive examinations;
The total duration of the two examinations was double that of a single examination; and
It was necessary to provide two fluorescent screens and two photocells.
The present invention proposes to eliminate these inconvenienccs by permitting the two desired readings to be obtained simultaneously by simultaneously applying the output current of a single detecting photocell to two different signal processing circuits.
To this effect, a preferred embodiment of the invention is shown in FIG. 1 to comprise an impedance converter 5 receiving the output signal from cell 4 and applying this signal to two separate signal processing circuits. One processing circuit comprises only an amplifier 6 and a recorder 7 producing a signal whose variation reveals the respiration pattern of the lung portion. The other circuit comprises, an addition to an amplifier 8, whose gain is greaetr than that of amplifier 6, and a recorder 9, a low-pass filter 10 which passes only those frequency components of the photocell output which are below a certain frequency, 10 c.p.s. for example.
Itthus results thattwo curves relating to exactly the same lung portion are recorded simultaneously, andpreferably on the same sheet 11. The first curve 12 presents an envelope whose amplitude varies in accordance with the overall opacity variations of the lung portion, these overall variations corresponding generally with the respiration. The second curve 13 varies in accordance with the blood circulation. It should be noted that the oscillations (of l to 2 c.p.s.) represented in curve 13 are also present in the envelope of curve 12, the principal frequency of oscillation of this latter curve varying between 0 (when the subject is holding his breath) and 0.1 to 0.3 c.p.s. (when the subject is breathing normally), but are not discernible therein as a practical matter since the amplitudes of these oscillations are around 100 times smaller than that of the respiration-induced oscillations of curve 12.
Comparison of these two curves should prove extremely valuable since they were both obtained under precisely the same conditions: such a comparison would enable one to determine, for example, whether a temporary and local stoppage of the blood circulation is related to a respiratory difficulty experienced by the subject.
Moreover, it takes no more time to obtain the two curves than it previously took to obtain a single curve and the number of photocells required is reduced to one.
FIGURE 2 shows a circuit diagram of a portion of a circuit which may be used as part of the system of FIG. 1.
In this circuit, the output 14 from cell 4 is connected to ground through load resistor 15 and to the grid of a cathode follower triode 16 whose principal function is to present a low output impedance which serves to eliminate the effects of wiring capacities, particularly that of the output lead from cell 4. The two electrical paths employed for the production of curves 12 and 13, respectively, begin at two points 17 and 1%, respectively, of a resistor 19 connecting the cathode of triode 16 to a source of negative high voltage.
The first of these points 17, is connected to the grid of an amplifier triode 20 whose cathode is connected to the negative high voltage source through a resistor 21 and whose anode is connected to another amplifier stage, indicated by 22, which is in turn connected to recorder 7.
The other point, 18, is connected to the grid of an amplifier triode 23 whose cathode is connected to the negative high voltage through resistor 24 and to filter 10. The output from filter 10 is connected to complementary amplifiers, indicated generally by 25, which are in turn connected to recorder 9.
Filter 10 is advantageously constituted by at least two filters in series separated by a cathode follower circuit which permits each filter to have a high output impedance.
It should of course be appreciated that any other known radiological or electronic techniques may be used to improve the operation of the above-described system without departing from the scope of this invention.
For example, in order to permit the small fluorescent screen, 26, forming the image 3 on the large screen 1 to be accurately positioned, it is desirable to render at least a part of the elements immediately surrounding screen 26 transparent to X-rays, the light produced by the screen being transmitted to cell 4 by a light guide 27 which is transparent to X-rays, such an arrangement having been described in applicants U.S. Patent No. 3,086,123, issued on April 16, 1963.
Because the present invention is capable of obtaining, at one time and during the same examination, electrical signals indicating both the average opacity s of a lung portion and the amplitude, at, of the opacity modulation caused by blood pulsations, an improved embodiment of the present invention includes means for automatically computing the ratio a/s which represents the circulatory coefiicien for the lung portion investigated.
One arrangement for attaining this result employs a value for a which represents the average of the amplitudes of modulation created by several successive blood pulsations. This provision serves to correct for the fact that opacity variations due to successive blood pulsations are not exactly identical to one another.
One arrangement for carrying out such a computation is shown in FIGS. 1 and 3 to comprise two peak-reading voltmeter assemblies 28 and 29 receiving, respectively the outputs of amplifiers 6 and 8. These assemblies are activated by impulses emitted by an electrocardiograph assembly 30, connected to the examined subject 33 and operating during the same time as the rest of the described apparatus, said emitted impulses being formed through a Schmitt trigger 34.
The impulses produced by said trigger 34 enter in two step-by-step switches 35 comprised respectively by each assembly 28 and 29. So the first impulse activates in each of said assemblies only a first relay R through a line L and a closed contact r of a relay R Said activation closes the contact r of the relay R which causes a first capacitor C to charge from the corresponding amplifier 6 (or 8), through a closed contact 1- of the relay R, until attaining a charge corresponding to the peak value of the current supplied to it at that instant by said amplifier (this peak value corresponding to s for assembly 28 and to a for assembly 29). The next impulse from trigger 34 activates, in each assembly 28 and 29, through the step-by-step switch 35 of said assembly, a line L and a closed contact r of the relay R only a second relay R The contact r of said second relay is then closed and a second capacitor C charges in its turn to the peak value .9 (or a of the corresponding current delivered by the amplifier 6 (or 8) at said instant. The third impulse isolates in its turn the two first capacitors C and C of each assembly 28 and 29 and permits the amplifier outputs to charge a third pair of capacitors C and so on. After a predetermined number of impulsions, five for the described example, the following impulse coming from the trigger 4 activates, through the step-by-step switch 35 of each assembly 28 and 29 and a line L the above mentioned relay R Said activation moves all the contacts r and consequently, activates all the relays R to R from a source 36 and connects all the capacitors C to C of each assembly 28 and 29 to inputs of a quotientmeter or ratiometer 31, which may be a logometer (sort of galvometer having two movable crossed frames and indicating the measured ratio by an angular deviation).
The output 32 furnished by meter 31, which indication may be in the form of a maximum angular deviation of the meter indicator, is proportional to the relation between the sum a +a +a +a +a and the sum assuming that five capacitor pairs are used. In other words, the indication is proportional to the quotient of the average value a of the variation of the opacity of the portion examined due to the blood circulation divided by the average value s of the absolute magnitude of this opacity.
it has previously been shown, by comparison with the results obtained by bronchospirometry and measurements of oxygen consumption, that this quotient a/s is directly related to the actual blood circulation in the examined region.
In practice, in order to reduce the number of blood impulsions utilized for obtaining the average values, and hence to reduce the number of capacitor pairs required in units 28 and 29, the examination may be carried out by having the subject take an average breath and hold it, with the result that all of the values s s etc., will be equal to the average s so that unit 23 may thus be simplified so as to comprise, for example, a single chargeaccumulating capacitor.
The diagrams of FIG. 4 relate to just such a procedure; the upper curve represents the continuous recording of amplitude s and the lower curve shows five successive oscillations, having peak amplitudes of a :1 caused by the blood circulation.
It would of course be desirable to have the output 32 also recorded on sheet 11.
It thus results that there is produced a device which is so arranged and constructed that a single photocell can be used to simultaneously determine the curves of both the average opacity and the opacity variation due to the blood circulation of the subject under study.
It should be noted that many variations can be made to the above-described structure without departing from the spirit of the present invention, such variations including, among others:
Those wherein the apparatus is equipped with a plurality of small screens 26, each associated with a light cell and appropriate signal processing circuitry, in order to permit several lung portions to be simultaneously examined;
Those wherein the means for supplying an electric current proportional to the intensity of the X-ray beam passing through the region under examination are directly responsive to these rays (Geiger counter, ionization chamber, etc.) instead of being indirectly responsive thereto through the intermediary of the fluorescent screen 26;
Those wherein the system of the present invention, rather than having its input interposed between the X-ray source and the large screen 2, has it interposed between this latter screen and the observer in such a way as to receive all or part of the light emitted by said screen;
Those wherein small screen 26 is constituted by a scintillator crystal capable of transforming the radiant energy received (produced by X-rays or other radiation) into light;
Those wherein the large screen 2 is replaced by the reception window of a brightness amplifier Coupled in a known manner to a television receiver through the intermediary of a camera tube of the Vidicon type, or other type (which technique permits a reduction in the X-ray dosage received by the subject while improving the quality of the resulting image); the resulting curves 12 and 13 might, with this arrangement, be reproduced on the screen of this receiver through the intermediary of a second camera tube;
Those wherein the device might be associated with any other computer arrangement such as one capable of determining the quotient of, or the difference between, average opacity values corresponding, respectively, to a forced inhalation and a forced exhalation by the subject, which quotient or difiference could then be, automatically or not, added to similar quantities corresponding to other lung portions or to other relations of different types for various diagnostic purposes.
It should therefore be understood that the breadth of the present invention should be limited only by the scope of the attached claims.
What We claim is:
1. In a radiographic device for performing densigraphic examinations on a subject and comprising a source of a high-frequency modulated X-ray beam to be projected through the portion of the subject to be examined and means detecting the beam after it has traversed the subject for producing an electrical signal which varies in proportion to the variation of the intensity of the X-rays passing through the portion of the subject under examination, the improvement comprising: first electronic signal processing circuitry having an input connected to receive the signal produced by said detecting means and an output upon which appears an amplified version of said signal; second electronic signal processing circuitry having an input connected to receive the signal produced by said detecting means and an output upon which appears a version of said signal from which said high-frequency modulation has been removed and which is substantially more amplified than the output of said first circuit; and recording means connected to simultaneously record the signals appearing on said two outputs.
2. A device as recited in claim 1 further comprising computing means connected to receive the outputs from both said signal processing circuitries for producing a signal which is proportional to the quotient of the value of the peaks of the output of said second circuitry divided by the output of said first circuitry.
3. A device as recited in claim 2 wherein said computing means comprises: first averaging means connected to the output of said first circuitry for obtaining a signal representing the value of the average amplitude of the envelope of the output from said first circuitry; second averaging means connected to the output of said second circuitry for obtaining a signal representing the average of several successive peaks of the output signal of said second circuitry; and comparator means connected to said two averaging means for producing a signal representing the quotient of the value of the signal obtained by said second averaging means divided by the value of the signal obtained by said first averaging means.
4. A device as recited in claim 3, wherein said comparator means is a ratiometer.
5. In a radiographic device for performing densigraphic examinations on a subject and comprising a source of a high-frequency modulated X-ray beam to be projected through the portion of the subject to be examined and means detecting the beam after it has traversed the subject for producing an electric signal which varies in proportion to the variation of the intensity of the X-rays passing through the portion of the subject under examination, the improvement comprising: first electronic signal processing circuitry having an input connected to receive the signal produced by said detecting means and an output upon which appears an amplified version of said signal; second electronic signal processing circuitry having an input connected to receive the signal produced by said detecting means and an output upon which appears a version of said signal from which said high-frequency modulation has been removed and which is substantially more amplified than the output of said first circuitry; recording means connected to simultaneously record the signals appearing on said two outputs and means connected to receive the outputs from both said signal processing circuitries for producing a signal which is proportional to the quotient of the value of the peaks of the output of said second circuitry divided by the output of said first circuitry, said computing means comprising first averaging means connected to the output of said first circuitry for obtaining a signal representing the value of the average amplitude of the envelope of the output from said first circuitry; second averaging means connected to the output of said second circuitry for obtaining a signal representing the average of several successive peaks of the output signal of said second circuitry; and comparator means connected to said two averaging means for producing a signal representing the quotient of the value of the signal obtained by said second averaging means divided by the value of the signal obtained by said first averaging means, said first and second averaging of said impulses and adapted to connect all said charged capacitors on an input of said comparator means.
References Cited UNITED STATES PATENTS 2,679,598 5/1954 Wright et al. 250 95 2,858,421 10/1958 Touvet 250 199 3,086,123 4/1963 Marchal 250 71.5 3,109,058 10/1963 Luhn 346-35 RALPH G. NILSON, Primary Examiner.
A. L. BIRCH, Examiner.