Apparatus and method for simultaneously displaying relative displacements of a fluctuating biological object

X-ray apparatus and method for producing discrete images of a human organ in fluctuating motion, e.g., the heart and related vessels. Each image is derived at a selected time related to the cardiac cycle. The images are independently presented on respective discrete areas within a common image plane. A source of X-rays irradiates the organ. A physiological synchronizer produces timing signals within the cardiac cycle for controlling the periods of transmission of the X-ray beam through the organ during, for example, end diastole and end systole. An antiscattering, masking frame has alternate parallel slits and bars at equal intervals exposing substantially half the area of presentation of an X-ray sensitive film in alternate, equally spaced area strips during, e.g., diastole. The frame is repositioned in response to a signal from the synchronizer for actuating it relative to the film such that the bars then cover the sensitized areas of the film and expose substantially the remaining half of the film during systole. The image elements are interdigitally juxtaposed to present the diastolic and systolic images in an interlaced pattern. Relative displacements of the organ during a cardiac cycle may be determined from the juxtaposed image elements.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates generally to the field of viewing a biological object 
by irradiation to expose the internal structure. More particularly, the 
invention relates to diagnosis of human ailments by the use of X-ray or 
nuclear radiation as modified to view specific organs, and associated 
vessels, while in fluctuation, whether or not recurrent, and to exposures 
taken during fluctuation at selected times related to a selected 
physiological state or states of the object. 
More especially, the present invention relates to producing a radiograph 
for simultaneously, statically viewing the heart and associated vessels, 
after exposure to radiation, at different times in the cardiac cycle, for 
example, during systole and diastole respectively. 
2. Conventional X-Radiological Diagnosis 
X-radiology is widely used noninvasively, that is, without invading the 
body by puncture or chemical agents, as part of routine health 
examinations and preliminary tests where pathology may be indicated. Where 
indicated clinically, the use of invasive, risky and complex arteriography 
or angiography is becoming more frequent. 
Chest X-Ray 
In modern X-radiology, for example, for a chest X-radiograph, an X-ray tube 
provides a source of X-radiation to illuminate a patient's chest. The 
X-radiation from the patient is transmitted through X-radiation sensitive 
film, normally enhanced by X-radiation transmitted through a fluorescent 
light screen positioned behind the film. The fluorescent screen is 
required because the film is more sensitive to light than to X-rays. 
Generally speaking, the X-ray tube anode voltage is approximately 70 
kilovolts. The exposure time required for a useful X-radiograph is 
typically in the range of 50-100 milliseconds. The exposure is initiated 
by applying the anode voltage to the tube, and it is extinguished by 
removing the voltage. 
The operator selects the amount of X-radiation exposure by means of (1) a 
calibrated timing mechanism for the period of an exposure or (2) a 
calibrated phototimer for counting and summing X-rays or photons, to 
control the application of anode voltage. The so-called phototimer 
typically employs a photomultiplier tube and integrating circuit to 
control the exposure in terms of a preselected photon count. To provide a 
proper radiograph for ready analysis, the exposure is so chosen as to 
provide an image varying in density with a maximum visible range for 
detecting variations in skeletal and tissue structure. Further, maximum 
contrast is considered desirable to enhance structural details. 
The apparent fine detail is further enhanced by minimizing undesirable, 
so-called scattered, radiation; that is, nonparallel or uncollimated 
X-rays. In a typical X-radiographic film a screening, or anti-scattering, 
web is used in front of the film to reduce the scattering by restricting 
exposure substantially to parallel rays. Mechanisms for reducing such 
scattering are fully described in the literature; and, particularly, 
reference is made to an article entitled "Radiographic Contrast 
Improvement by Means of Slit Radiography" by Jaffe et al appearing in 
Radiology Vol. 116, pages 631-635, September 1975. 
The resultant X-radiographic image obtained is derived from direct 
X-radiation and indirectly from the light from the fluorescent screen, 
produced in accordance with the photoelectric effect by X-radiation 
impinging upon fluorescent materials. 
A minimal effort is made to control the patient exposure to radiation to 
normalize one radiographic image relative to another. More particularly 
with regard to specific physiological states, it is not currently widely 
considered important to synchronize the X-ray exposure with any particular 
physiological state. Nor is it considered important, in a precise manner, 
to normalize the radiograph in other respects, such as density and 
contrast. Thus, if one is taking a normal chest X-ray, the exposure can 
take place during a period when the fluctuations or displacements of any 
organ, particularly the heart, are most rapid. This has the effect of 
obscuring or blurring the image, particularly the outlines. Consequently, 
incipient calcification, for example, frequently fails to show up without 
such synchronization. Such radiographic images may be, in part, totally 
obscured; at the very least much of the image is extremely difficult to 
interpret. 
In any event, the normal or conventional chest X-ray gives one no 
indication of what happens dynamically, when the heart is in motion. The 
time during the cardiac cycle when the exposure takes place is unknown; 
that is, the exposure is taken without relation to the heart motion. In 
addition relative displacements or changes in condition are not shown. 
Angiography 
At this time angiography has proven to be the most reliable procedure for 
diagnosing cardiovascular pathology because the heart motion and blood 
flow may be viewed dynamically. This risky, complex and invasive technique 
requires the insertion of a catheter through the main artery, the aorta, 
to inject a dye into the arteries feeding the heart, the coronary 
arteries. A large number of X-radiographs are taken sequentially and 
edited to provide, by time-lapsed radiography, a radiographic motion 
picture depicting the amplitude and character of heart fluctuation and 
blood flow during the cardiac cycle. 
Angiography requires a highly trained team. The necessary time involving 
the patient ranges from 2-6 hours and, indeed, must occasionally be 
repeated. Ideally angiography should be repeated after surgery to 
establish the efficacy of the surgery. 
This technique impacts heavily on the patient requiring a high level of 
cooperation. The patient is immobilized during the entire procedure, 
supported only on a hard, flat surface. 
3. Problems with Conventional Techniques 
Static X-Radiographs 
The procedure widely accepted, at this time, as standard X-radiology for 
routine examinations and preliminary testing is inadequate because: 
1. The radiographic image tends to blur if the exposure is taken at random; 
that is, unsynchronized with the time of minimum motion of the heart; and 
2. No information is presented as to the relative displacements of the 
heart during the cardiac cycle. 
Disadvantages of Angiography 
Angiography in its present form is limited in use to an indication of 
severe heart disease because: 
1. It is dangerous. The risk of a catastrophe at the best facilities in 
1976 was 1%, with a 0.5% mortality rate. In lesser facilities the 
catastrophe rate was much higher; 
2. A large team of highly trained specialists is required; 
3. The procedure is lengthy, complex and expensive; 
4. It is difficult and sometimes impossible to apply to comatose patients; 
5. The X-radiation exposure time is enormous with typical 50-150 
milliseconds for standard chest X-ray; and 
6. The patient is subjected to a high level of discomfort and debilitation. 
In 1976 about 70,000,000 chest X-rays alone were taken and less than 50,000 
angiographs. If every patient who requires angiography were so diagnosed, 
existing facilities would be severely overtaxed. Clearly neither the 
presently accepted standard or angiographic radiological procedures are 
adequate as a routine diagnostic tool for cardiovascular disorders, let 
alone all other disorders requiring X-radiological diagnostic procedures. 
4. What Is Needed? 
Broadly, an X-radiological diagnostic technique is objectively needed as 
convenient as the standard, routine procedure and providing as much, or 
more, information of diagnostic interest as angiography. At the moment, an 
intermediate solution, as close as possible to the ideal objective 
described above, would be enormously important for: 
1. Screening candidates for angiography and other complex procedures; 
2. Increasing the validity of stress tests; and 
3. Increasing the validity of diagnosis for routine health examinations and 
preliminary tests. 
More particularly, there is a clear and present need for an X-radiological, 
diagnostic procedure which: 
1. Is not invasive; 
2. Minimizes patient exposure to radiation; 
3. Is compatible with current standard practice for routine radiography; 
4. Presents more useful diagnostic information without substantially 
degrading the current radiographic image. In providing information as to 
heart motion, for example, the lung tissue structure must be undisturbed; 
5. Is compatible with readily retrofitting existing installations; 
6. Has minimum impact on the number and training of personnel required for 
performing the radiography; 
7. Has minimum impact on the time, precision and equipment necessary; 
8. Is relatively inexpensive; and 
9. Presents information, for example, with respect to pulsation amplitudes 
of an organ in such a manner as to be readily assimilated by eye, clearly 
and unambiguously. 
5. Disadvantages of Prior Art Solutions to the Conventional Problems 
The need for observing X-radiographs of the heart in motion to observe 
relative displacement has long been recognized. A technique commonly 
referred to as kymography has been the subject of extensive 
experimentation since 1911 for use in cardiovascular diagnosis. 
More recently the need for synchronizing X-radiation exposures with 
selected physiological states is well known. More particularly the use of 
a physiological synchronizer to synchronize radiation exposure with 
minimum motion during, for example, the cardiac cycle is well understood. 
Kymography 
Kymography is widely described in the literature and particularly 
summarized recently in a book entitled "The Heart and It's Action: 
Roentgenkymographic Studies", by Dr. Gilbert H. Alexander, published 1970 
by Warren H. Green, St. Louis, Missouri. 
In the preferred mode as described by Alexander, a patient is continuously 
X-irradiated for periods in excess of 1.5 seconds. A horizontal slit in a 
curtain shutter, similar to the well-known focal plane camera shutter and 
positioned between the patient and the image plane, continuously moves 
vertically downward to expose X-ray film continuously to depict the 
cardiac image as it fluctuates during the cardiac cycle. The resultant 
kymograph reveals a wavelike, or kyma, effect in the heart outlines. 
The slit width is chosen to be as narrow as possible consistent with other 
considerations relevant to image quality. The exposure time required is 
nominally in the range of 40-100 milliseconds. Given a fixed slit width 
and selected exposure time, the rate of travel of the slit becomes 
determined. Frequently, three or more cardiac cycles are required, giving 
rise to patient exposure to radiation greater than 5 seconds, or more. 
This is 100 times the nominal 50 milliseconds exposure required in current 
practice. 
Disadvantages of Kymography 
Kymography is now substantially obsolete. Some of the disadvantages are: 
1. Excessive exposure to radiation; 
2. Since the heart is in diastole for 70%, or more, of the cardiac cycle 
and in systole 30% or less, the systolic image, particularly during rapid 
motion, appears very compressed in the radiograph. The systolic image, 
therefore, appears blurred and ambiguous as to structure; 
3. The kymograph is not synchronized with the electrocardiographic signal, 
thereby leading to an uncertainty as to which parts of the image reveal 
known displacements of the heart relative to the cardiac cycle; 
4. Since the slit motion is continuous, the slit width, exposure time and 
rate of slit motion are interdependent and, hence, constrained; and 
5. Precise measurements of displacements during the cardiac cycle are 
difficult to make, particularly between extreme positions. 
Physiological Synchronizing and Comparison 
For the purpose of synchronizing exposures to minimum motion of the heart, 
physiological synchronizers are typically used for nuclear medicine in 
cardiology. Since radioactive tracers taken internally are necessarily 
limited to relatively low levels of radiation, a long exposure of the 
film, for example 15 minutes, is required during periods of minimum heart 
motion, such as end systole and end diastole, to obtain a useful image. If 
the exposure were continuous, the image, of course, would be blurred. 
In nuclear medicine as applied to the heart, the source radiation is 
continuous. A shutter is used to expose the radiation sensitive film 
within a cardiac cycle only for 50-100 milliseconds each at end systole 
and/or end diastole, respectively, during minimum heart motion. The 
resultant image is obtained over a large number of cardiac cycles. Given a 
nominal 60 beats per minute, an exposure of a nominal 15 minutes implies 
900 cardiac cycles to provide a useful image. 
The use of synchronized X-radiographs for cardiology has been proposed. One 
suggestion was proposed by Hipona et al in a journal article entitled 
"Intercalative Chest Roentgenography", in Radiology, Vol. 82 Pages 
304-306, February, 1964. It involves the use of an ECG signal as provided 
by a physiological synchronizer to produce two X-radiographs, one at end 
systole and one at end diastole. The resultant radiographs are then 
compared (1) side by side or (2) superimposed one over the other. This 
suggestion has not proved useful because of the difficulty in obtaining 
meaningful information as to relative displacements between systole and 
diastole. Since the displacements of interest are as low as 1 or 2 
millimeters, the measurement can be made only with considerable 
difficulty. Furthermore, proper registration of the radiographs is 
exceedingly hard to obtain. 
In the latter case, superposition suffers from unacceptable obscuration of 
image structure in addition to the registration and measurement problems. 
The suggestion has proved unworkable because it violates the requirement 
for ready assimilation by eye of the information, clearly and 
unambiguously. Further, superposition degrades image resolution and 
violates the criterion of preserving the integrity of the image. 
A physiological synchronizer for practising the synchronized comparison 
method for two separate radiographs, one taken, for example, in systole 
and the other in diastole, is described and illustrated in U.S. Pat. No. 
3,871,360 for "Timing Biological Imaging, Measuring and Therapeutic 
Systems" issued Mar. 18, 1975, to Van Horn et al and assigned to the 
present assignee. U.S. Pat. No. 3,871,360 is hereby expressly incorporated 
herein by reference as an integral part of this specification and 
disclosure. 
An effort to overcome the problems inherent in separate radiographs is 
described and illustrated in U.S. Pat. No. 3,626,923, issued to Hal C. 
Becker on Dec. 14, 1971. In Becker's "EKG Synchronized X-Ray Double Pulse 
Exposure Apparatus and Method" a single X-ray film is double-exposed, one 
exposure corresponds with end systole, and the other with end diastole. 
Unfortunately, this approach has not proven useful because of poor 
resolution. Although there is an improvement in registration, the total 
exposure represents a net compromise in exposure, tending to degrade the 
image. The image detail is further degraded by the effect of superposition 
of the two images; that is, the systolic and diastolic images are not 
distinct, discrete images. Nevertheless U.S. Pat. No. 3,626,932 is 
expressly incorporated herein by reference as an integral part of this 
specification and disclosure. 
SUMMARY OF THE INVENTION 
In accordance with the preferred mode of the invention, a chest 
X-radiograph is taken simultaneously presenting two discrete images, each 
occupying substantially half the area of presentation, one corresponding 
with end diastole, relaxation or dilation, and the other with end systole, 
contraction. The exposures are preferably taken within one cardiac cycle 
during the periods of minimum heart motion in diastole and systole. Thus 
the diastolic and systolic images are separated in the time domain by a 
discrete time interval. 
Each image is composed of a set of discrete image elements, each element 
corresponding with an alternating band or discrete area segment. Thus the 
diastolic image elements are interdigitally presented with the systolic 
image elements in corresponding indexed area segments. The diastolic and 
systolic images then appear in an interlaced pattern with each diastolic 
element in juxtaposition, side by side relation, with a systolic element. 
In this manner, the systolic and diastolic images are separated in space 
as well as time, though presented simultaneously in a static radiograph. 
In the preferred mode, each pair of juxtaposed image elements represents 
contiguous regions of the irradiated patient. A more complete discussion 
is presented below with reference to the drawings. 
The X-radiograph of the present invention clearly includes all of the 
advantages of the prior art synchronized-comparison procedures without any 
of the disadvantages. In particular no substantial degradation of the 
conventional X-radiographic image takes place because each image element 
is properly exposed and is discrete. Displacements or other changes in 
condition are readily perceived by the radiologist because the differences 
revealed by side by side comparison of image elements are enormously 
enhanced and the images inherently in excellent registration. Thus, 
diagnostic information to be defined from the pulsation amplitudes is 
presented in such a manner as to be readily perceived by eye, clearly and 
unambiguously. 
Heart outlines, for example the left wall of the left ventricle, appear 
serrated in the radiograph of the invention. These serrations indicate a 
measure of wall displacement, between, e.g., end diastole and end systole. 
For image elements about 3 millimeters wide, a standard 14" by 17" 
radiograph viewed from a distance of 30 feet, the serrations are 
unexpectedly clear. 
1. Definitions 
Radiation--the term "radiation" as used herein means all forms of radiation 
or radiant energy useful in representing an image of a biological object. 
The term includes all such useful forms of electromagnetic and mechanical 
radiant energy in all such useful frequencies. 
Electromagnetic--the term "electromagnetic" as applied to radiation herein 
includes, without limitation, radio waves, light and near light, X-rays, 
nuclear radiation, alpha, beta and gamma particles. 
Light--the term "light" as used herein includes all such energy in the 
frequency range from far infrared to ultraviolet, whether or not visible. 
Sound--the terms "sound" or "sonic" as applied to radiation herein includes 
all mechanical radiant energy in all frequency ranges, whether or not 
audible. 
Photon--the term "photon" as used herein means an elementary discrete bit 
of electromagnetic radiant energy. 
Phonon--the term "phonon" as used herein means an elementary discrete bit 
of sound energy. 
Electrocardiograph--the term "electrocardiograph" as used herein means an 
instrument for producing an electrocardiac signal, e.g., the well-known 
QRS complex. 
Electrocardiogram--the term "electrocardiogram" as used herein means a 
tracing of the QRS complex, e.g., as produced by a strip-chart recorder. 
Radiograph--the term "radiograph" as used herein means, without limitation, 
a recorded image derived from image forming radiation. 
Fluorescent image--the term "fluorescent image" as used herein means an 
image derived from fluorescent material. 
Inchoate image--the term "inchoate image" as used herein means data from 
which an image may be displayed or recorded. 
2. X-Ray Apparatus 
In the preferred mode of the invention, a physiological synchronizer is 
connected through electrodes to a patient. The synchronizer produces an 
electrocardiographic signal, ECG signal, in response to the cardiac QRS 
complex signals from the patient. The synchronizer is coupled to an X-ray 
apparatus to control the period of irradiation of the patient in 
accordance with diastolic and systolic timing signals derived from the ECG 
signal. A masking frame, having parallel fixed bars and slits of equal 
widths, is interposed between the patient and an X-radiographic film at an 
image plane, is electromechanically positioned, a distance equal to a slit 
width, for selectively exposing the film to the diastolic and systolic 
images by a solenoid. The solenoid is coupled to the synchronizer and 
actuated by the diastolic and systolic timing signals in synchronism with 
the patient irradiation. 
The X-ray technician initiates the procedure by preselecting the desired 
amount of exposure and enabling the synchronizer. The patient is 
X-irradiated in response to the diastolic signal from the synchronizer. 
The X-radiation from the patient passes through the masking frame which 
exposes one-half the area of presentation of the film, in alternate bands, 
to produce a diastolic image. After repositioning the masking frame in 
such a manner as to mask the previously exposed areas of the film, the 
remaining half of the presentation is exposed in alternate bands 
corresponding with a systolic image. The film is then developed to provide 
the diastolic and systolic images in an interlaced pattern of 
interdigitally, juxtaposed diastolic and systolic image elements. Each 
band or area segment is indexed to identify it with respect to diastole 
and systole. 
The images are viewed element by element for evidence of displacement. One 
may look at the outline, for example, of the wall of the left ventricle. 
The images thus presented appear serrated, and the distance between the 
apparent outlines is a measure of the relative displacement of the wall of 
the left ventricle during the discrete time interval between diastole and 
systole. 
The radiologist can now determine at a glance whether or not the motion of 
the heart is normal. The evidence to date indicates that normal motion is 
represented by displacements in the range of 2-4.5 millimeters. 
Displacement of 5-10 millimeters is considered abnormal at this time. 
On the evidence examined to date, the apparent motion observed from 
radiographs taken in accordance with the invention very strongly 
correlates with the results of angiography, that is, in excess of 90%. it 
is noteworthy that the integrity of the lung tissue structure remains 
substantially intact. 
There are a number of occasions when the organ outline in systole crosses 
over the organ outline in diastole, as in dyskinesis, resulting in an 
uncertainty as to which outline corresponds with systole or diastole. 
Because the invention contemplates the use of synchronized, discrete 
areas, such an ambiguity is precluded by identifying indicia. Thus, in the 
event of a heart aneurism, a wall outline appears to extend under pressure 
beyond its position in diastole. For instance, ordinarily the left 
ventricle contracts during systole and dilates during diastole. An 
apparent inversion of the wall outlines takes place in the event that 
there is a significant ventricular aneurism. The apparent ambiguity is 
easily resolved by referring to the area segment indicia, thereby 
differentiating diastole from systole. 
The apparatus and method, and a discussion of the results of an experiment 
conducted at Massachusetts General Hospital in Boston, Massachusetts, are 
described and illustrated in an unpublished article by Dr. Robert E. 
Dinsmore, Chief of Cardiac Radiology at Massachusetts General Hospital. 
The article is entitled "The Evaluation of Left Ventricular Free Wall 
Asynergy due to Coronary Artery Disease: The Use of an Interlaced 
ECG-Gated Radiographic System" and has been submitted for publication to 
the American Journal of Roentgentology. The article is hereby incorporated 
herein as an integral part of this specification and disclosure. A copy of 
the article is attached to the specification. 
DETAILED DESCRIPTION OF THE INVENTION 
There follows a detailed description of the preferred embodiments and 
methods of the invention, taken in connection with the accompanying 
drawings, and its scope will be pointed out in the appended claims.

DESCRIPTION AND OPERATION OF THE SYSTEM IN FIGS. 1-4 
Referring now to FIG. 1, there is here illustrated an X-radiation system 
for practicing the method of the invention. The system is generally 
indicated at 10. An X-ray apparatus 11 includes a source of X-radiation 61 
directed to the chest of a patient 12. The apparatus 11 and patient 12 are 
radiation coupled through a masking frame 13 to radiographic film in a 
film cassette 14. A physiological synchronizer 15 incorporates an 
electrocardiograph which produces an electrocardiographic signal derived 
through electrodes 16 from the patient 12. the synchronizer produces an 
electrocardiogram 15A and is coupled to the apparatus 11 as shown. The 
synchronizer is also coupled to the masking frame 13 and the film cassette 
14. The masking frame 13 and film cassette 14 are shown in perspective and 
in position for a diastolic exposure. 
The masking frame 13 in FIG. 2 is shown in position for systole relative to 
the film cassette 14. As shown in FIG. 3 the thickness g and slit width h 
may be proportionately varied to provide any degree of antiscattering, 
that is, collimating of the X-ray beam. Since the reduction of undesirable 
scattering radiation, that is, uncollimated radiation, serves to increase 
the contrast of the image in the radiograph, the exposure necessary for a 
good image tends to be reduced. Furthermore, by a suitable choice of the 
g:h ratio, any degree of antiscattering desired may be obtained. In the 
film cassette, as described in the above referenced Jaffee et al article, 
an antiscattering screen is required. Such a screen has a very substantial 
insertion loss, requiring an effective increase of patient irradiation of 
the order of 50%. By substituting a mask having suitable antiscattering 
properties the patient dosage may be considerably reduced. Thus using a 
single such mask, with two exposures, the total exposure is less than the 
expected sum of two noraml exposures. 
The mask 13 has alternate parallel bars 24 and slits 25 of equal widths, as 
shown. That is to say the exposure area presented by the slit 25 is equal 
to the absorption area presented by the bar 24. The frame is movable 
vertically, as shown, to expose substantially half the area of 
presentation of the radiographic film 21 at end diastole, and the other 
half during end systole, after the mask is suitably repositioned a 
distance h. The slits of the mask 13 correspond with and define respective 
parallel area segments of the radiographic film. 
In FIG. 3(a) an electrocardiogram is presented showing the elements of the 
QRS complex. In FIG. 3(b), the corresponding timing signals for 
controlling the occurrence of X-radiation are shown. In FIG. 3(c) a graph 
of ventricular expansion and contraction is shown correlated with FIGS. 
3(a) and 3(b). The diastolic gate or timing signal is indicated D; the 
systolic S. The diastolic gate is initiated by the R.sub.2 wave and the 
systolic gate is initiated proportional to T.sub.O, the timing between the 
preceeding successive two R waves, R.sub.1 and R.sub.2. 
In FIG. 4(a) a radiograph 18 is shown illustrating an organ 19 at the time 
of end diastole. In FIG. 4(b) the organ 19 is shown in a radiograph 20 at 
the time of end systole. 
In a radiograph 21 of FIG. 4(c) the organ is presented, as shown, in both 
end diastole and end systole simultaneously, in accordance with the 
present invention. Here every other discrete area segment corresponds with 
a discrete image element; the diastolic elements 22 and the systolic 
elements 23 alternate, as shown, in parallel bands. 
The resultant discrete diastolic and systolic images appear in juxtaposed 
image elements, interdigitally in bands, corresponding with the respective 
area segments. The diastolic and systolic images are thus presented in an 
interlaced pattern. The organ outlines are serrated, readily presenting 
the relative displacement between diastole and systole as shown at 26. The 
outline drawings of FIG. 4 are taken from actual angiographs depicting the 
left ventricle and aorta in end systole and end diastole. 
The schematic presentations in FIG. 4(d) illustrate the relative wall 
outlines of the left ventricle in end systole and end diastole. The 
drawings cover (1) the normal heart displacement, (2) the heart in 
hypokinesis, less than normal motion, (3) the heart in akinesis, partially 
in no motion and (4) the heart in dyskinesis, motion contrary to normal 
where the left ventricle wall extends, in part, beyond the wall in 
diastole; the wall outlines actually cross over. 
Operation 
The operator interconnects the patient 12 with the electrodes 16 to the 
synchronizer 15. At that time the mask 13 is in the position shown in FIG. 
1 for end diastole. The operator selects the exposure time and enables the 
synchronizer 15, which then assumes control of initiating the X-radiation. 
The strip chart recorder in the synchronizer 15 produces an 
electrocardiogram 15a. The synchronizer verifies the R wave and receives 
the QRS complex or ECG signal, shown in FIG. 3, curve (a), from the 
patient 12, stores the time between the R-waves of the previous cardiac 
cycle and then initiates the diastole timing gate D as shown in FIG. 4, 
curve (b). The gate D is wide enough to permit of an exposure sufficient 
to cover the useful range required, for example, 40-80 milliseconds. The 
exposure is chosen at the time of minimum cardiac motion during diastole 
and systole. Typically the timing gate for diastole is 100-130 
milliseconds which, at the end of the timing signal D, irrespective of the 
selection chosen by the operator, the X-ray source 11 is disabled and the 
exposure is terminated. 
As shown in curve (a), the interval T.sub.O from R.sub.1 and R.sub.2, the 
previous cardiac cycle, is stored. At the end of the interval coinciding 
with at least 80% of the rise time of the R.sub.2 wave, the diastolic 
gate, as shown in curve (b), initiates the exposure. The X-radiation 
continues until terminated internally by the X-ray apparatus or the end of 
the gate D, whichever occurs first. 
The systolic timing gate signal S, FIG. 4, curve (b), in internally 
generated by the synchronizer 15. The center of the gate S is chosen 
substantially to coincide with end systole which typically occurs 
approximately at the time of the T wave in the QRS complex, as shown in 
the curve (c) of FIG. 3. 
Here the synchronizer generates the systolic gate at a time t preferably 
chosen in accordance with: 
EQU t=a+bT.sub.O Equation 1 
where a=140, b=2, T.sub.O is the period of the previous cycle an all values 
are in milliseconds. 
For an average heart pulsation rate of 60 beats per minute, the period 
T.sub.O is one second, diastole may be 600-800 milliseconds and systole 
200-400 milliseconds. 
The S gate is the same pulse width as the D gate. As with the diastolic 
gate D, the gate S initiates the systolic exposure; the exposure again is 
terminated internally by the X-ray apparatus or the end of gate S, 
whichever occurs first. 
The patient then is X-irradiated during the peirod of the diastolic gate D, 
as in FIG. 4, curve (b), and then again during the period of the systolic 
gate S in curve (b). The X-radiation from the patient passes through the 
masking frame 13 to expose one-half the area of presentation of the film 
in alternate bands to produce a diastolic image. During systole the 
masking frame is repositioned in such a manner as to mask the previously 
exposed areas of the film, the remaining half being exposed in alternate 
bands corresponding with the systolic image. 
The film is then developed to provide the diastolic and systolic images in 
the interlaced pattern of juxtaposed, interdigital diastolic and systolic 
image elements. Each systolic band or area segment is preferably indexed, 
as shown, to discriminate the diastolic image elements from the systolic. 
As shown in FIG. 1, the synchronizer is coupled to the film cassette. In 
the typical modern installation the film cassette automatically changes 
film at the end of each exposure. The synchronizer inhibits the film 
chaange to allow for a second exposure on the same film. At the end of the 
second exposure, the automatic film change is allowed to operate. 
The organ shown in the radiographs of FIG. 4(c) may, for example, be the 
heart outline, in particular, the wall of the left ventricle. Since, as 
noted above, the image outlines appear serrated, the radiologist can 
readily derive a measure of the wall displacement at a glance. 
With an 11.times.17 radiograph prepared in accordance with the invention 
where the left ventricle outline displacements were of the order of 3-5 
millimeters, the serrations were clearly apparent from a distance of 30 
feet. The typical bands as used in the preferred embodiment are 3 
millimeters wide, and indicia at the ends of the bands identifying systole 
as S, enable the radiologist readily to distinguish the diastolic image 
elements and outlines from the systolic. 
DESCRIPTION OF THE MASK IN FIG. 5 
Referring now to FIGS. 5(a) and 5(b) there is here illustrated a masking 
frame and housing assembly. The mask has a plurality of cylindrical rods 
embedded in spaced, parallel relation in a rigid plastic slate. An end 
view is shown in FIG. 5(b) of the mask. 
The diameter of each rod is equal to each slit formed by the space between 
each pair of rods. The mask is affixed to a pair of end support members in 
frictionless, flexing attachment to the housing to maintain the mask 
suspended with motion restricted to the vertical axis. A pair of springs 
connected between the housing and end support members hold the mask 
normally in an extreme upward position for the diastolic exposure. 
A solenoid mounted to the housing is electrically coupled to the 
synchronizer and mechanically coupled to the mask to move the mask 
vertically downward against the restraining force of the springs for the 
systolic position. A mask position switch, coupled to the synchronizer, 
senses the vertical position of the mask. A pair of identification masks 
are mounted in the housing in fixed position adjacent the mask to expose 
indicia correlated with systolic exposure. 
Thus the rods 22 are rigidly embedded in spaced relation in the plastic 
plate 51. The plate is inserted into channels formed in the end members 45 
and rigidly adhered thereto. Each rod 22 has the same diameter d as the 
width of each slit 23. The total period from the edge of one rod to the 
edge of the next is then 2d, as shown. The rods are chosen to be 
cylindrical to minimize edge effects between image elements. 
The mask is flexibly secured to the housing 40 by four resilient suspension 
elements 46. Each element 46 is firmly attached at one end to fastener 54 
secured to the housing. The other end of each element 46 is attached to 
the end member 45 by a clamp 55. 
Each of a pair of restraining springs 42 is fastened at one end to a 
fastener post 43 fixed to the housing 40 at the upper corners, as shown. 
The other end of each spring 42 is attached to a fastener post 41 affixed 
to each member 45. 
A solenoid 27 has a threaded shaft 29 affixed in threaded engagement to a 
bracket 30 mounted on the housing 40 below the mask, as shown. An armature 
31 of the solenoid is coupled through an L-shaped rocker lever 34 to a 
central extension piece 58 affixed to the mask. Actuator pin 33 extends 
from the lever 34 into a slot 32 in the armature 31. The corner of the 
lever 34 has a bearing point about a pivot pin 35 extending from the 
bracket 30. Affixed to the upper left arm, as shown, of the lever 34 is an 
actuating pin 38 which travels in a slot 39 formed in the lower piece 58 
of the mask. A U-shaped bracket 59 is attached to and extends below the 
piece 58. A stop bar 37 affixed transversely to the bracket 30 limits the 
vertical motion of the mask. 
The mask is normally in position for diastole. Here the mask is shown in 
position for systole and the solenoid 27 actuated with the armature 31 
withdrawn into the solenoid. 
The solenoid is actuated in response to a signal from the synchronizer 
after the diastolic exposure has been complete to pull the frame down in 
position against the restoring force, through the rocker lever 31 linkage, 
of the springs 42 to meet the bar 37, as shown. When the solenoid 27 is 
deenergized after the systolic exposure has been taken, the armature is 
restored to the right, as shown, allowing the springs 42 to move the mask 
upwardly, limited by the stop bar 37 and bracket 59. A single pole, double 
throw mask position switch 28, mounted between the cover plates 52 and 53, 
has a lever arm 50 which contacts the mask. The switch 28 responds to 
provide a signal at its output terminals 47 and 48 indicating the mask to 
be in the upward or diastolic position. Conversely when the mask is down, 
as shown, a signal from the terminals 48 and 49 indicates that it is in 
the position for systole. The signal from the position switch 28 is 
coupled to the synchronizer, as will be described further below. 
Description and Operation of the Synchronizer in FIGS. 6-8 
Referring now to FIG. 6(a), there is here illustrated a schematic, block 
diagram of the physiological synchronizer as used in the present 
invention. The basic synchronizer used in the preferred embodiment is a 
modification of the synchronizer described and illustrated in the above 
referenced U.S. Pat. No. '360, incorporated herein. 
The modified synchronizer has two principal modes of operation. In both 
modes, the command to initiate the radiation exposure is taken away from 
the X-ray apparatus and assumed by the synchronizer. In one mode of 
operation, the primary control of exposure termination is contained within 
the X-ray apparatus. The synchronizer initiates the exposure which takes 
place for a selected period determined by the operator. In the event that 
the exposure is within the enabling time as provided by the synchronizer 
timing gates, the termination of the exposure takes place on command from 
the X-ray apparatus. If the exposure tends to exceed the enabling time, 
then the termination is affected by the synchronizer. 
In the other mode of operation the synchronizer, in combination with a 
sensing device, either part of the X-ray apparatus or provided separately, 
determines the photon count for the first or diastolic exposure and stores 
that count. The systolic exposure is controlled substantially to equal the 
diastolic photon count during the second exposure; when the second 
exposure photon count is equal to the first one, the exposure is 
terminated. In another variation of the mode of operation, the elapsed 
time for the initial photon count is stored. The actual length of systolic 
exposure time is then controlled to equal the elapsed time of the first 
exposure. In a variation of this mode, the synchronizer counts and stores 
the actual length of the first or diastolic exposure time. The actual 
length of systolic exposure time is controlled to equal the diastolic 
exposure time. 
The QRS complex is received by the synchronizer and coupled to an isolated 
preamplifier. The output of the amplifier is coupled to an R-wave detector 
and verifier circuit and to a strip-chart recorder of an 
electrocardiograph. The R-wave detector, given the presence of an R-wave, 
is then coupled to a diastolic or D gate generator and a systolic or S 
gate generator. The diastolic and systolic gate generators are coupled to 
a sequence control logic circuit, an exposure logic circuit and thence to 
a display circuit. An input to the sequence control logic circuit is 
derived from a remote start switch in the X-ray apparatus, upon actuation 
by the operator. A further input to the sequence control logic is from 
diastole only command and/or systole only command switches located at the 
synchronizer. An output of the sequence logic circuit is coupled to a mask 
driver circuit which is coupled to the mask. An output of the mask circuit 
is coupled back to the sequence control logic circuit. Another output of 
the sequence control logic circuit is coupled to isolated drivers which 
couple film advance inhibit, anode spinup, and exposure command signals to 
the X-ray apparatus. An output of the exposure logic circuit is coupled to 
the isolation driver circuit. The exposure in progress or EIP signal is 
derived from the X-ray apparatus and coupled through an isolated receiver 
to the strip chart recorder. The EIP signal is also coupled from the 
receiver to the display circuit which indicates EIP. The display circuit 
has indicators for the diastolic and systolic gates. 
In the case where the synchronizer counts the elapsed time of the exposure 
and stores that count, an exposure duration counter circuit is included 
coupled to an isolation transmitter-receiver circuit. Both of those 
circuits receive input signals from the sequence control logic circuit. 
The EIP signal from the receiver is coupled directly to the exposure 
duration counter. The exposure duration counter is also coupled to the 
exposure logic circuit. The isolation transmitter-receiver is coupled in 
both directions to an exposure command monitor in the X-ray apparatus. 
In the case where we wish to normalize the exposures in terms of integrated 
X-ray flux, the X-photons for the first exposure are converted into 
electrical signals and coupled by a photon transducer through a 
preamplifier to an integrator to produce a signal indicative of the count. 
An input to the intergrator is derived from an optically isolated 
transmitter-receiver which is coupled in both directions to the exposure 
command/monitor in the X-ray apparatus. The output of the integrator is 
coupled to a peak detector circuit which derives an input from the 
sequence control logic circuit. The outputs of the peak detector and 
integrator are applied to a comparator which is coupled to the sequence 
control logic circuit to produce a signal coupled to the exposure logic 
circuit. Another output of the comparator is coupled to the isolation 
transmitter-receiver circuit, which receives a further input from the 
sequence control logic circuit. 
Condition I--Exposure Termination Control in X-Ray Apparatus 
Referring now to FIG. 6(a) there is here generally illustrated the modified 
synchronizer, as indicated at 100, for use in the preferred mode of the 
invention. 
A pair of electrodes 16 are shown coupled from the patient to a 
preamplifier 101. One output of the amplifier is coupled to an R-wave 
detector circuit 102 and the other output to a strip-chart recorder in an 
electrocardiograph 103. The detector 102 is coupled to a diastolic gate 
generator 104 and, through a systolic interval process circuit 105(a), 
systolic gate generator 105. The D gate is coupled to a D exposure enable 
circuit 106(a) in a sequence control logic circuit 106, an exposure logic 
circuit 107, and a display circuit 108 with a diastole indicator light 
109. 
The sequence control logic circuit 106 is shown in detail in FIG. 6(b). It 
includes a diastolic exposure enable circuit 106(a), an initial delay 
circuit 106(b), a systolic exposure enable circuit 106(c), a final delay 
circuit 106(d), an enable flip-flop circuit 106(e), and a mask control 
logic circuit 106(f). 
The logic circuits 106(a)-106(f) within the sequence control logic circuit 
106, as shown in FIG. 6(b), are coupled together as follows: 
The delay circuit 106(b) has an output coupled to the enable circuit 
106(a). The enable circuit 106(a) is bidirectionally coupled to the 
systolic enable circuit 106(c). An output of the diastolic circuit 106(a) 
is coupled to the input of the mask control logic circuit 106(f). The 
systolic or S exposure enable circuit 106(c), the diastolic circuit 106(a) 
and the mask control logic circuit 106(f) are each coupled to the output 
of the enable flip-flop circuit 106(e). The delay circuit 106(d) is 
coupled to the input of the flip-flop circuit 106(e) and derives an input 
from the systolic exposure enable circuit 106(c). 
The S gate is coupled to the S exposure enable circuit 106(c), the exposure 
logic circuit 107, and the display circuit 108 to a systole indicator 
light 110. An output of the mask control logic circuit 106(f) is coupled 
to a mask driver circuit 111 to energize the solenoid 27 in the mask 
assembly of FIG. 5(a) to position the mask 13. Outputs from the mask 
position switch 28, shown in FIG. 5, are coupled to the D exposure enable 
circuit 106(a) and S enable 106(c), as shown, indicating mask position. 
A manual diastole only command switch 112 on the front panel of the 
synchronizer is coupled to the D enable 106(a) and mask logic 106(f). A 
manual systole command switch 113 is coupled to the enable 106(c) and mask 
logic 106(f). An exposure in progress, EIP, signal is derived from the 
X-ray apparatus and coupled to an isolation receiver circuit 114 which in 
turn is coupled to the strip-chart recorder 103 to provide exposure event 
marks correlated with the electro-cardiogram. The EIP signal from the 
receiver 114 is also coupled to the display circuit 108 to the EIP light 
115. 
A remote start switch 116 located in the X-ray apparatus is coupled to the 
delay 106(b) and enable 106(e). The logic circuits 106(e) and 107 are 
coupled to the drivers 117. The driver circuit 117 produces the film 
advance inhibit, the anode spinup and the exposure command signals for 
coupling to the X-ray apparatus 11. 
Condition II--Synchronizer Terminates Systolic Exposure 
Referring to FIG. 6(c) for the case where the synchronizer determines the 
exposure time of the first exposure and then controls the exposure time of 
the second exposure in accordance with that stored count, an exposure 
duration counter circuit 120 is coupled to a transmitter-receiver circuit 
121. The circuit 121 is coupled to the exposure in progress and control 
circuits in the X-ray apparatus. The circuit 12 derives an input from the 
S exposure enable circuit 106(c) and the counter 120. The counter 120 
receives an input from the exposure logic circuit 107 and from the 
isolation receiver 121. 
In FIG. 6(d), an actual count of the X-photons for the first exposure is 
compared with the X-photon count for the second exposure until they are 
equal and the synchronizer totally controls the second exposure. For this 
case, an X-ray transducer 122 is coupled to a preamplifier 123 and 
integrator 124. The integrator has an output coupled to a peak detector 
125 and a comparator 126. The detector 125 and comparator 126 each derive 
an input from the exposure logic circuit 107. An output of the comparator 
127 is coupled to the exposure logic circuit 107. A transmitter-receiver 
circuit 127 derives an input from the sequence control logic circuit 106. 
A bidirectional signal is coupled from the circuit 127 to the X-ray 
apparatus exposure in progress and control circuit. An output of the 
circuit 127 is coupled to the integrator 124. 
Referring now to FIG. 6(e), there is here illustrated an exposure in 
process, EIP, signal circuit for internally developing an EIP signal. When 
no such signal is available in the X-ray apparatus, this circuit is added 
as a modification to the synchronizers. 
Thus an X-ray transducer 152, such as a photomultiplier tube, is coupled to 
a preamplifier 153 and threshold comparator 154. The output EIP signal can 
then be used in place of the output of the receivers 114 in FIG. 6(a) or 
the receiver 127 in FIG. 6(d). 
Operation--Condition I 
The power is turned on and the system in FIG. 1, including the mask of FIG. 
5 and synchronizer of FIG. 6(a) and (b) is in a standby condition. The 
operator couples the electrodes 16 to the patient. An ECG signal is at 
that time coupled to the preamplifier 101 and R-wave detector 102. If 
there is in fact a QRS complex wave at the input of the detector 102, the 
R-wave exceeds a preselected threshold level. The detected value of the 
first R-wave increases the threshold to approximately 80% of the amplitude 
of the first R-wave. The threshold tends to decay since it represents, for 
example, the voltage from an RC network. The next R-wave to come along 
must exceed the new threshold level to enable the diastolic and systolic 
gate generators 104 and 105. Thus once the electrodes are coupled to the 
patient, the QRS signal is presented to the electrocardiograph 103 and the 
R-wave detector circuit 102. This has the effect of continuously producing 
D and S timing signals from the generators 104 and 105 and QRS signals to 
the ECG 103. However, nothing else happens at that point until the remote 
start switch 116 is pressed by the operator. In particular the mask is in 
the up position, ready for a diastolic exposure, the electrocardiograph 
130 strip chart recorder is disabled, the film inhibit, anode spinup and 
exposure commands disabled. 
After the operator presses the remote start switch 116, the sequence as 
shown in FIGS. 7(a) and (b) is initiated for Condition I. The enable flip 
flop 106(e) and initial delay circuit 106(b) then change logic state. The 
enable circuit 106(e) signals a change in state to the driver circuit 117 
to produce the film advance inhibit and anode spinup signal directed to 
the X-ray apparatus. At the same time the output of the enable circuit 
106(e) activates the strip-chart recorder in the ECG 103. At this point 
the exposure sequence is inhibited by an output from delay circuit 106(b) 
inhibits D enable 106(a) thereby inhibiting S enable 106(c). 
Pending the end of the initial delay signal,curve (j) in FIG. 8, the enable 
flip-flop 106(e) sets the D exposure enable 106(a), S exposure enable 
106(c) and the mask control logic 106(f). When the delay 106(b) signal 
terminates, the inhibit of the D exposure enable 106(a) is removed, 
returning control of S enable 106(c) to D enable 106(b). If the D switch 
112 is selected and the mask is up, the next diastolic signal that comes 
along, the leading edge of the next D gate, curve (c) of FIG. 8, allows 
the exposure logic 107 to pass a D expose signal to the drivers 117 and 
enable the X-ray machine to initiate the D exposure. The enable 106(a) 
allows the systolic exposure enable 106(c) to accept a systolic S gate, 
curve (d) FIG. 8. When the diastolic exposure terminates, curve (i) FIG. 
8, the EIP signal is removed and the D circuit 106(a) produces a signal to 
mask control logic 106(f) to activate the mask driver 111 and energize the 
solenoid 27, in FIG. 5(a), to position the mask down for an S exposure. A 
down signal from the mask position switch 28, in FIG. 5(b), allows the S 
enable 106(a) to respond to the next S gate, if the S switch 113 has been 
selected by the operator. The leading edge of the next S gate removes the 
inhibit condition from the S enable. This enables exposure logic 107 to 
pass a S exposure gate, curve (h) FIG. 8, to the drivers 117 and exposure 
command to the X-ray machine. When the S exposure is terminated, the EIP 
signal is removed, disabling D enable 106(b) and enable 106(c). The final 
delay 106(d) signal is initiated to remove the film advance inhibit and 
anode spin-up command signals to return the control of film advance to the 
X-ray apparatus and stop anode spin. The termination of the final delay 
signal, curve (k) FIG. 8, returns the D and S enable circuits 106(b) and 
106(c) to standby and denergizes the solenoid 27 to allow the mask to 
return to its normal up position for a D exposure. 
Operation--Condition II 
In Condition II the S exposure termination control in the X-ray apparatus 
is removed, curve (e) FIG. 8. The synchronizer exercises control over S 
exposure termination in accordance with the D exposure. 
In the modification of FIG. 6(c), the counter 120 receives an EIP signal 
from the receiver 12 and, in response to a signal from exposure logic 107, 
curve (m) FIG. 8, monitors the period of the D exposure. Where D exposure 
is terminated by a signal from the X-ray apparatus, curve (n) FIG. 8, to 
logic circuit 107 disables the exposure termination control in the X-ray 
apparatus. The counter stores the elapsed time of the D exposure, and in 
response to EIP from the receiver 114, signals the exposure logic 107 to 
terminate the S exposure at such time as the S exposure equals the D 
exposure. 
In FIG. 6(d) the modification shown operates to monitor and store the 
photon count during the D exposure and terminate the S exposure when the D 
and S counts are equal. The transducer 122, preamplifier 123 and 
integrator 124 monitor and sum the D photon count, which is stored in the 
peak detector 125. During the S exposure, the S photon count signal is 
coupled from the integrator 124, in response to the EIP signal from the 
X-ray apparatus, to the comparator 124. A signal from the exposure logic 
107 enables the detector 125, and comparator 126, to couple a signal 
representative of the D exposure to the comparator 126. An output from 
comparator 126 to the transmitter 127 and the X-ray apparatus terminates 
the S exposure. The S enable 106(c), in response to termination of the D 
exposure gate, couples a signal to the transmitter 127 to disable the 
X-ray apparatus exposure termination control during systole. 
Description and Operation of the System In FIGS. 9 and 10 
Referring to FIG. 9 a modification of the system in FIG. 1 is illustrated. 
Here a synchronizer 160 is coupled to an X-ray apparatus 161 and a pair of 
masking frames 162 and 163. As shown in FIG. 9, masks 162 and 163 are 
controlled by the synchronizer 160. A patient 164 is positioned between 
the masking frames and a film cassette 165 adjacent, as shown, to the mask 
162. A photon sensor 166 is coupled to the synchronizer 160. The photon 
sensor 166 senses X-rays directly from the source 161. Another photon 
sensor 167 is positioned behind the film cassette 165, as shown, and is 
coupled to the apparatus 161. In one mode of operation the sensor 167 is 
coupled, as shown by the dashed line 168, to the synchronizer 160. 
The photon sensor face is covered by a mask 169 with a circular opening 170 
behind the mask bars 22 as shown in FIG. 10. Because of the circular 
opening of the mask 169, the motion of the masking bars from diastole to 
systole takes place substantially without changing the field of view of 
the photon sensor 167. 
As described above the synchronizer controls the position of the mask 162 
to synchronize with diastolic and systolic exposures, respectively. The 
effect of positioning a mask between the source of X-radiation and the 
patient is to limit radiation of the patient to those regions 
corresponding with the diastolic and systolic images, respectively. 
The photon sensor 166 is positioned to receive radiation directly from the 
apparatus 161. In one mode of operation the output of the photon sensor 
167 is coupled to the X-ray apparatus 161 and integrated to provide a 
photon count during a first, for example diastolic, exposure. The 
apparatus 161 is coupled to the synchronizer which stores the count. As 
described above, the synchronizer normally controls the initiation of the 
exposures, and the X-ray apparatus controls the termination of the 
exposures; provided, of course, that it does not exceed the enabling time 
controlled by the synchronizer diastolic and systolic gates, respectively. 
Where, however, there is no provision in the apparatus for coupling to the 
photon sensor 167, the sensor 167 is coupled by the dashed line to the 
synchronizer 160 where the photon count for the first exposure is derived 
to terminate the first exposure in accordance with the operator's 
selection. 
The photon sensor 166 is coupled to the synchronizer to provide a photon 
count for the first interval. The output of the photon sensor 167 as 
coupled to the apparatus 161 controls the termination of the first 
exposure. The synchronizer stores the photon count derived directly from 
the X-ray source 161 for the first exposure and then controls the second 
exposure to be substantially equal to the stored photon count derived from 
the sensor 166 for the first exposure. 
In another mode of operation, a timing mechanism in the apparatus 161 
controls the first exposure to terminate within the time allowed by the 
enabling gate from the synchronizer. During that time the synchronizer, 
through the sensor 166 and counting circuit in the synchronizer, monitors 
the radiation directly from the apparatus and stores a photon count signal 
for the first exposure. When the second exposure takes place, the 
synchronizer continues to monitor the photon count with the sensor 166 and 
a counting circuit in the synchronizer. When the second photon count 
substantially equals the first photon count, the second exposure is 
terminated by the synchronizer. 
Relative Mask Motion--FIGS. 11 and 12 
Referring now to the mask 13 and film cassette 14 as shown in FIGS. 11 and 
12, another mode of operation of the system in FIG. 1 is illustrated. Here 
the mask 13 is fixed in position and the film cassette moves. This has the 
effect of exposing the same regions of the patient to the film at 
different times. This is to be contrasted with the system in FIG. 1 where 
the mask moves. exposing neighboring regions of the patient. In the system 
as shown in FIG. 1 the diastolic image is different from the systolic 
image in that juxtaposed image elements are, in fact, images of different, 
neighboring regions of the patient, taken at different times. 
Here, the same region is taken twice, but at different times. Effectively, 
half the total image taken conventionally is eliminated in favor of 
comparing identical regions at different times. 
Separate Radiographs--FIGS. 13-15 
Referring now to FIG. 13 there is here schematically illustrated a contact 
printer light box generally indicated at 187. FIG. 13 is a plan view of 
the light box, with the cover not shown, the photosensitive film, two 
masks and two radiographs shown partly in section and oriented in planes 
normal to the plane of the drawing. One radiograph has a systolic image of 
an organ; the other has the diastolic image, as indicated. 
Thus, the box 175 has a housing 186 in which are positioned a plurality of 
light sources 181. The systolic image is projected through the radiograph 
176 and systolic mask 178 to the left side, as shown, of an exposed 
photo-sensitive transparency film 180. The diastolic image is projected 
through the radiograph 177 and mask 178 to the right side, as shown, of 
the film 180. 
A plurality of light sources 181 are positioned as shown on both sides of 
the contact printer or light box. 
The unsensitized photo film is shown in cross-section to distinguish it 
from the masks and the radiographic images on the systolic radiograph 166 
and diastolic radiograph 167. Note that each of the masks 178 and 179 have 
fixed parallel bars 182 and slits 183 of equal widths. The bars 182 and 
slits 183 of the mask 178 are precisely out of phase with the bars 184 and 
slits 185 of the mask 179. When the exposure is made half of the 
sensitized film 180 receives a systolic image and the other half receives 
a diastolic image, with the image elements interdigitally juxtaposed to 
provide, after the film is developed, the systolic and diastolic images in 
an interlaced pattern as taught by this invention. 
Referring to FIG. 14, there is here schematically illustrated a light box 
for viewing two separate radiographs, one taken during systole and the 
other taken during diastole in such a manner to provide the systolic and 
diastolic images in an interlaced pattern to an observer in the manner of 
the present invention. 
The box is generally indicated at 190. A housing 191 has a systolic image 
radiograph 192 and a diastolic image radiograph 193 intimately in contact 
with a systolic mask 194 and diastolic mask 195, respectively as shown. A 
pair of light sources 196 illuminate the images through the radiographs 
and masks to a pair of 45 degree mirrors 197 and 198. The mirrors 197 and 
198 couple the systolic and diastolic images to another pair of 45 degree 
mirrors 199 and 200, respectively. The images are coupled from the mirrors 
199 and 200 to a pair of 45 degree coupling mirrors 201 and 202 for 
viewing by an observer as shown by the eyes 203 and 204. 
With the lights on, the systolic image is transmitted through the mask 194 
to the mirror 197, to the mirror 199, to the mirror 201 to the left eye 
203, as shown, of an observer. The diastolic image is produced by light 
through the radiograph 193, the mirror 200 and a mirror 202 to the right 
eye 204, as shown, of the observer. The observer sees the images displaced 
in space and merges them with the image elements interdigitally juxtaposed 
to produce the systolic and diastolic images in an interlaced pattern in 
accordance with the instant invention. 
Referring now to FIG. 15 there is here illustrated a light viewing box 
generally indicated at 210. A housing 211 carries a pair of light sources 
212 for transmitting a light through a diastolic image radiograph 213 and 
a diastolic mask 218 to a mirror 214 coupled to a mirror 215 from which 
the image is projected to an eye 216 of an observer outside the box. Light 
is transmitted from the light source 212 through a systolic image 
radiograph and a systolic mask 218 to a mirror 219 coupled to a mirror 
220, which transmits the systolic image through the half reflecting mirror 
215 to the eye 216 of the observer outside the box. 
Here again the masks are precisely out of phase, as shown, so that the 
systolic and diastolic images appear in an interlaced pattern to the 
observer, in accordance with the instant invention. 
DESCRIPTION AND OPERATION OF THE CONVERTER IN FIG. 16 
Referring now to FIG. 16 there is here illustrated a schematic block 
diagram of a data processing system for converting X-radiation images into 
electrical signals which are stored as inchoate diastolic and systolic 
images in a computer memory. The outputs of the memories are coupled to a 
data processor which is in turn coupled to a video display. 
Thus an X-ray apparatus 225 transmits X-rays indicated at 226 through a 
patient 227 to an X-ray photoelectric converter 228. The converter 228 is 
coupled along a diastolic conductor to a diastolic storage portion 229 of 
an inchoate images storage unit generally indicated at 230. Another output 
of the converter 228 couples systolic signals to a systolic storage 
portion 231 of the storage unit 230. The diastolic storage is coupled to a 
data processor 232, the output of which is coupled to a video display 
circuit 233. A synchronizer 234 is coupled to the converter 228 and the 
X-ray apparatus 225. The synchronizer is also coupled to the patient 227, 
as shown. 
The synchronizer, in response to the ECG signal from the patient, controls 
the X-ray apparatus as described above to synchronize the exposures with 
systole and diastole. During systole the converter produces electrical 
signals representative of the diastolic image, which are coupled to the 
diastolic storage unit 229 and stored. During systole the converter 228 
couples the systolic image signals to the systolic storage unit 231. The 
data processor 232 derives the diastolic signals from the diastolic 
storage unit 229 and the systolic unit 231 to control the video display 
233 to provide the systolic and diastolic images in an interlaced pattern 
in accordance with the invention. 
Apparently Continuous Images--FIGS. 17(a) and 17(b) 
It is sometimes desirable, particularly with respect to organ wall 
outlines, to present both images as appearing substantially continuous. In 
the case of a mask of the type described and illustrated with reference to 
FIGS. 5(a) and 5(b), the bars and slits must be sufficiently narrow that 
image outlines appear to be continuous. It is to be noted, however, that 
irrespective of how narrow the image elements may be, they are indeed 
finite and are therefore identifiable. 
Referring now to FIG. 17(a) there is here illustrated an outline drawing of 
a radiograph 260 of the left ventricle 261 of the heart. The inner outline 
of the left ventricle is shown at end systole as indicated by the 
reference letter S. The ventricle 261 is illustrated at end diastole by 
the outer outline referenced D. Note that both outlines appear continuous. 
A circular portion 262 is shown substantially enlarged in FIG. 17(b). From 
FIG. 17(b) it is apparent that the systolic outline S occurs in image 
elements of finite width corresponding with the systolic image. Every 
other systolic area segments of the radiograph is indexed with an S, as 
shown. The diastolic image elements appear in the remaining bands, as 
shown. Under enlargement the image elements are interdigitally juxtaposed. 
The displacement between any part of such juxtaposed elements is, then, 
readily apparent. 
DESCRIPTION AND OPERATION OF THE INVENTION IN THREE DIMENSIONS 
A modification of well-known tomographic techniques as applied to nuclear 
cardiac scanning is used herein in accordance with this invention for 
isometrically projecting a three dimensional image. Here the patient 
receives internally a radioactive tracer, such as thallium.sup.201 
chloride, which lodges in the myocardium, or heart muscle and radiates to 
a nuclear camera. 
A synchronizer, as described in the '360 patent referenced above, is 
coupled to the patient and a computer with systolic and diastolic 
memories. The synchronizer control repetitive imaging at end diastole and 
end systole to store inchoate D and S images in the computer memories. The 
images processed to provide S and D boroidal images elements which are 
coupled to output S and D memories, respectively. The output memories 
coupled to a display processor to control the presentation of a composite 
image on a cathode ray tube. A display control console is coupled to a 
switching circuit and display processor for alternately interlacing D and 
S image elements for isometric or planar sectional projection. A 
tomographic system which may readily be modified for use herein is 
described and illustrated in an article by Vogel et al entitled "New 
Method of Multiplanar Emission Tomography Using a Seven Pinhole Collimator 
and an Auger Scintillation Camera" (Jour. Soc. of Nuclear Medicine, 19, 6, 
648-654, June 1978) and is hereby incorporated herein as an integral part 
of this specification and disclosure. 
The system of Vogel as used in nuclear scan cardiology maps in three 
dimensions the distribution of thallium.sup.201 in the myocardium of, 
e.g., the left ventricle. 
The tomographic system of Vogel et al used in nuclear medicine to map in 
three dimensions the distribution of thallium.sup.201 in the human 
myocardium in vivo is ideally suited to demonstrate a three-dimensional 
embodiment of the interlaced gated system. 
Referring now to FIG. 18 there is here illustrated a schematic block 
diagram of a tomographic system embodying the invention. The system 
includes a gamma camera 240 equipped with a special, 7-pinhole collimator, 
which derives information about the spatial distribution of radioactive 
201 T1 on the patient to a computer 242. The computer is programmed to 
accept seven images of the LV at end D and end S, store them, and compute 
the distribution of 201 T1 in seven discrete image elements in toroidal 
slices of the left-centricular myocardium. By imaging from the 50.degree. 
left-anterior oblique projection, the slices are taken normal to the long 
axis of the left ventricle. 
A physiological synchronizer 252, as described in the '360 patent 
referenced above, is coupled to the patient 240 and to the computer 242. 
The synchronizer 252 receives a QRS complex signal from the patient along 
conductors 243 and, after computing the times of occurrence of the extreme 
of the heart cycle, transmits D and S timing pulses along conductors 244 
to the computer to control a switching circuit 245 for directing S and D 
image data from the camera 241 to S and D memories 246 and 247, 
respectively. Once the scan is completed, the computer 241 processes the 
contents of each memory 246 and 247, e.g., in accordance with algorithms 
described in the cited Vogel article. The output of the computer 241 is 
coupled to S and D output memories 248 and 249, respectively. 
Each output memory contains inchoate toroidal image elements or slices of 
the myocardium corresponding to the S and D image elements. The image 
elements are coupled through another switching circuit 211 to a display 
processor 250 and intermixed as selected for a cathode ray tube 251. A 
display control console 210, coupled to the switch 211 and processor 250, 
enables the selection of the form of display. An isometric projection, as 
shown in FIG. 19, may be rotated about an axis or sliced along any plane, 
as shown in FIG. 20, as controlled by the console 210. By this means, 
successive S and D toroidal slices may alternately be taken from each 
output memory 248 and 249 and coupled to a common imaging medium, the 
display tube 251. The discrete image elements are intermixed and produce 
the discrete D and S images simultaneously independently in an 
interstitial pattern as shown in FIG. 19 or interlaced as shown in FIG. 
20. 
A typical isometric presentation of the left ventricle is shown in FIG. 19, 
and one of its cross-sections is shown in FIG. 20. In FIG. 19 a 
fluorescent medium 253 displays the D toroidal slices 254 and S slices 
255. 
Relative wall displacements and variations in wall thickness is readily 
apparent to the cardiologist. The displacements between systole and 
diastole are shown by the dimensions a for D thickness, b for D and S 
inner wall outlines, c for S thickness, d for D and S outer wall outlines, 
e for S inner wall diameter, f for D inner wall diameter, g for S outer 
wall diameter and h for D outer wall diameter. 
Stepped Slit Mask--FIGS. 21 and 22 
Instead of the mask in FIG. 5, a stepping mask may be used to expose a step 
at a time. Effectively with a single slit, one image element wide, say 3 
millimeters, over a number of cardiac cycles, every other step is end D 
and each alternate, juxtaposed step is end S, to cover the entire area of 
presentation. For an area 300 mm long, 100 steps would be necessary. 
Assuming two steps per cardiac cycle, an entire exposure would require 50 
cycles or from 20 to 100 seconds, depending upon heart rate. 
By using multiple slits of width m spaced 2 Km apart, where K is an 
integer, the exposure time can be reduced accordingly. If K=1, the mask of 
FIG. 5 is reproduced. If K is 10, 10 cardiac cycles are required. The 
exposure is then reduced by a factor of 5 or 4 to 20 seconds. 
If more than two samples per cycle are required for 6 mm area segment width 
per cycle, the slit width is reduced proportionately. For three samples 
per cycle, the slit width is 2 mm and requires three steps per cycle for 
the exposure. Note, however, that the exposure is independent of the slit 
width. If 50 millisecond exposures are required for an adequate image, 
then for a cardiac cycle of 1000 milliseconds, 20 exposures may be taken 
in successive steps. For the 6 mm segment, the slit width becomes 300 
microns and requires 20 steps. The slit width may, of course, be further 
reduced, e.g., to 100 microns, thereby requiring three cardiac cycles to 
complete the exposure. This has the effect of apparently increasing the 
number of steps to thirty per cycle to present an interlaced image closely 
resembling a continuously moving 100 micron slit. Each image element, 
however, is synchronized with cardiac pulsations and, therefore, can be 
indexed to correlate, e.g., with an ECG signal or QRS complex. Here the 
serrations of organ outlines would be smaller per pair of juxtaposed 
elements, tending to degrade the ease of diagnosis derived from relative 
displacements between the extreme of cardiac motion. 
Referring then to FIGS. 21 and 22, there is here illustrated a mask 
operated by a stepping motor to implement the modes of operation discussed 
above. The system of FIGS. 1 and 9 are readily modified to incorporate a 
stepping mask by a suitable interface with the synchronizer. 
Here, in FIG. 21(a), schematically illustrated is a mask 270 having a 
single slit 271 formed therein. A stepped motor 272 is coupled to the mask 
270 for moving the mask vertically in successive steps, or discrete lineal 
increments, synchronized with cardiac motion. The motor receives step 
commands from a modification of the synchronizer in FIG. 6. An end view of 
the mask 270, in section, is shown in FIG. 21(b). 
Referring to FIG. 22(a) a mask 275 is shown with a plurality slits 276 
formed therein. The mask 275 is mechanically coupled to a stepping motor 
277. An end view of the mask 275, in section, is shown in FIG. 22(b). 
While there has hereinbefore been described what are now considered to be 
embodiments of the invention, it will be apparent that many modifications 
and changes will be made, thereto, without departing from the true scope 
of the invention. All such changes and modifications, therefore, are 
deemed to be a part of this invention.