FIELD OF THE INVENTION

This invention relates to display apparatus for displaying a series of images. The invention is parti¬ cularly advantageous for displaying "a series of stored X-ray images representing the action of the heart, the circulation of the blood, or other bodily functions in certain situations.

BACKGROUND OF THE INVENTION

The present invention is particularly well adapted for displaying a series of X-ray dif erence images, pro¬ duced as disclosed and claimed in U.S. patent No. 4,204,225, issued May 20, 1980, upon the application of the present applicant, Charles A. Mistretta, or as disclosed and claimed in U.S. patent No. 4,204,226, issued May 20, 1980, upon the application of Charles A. Mistretta, Robert A. Kruger and Theodore L. Houk. A series of such X-ray difference images will show the action of the heart, the circulation of the blood as, for example, in the coronary arteries, the carotid arteries, or bypass grafts around such arteries, or other bodily functions.

OBJECTS OF THE INVENTION One object of the present invention is to provide a new and improved display apparatus for repetitively displaying a series of images, such as a series of X-ray images showing the action of the heart or the circulation of the blood, so as to maximize the ^' amount of information which can be obtained from observing such images.

A further object is to provide a new and improved display apparatus of the foregoing character which will enable the radiologist to observe and study the series of

X-ray images for an indefinitely long period of time, as needed, while limiting the radiation exposure of the patient to a single series of images.

STJMMARY OF THE INVENTION To achieve these and other objects, the present invention preferably provides display apparatus for dis¬ playing a series of X-ray images or the like, comprising image storage means having forward control means for causing the image storage means to reproduce the images in a forward sequence, the image storage means having reverse control means for causing the image storage means to reproduce the images in a reverse sequence, ^' the image storage means having label means for producing label information to identify each of the stored images, upper limit means for establishing an upper limit of the label information, lower limit means for establishing a lower limit of the label information, upper comparison means for comparing the currently produced label inform¬ ation with the upper limit and for actuating the reverse control means when the current label information corre¬ sponds with the upper limit, and lower comparison means for comparing the current label information with the lower limit and for actuating the forward control means when the current label information corresponds with the lower limit, whereby the images are repetitively re¬ produced in forward and reverse sequences between the upper and lower limits.

Display means, such as a television monitor, may be provided to display the images reproduced by the image storage means.

The image storage means may be ^' in the form of an analog disc video recorder, a digital disc video recorder, some other video recorder, a digital memory, incorporated in a computer or otherwise, or means for utilizing images stored on photographic film.

Means may be provided for varying the rate at which the images are reproduced -by the image storage means.

The label means may produce the label information in the form of label number signals. The upper and lower limits may be established by upper and lower registers which may be set or loaded with the label number signals when the image storage means is adjusted to the images at the desired upper and lower limits.

The upper and lower comparison means may take the form of upper and lower digital comparators for comparing the currently produced label number signals with the upper and lower limits, loaded in the upper and lower registers.

BRIEF DESCRIPTION OF THE DRAWINGS Further objects, advantages and features of the present invention will appear from the following descript¬ ion of illustrative embodimen s, taken in connection with ' the accompanying drawings, in which:

Fig. 1 is a schematic block diagram of a display apparatus to be described as an illustrative embodiment of the present invention.

Fig. 2 is a fragmentary schematic block diagram, corresponding to a portion of Fig. 1, but showing a modi¬ fied embodiment.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

As just indicated, Fig. 1 illustrates a display apparatus 10 for displaying a series of X-ray images or the like. The display apparatus 10 comprises image storage means 12 for storing a series of images, such image storage means preferably being in the form of a video disc recorder which may be of the analog type, as contemplated in Fig.l, or the digital type, as contemplated in Fig. 2. However, any other suitable video recorder may be employed, for recording the images magnetically or otherwise.

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Moreover, the image storage means 12 may be in the form of a memory, such as a digital electronic memory, whether incorporated in a computer or otherwise. Further¬ more, the image storage means 12 may be in the form of means for utilizing images stored on photographic film, such as motion picture film.

In Fig. 1, the display apparatus 10 involves a tele¬ vision or video system. The sequential images stored by the image storage means 12 are in the form of video or television signals, derived from a television camera by way of an image subtraction system, as disclosed and claimed in the previously mentioned background patents, for example. The television camera may be trained upon an X-ray image intensification screen. The X-ray images may be produced in rapid succession, to show the action of the heart, the circulation of the blood, or some other bodily f nction.

As shown in Fig. 1, the image storage means 12 has a video input channel 14 for receiving the video signals representing the successive X-ray images to be stored. It is only necessary to produce and store a single series of X-ray images. Thus, the radiation exposure to the patient is minimized.

For brevity in the following description, the image storage means 12 will often be referred to as a video recorder, but it will be understood that other image stor¬ age means may be employed.

The video recorder 12 is capable of reproducing the stored images in either a forward sequence or a reverse sequence. In reproducing the images, the video recorder

12 produces video signals which are supplied to a video or television monitor 16, for converting the video signals into visible television images, corresponding to the X-ray images. The video recorder 12 of Fig. 1 has a speed control 18, for varying the rate at which the stored images are

reproduced. The video recorder 12 also includes adjust¬ ing-means 20, illustrated as a stepping control, whereby the video recorder can be adjusted to reproduce any stored image in the recorded series. The video recorder 12 of Fig. 1 has forward control means for causing the video recorder to reproduce the stored images in a forward sequence, such forward control means including a fast forward input 22, adapted to receive a control signal which will cause the video recorder 12 to reproduce the stored images in a forward direction. The video recorder 12 also has reverse control means for causing the recorder to reproduce the images in a reverse sequence, such reverse control means including a fast reverse input 24 for receiving a control signal to actuate the reproduction of the stored images by the video recorder in a reverse sequence.

The video recorder of Fig. 1 ^' also has label means for producing label information to identify each of the stored images. Such label information may comprise image label numbers,- stored by the video recorder along with the images, and adapted to be reproduced in the form of label number signals, accompanying the reproduced video signals corresponding to the stored images. In the video recorder 12 of Fig. 1, such label means may include a plurality of image label number output channels 26, adapted to supply output signals corresponding to multi- digit binary image numbers in parallel form, four such channels being shown in Fig. 1. When a larger number of digits is needed, a correspondingly larger number of output channels may be provided. The system of Fig. 1, involving four digits or bits, has a capacity of sixteen

4 (2 ) different image identification numbers. By adding additional digits, the capacity can be increased to thirty-two, sixty-four or any higher number. The display apparatus 10 of Fig. 1 includes upper and lower limit means 28 and 30 for selectively estab-

lishing upper and lower limits of the label information. Such upper and lower limit means 28 and 30 are illus¬ trated in the form of upper and lower limit data re¬ gisters which can be selectively loaded to any label number within the capacity of the system. The illus¬ trated data registers 28 and 30 have respective multi¬ channel inputs 32 and 34 which are connected to the corresponding outputs 26 of the video recorder 12. Thus, the image number signals being reproduced, by the video recorder 12 are applied in parallel form to the inputs 32 and 34 of the upper and lower data registers 28 and 30. The data registers 28 and 30 also have selectively operable loading or setting controls 36 and 38, illus¬ trated as setting switches, which may be operated to load any desired input signals into the respective data re¬ gisters 28 and 30.

For example, the upper limit may be set by using the stepping control 20 to adjust the video recorder 12 to the image which is desired as 'the upper limit. The video recorder 12 then supplies a corresponding image number to the upper limit data register 28, by way of the output channels 26 and the input channels 32. This image number may be loaded into the data register 28 by operating the loading or setting switch 36. Similarly, the lower limit may be set by operating the stepping control 22 to adjust the video recorder 12 to the image which is desired as the lower limit. The video recorder 12 then supplies the corresponding image number to the lower limit data register by way of the output channels 26 and the input channels 34. This image number is loaded into the data register 30 by operating the setting switch 38. The upper and lower limit image numbers remain loaded in the upper and lower limit data registers 28 and 30, until the setting switches 36 and 38 are again operated, when some change in the limits is desired.

The display apparatus 10 of Fig. 1 includes upper

and lower comparison means 40 and 42 for comparing the currently produced label information from the video re¬ corder 12 with the respective upper and lower limits established by the data registers 28 and.30, such upper and lower comparison means being illustrated as compris¬ ing respective upper and lower comparators 44 and 46, which, through the medium of a flip-flop 48 are adapted to supply actuating control signals to the forward and reverse input channels 22 and 24 of the video recorder 12 The upper limit comparator 44 of Fig. 1 is adapted to compare the currently produced image label signals from the video recorder 12 with the upper limit label signals from the data register 28. Thus, the upper limit comparator 44 has a first set of input channels 50 con- nected to the output channels 52 of the upper limit data register 28, and a second set of input channels 54 con¬ nected to the output channels 26 of the video recorder 12.

Similarly, the lower limit comparator 46 of Fig. 1 compares the currently produced image number signals from the video recorder 12 with the lower limit output signals from the data register 30. Thus, the lower limit compar¬ ator 46 has a first set of input channels 56 which are connected to the output channels 58 of the lower limit data register 30, and a second set of input channels 60 connected to the output channels 26 of the video recorder 12.

The flip-flop 48 of Fig. 1 is of the R-S type, having set and reset inputs 62 and 64. The set input 62 is con¬ nected to the output 66 of the lower limit comparator 46. The reset input 64 is connected to the output of the upper limit comparator 68. As shown, the flip-flop 48 has a Q output 70, connected to the fast forward input 22 of the video recorder 12, and a complementary or Q output 72 connected to the fast reverse input 24 of the video recorder 12. A double pole stop-start switch 74 is con¬ nected into the lines 76 and 78 between the outputs 70

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and 72 of the flip-flop 48 and the control inputs 22 and 24 of the video recorder 12. During normal operation of the video recorder 12, the double pole switch 74 is closed. The opening of the switch 74 is effective to stop the video recorder 12.

In the operation of the display apparatus 10 of Fig. 1, the video disc recorder 12 serves as image stor¬ age means, to record or store a series of images, as, for example, X-ray images representing the action of the heart, the circulation of the blood, or some other bodily function. To cite a more specific example, the X-ray images may represent the movement of an X-ray contrast medium through the coronary arteries of the heart, or through bypass grafts around the coronary arteries. It is difficult and tedious to analyze a series of such X- ray images, using an ordinary display system.

With the display apparatus 10 of Fig. 1, the X-ray images are repetitively displayed in forward and reverse sequences between upper and lower limiting images. To set up or program the display apparatus 10 for such oper¬ ation, the stop-start switch 74 is opened, to prevent automatic operation of the display apparatus 10. By using the stepping control 20, the video recorder 12 is adjustsd to the desired upper limit image, which is viewed on the video monitor 16. At this time, the image number outputs 26 of the video recorder 12 produce image number signals to identify the upper limit image. These image number signals are loaded into the upper limit data register 28 momentarily operating the upper limit set switch 36. To set the lower limit, the step control 20 is again operated to adjust the video recorder 12 to the desired lower limit image, as viewed on the video monitor 16. The video recorder 12 then produces image number signals at its output channels 26, corresponding to the lower limit image. These image number signals are loaded into the lower limit data register 30 by momentarily operating the

lower limit set switch 38.

To commence automatic operation of the display apparatus 10, the stop-start switch 74 is then closed. The video recorder 12 reproduces the stored images in a forward sequence, until the upper limit image is reached, at which time the upper limit comparator indicates that the image number signals at both ends of input channels 50 and 54 are the same, whereupon the upper limit compa¬ rator 44 supplies an output signal to the reset input 64 of the flip-flop 48. The Q output 72 of the flip-flop 48 then supplies an actuating signal to the fast reverse input 24 of the video recorder 12. Such control signal causes the video recorder 12 to reproduce the stored images in a reverse sequence, until the lower limit image is reached. The lower limit comparator 46 then indicates that the image number signals at both sets of input chan¬ nels 56 and 60 are the same, whereupon the comparator 46 supplies an output signal to the set input 62 of the flip- flop 48. The Q output 70 of the flip-flop ^' 48 then supplies an actuating signal to the fast forward input 22 of the video recorder 12. Accordingly, the video recorder 12 is again caused to reproduce the stored images in a forward sequence. Thus, due to the alternate functioning of the upper and lower limit comparators 44 and 46 at the upper and lower limiting images, and the alternate setting and resetting of the flip-flop 48, the video recorder 12 is caused to reproduce the stored images in a time reversal mode, in which the images are alternately reproduced in forward and reverse sequences, for as long as may be desired by the operator.

By closely watching the time reversal sequencing of the images, as displayed on the television monitor 16, an expert radiologist can analyze and evaluate the X-ray images much more accurately and rapidly than with ordinary display systems. The display apparatus of the present invention is particularly valuable for evaluating the

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circulation of the blood through the coronary arteries, or through bypass grafts around the coronary arteries. In some cases, it is advantageous to employ the speed control 18 to vary the rate at which the images are reproduced by the video recorder 12. For example, increasing the speed of the video recorder 12 may in¬ crease the amount of available information to be derived by observing the time reversal display of the images on the television monitor 16. By displaying the images faster than they were taken originally, the temporal integration properties of the eye can be used to perceive a greater quantum of statistical X-ray information per unit time than that which was present during- the original X-ray exposure sequence. The display apparatus 10 can be used very advanta¬ geously to provide a. dynamic time reversal display of sequential X-ray images, 'such as those obtained using image subtraction techniques as disclosed and claimed in the previously mentioned background patents. A single series of radiographic images may be taken originally, to minimize the exposure of the patient to radiation. These images may then be displayed repetitively in for¬ ward and reverse sequences, using the display apparatus of the present invention. Because only one series of radiographic images is required, the images can be taken under optimal high exposure conditions at separated time intervals and under optimal readout conditions, such as slow scan television readout. The images are then stored so that they can be reproduced with the dynamic time reversal display. The speed of the video recorder, or other image storage device employed -in the apparatus, can be increased to increase the rate at which the images are reproduced and displayed.

As already indicated, Fig. 2 illustrates a modified embodiment in the form of a modified display apparatus 110 including a digital video disc recorder 112, instead of

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the analog video recorder 12 of Fig. 1. Otherwise, the display apparatus 110 is generally similar to the display apparatus 10 of Fig. 1. The description of Fig. 1 is also applicable to Fig. 2, except as may be described herein. To facilitate the extension of the description of Fig. 1 to Fig. 2, many of the components shown in Fig. 2 are being given the same reference characters as in Fig. 1, or the same reference characters increased by 100. Thus, it will be understood that the digital video disc recorder 112 of Fig. 2 is adapted to record images in the form of digital video signals. The recorder 112 has a video input channel 114 for receiving the digital video signals to be recorded. Such digital video signals may represent the successive X-ray images to be stored. The digital video recorder 112 of Fig. 2 has a speed control 118, for varying the rate at which the stored images are reproduced. The recorder 112 also includes adjusting ^' means 120, illustrated as a stepping control, whereby the video recorder can be adjusted to reproduce any stored image in the recorded series.

The digital video recorder 112 of Fig. 2 has for¬ ward control means, as in Fig. 1, for causing the recorder to reproduce the stored images in a forward sequence, such forward control means including the fast forward input 22, as in Fig. 1, adapted to receive a control signal which will cause the recorder 112 to reproduce the stored images in a forward direction. The digital video recorder 112 also has reverse control means for causing the recorder to reproduce the images in a reverse sequence, such reverse control means including a fast reverse input 24, as in Fig. 1, for receiving a control signal to actuate the reproduction of the stored images by the recorder 112 in a reverse sequence. The digital video recorder 112 of Fig. 2 also has label means for producing label information to identify

each of the stored images. Such label information may comprise image label numbers, stored by the recorder along with the images, and adapted to be reproduced in the form of label number signals accompanying the reproduced video signals corresponding to the stored images. In the digii_- al video recorder 112 of Fig. 2, such label means may in¬ clude the image label number output channels 26, as in Fig. 1, adapted to supply output signals corresponding to multidigit binary image numbers in parallel form, four such channels being shown in Fig. 2, as in Fig. 1. When more than four digits are desired, a correspondingly larger number of output channels may be provided.

The television or video monitor 16 may be the same in Fig. 2 as in Fig. 1. However, the digital video recorder 112 of Fig. 2 preferably feeds its digital video output signals to a buffer memory 131, which in turn supplies its output tP a digital-to-analog converter 133. At its output, the converter 133 supplies analog video signals which are fed to the television monitor 16, so that the images reproduced by the digital video re¬ corder 112 will be displayed by the television monitor 16.

Otherwise, the display apparatus 110 of Fig. 2 may be the same as the display apparatus 10 of Fig. 1. The connections to the forward control input 22, the reverse control input 24, and the image number signal outputs 26 may be the same in Fig. 2 as in Fig. 1.

The operation of the display apparatus 110 of Fig.2 is the same as described in connection with Fig. 1, except that the images are supplied to the digital video recorder 112 in the form of digital video signals, and are recorded and reproduced as digital video signals. The buffer memory 131 and the digital-to-analog converter are effect¬ ive to convert the digital video signals into analog sig¬ nals, which are converted into visible images by the tele- vision monitor 16.

The time reversal mode of operation, as described in

connection with Fig. 1, as to the display apparatus 10, is the same, with respect to the display apparatus 110 of Fig. 2.

Other modifications, alternative constructions and equivalents may be employed, without departing from the true spirit and scope of the present invention.

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