DE2647761A1 - AXIAL-TOMOGRAPHICAL SYSTEM FOR RADIATION DIAGNOSTICS - Google Patents

Description

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Axiai-tomographic system for radiation diagnostics,

In US Pat. No. 3,778,614 there is a method and apparatus for Examination of an object using X-rays or gamma rays described. One practical embodiment includes an x-ray beam source of radiation, which sends an X-ray beam through a flat layer of the examination subject sends, furthermore a detector for reception of the beam that has passed through the object to be examined and a drive for sequential rotation and translation or displacement the radiation source and the detector around the examination object during the radiographic examination. Since the sent Beam v / uring each lateral shift or displacement of radiation source and detector parallel to all other emitted Radiation, data processing can be carried out for the relevant

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sampling can be carried out at the same time as data acquisition. This means that the reconstruction of the acquired data is available immediately or at least shortly after the data acquisition has been completed. In a more recent practical embodiment with fan-shaped radiation, the actual scanning time is shortened. However, since the display has to wait until the data acquisition and data processing is complete, there is a significant delay on the order of minutes before the reconstruction can be viewed. However, with these systems, one cannot view the results of a particular scan until the data acquisition and processing is complete. In addition, data acquisition and processing cannot be performed at the same time as the playback of a previous scan. For this reason, the number of patients who can be handled in a certain time unit is clearly limited, since the main scanning or data acquisition device cannot acquire any data from further scans for the duration of the reproduction of a specific scan. In addition, the mentioned system is based on a single computer which controls all details of data acquisition, data processing and display. If that single computer fails, the entire system comes to a standstill; none of the aforementioned functions, namely data acquisition, data processing and display, can then be carried out. '■

Others currently in competition with the system discussed Systems have similar disadvantages, although they have an independent

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pending display is possible during the time during which the data acquisition and data processing for a subsequent scan takes place. However, even with this system there will be competition as in the case of the system described above, the originally recorded data, i.e. the raw data during processing and reconstruction destroyed so that they are not available for later recourse. The radiologist can therefore use the raw data later don't reprocess it to make a different reconstruction or to receive evaluation of the same. Instead, one or more new scans must be used to provide additional raw data for processing according to the required technology will. !

Accordingly, it is an object of the invention to provide one axial tomographic system for radiation diagnostics, which due to the possibility of extensive temporal overlap its individual functions work particularly time-saving and preferably without destroying the originally recorded raw data.

According to the invention, this object is achieved with an axial tomographic system which has a scanning device for detecting several Has amounts of data that reflect the transmission or absorption of at least one beam of hard or penetrating radiation behind a correspond to a flat or planar layer of an examination object, furthermore a processing device for the recorded amounts of data, which have a damping coefficient for each of several individual matrix

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elements of the flat layer supplies, as well as a display device for reproducing the matrix of attenuation coefficients corresponding to the flat layer, and which is characterized in that the scanning device, the processing device and the display device are designed to operate independently of one another are such that the main functions of the system, namely data acquisition, the processing of the data sets and the reproduction of the attenuation coefficient matrix can be carried out independently of one another are.

The system according to the invention is preferably designed to

that the scanning device or the axial tomographic input

direction for the acquisition of the several data sets or groups one Frame with an opening therein for receiving the object to be examined, a hard radiation source and a frame-mounted detector on which at least one of the radiation source Beam of hard radiation is directed, and that a rotary drive for rotating the frame together with the radiation source and the detector the opening and the examination object located therein are provided in this way is that several data sets are recorded according to the transmission or absorption of each beam in the examination subject. Optionally, a sliding drive can also be provided, which of the radiation source and the detector is a translational one Movement granted relative to the examination subject.

With the new axial tomograph!

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The disadvantages inherent in the prior art are mainly avoided in that the scanning device, the processing device and know the display device to work independently of one another. This enables a substantial time overlap in the functional sequence and also avoids that the initially acquired raw data must be destroyed during processing and reconstruction. the Raw data are much more unchanged for repeated access and a possible renewed use available. Overall, this results in a significant increase with the system according to the invention the examination speed and a correspondingly increased Patient throughput achieved.

The scanning device or axial tomographic device for capturing the multiple data sets comprises a hard radiation source which sends a beam of hard, penetrating radiation through the plane layer of the examination object, furthermore the detector for receiving the emitted beam after passing through the examination object, and the drives for sequential displacement or translation as well as rotation of the radiation source and the detector around the examination subject during the radiographic examination. Such an axial tomographic device is described, for example, in the aforementioned US Pat. No. 3,778,614. With another "= ■

'- "---- - build-up becomes a fan-shaped beam

hard radiation through the flat layer of the examination subject sent to a radiation-sensitive detector and thereby an amount of data derived which is the transmission or absorption of the

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Radiation in the examination object corresponds to several diverging lines extending from the radiation source to the detector. Several data sets are recorded for different angles of rotation of the fan-shaped beam relative to the center of the plane layer examined. The difference between this structure and the previous structure according to US -PS is ₅ that in this structure, no lateral displacement of the radiation source and the detector is NOTV / Endig. the radiation source and the detector are instead rotated about the object under examination, in order to produce quantities of data sufficient for the necessary reconstruction of the respective analyzed planar layer A fan-shaped radiation can also be used in connection with scanners which require a lateral displacement of the radiation source and detector Form invention. If desired, however, other axial tomographic configurations can also be used which differ from the above configurations.

The following is the invention with further advantageous details on the basis of a schematically illustrated embodiment. purifies. In the drawings show:

Figure 1 is a block diagram of the scanning, processing and display subsystems an axial tomographic system according to the invention,

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FIG. 2 - a schematic diagram partially executed as a block diagram the scanning subsystem,

FIG. 3 - a graphic representation to explain the transformation the original x-ray or screen image data in parallel screen image data,

Figure 4 is a graph showing the correlation of center ray data I with I ',

FIG. 5 - a schematic diagram of a phantom used to determine the correlation according to FIG.

For the following description of the invention it is assumed that that the special electronic circuits and components for implementing the invention are known per se or are known to those skilled in the art of the present disclosure are accessible without any inventive effort. Therefore, a detailed explanation of such Circuits and components which, taken by themselves, do not form part of the invention, are dispensed with.

FIG. 1 shows an axial tomographic system 10 according to the invention. The system 10 specifically comprises three independently operable subsystems, namely a scanning subsystem 12, a processing subsystem 14 and a display subsystem 16. A scanner 18 scans the

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Object to be examined and generates 180 or more data sets or groups, which are recorded in a tape device 20 on magnetic tape.

net. The magnetic tape then becomes the processing subsystem 14 transports, which processes the data from the magnetic tape and uses it to generate a matrix of damping coefficients, which of the investigated corresponds to the plane layer of the examination subject. The data representing the damping coefficient matrix are stored in a Disk device 22 on a floppy disk, i.e. a flexible recording disk, recorded. The disk then becomes the display subsystem 16 transports, v / o the data stored on the diskette read out, in a third, equipped with storage and processing functions Computing unit 24 processed and on a display console or a

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Display device 26 can be reproduced. Using a copy unit

a hard copy of the advertisement can be made if desired.

The scanning subsystem 12 of the overall system operates as follows: The operator keyed in commands on the keyboard 29 of the console, which one equipped with a storage and processing function Computing unit 30 and then to other parts of the system to operate the scanner. In detail, the operator gives Commands to start the system. The system then checks to determine whether certain security elements are in order. These elements include that the X-ray tube in the scanner 18 is supplied with a sufficient amount of oil for cooling, optionally that the Examination room door is closed to prevent unwanted exit of x-rays in other areas to avoid getting the

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Clock of the arithmetic unit 30 is ready for operation, and that power supply exists for all subsystems. If the test of all the first security elements has been concluded with a positive result, the processing unit signals the safety device that be able to properly ground all power sources of the sensing subsystem for a short period of time. During this short period of time the processing unit performs a second series of tests. In detail, it is checked whether the by a reference detector 92, See Figure 2, received radiation is within prescribed limits, whether a radiation source 60 has the correct voltage and receives the correct current, and whether the sampling clock is operational

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ready. In addition, another safety signal is emitted at this point in time generated in-which a series of pulses, the pulses with a short interval of, for example, one second or less on each other is sent out by the computing unit 30 to power the X-ray tube. If an error in the arithmetic unit 30 or another malfunction of the system is present, the transmission of further impulses is interrupted and thereby the system in its normal shutdown state in which all power sources of the sensing subsystem are electrically powered by those fed by them Units are separated. However, if the arithmetic unit is working properly and all measured system parameters are within their prescribed limits, the scanner begins a lateral traverse of the examination subject, in which the radiation source 60 is moved laterally out of a shielded area, which is covered by a shield 88 is formed. At this point in time, the arithmetic unit

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called 30, a third series of safety checks was carried out. Specifically, the third series of safety checks includes determining whether individual detector elements 76 are all operating within correct operating _ranges, whether the lateral speed of the radiation source is within the prescribed limits, and whether the scanner actually rotates to the next angular position after a certain lateral scan has been completed .

The arithmetic unit 30 acquires data during the lateral scan of twelve detector elements 76 and from reference detector 92. During Every time the examination object is crossed laterally, the arithmetic unit 30 records data from 750 data points, which is one data point corresponds to the lateral displacement of the scanner per 100 micrometers. The data recorded with each crossing is stored in the tape device 20 recorded on magnetic tape. For a system with one detector from zv / oil f detector elements (without the reference detector) in the angular distance of 1 °, the arithmetic unit 30 rotates the scanner 18 after each lateral crossing or shift by 12, and locks the scanner in the new angular position and reverses the lateral scanning direction for the next following crossing around. An angle encoder 94 detects the exact angular position of the scanner relative to the examination subject. A side scan is performed for 15 or more different angular positions, producing 180 or more amounts of screen data can be obtained. There is an amount of screen data per 1 of the angular rotation relative to the examination subject. After graduation

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of crossings in all fifteen or more angular positions the arithmetic unit 30 controls an object transport (not shown) and effects an automatic advance over a predetermined one Distance in the axial direction so that the data of a second flat slice of the examination object can be recorded. The work sequence for η-shifts is specified by the operator repeated; after completion of the η-th layer, the computing unit 30 automatically switches off the radiation source and rewinds the magnetic tape in tape device 20.

In a typical example, the computing unit comprises 30 of the scanning subsystem 12 the following essential components: a central unit Nova 1200 with a 16K memory (model 8189 from the company Data General Corp., - Southborough,. Massachusetts, USA); An additional 16K memory (Model 8117 from Data General Corp.); an I / O (input / output) main unit with a clock (model 4007/4010 made by Data General Corp.); a tape drive controller (Model Nova-Pertec 3120 from Ball Bros. Research Corp., Santa Clara, California, USA); a 22cm tape drive (model 5840-9 from Pertec Peripheral Equipment Division, Chatsworth, California, USA); a screen station (model Mini-Bee 4 of the Beehive Medical Computer Systems, Inc., Sunnyvale, California, USA); and associated circuitry for controlling the subsystem functions. The descriptions and flow charts based on subroutines of the programs for the arithmetic unit 30 of the scanning sub-

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systems 12 are attached as Appendix A. The actual printed program for the scanning subsystem in the Fortran IV language is _{attached as Appendix A 5} parts Ι-ΧΓ. ^R

Processing subsystem 14 includes processing console 31 a data station with input via a keyboard 32 and screen output. The data station is in operative connection with a second, arithmetic unit 34 equipped with a storage and processing function, which in turn is coupled to a tape recorder 36, which the recorded raw data (or preprocessed data) from the Magnetic tape reads, t, from the tape device 20 of the scanner to the tape device 36 has been transported. The processing subsystem 14 processes the raw (or preprocessed) Screen image data and generates reconstructed tomographic ones therefrom Data, i.e. a matrix of absorption coefficients corresponding to the plane layer of the examination subject, which is then placed on a Floppy disk, i.e., a flexible magnetic disk stored in disk device 22 will. A separate diskette is preferably used for each patient.

The data supplied to the processing subsystem are as follows processed: First, the screen image data are processed by the processing unit 34 to displacements of the received from the detector elements 76 Measured values corrected in that the measured values I., which are obtained, if the radiation source is covered by the lead shields 88,

• / 13

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are subtracted from the measured values I, which from the detector elements 76 can be obtained while the radiation source 60 is scanning the examination subject. This will cause errors due to Measured value shifts in the individual detector elements reduced to a minimum.

Next, the arithmetic unit 34 corrects with respect to time fluctuations in the detected signals I, which arise from fluctuations in speed of the scanner during its lateral displacement, and with respect to intensity fluctuations of the hard radiation source. This is done by further standardizing the standardized data in relation to the signal V from the reference

detector 92 reached. The processing sub-system 14 then sets a scaling factor for each screen image data set to the absorption level which corresponds to the determined absorption in a plastic block 70, so that only the differences from the absorption coefficient of the plastic are reflected in the data. With this normalizing correction, the absorption scale factor measured for the plastic block 70 must be compensated for with respect to changes in path length for the corresponding parallel rays through the plastic. This is shown in FIG. 3, where the left beam 1 of a fan arrangement is shown in opposite end positions of the lateral displacement path of the fan-shaped partial beam arrangement. The rays 1 form a ^Me "" ge parallel rays. In the same way, the middle ray c

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and the right ray r of the fan-shaped partial ray arrangement in the two end positions two rays of a second and a third ^{line of} parallel rays.

The parallel screen data for the parallel ray sets c, 1 and r are shown in the screen data sets (a) of FIG. It can be seen that the center points of the individual sets of parallel screen image or beam data are laterally offset from one another, and it is desirable to align the sets of parallel screen image data to a center and to look at the screen image data which fall out of the image area of interest. Correspondingly, the processing subsystem 14 discards the parallel screen image data obtained outside the desired image area, leaving about 509 data points, and shifts the midpoints c ₁ , C 2 and C _{3 of} the individual sets of parallel screen data to the same point, viewed from the side, as this is illustrated with the screen image data curves c, 1 and r in group (b) of FIG.

The processing unit corrects in a further processing step 34 every single amount of parallel screen image data for compensation versus the presence of high Z material, e.g. Bone, the Compton scattering of X-rays on the examination subject, the openings of a source collimator 62 and a detector collimator 74, the fluctuations in the X-ray energy, i.e. the polychromaticity, and the detector hysteresis. This is done by correlation with data that are shown graphically in FIG. 4 and by means of a Phantoms 38 according to FIG. 5 were generated. The phantom 38 includes one

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wedge-shaped section 40 made of bone or a bone-equivalent material and a wedge-shaped section 42 made of water such that the thickness of the phantom varies between 100% bone and 100% water. Both sections are held in thin, wedge-shaped sections made of plastic, for example made of polymethacrylate. The phantom is laterally scanned by the scanner 18 and the center _beam data In is recorded. These data are first converted into the corresponding natural logarithm and then plotted against the natural logarithm of the value L ·, which would have been achieved if the jet had always passed through 100% water. This correlation is shown in the arithmetic unit 34 in the form of a look-up table is stored, which is shown graphically in Figure 4, so that by resorting to this table, a certain value I for a scan of an object to be examined, for example a head, can be corrected with respect to the amount of bone through which the beam has passed the preprocessing of the data is completed, which can be carried out entirely or partially in the processing unit 30, but is preferably carried out in the processing unit 34.

Next, each corrected data amount, i.e. corrected amount parallel screen image data, folded around 'unwanted background in the attenuation coefficient matrix in the back projection of the 180 data sets in a later stage of the reconstruction process to eliminate. More specifically, the screen image data is convolved using a certain preferred convolution function provided by

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Was LA Shepp and BF Logan indicated (IEEE Transactions, Nuclear Science, NS-21, 21-43 June 1974) to folded umbrella _t image datasets derived. Various other convolution functions can also be used in this processing stage. This depends on which properties of the damping coefficient matrix are to be emphasized. For example, a folding function can be used to highlight relatively large differences in density, such as are present between bone and tissue. On the other hand, a second, different convolution function can be used at the request of the radiologist to highlight small differences in density within the examined tissue. The operator or the radiologist can freely choose a desired folding function in this processing stage. After all corrected data sets have been folded, the 180 data sets are back-projected to derive the absorption coefficient matrix.

With the rear projection a matrix with 256x256 elements is formed, which means a total of 65,536 matrix elements. However, Each amount of data corresponds to parallel rays, the width of which is clear is smaller than the width of a single matrix element traversed by the corresponding beam. Accordingly, an interpolation method becomes which converts the approximately 509 parallel screen points to approximately 2,000 parallel screen data points expanded and each individual matrix element an absorption coefficient which corresponds to the absorption coefficient of the beam which is closest to the center of the matrix cell.

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After the rear projection has been carried out for a specific flat layer is, v / ird is the absorption coefficient matrix in the disk device 22 stored on a floppy disk.

In the present preferred embodiment, a floppy disk High density storage uses 300,000 words on each page can save. With a typical tomographic absorption matrix, which corresponds to a flat layer of an examination object, the values of the absorption coefficients can be between +1,000 and -1,000, which would require 11 bits per word. Typically "is 65,536 words to describe a 256x256 matrix necessary. However, the amount of information to be saved

by reducing the number of matrix elements to about 50,000 can be reduced considerably. This is done by eliminating parts of the image that are not of interest, e.g. the corners of a rectangular one Images that lie outside the circle of interest representing the plane layer. Furthermore, the word length can be 8 bits can be reduced by only the density difference between successive Matrix elements of a certain pattern is recorded. Two 8-bit words can be in each 16-bit machine word get saved. So the matrix can be reduced to about 25,000 words, which means storing 12 images on each page the floppy disk allowed. Of course it's free, if you want also save less than 12 images on each side of the floppy disk or to waive the implementation of the changes explained above. After saving the data of a certain level layer

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on the floppy disk the process of saving the complete Repeated number η of plane layers recorded by the scanner. The processing subsystem then ends its sequence of operations and rewinds the magnetic tape onto the supply reel on which it was brought to the tape device 36.

In a typical embodiment, this includes processing. Subsystem 14 an Eclipse 5200 arithmetic unit with a 16K memory (Model 8404) together with a writable control memory (model 8415), furthermore a floating point processor (model 8413), four 8K storage units (Model 8418), one main I / O unit with a clock (model 4007/4010), a disk control unit (model 4046) - all of the above components are manufactured by the company Data General Corp. supplied *, a floppy disk control unit (model I / F from Advanced Electronic Design, Inc., Sunnyvale, California, USA), a tape drive control unit (model Nova-Pertec 3120 from Ball Brothers Research Corp., Santa Clara, California, USA), a plate unit (model 31 from Diablo Systems Inc., Heywald, California, USA), a 22 cm tape drive (Model 5840-9 from Pertec Peripheral Equipment Division), a dual disk device for recording on floppy disks with associated Drives, memories and sliders (models 3100P, FD400, PFD / E, SB and CS from Advanced Electronic Design), a monitor station (Model Mini-Bee-4 from Beehive Medical Computer Systems Inc., Sunnyvale, California, USA) and a plate connection (Model 4047 from Data General Corp.) and assigned

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Circuits for controlling subsystem functions. The descriptions and flow charts based on subroutines of the programs for the computing unit 34 of the processing subsystem 14 are attached as Appendix B. The actual printed program for the processing subsystem in the Fortran V language is as Appendix "Appendix B, parts I-X" attached.

According to Figure 1, the display subsystem 16 includes a display console 48 with a keyboard 50, which is in operative connection with the third, arithmetic unit equipped with storage and processing functions 24, "which in turn is operable with a disk device 52 for reading floppy disks and the display screen device 26 connected is.

During operation, the disk on which certain tomographic data are recorded is placed in a file envelope together with other diagnostic information, for example conventional X-ray reports and the like. The viewer removes the diskette from the file envelope and inserts it into the disk device 52. Upper keyboard 50 aer display console 48, the operator inputs information for selecting a desired tomographic layer a of the examination object. The arithmetic unit 24 causes the disk device 52 to read out the tomographic data which correspond to the selected slice.

The arithmetic unit 24 sets the high-density data in the floppy disk

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converts a video raster format and feeds this to the screen device 26 for display. If desired, a paper copy of the ^r

Display can be created, what happens by entering the appropriate command on the keyboard 50, whereupon the paper copy the information displayed on the screen device 26 is generated will.

The arithmetic unit 24 can be programmed to select certain data for display on the screen device 26 which are within a certain window of variable width and position. More precisely, data are stored on the floppy disk within a certain range of values which corresponds to a certain density range of the absorption coefficients in the tomographic matrix of these coefficients. The arithmetic unit 24 can select a specific value range and display it in accordance with commands from the keyboard 50.

In a typical embodiment, the display subsystem comprises 16 a computing unit Nova 1200 with a 16K memory (model 8184), a 16K storage unit (Model 8117), a master I / O unit with a clock (model! 4007/4010) - all of the above components are made by Data General Corp. delivered -, a floppy disk control unit (Model I / F from Advanced Electronic Design), a video display electronics (model 200 from Lexi-Data Corp., Lexington, Massachusetts, USA), a keyboard (model mini

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Bee 4 from Beehive Medical Computer Systems Inc.), one 43cm television monitor (model TV17C from Ball / Miratel Division, St. Paul, Minnesota, USA), and a disk device for floppy disks with an associated drive, memory and sliders (models 3100P, FD400, PFD / E, SD and CS from Advanced Electronic Design)

so / ie associated circuits for controlling subsystem functions. The descriptions and flow charts based on subroutines of the program for the computing unit 24 of the display subsystem 16 are attached as Appendix C. The actual, printed program for the display subsystem in the Fortran IV language is attached as Appendix "Appendix C, part I ₁ ".

It should be noted that compilers are used to translate Fortran IV or V into other desired machine languages, e.g. RDOS (rev 4.0 or 4.02), which is required for the Nova 1200, or in BRDOS (rev 4.02), which is required for the Eclipse 5200, are currently available.

FIG. 2 shows the scanning subsystem 12 of the axial tomographic system 10 in further details. The scanning subsystem 12 comprises the scanner 18 with the radiation source 60, which hard, emits penetrating radiation, e.g. X-rays. The X-ray beam originating from the radiation source 60 is on a source collimator 62 directed, which collimates the X-ray beam into a fan-shaped arrangement of twelve individual partial beams 64, each of which has a depth (direction into the paper) of

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Learn more and a thickness in the plane of the fan of approximately 1.2mm has.

The fan-shaped arrangement of precisely collimated partial beams 64 the X-ray radiation is directed onto an examination subject 66. This can be, for example, the head or a part of the body of a patient. When the head is examined, it can be removed from a support 68 filled with water, which in turn is surrounded by the plastic block 70, for example made of polymethacrylate. Of the Plastic block has a cylindrical bore 72 which surrounds the outside of the support 78 and rotates relative to the support, which in turn is stationary together with the patient's head.

The second collimator 74 is arranged on the other side of the examination subject opposite the source collimator 62. This has slots which are each in alignment with one of the individual partial beams 64. The collimator 74 reduces the detection of Compton scattered X-ray radiation emanating from the examination subject 66. The twelve detector elements 76 already mentioned are X-ray sensitive photo receivers and form an arrangement which is located behind the exit of the collimator 74. They receive the individual partial beams 64 after passing through the examination object 66 and the collimator 74. The output of each detector element 76 is fed to two Miller integrators 78 for integration and from there to the input of a multiplexer 80.

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The scanner 18 performs both a rotational or rotational movement and a translational or displacement movement relative to the examination object 66. More precisely, the scanner 18 rotates about an axis of rotation 82, which preferably passes through the central region of the flat layer of the examination subject. The angular rotation of the scanning device is represented in the drawing by the angle θ. In addition, the fan-shaped partial beam arrangement is given a lateral scanning movement over the examination object 66 in every angular position of the scanner. In a system with 12 detector elements (without the reference detector) at an angular distance of 1 °, the scanner 18 is rotated in steps of 12 ° relative to the examination object 66 and the fan-shaped partial beam arrangement is shifted laterally over the examination object in each angular position thus reached. The radiation source 60 is given the lateral displacement movement by a belt drive 84, the exact respective lateral position of the radiation source 60 being detected by a section encoder 86, the output of which is fed to an input of the arithmetic unit 30.

At the ends of the lateral displacement path of the radiation source 60 two lead shields 88 are arranged, which protect the examination subject 66 from the X-rays during the pauses in reversal shield when the radiation source is in the two opposite end positions of their lateral shift

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finds. A thirteenth partial X-ray beam, which originates from the radiation source 60, is directed through an X-ray attenuator 90 ^r with known attenuation to the reference detector 92, from which an output signal is obtained which is proportional to the intensity of the X-ray radiation emitted by the radiation source 60 . The angular position of the scanner is detected by means of an angle encoder 94 and transmitted to the arithmetic unit 30 as an input signal.

The arithmetic unit 30 causes the scanner via a motorized one Drive 96 for stepwise adjustment of the angular position θ of the scanner 18 by 12 ° and to the side Displacement of the radiation source 60 over the body once in each angular position of the scanner. In a typical embodiment the lateral displacement of the radiation source 60 takes place in one second, with the path encoder 86 at intervals of 10 micrometers of the displacement path covered the radiation source 60 encoded position information to the Computing unit 30 outputs.

The data of the received x-ray radiation derived from the individual detector elements 76 are each in the assigned pair Mi11er integrators 78 integrated and then sampled by the multiplexer 80. The output of the multiplexer 80 arrives at an A / D converter 98, which digitizes the measured analog data and supplies it to the arithmetic unit 30 in digital form.

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The output derived from an associated detector element 76 of two individual Mi11 er integrators 78 is for one detector element 76 is shown in Figure 2 with waveforms (a) and (b). in the the output of a single detector element is over integrates a period of time which is a lateral displacement of the corresponding x-ray partial beam 64 relative to the examination subject 66 corresponds over a distance of 50 micrometers. Initiated after each completed 50 micron shift the computing unit 30 a sampling of the integrated output by the multiplexer 80 and then a deletion or resetting der'individual integrators 78 via an output power and individual switches 102. The switches 102 are in each detector channel during an interval of lateral displacement until the end of the integration portion of the operating cycle of the adjacent one Integrator closed as shown with waveform (b). During the interval in which integrator (a) is "read out" and "reset", integrator (b) integrates the detector current. During the subsequent interval, the Roles of the two integrators (a) and (b) reversed. In this way, dead times are avoided during which photons at the Detector elements arrive but are not received. The arithmetic unit 30 adds the two data points to one another. The output of the multiplexer and A / D converter fed to the arithmetic unit 30 thus corresponds to an X-ray screen image with 750 measuring points, one data point being recorded per 100 micrometers of lateral displacement with respect to the examination subject 66. the

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Data are either in raw form or stored in tape device 20 after preliminary preprocessing.

The axial tomographic system according to the invention, in which the scanning subsystem 12, the processing subsystem 14 and the Display subsystem 16 are all operated independently of one another, has the following advantages, among others: The processing Subsystem 14 can process data while the scanning subsystem is receiving new data; the operator can be that of the scanning subsystem 14 recorded screen image data with various Convolution algorithms process certain differences highlight the absorption coefficient; the radiologist or doctor can access the tomographic data at freely chosen times completely independent of the use of the scanning subsystem or of the processing subsystem 14; after all, the originally recorded screen image data is not destroyed, but are available for any further processing that may be required. In addition, if one or two subsystems, the remaining subsystems can continue to be used to carry out their function. For example, if the scanning subsystem falls for any reason, the processing subsystem can still process previously recorded data, and the radiologist or doctor can still view processed data. In addition, the system of the invention is straightforward for operation in connection with several scanning subsystems, which are possible

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1 are certainly provided in different places, suitable, with only one processing subsystem and one display subsystem available. Optionally, of course, several display subsystems can also be used may be used in conjunction with a single scanning subsystem and a single processing subsystem. this comes into question, for example, when the reconstructed data is viewed by the radiologist or doctor at different remote locations should be.

The system described has the further advantage that processed Data for fine or multiple layers in the processing subsystem can be recorded on a separate floppy disk. This makes it possible to use the first disk while recording further Already bring samples to the independently operational display subsystem and their contents on a second, separate floppy disk there, so that, for example, it can be determined whether the examination object is correctly positioned or whether the recorded planar layers actually deliver the desired information, and so it is certain at an early point in time that the investigation is proceeding properly.

... Expectations

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ΛΝΙΑΟΓ R / Let TE SYNTKX A = -: ALΠ ¹ ! C / L TA.SW? J £ ulTo _t Ii-C,

PROCESSING (PROCESSOR) SOFTWARE

30th

PURPOSE

PROCESSING 6

Main program Reads initial patient intent and initializes all control files.

RFSCAN main program Reads scan data from magnetic tape and saves it them on disk for use by the folder.

NOPCL (OPCL) subroutine opens and closes all files and processes all parameter initializations.

NPROC (PROC) subroutine Corrects each detector using the reference and subtracts the background.

INTER subroutine Performs double precision interpolation from 523-509 points.

REFC subroutine

TAPIO task priority divides the detector value by the reference (retrieval by NPROC).

Reads a record from the magnetic tape.

DSKIO task priority Writes a data record to disk. The program assumes double buffering by the user.

KORR Subroutine Enters the calibration file from the plate.

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B / 2

FOLDING

C0MV0L2 (CO) main program

Executes the data folding and creates a file for the rear projection program.

CONIT
Subroutine Causes initialization and opens all disk files.

COMVOL
Subroutine Multiplies the data set with the (imaginary) convolution function in the Fourier domain.

COMPCK
Subroutine Brings the real parts of a complex field together in one real field.

COMUNP
Subroutine Dissolves a real field into the real parts of a complex field.

DFT5
Subroutine Establishes the connection between a program in Fortran V and the discrete Fourier transform program (DFTE) in machine language.

COBD
BLOCK data Causes the memory to be preset with constants.

DFTE
Subroutine Performs a discrete Fourier transform,

REAR PROJECTION

EC4DRV7 (C4DRV) main program Carries out the rear projection of a folded file over a reconstruction field.

EC4BKP7 (C4BKP) Subroutine Performs the back projection of an individual 64 χ 64 segments of a reconstruction grid

709838/0550

B / 3

EC4EXP7 (MEXP) subroutine

EC4XNM (C4XNM) subroutine

EC4MRD (MREAD) Task

XOPI

Write control memory

Extends a measurement data set (data from the convolution process), whereby four interpolated integer measurement values result from each floating point measurement; then backprojects the whole tooth values according to the closest neighborhood method onto the current reconstruction gate segment.

Standardizes the current reconstruction mesh segment by shifting every other word value 10 bits to the left and merging the resulting higher order words into a single precision 4K word arrangement.

Plate input task for reading the measurement file (convolution output) for the rear projection.

Writes control commands that effect service functions rken.

FILE BACKUP

SLICE
Main program

Has a twofold task:

1. Writes the reconstructed field to a second disk (or floppy disk).

2. Brings the control file up to date and feeds the magnetic tape up to to the beginning of the next file.

SERVICES (BLOCK)

STCON
subroutine

Causes the memory to be preset with un.numbered Constants.

TQ9838 / 055Q

/ 4

B / 4

FSTCON subroutine

33

2 & 47761

Limits presetting of the memory with Floating point constants.

BMOVE subroutine Moves a block of data from a memory chersteile to another.

70 9838/0550

XRAY.FR

PURPOSE: Initializes data files at the beginning of each patient

Tape from the scanner. *

METHOD: Reads the patient's header and forms the patient's

Header file on the plate. Initializes counter in aer patient header file that is used by the following programs in the reconstruction process.

OPERATING INSTRUCTIONS:

1. Insert the patient tape (from the scanner)

2. XRAYV

3. The program asks whether the magnetic tape has been inserted "4. Credit ''

INPUT:

1. CALIB.SC

2. Scanner output tape

OUTPUT:

1. C4PAT.SC

2. C4ANGLE.SC

ERROR MESSAGES ii

1. "MT OPEN ERROR" (open error MB (magnetic tape))

2. "MT INIT ERROR" (initial error MB)

3. "MT READ ERROR" (read error MB)

4. "DISK ERROR" (disk error)

VARIOUS:

This program is coupled with RFSCAN as follows: CALL (call) FCHAN ("RFSCAN.SV")

TO 9838/0550 / 6

XRAY

Open fE / A files \ V ^ J

Patients read tape

Read calibration file

Write patient resolution

\ l

Write initialized angles

TCHAN

RFSCAN

709838/0550

P 26 hj 761.2 ? Sjnt- ~ v. '. (TT.5.A,) Ine, (Appendix B)

- ΡΛ-776

eEf - ;: dOi π

RFSCAN

Dissolve running detector

running detector dissolve

/ nproc \

ΓΤΑΡ (Ο ~ \ \ REC I / last DQtektcn gufqetos

Insert recording

PARALLEL TASK

i 1-v

/ ταρϊοΛ.

\ RECIII /

709838/0550 WÖRCS ^ l \ NORCS + 1 \

Yes

fWhkel-Date! \ [write ^)

(Parameter file) write /

C O. SV

? 26th

3 *

RFSCAN

RFSCAN

NOPCL (+1)

(corr)

PRI = 5 NORCS = 1

MRAJLEL-TASK

JL

/ TAPfO \ SJREC I) /

Initialize loop

JREAD = Φ

Attention:

\ ^f

REC I 3760 words REC II 3760 words RECIII 300QWOdQr

Dissolve running detector

Yes ΓΤ / ^

PARALLEL TASW

JAPJO

(nproc)

reference dissolve

Yes

709838/0550

COVOL 2

{CONIT)

\ l

{FSTCON)

(COMUMP)

(DFT 5)

{COMPCK)

'Output file ^ write.

(qonit )

α -sv

P 26 47 761.2 Syntex (U.S.A.) Inc, (Appendix B)

- PA-776

TO9838 / 0550 *

Rear projection

B2UDRV7.FR; Main flow

Read parameters

Rear projection Gasamtü & 'Qth: Access to CUBKP

■ Input file CU TMP7

X-SECMENT: = Y-SEGMENT: =

\ l

Rear projection of the current segment

X segment inkremsnii-zren

Title File Output Increment the Y segment

X SEGMENT: =

■ File Cü TITLE.xx

Specify the Versatec parameter file File CU OUT

SLTD. SV on chains

-π ¹ .sz (U.;:. Λ.) Inc. - PA-77S

709838/0550

tJ ..j

Rear projection

ECU BKP 7. FR: rear projection crossing

(SUBROUTINE CUBKP)

Measurement of active read task (MREAD)

T? Ij everyone. Calculate ZsHq those in rear projection *

Circle is to be included. Call up CU LTM

Angle: = Φ

Read measurements (in the MREAD task)

\ y

[Call up CUEXP \

V /

EC U EXP 7. SR:

Rear projection (machine language)

Part of the measurement data set to be used interpolate

Field-cell passage, back-projection onto one line at a time by calling the WCS routine in CU WCS ₁ SR

Increment the angle

A.) Ine, -? Λ ~

7 09838/0550

EC UBKP7.FR

Rear projection

BackprojQkttosfsld Standardized by Abi Uf from CUXNM (inüusllQn file ECUEXP7 SR), the in turn, the WCS routine in CL WCS. SR used

Output field

{Return to the retriever

CUARRAY

P 26 47 761.2 Syrvbex (U, 3. A.) Ine. (Appendix B)

- PA-776

f09838 / 0550

Rear projection _t Versatec output program

ECU OUT7, FR

succeed

Identify controlled output

Sampling of 17 data sets by calling up Print CUSCN

try

Einaabe-Rirame ter atei to

Chain RFSCAN.SV

Input file CU OUT

(is not called up as part of the normal reconstruction process )

Accept parameters entered by the operator via the keyboard and output data set at the discretion of the operator

or

[STOP Chain Ct> E3.SV, a Rear projection program in which the operator has to reconstruct the ~ determine the area kirn

F 25 47 761.2
Syntex (USA) Inc "(ül B)

- PA-776

909838/055

SLICE

parameter

DatQi

read

/ Patient ~ [intent \ Jesen

\ i

le Konstruk; tion DatQi iQsen

Normisrungi data

FbrairiGter file up to date

bring

<PätJenten \ intent ) write ^ /

Reconstruction file

to write

File) J

Yes

/ Exit RÜOS MONITOR

909838/0550

APPENDIX A / Page I.

SCANNER SOFTWARE Oopvrlrlrl '■ -. C.

INSTROII

NAfC

HODELZ main program! PRIORITY PURPOSE

Controls data acquisition and output to tape. Provides control of scanner, display and general operating communication.

SCANO subtask priority

OPERAT subroutine priority of the retrieval task Sampling Data Output Utility:

1. opens magnetic tape I / O on channel 15, rewinds.

2. Writes a 12 logical data record (Set) - 3 physical sets.

3. Write a shift resolution.

4. Writes two file ends and resets over one.

5. Rewinds the tape.

6. Automatic error detection - moves back one block and executes (4)

Visual display / keyboard I / O utility:

1. Clears screen and displays patient data on screen.

2. Queries patient data and inserts in intent when released.

3. Condition message with response request.

4. Operation / status message output no response (lines 1 to 7).

δ. Additional data on the last message. 6. Brings the clock display up to date.

Il

T09838 / 0550

ABREAK
subroutine

ks

Console telex pre-rong processing - Procedure "A". Switch off X-ray and exit.

CBREAK
Console Telex Priority Processing Subroutine - Sequence "C". Switch off X-ray, delete BREAKS and exit (Exit).

CONV
Subroutine Converts positive 16-bit integer numbers into right-justified three-word series (chain) according to ASCII (American Standard Code for Information Exchange), padded spaces in front of valid digits with zeros.

CONVS
Subroutine Converts an integer 16-bit two's complement to a right-justified series with a sign according to ASCII, assuming that the decimal digit with the lowest value is to the right of the decimal point.

ENCODER
subroutine

SET
Subroutine Selects and stores selected encoder position register.

Clears the selected encoder position register to zero.

READZ
Subroutine Starts the motor-drive assigned to the selected position register and continues to run until the device is finished, saves encoder position registers at the finished time.

J09838 / 0 55

A / 3

ENGINE
subroutine

Starts the selected position register assigned motor-drive and continues to run until register with transmitted Position matches.

NOXRAY
Subroutine Deletes the X-ray Eiri bit in the drive command word and issues the command to switch off the generator.

XRAY
Subroutine sets X-ray on bit in drive command word and issues command to switch on generator. Checks detector PVF (photomultiplier tube) value for at least 1,000 counts. Returns control to the calling program when the selected PVF has reached it. Deletes the drive word and returns to the error state if the selected PVF has not exceeded the value in eight seconds.

SCAN
Subroutine Starts the linear drive motor in the selected direction and records 13 PVF values in 750 controlled intervals.

REBREAK
Subroutine initializes console breakpoints for ABREAK and CBREAK.

DISPLAY
Subroutine format-free byte output to the display screen,

RDISPLAY
Subroutine format-free byte input from the display keyboard.

RBLOCK
subroutine

Format-free block entry from the display memory for Beehive broadcast operation, terminated by a sequence "C" with blocked console interruptions.
709838/0550

MODEL 2.FR

PURPOSE: This program controls data acquisition and output to tape. It also provides full monitoring and position control of the scanner and furthermore the entire service exchange to create a general set of instructions.

METHOD: It is a program for controlling data acquisition, which as such does not offer any solution or data compression. There are position registers that are tested, in order to arrange the X-ray tube via scanned areas, as well as an A / D conversion of the X-ray intensity _(the sample used for the query. These are the data which are written to tape.

OPERATING INSTRUCTIONS:

1. Insert working tape with writing ring.

2. Write M0DEL2

3. Follow the instructions on the bottom four lines of the display.

4. To return control to the operating system Exit (exit) or, if not acceptable, Control A (process A) to write.

709838/0550

Model 2 ^ input /

Abbot ast Qr

initialize

Patient ■ data form

\ <f

Bard subtask in it

Initialize encoder

both motors above zero

travel

to Fätierr drive

load

Switch off X-ray

Query patient data and wait

709838/0550

P 26 47 761.2 Syntex (U.S.A.) Inc. (Annex A)

PA-77S

Scanner

<Query command and wait

specify Fehlernachrtht

no

Roentgen-

Check cycle

Magnetic tape rewind

Rewind magnetic tape

RDOS

709838/0550

50

P 2-5 47 7G1..2. ■ • Syntax (U.S.A.) e A)

Photo multiple & r a

(ScanA \ scNeifeJ

\ t

^ scan}

ongoing position

to calculate

/ Magnetic tape ^ \ Task /

no

Increment the angular position

Let the rotary drive run

Jfr

Scanner

Ya two Write end of file

(Command , loop .,

709838 / 05B0

P 25 47

ztecc {"J

ANLASiI C /

ΛΝ7ΓΙΟ- (BILDSrIURHV-SOFTWARE

PURPOSE

DISPLAY main program Causes a licensing mediation to determine the shift number and the window DiniensionGn. Calls DSPLY to write out more data, writes. Prefix information and waits for the next command.

DSPLY
Subroutine Starts a task at priority 2, which waits for the address for the Dstenblock to be displayed on the Ramtek (screen). Main task reads the data from disk and sends address to subtask for display on Ramtek.

INPUT
Subroutine Reads teletype input and checks for a valid command. Returns the command number to DISPLAY.

D64
Subroutine Displays a field of 64 χ 64 elements on the Ramtek.

DAN
Subroutine Gives ASCII information for display.

DERS
Subroutine Clears the Ramtek screen.

RMTK
Subroutine Provides the main services for Ramtek including the actual code for exceeding the data to Ramtek and for handling Ranitek interruptions.

709838/0550

C / 2

DSQ
subroutine

53

Write a block of the Grsuskc-Ia In c! <: - r specified body and specified with dcir Intensity off.

DLU
subroutine

Loads the reference board into the Ramtek with values for the gamma correction.

CNVBA subroutine

Sets a binary pure in an ASCII series around.

CNVAB subroutine

DISPLAY.!

Converts an ASCII series into a dinar series.

PURPOSE:

METHOD:

The program outputs the patient resolution file and the Patient data on the Ramtek lOOB display v / i de! ".

Asks the operator for the shift number and then reads out the data. the data file and the intent from the header file and sends it to the Ranitek display again.

OPERATING INSTRUCTIONS:

1. Write display | (display)

2. The program asks for the shift number. Answer with the layer to be displayed.

3. The layer will have a window width of 50 and a center value of 10. The following keys do the following:

^ Elevates window by value used in 0 command is; The default is 10.

4 / Decreases the window by the value used in the O command is; The default is 10.

<- Narrows the window by the value that is used in the O command; The default is 10.

- = y Widen the window by the value » ocr is inserted in the O command; The default is 10.

709838/0550

INPUT:

FAILURE:

0 Pray Ccidienungs- pearls to change ^ rur.g aer used by the above four key values ;.

1. Asks u: r. new shift numbers.

2. Deletes dan screen.

3. Asks the service person to enter one Window according to format, middle text, width,

4. Terminates the Proqran. ^.

1. C4PAT.SC - patient attachment

2. C4ARRAY.SC - patient data file

1. If the shift number is invalid, the question

repeated.

2. If the window width is 0, nothing is displayed. program waiting for the next command.

3. Disk read error - program goes back to CLI.

709838/0550

Si

advertisement

DISPLAY

) Input

Input-f files (

...to open

Delete display \ \ J

Load gamma correction

anranguciiQ F '

Set values

.— "

Specify shift start and end of shift

<Ask the operator for the shift number

Shift function \ intent J show J

V 3

709838/0550

S yntaic (U, 3rd A.) Ine

- Fa-776

advertisement

Window around current value to lift

Windows around

Worth verena en

Windows around

Broaden value

Window around running Lower value

next command With operator hsnster-Miter and - Inquire about the width

Change value for Fensler increase or decrease

Change the value for window narrowing or widening

Clear screen λ J

709838/0550

DJnI 1 -.-. Γ Wi-tK

Di-. '·. ·. ·. i -1, Or D. Gude! ^
'6 Frankfurt .- £. Gr trchenheim 'St! 39

P 26 47 761.2 April 1, 1977

Syntex Inc. Gu / Pi.

PA - 776

The documents originally filed for this application also include appendices A, B and C due to printing difficulties in the laid-open specification are not printed. However, these systems are due to Section 24, Paragraph 4, Sentence 1 of the Patent Act is open to anyone to inspect the files, including making copies.

709838/0550

Claims (8)

20, Ok-tor.e-r 19? R- SYKXEX (U.B.A.) IKC. Case P.A- 7 '.' 5 Ar. Claims j subsequently submitted , 'Axial tCiiiographic system with a scanning device ? ErTaSSLTi;] several amounts of data, which correspond to the transmission or absorption of at least one beam of hard radiation behind a flat layer of an examination object, with a preprocessing device for the recorded Dstcnr.c-ngen, which has an attenuation coefficient for each of several individual liatric elements of the provides planar layer, and _rr: it a Anzeigseinrichtung for reproducing the matrix of Däiripfungskoeffizicnten corresponding to the planar layer "characterized in that formed the sensing means (12) Verarbeituncjseinnchtung (14) and the display device (16) for an independent operation such in that the data acquisition, the processing of the Datenir ^ gs and playback DER attenuation coefficient matrix is independently carried out. 2. System according to claim 1, characterized in that the scanning device (12) is a frame (70) with an opening (72) - ;;? · for receiving the investigation sub; jek "cos (65) _s a hard line] .unr;: 3qii.slle ( 60) and a i n a ^r Rchnen mounted detector (76) vcufaF / c, directed to the the Strohlur ^ -ccuelle inindenytens ha.rter a beam radiation, rt, and that a Drehantrip-b (96, 82) for rotation ! the Rahmeni; -iitcamt clei- Strahluiif-.Oquf \ 1ο and the detector to the OEF faung so forth · · fiücehi ':: int, dr3 rncnV (-; re Datenraengen entcprechend of ¹ Ir anstnission ou ^£ r ^ From or-ptiori of each ray in the smoke object detected by it. 709838/0550 ORIGINAL INSPBCT-ED 264776] 3. System according to claim 1 or 2, characterized in that the radiation source (60) directs a diverging beam (64) of hard radiation onto the detector (76). 4. System according to claim ί or 2, characterized in that the radiation source (60) directs a fan-shaped beam (64) of hard radiation onto the detector (76). 5. System according to claim 2, characterized in that the radiation source (60) directs a diverging, planar, fan-shaped beam (64) of hard radiation onto the detector (76). 6. System according to claim 2, characterized in that the radiation source (60) at least one tightly bundled beam directs hard radiation onto the detector (76). 7. System according to claim 2 or 3, characterized in that the rotary drive (96, 82) an angular displacement practically free of mutual lateral displacement for the frame (70) the beam (64) of hard radiation and the object to be examined (66) causes relative to each other. 8. System according to claim 2 or 3, characterized in that the scanning device (12) has a sliding drive (76, 84) for the lateral Displacement of the radiation source (60) over the opening (72) between successive rotations of the frame (70) by means of the rotary drive (96, 82). 709838/0550