US 3101407 A
Description (OCR text may contain errors)
Aug. 20, 1963 J. D. SHIPMAN, JR 3,101,407
FLUOROSCOPE SYSTEM UTILIZING AN IMAGE STORAGE TUBE 2 Sheets Sheet -1 Filed April 9, 1959 mm mm |.|.l mozmmzmo "Guam JEzoNEoI +5558 6528 2m;
MN SEES? mmnEoIQ a INVENTOR ATTORNEY Aug. 20, 1963 J I JR 3,101,407
'FLUOROSCOPE SYSTEM UTILIZING AN IMAGE STORAGE TUBE Filed April 9, 1959 2 Sheets-Sheet 2 INVENTOR JOH N DANIEL SHIPMAN,"JR.
ATTORNEY United States Patent O 3,101,407 FLUOROSCOPE SYSTEM UTILIZING AN IMAGE STORAGE TUBE John Daniel Shipman, In, Alexandria, Va., assignor to the United States of America as represented by the Secretary of the Navy Filed Apr. 9, 1959, Ser. No. 805,351 2 Claims. (Cl. 250-715) (Granted under Title 35, US. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.
The present invention relates to the -art of producing visible images of a body or object by the fluoroscopic procedure and more particularly to a method and apparatus for producing a visible image of a body or object subjected to a minimum radiation dose.
Heretofore, prior art devices have employed the use of fluoroscopes and X-ray machines wherein a patient can be viewed by the fluoroscopic method and by use of films by subjecting the patient to a large dose of X- rays. Not only is the patient subjected to large doses but in the case of fluoroscopes the physician is also, subjected to the dose. In the fluoroscopic devices, the patient is viewed only while subjected to the radiation which requires simultaneous study of the picture presented. In the X-ray method, using a film, there is a delay in viewing the picture because of the time required to ,develop the picture. Thus the patient is subjected to large doses of radiation and at times, more pictures are required which requires more dosage of the patient or object.
The device of the present invention makes use of a beam of radiation, for example cobalt 60, X-rays, etc, collimated into a narrow fan shaped beam in a plane perpendicular to the patient or object wherein the beam source is moved parallel with the patients body over the required distance to complete the required picture. A number of small radiation detectors are placed side by side to form a detector bar on the opposite side of the patient from the radiation source. The detectors detect the radiation passing through the body and transmits their outputs to the write grid of a memory display tube where :a picture is formed at the memory tube.
Thus the fluoroscopic picture can be studied for long periods of time and the patient is subjected to the radiation only while establishing the memory picture and at a much reduced radiation dose.
It is therefore an object of the present invention to provide a device for observation by radiation which provides a long lasting image for continuous observation.
Another object is to provide a device for observation by radiation which requires small doses of radiation.
Still another object is to provide a device which does not subject the operator or observer of an image to radiation during irradiation.
Yet another object is to provide a device for immediate viewing of the patient exposed to the radiation.
Other object-s and advantages of the invention will 3,101,407 Patented Aug. 20, 1963 Ice The device of the present invention incorporates a radiation source and detection, device which is moved along apposite sides of the body of a patient and electrically coupled to a memory tube to display an image of the patient or object irradiated. The system includes a radiation source of gamma, X-rays or any other suitable source which is collimated into a thin fan-like beam of radiation having a width suflicient to irradiate a patient or desired object. The radiation that passes through the body is directed onto suitable radiation to current conversion devices such as fluorescent crystals closely coupled optically to a number of small photomultiplier tubes which detect the corresponding light emission of the crystals due to the incident radiation passing through the body. The output signal of each tube is then amplified and applied to the write grid of a memory display tube.
' m'n g the subject.
The horizontal and vertical sweeps of the memory tube are appropriately connected in the system such that in the time required to scan the subject a fluoroscope picture is stored line by line in the memory tube and can be viewed directly during scanning as well as after scan- Suitable memory tubes store the image for long periods of time which permits ample study time even while the subject is not being irradiated.
Referring now to the drawings wherein like references refer to like parts there is shown in FIG. 1 a schematic presentation of the device or system. The system includes a radiation source 9 controlled by a conventional control system 10. The radiation from the source is blocked and directed into a thin fan-like beam by a shield 1-1 positioned to prevent passage of radiation except through an aperture 11a. The radiation is adapted to irradiate a subject such as an object or patient, not shown, and the radiation passing through the subject is incident on a detector bar '12 comprising a multiple number of radiation detectors assembled side by side in a horizontal plane with the radiation beam. A suitable detector bar can be formed by any means which produces a current due to excitation by the incident radiation such as semi-conductors, crystals of various types, scintillator's, ionization chambers, etc. For the purposes of illustration, the detection means shown in the present invention comprises closely aligned Nal(Tl) scintillant crystals 13 closely coupled optically to closely aligned photomultipliers v14 (one for each crystal). A suitable photomultiplier tube being a RCA 6472. The output of each photomultiplier tube is supplied in consecutive order hereinafter become more [fully apparent from the following description of the annexed drawing which illustrates to contacts of a commutating device 16 such as a mercury jet switch known as a Deltas-witch made by the Detroit Controls Division of American Standard. A commutator 17 is rotated making contact with each of the contacts 15 wherein the output of the commutator switch is appropriately amplified by a preamplifier 18 and a chopper amplifier Z1 and then applied to the write grid 22 of a memory display tube 23 such as a RCA 6866, Du Mont K1586 or a Hughes Memotron. The information may be stored in devices other than memory display tubes, such as storage tubes with separate display, magnetic'core memories with :a suitable display or other methods. To control the horizontal and vertical deflee-tors of the tube, a horizontal sweep generator 24 is synchronized with the commutator switch sampling the detectors and the vertical sweep is connected with a contact 25 that moves along voltage dividers 26 and synchronized with the movement of the source and detectors across the subject being irradiated.
The detectors and radiation source are moved simultaneously across the subject being exposed and for this purpose a suitable mechanical arrangement is used. For illustrative purposes, an arrangement is shown in FIG. 3 which comprises appropriately positioned idler wheels upon which cables are supported and separately attached to the detector bar and the radiation source and to a motor which takes up or lets out the cables for simultaneously lowering or raising the detector bar and radiation source. As shown, the detector bar and radiation source are guided for vertical movement along standards 31 and maintained in alignment by a key 32 in the sleeve 33 to which the bar is secured and a slot 34 in the standard to prevent rotation about the standard with respect to each other.
The detector bar has attached thereto :a cable 35 which is supported by idler wheels 36 supported by the adjacent structure and is adapted to be wound about a pulley wheel 37 which is rotatable by a shaft 38 which is driven by drive shaft 39 extending from a motor 40 and any suitable drive wheels 41. The shaft 38 is supported at the floor surface by suitable supports and has connected thereto pulley wheels 42 and 43 for respectively controlling a cable 44 connected to the structure 45 supporting the radiation source and a cable 46 connected with a counterweight 47. Cables 44 and 46 are secured to their pulley wheels for opposite takeup and theerfore as the radiation source is raised the counterweight is lower and as the radiation source is lowered the counterweight is raised. The counterweight is not strictly necessary butpermits smoother operation of the motor for movement of the detector bar and radiation source by providing opposite pull on the drive shaft 38 and the motor 40. Cable 44 is connected with the structure supporting the radiation source and is threaded about idler wheels 36 which provides supporting means for the cable from the radiation source support to the pulley wheel 42. The counterweight cable 46 is supported by similar idler wheels 36 and adapted for take-up by pulley wheel 43.
Cables 35 and 44 are connected to their pulley wheels "such that they will take-up with the same directional rotation of the drive shaft and. consequently let out together when the drive shaft is rotated in the opposite direction. The cable 46 is connected to its pulley such that the cable winds up as the detector and radiation source cables unwind to lower the detector and radiation from an upper position to the bottom or lower position. As the detector cable and radation source cable permits the detector and source to be lowered simultaneously, the counterweight will be raised by its cable being wound upon the pulley 43. Consequently, as the detectors and source are moved across the subject to a raised position, the counterweight cable is let out or unwound from its pulley and the counterweight is lowered.
For convenience double acting normally closed switches may be located at the top and bottom of the standard in the path of travel of the radiation source for the purpose of automatically turning the drive motor and the radiation source oil? at the end of travel of the radiation source in each direction. For the purpose of turning off the commutator motor at the end of travel of the detector bar, suitable switches may be located at the top and bottom of the standard in the path of travel of the detector bar. For the purpose of operating the cable drive motor a normally open hand or foot operated switch may be used in the line and a reversing switch is placed in the circuit from the source to the motor in order to drive the motor in opposite directions, the type of reversing switch depending on the type of motor used.
FIG. 2 illustrates one unit of the detector device which includes the detecting crystal 13 and a photomultiplier tube 14 coupled optically thereto. As shown, the crystal is mounted on the side of the tube adjacent to the photocathode and is provided with an aluminum cover 19 for protection from atmospheric and other efliects. For the purposes of operation the detector bar comprises 119 crystals and photomultiplier tubes in alignment such that the bar formed lies within the beam from the radiation source and is of equal width.
In operation, the electrical systems are turned on for i a short warmup period and the subject to be viewed is positioned between the detector bar and the radiation source. Assuming that a foot operated switch is used, the reversing and foot operated switches to the drive motor are positioned near each other in a position such that the operator may view the subject. Having set the reversing switch in the correct position and assuming the radiation source and detector bar to be positioned at the bottom of the standard, the foot operated switch is pressed and the motor is made operative. The motor will take-up the cables to the radiation source and detector bar thereby moving the source and detector simultaneously across the subject. The radiation is confined to a thin fan-shaped beam which is continuously incident on the detectors as the apparatus is moved along its path. The intensity of radiation incident on the individual detectors depends on the subject irradiated land the amount of radiation that passes through the subject. The radiation incident on the NaI(Tl) fluorescent crystals causes fluorescence in the crystal proportional to the incident radiation and consequently the photomultiplier tubes adjacent the crystals produces a voltage proportional to the fluorescence of the crystals. The voltage produced by the individual photomultiplier tubes are fed to their respective contacts on the mercury jet switch. The commutator of the switch scans the switch contacts in consecutive order from one side to the other in the time taken by the bar to move a distance equal to the width of the crystal in the direction of travel and feeds the output signal of the photomultiplier tubes through suitable amplifier equipment to the write grid of the memory tube. The horizontal sweep of the memory tube is synchronized with the commutator switch sampling the detector contacts to provide the horizontal sweep signal. The vertical sweep of the memory tube is synchronized with the movement up or down of the source and the detector bar. Thus in the time required to scan the subject or to move the source and detector bar throughout its entire movement, a fluoroscopic presentation of the subject is stored in the memory tube and can also be viewed while being stored line by line as well as for a long period after stonage.
The radiation used depends on the subject matter being studied. For instance for most medical studies X-rays would be used. For studies with gamma rays cobalt 60 could be used. When using cobalt 60 the cobalt 60 would be placed in a lead or tungsten alloy shield container with a covered slit therein through which the radiation would emerge to irradiate the subject. In use the lead shield cover would be removed and the source moved across the subject simultaneously with the detector bar as described above. As an example in using a cobalt 60 source and irradiating the same subject matter, the system of the present invention required a dosage of 0.000025 roentgen whereas the old type of device used for flooding the entire subject at the same time using a large NaI(Th) screen and a closed television system required 0.100 roentgen or 4000 times as much radiation as required for the present device. The results obtained being of equal quality.
The device and system of the present invention provides a simple means for obtaining a fluoroscopic picture of a subject with small dosage of radiation wherein only a small portion of the subject is subjected to the radiation at any one instant. Further the fluorescent presentation of the present device can be retained and viewed for long periods after being irradiated and does not subject the viewer or workers to any radiation.
Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.
What is claimed is:
1. In a system for presenting a fluoroscopic presentation of a subject adapted to be irradiated which comprises a radiation source arranged to emit radiation across a space in which a subject to be irradiated is positioned for examination, means for confining said source of radiation emitted across said space to a thin fan-like beam in a plane perpendicular to a plane through said source, a radiation detector means positioned in alignment with said beam in the same plane with said radiation source and adapted to receive incident radiation, said radiation detector means comprising a plurality of aligned crystals adapted to effect translation of said incident radiation into corresponding light pulses, means positioned in optical alignment with said crystals for receiving said light pulses and translating light into electrical signals in proportion to said incident radiation, each of said signals being dirooted to separate contacts of a switch means, an image presentation storage tube, said tube comprising an electron intensity control grid and vertical and horizontal beam deflection plates controlled by vertical and horizontal sync generators, means for scanning said separate contacts and feeding said electrical signals to said grid of said memory tube, said signals controlling the intensity of the electron beam of the memory tube, means for simultaneously moving the radiation source and detector means in planes parallel to each other across the space in which the subject is adapted to be placed and means for controlling said vertical and horizontal sync generators as said radiation source and detector means are moved across said subject.
2. In a system for presenting a fluoroscopic image presentation of a subject adapted to be irradiated with a radiation source which comprises an image storage tube, said tube comprising an electron control grid, an image storage element operative by electron excitation and vertical and horizontal deflection plates controlled by vertical and horizontal sync generators, a radiation source arranged to emit a thin fan-like beam of radiation across a space in which a subject to be irradiated is positioned for examination, a radiation detector means positioned to receive incident radiation, said detector means comprising a plurality of closely aligned crystals adapted to effect translation of incident radiation into light pulses in proportion to said incident radiation, a plurality of photomultiplier tubes adapted to be positioned in optical alignment with said crystals to view said light to eflect translation of said light pulses into electrical signals in proportion to said light pulses incident on said photomultiplier tubes and adapted to feed said electrical signals to separate contacts of a switch means, said switch means comprising a commutator adapted to scan each of said contacts to feed the signals of each photomultiplier in consecutive order to the control grid of said storage tube to control the intensity of said electrons incident on said storage element, means for simultaneously mov ing said radiation source and detector means in planes parallel to each other across the space in which the subject is adapted to be positioned, and means for controlling said vertical and horizontal sync generators as said radiation source and detector means are moved across said subject.
References Cited in the file of this patent UNITED STATES PATENTS 2,281,931 Frank May 5, 1942 2,680,199 Abel June 1, 1954 2,730,566 BartoW et a1. Jan. 10, 1956 2,837,657 Craig June 3, 1958 OTHER REFERENCES Moon Amplifying and Intensifying Fluoroscopic Image by Means of a Scanning X-Ray Tube, Science, vol. 112,
pages 389-395, October 6, 1950. r