UK Patent Application (,„GB „,, 2 109 626 A (21) Application No 8220258 (71) Applicant (54) Cold cathode diode X-ray (22) Date of filing 9 Jul 1979 Butler-Newton Inc., source Date lodged 13 Jul 1982 (USA—Massachusetts), (30) Priority data 389 University Avenue. (57) A cold cathode diode X-ray source (31) 922982 Westwood, for radiation imaging, especially (32) 10 Jul 1978 Massachusetts 02090, (33) United States of America United States of America computed tomography, comprises a (US) (72) Inventors rod-like anode (48) and a generally (43) Application published Gerald Cooperstein, cylindrical cathode (52), concentric 2Jun1983 Richard C. Lanza, with the anode. The spacing between (51) INT CL3 A. Robert Sohval anode and cathode is so chosen that H01J 35/04 (74) Agent and/or address for the diode has an impedance in (52) Domestic classification service excess of 100 ohms. The anode may H1D 17D 18L1 18LY2A John Orchard and Co., be of tungsten, or of carbon with a 2X 32 7X 9G 9Y Staple Inn Buildings tungsten and carbon coating. The North, (56) Documents cited cathode is insulated from a spacing None High Holborn, conductor by a high voltage insulator (58) Field of search London, which is shielded (41a) from the UV HID WC1V7PZ (60) Derived from Application formed during X-ray production at the No. 7923921 under anode. Section 15(4) of the An array of such diodes may be Patents Act 1977 used with a closely packed array of detectors to produce images of rapidly moving body organs, such as the beating heart. The drawings originally filed were informal and the print here reproduced is taken from a later filed formal copy. This print takes account of replacement documents later filed to enable the application to comply with the formal requirements of the Patents Rules 1978. 210362S FIG.2 FROM PULSE GEN. 22 FROM VAC. PUMP 24 2109626 2ft FIG. 5 FIG.4 CHARGING CIRCUIT HVOC •rrrg-cgg POWER I SUPPLY 72' ^r TRIG SIGNAL 2109626 3/4 rC D—C D- ~C D- FROM Q- CIRCUIT o- •36 76 90 FIG. 7 TRIG SIGNAL 40 KV 20KV UJ CD § § TIME (msec)' FIG.8 2109626 FIG. 9 10 GB 2 109 987 A 1 SPECIFICATION 65 parts of the picture and confuse the radiologist. Radiation imaging apparatus More importantly, however, because they are so slow, such prior scanners are incapable of This invention relates to a radiation imaging achieving a rapid sequence of images of dynamic apparatus. It relates more particularly to organs such as the beating heart. 5 apparatus of this general type which employs 70 More recently, there has been developed a CT stationary X-ray source and detector arrays scanner having a fixed circular detector array capable of acquiring multiple ultrafast scans per which encircles the patient's body and a radiation second to facilitate the dynamic study of moving source which rotates about the body illuminating human organs such as the beating heart. While a selected plane or slice thereof with a radiation 10 the invention has many applications, it has 75 fan beam. The unabsorbed radiation is detected particular utility in connection with computerized by a different set of detectors for each source tomographic (CT) scanners. Accordingly, it will be position and the information from all ofthe described here in that context. detectors is correlated to produce an image of The computerized tomographic (CT) scanner is that body slice. 15 a fairly recent development which facilitates 80 While this prior scanner is advantaged in examining a body by means of high energy having a fixed detector array, it still requires the radiation such as X- or gamma-radiation. Using mechanical structure to rotate the source in order such apparatus one can produce radiographs in to produce usable information. Accordingly, it also any convenient form such as a picture on a has a relatively slow scan time, e.g., several 20 cathode ray tube or other image forming device or 85 seconds for an accuracy of ±.5% or better which a photograph of such a picture. is too slow to produce snap shot images of Scanners of this type direct radiation from an dynamic organs such as the heart. Moreover, it is external source through the part of the body of still relatively complex and expensive because it interest The radiation is in the form of a set of requires the mechanical structure and motive 25 beams which are directed from a plurality of 90 means necessary to rotate the source. A scanner different directions toward one or more radiation of that type is made by American Science and detectors disposed on the opposite side of the Engineering Inc. and is disclosed in that body part from the radiation source. Each beam is company's publication ASE-3869, dated April detected after it has passed through the body and 1976 entitled Computerized Tomographic 30 the outputs of the detectors are processed and 95 Scanner. correlated by a computer in such a way as to determine the absorption or transmission co- It has also been proposed to construct a efficients of the elements in a two dimensional scanner in which both the source and the detector matrix of elements disposed in a plane of the array are fixed to avoid some of the aforesaid 35 body. This processed information is then used to problems. Two different species have been produce a picture of that plane or slice through 100 proposed. In the first, presently under the body. construction at the Mayo Clinic, Rochester, MN, In the original type CT scanner made by EMI the source array consists of a fixed array of Limited, the body to be examined is inserted in an separate X-ray tubes situated on a semicircle 40 aperture in a scanning and locating structure around the patient's body. These tubes are pulsed which structure supports a radiation source and 105 in sequence to develop a rotating radiation beam detector means therefor on opposite sides of the which illuminates multiple slices ofthe patient's aperture. The source and detector means are body. The emergent radiation is then detected by movable back and forth on the structure so as to a fixed semicircular array of detectors 45 scan the radiation laterally across the body in a diametrically opposed to the radiation source. The plane and the structure is also rotatable around 110 signals from the detectors are then processed to the body about an axis perpendicular to that develop the picture of the body slice. plane. A scanner such as that is shown, for While this arrangement has no moving source example, in U.S. patent 3,919,552. and detector structure, it is extremely expensive 50 The main problem with that prior scanner is because in order to obtain a resonably good that the radiation source and detector arrays and 115 picture, as many as 28 separate X-ray tubes the supporting structure therefor are relatively complete with supporting circuitry and shielding massive and their movement relative to the body are required. Further, these tubes are relatively as described above requires motive means and bulky so that the different source positions are 55 other ancillary equipment which makes the necessarily spaced relatively far apart. overall apparatus relatively complex, massive and 120 Consequently, the resultant picture does not expensive. Also because the body is scanned contain as much information as it should. To mechanically, the scanning operation is slow. compensate for the small number of source Resultantly, a relatively long time, i.e. many positions, the device may have to be rotated 60 seconds, is required to complete a scan in order to slightly during the scan. This requirement, which develop a useful image of a body slice. 125 partially negates the advantages afforded by a Consequently, movements ofthe patient's organs stationary scanner, will add to the mechanical or body during the scan time introduce artifacts complexity and also increase the scan time of the into the resultant picture which may obscure device. 10 GB 2 109 987 A 2 The other proposed species of stationary for a sequence of images ofthe beating heart. scanner described in The Journal of Computer A further object of the invention is to provide a Assisted Tomography, Vol. 1, No. 4 dated October cardiac CT scanner which should accomplish both 1977 employes a fixed radiation source in the static and dynamic tasks without resorting to 5 form of an electron beam gun oriented along the 70 cardiac gating techniques. patient axis. A ring of X-ray emitting material A further object of the invention is to provide a encircles the patient as does an adjacent fixed CT scanner which is relatively compact. circular detector array. The beam from the A further object of the invention is to provide electron gun is deflected in a circle so that it such radiation imaging apparatus which has a 10 scans around the target ring causing that ring to 75 relatively low input power requirement. emit X-rays radially inward toward the patient. Still another object is to provide an improved The radiation emerging from the opposite side of pulsed X-ray source capable of producing a the patient is detected by the detector array and relatively constant optimized radiation output for the detector signals are processed to develop the an appreciable time interval. 15 picture ofthe selected slice through the patient's 80 Another object is to provide a compact X-ray body. source having a relatively long operating life. While this type of scanner may have a potential A further object is to provide such a source scan time which is fast enough to depict the which facilitates obtaining relatively high contrast beating heart in real time, it would be extremely radiation images ofthe body.