Patent GB-790773-A (GB)
Title: Equipment used for medical therapy and research using radioactive matter as a source of radiation
Inventor: STEIN STEPHEN
IPC: G21F5/02
Filed: 1954-11-26
Abstract: 790,773. Radiation apparatus. NUCLEAR ENGINEERING, Ltd. Nov. 23, 1955 [Nov. 26, 1954], No. 34329/54. Class 98(1) Apparatus using radiations from radioactive substances consists of a container for a source pencil of radiation formed of heavy metal and mechanism for moving the radioactive source from a shielded or enclosed position to a partially exposed operative position, wherein the source pencil consists of la radio-active source attached to one end of a heavy bar of sufficient length to provide the required degree of shielding and wherein the bar is mounted in a drum of heavy metal mounted on bearings to rotate about its axis in a steel shell containing a large mass of shielding metal. As shown in Figs. 1 and 2, the source pencil, consisting of a radio-active source 1 mounted at the end of a rod 2, is inserted in the bore of a drum 3, the axis of the source pencil being parallel with but spaced from the axis of the drum 3. A "light pencil", consisting of a rod 4 with a lamp 5 mounted at the end thereof. is accommodated in a bore in the drum 3 in a position symmetrical with that of the source pencil 2. The drum 3 is rotatable about its axis in a bore within the filling 9 of a shell 8. A conical aperture 10 in the shell 8 and filling 9 extends from the vicinity of the lamp 5, and by rotation of the drum 3 on its bearings 6, 7, the radio-active source 1 may change places with the lamp 5. Rotation of the drum is effected by an electric motor, the rotor of which consists of a conducting ring 14 connected to the drum 3, while the stator of the motor consists of laminations 15 and windings 16. From the position .shown in Fig. 2, the drum 3 rotates, when the windings 16 are energized, through half a revolution until pneumatically cperated stops between the drum and the casing bring the drum to rest. The windings 16 are so designed that current may continue to flow therein with the motor stalled. During the rotation of the drum, a spring 22 is wound, and when the windings 16 are de-energized this spring causes the drum to return to its initial position, in which further' pneumatically operated stops come into play. While it is not possible to expose the source 1 except by energization of the motor, a handle 24 is provided so that the source may be shielded manually in emergency. The rotation of the drum 3 also operates microswitches for actuating interlock devices, warning lights &c. As shown in Fig. 5, the source container may be rotatably mounted in a yoke 27, which is carried by a 'horizontal telescopic arm 28 rotatably mounted in a carriage 29 supported in a part 30 so that it may be raised and lowered in the vertical direction. The movements of the head are controlled from a pedestal 31 having control switches 36 and a foot pedal 37, and adjustable stops are provided for each movement in order that the beam of radiation emerging from the head may be restricted within a definite solid angle. The motor which energizes the source can only be operated from a control desk 38 outside a radiation-proof harrier if interlock switches are closed, such as a switch in the treatment room door 39, and an interlock which is closed when the timing mechanism has been set. 'The source is exposed by energizing the motor by pressing a button on the control panel, the supply being interrupted after a set period by a timing mechanism 41. An exposure recording mechanism may be provided on the control panel, and an audible signal may be given during the time that the motor is energized. A push button is provided for interrupting the current of the motor to terminate the exposure at an time independently of the timing mechanism. Further, a switch is provided to reverse the motor actuating the drum 3, for use in the event of a failure of the spring mechanism 22. If desired, a system of key interlocks may be provided, so that the source cannot be exposed from the control desk 38 while power is switched on to the mounting control gear on the pedestal 31. Coloured lamps 33, which indicate that the source is shielded, moving or exposed, is provided on pedestal 31, control desk 38 or close to the treatment room door 39. When the apparatus is used to treat a live subject, a pressure switch may be arranged in such a way as to be actuated if the subject should move, in order to switch off the power to the motor controlling the drum 3. The treatment head may be fitted with standard accessories such as applicators. diaphragms and pointers. The conical aperture 10 may be closed by one or more shielding blocks so that matter mounted on these blocks may be irradiated without risk of exposure of an operator. In order to exchange the radioactive source for another, the cover plate 13 (Fig. 2) is removed and a shielding plug 48 is withdrawn. A transport container is then aligned with the rear end of the drum 3 and a cable connection from a transport container is secured to the source pencil 2. A thick wall cylinder forming part of the shielding of the transport container is moved to surround the gap between the head and the container and the source pencil is withdrawn into the transport container. A new source pencil may be similarly loaded into the drum. The Provisional Specification also refers to a reflector on the applicator for positioning; further remote controls and indicators; and an applicator to be attached to the treatment head for research purposes.