Computed tomography apparatus

90.22 - Apparatus based on the use of X-rays or of alpha, beta or gamma radiations, whether or not for medical, surgical, dental or veterinary uses, including radiography or radiotherapy apparatus, X-ra tubes and other X-ray generators, hi h tenslon generators, control panels and des s, screens, examination or treatment ta les, chairs and the like (+). Z % - Apparatus based on the use of X-rays, whether or not for medical, surgical, dental or veterinary uses, including radiography or radiotherapy apparatus : 9022.13 - - Computed tomography apparatus - - Other, for dental uses 9022.14 - 9022.12 9022.19 - Other, for medical, surgical or veterinary uses - - For other uses - Apparatus based on the use of alpha, beta or gamma radiations, whether or not for medical, surgical, dental or veterinary uses, including radiography or radiotherapy apparatus : 9022.21 9022.29 9022.30 9022.90 - - For medical, surgical, dental or veterinary uses - - For other uses - X-ray tubes - Other, including parts and accessories (I) APPARATUS BASED ON THE USE OF X-RAYS The fundamental element of this apparatus is the unit containing the X-ray tubes. This unit, which is usually suspended or mounted on a pedestal or directing or elevating mechanism, is fed with appropriate consisting of an assembly of transformers, rectifiers, etc. In most charactenstics of X-ray apparatus vary according to the use for example : (A) X-ray apparatus used in diagnosis. These depend on the facts that X-rays can penetrate bodies which are impervious to ordinary light and that their absorption increases with the density of the bodies traversed. They include : (1) Radioscopic (fluoroscopic) ap aratus. X-rays which have traversed the organ under examination are made to cast a s adow on a screen; the varying densities of the shadow image represent the state of the organ. ?I (2) Radiographic a paratus. After leaving the body under examination, the X-rays strike a photographic p ate or film and are recorded thereon. The same apparatus may be used for radioscopy and radiography. P (3) Apparatus consisting of X-ray apparatus combined with a specially designed camera. These photograph the image of which is produced on an X-ray screen mounted in the camera itself. Provlded the ap aratus and specigised camera are presented at the same time, they are to be class1!i ed to ether in ths heading even if they are separately acked for convenience of transport. ieparately presented cameras, however, are classi led in heading 90.06. P (B) Radiotherapy a paratus. Both the enetrating power of X-rays and their destructive effect on certain iving tissues are use in the treatment of many diseases, e.q, certain skin diseases and certain tumours. This treatment is known as " supefltcial ' or " deep " according to the depth reached by the rays. f' d' (C) X-ray apparatus for industrial use. There are man industrial appIications of X-rays. They are used, for example, in metallurgy to locate b isters or to check the uniformity of alloys; in engineering to check the accuracy of assemblies; in the electrical industry to check heavy cables or frosted glass lamps; in the rubber industry to check the reactions of the inner casings of tyres (e. ., stretching of canvases); in various industries for checking or measuring the thickness o materials. For all these various ap lications the apparatus enerally resembles that used for diagnostic purposes described a ove, except that it may f e equipped with adaptors and ancillary equipment for particular purposes. ?' d g The heading also covers : (1) Special apparatus (X-ray diffraction and X-ray spectrometry equipment) used for the examination of the crystalline structure as well as the chem~calcorn osition of materials; the X-rays are diffracted by crystals and then made to fall on a p otographic film or an electromc counter. R (2) Apparatus for radioscopic examination of bank notes or other documents. (II) APPARATUS BASED ON THE USE OF ALPHA, BETA OR GAMMA RADIATIONS Alpha, beta or gamma radiations emanate fiom a radioactive substance with the property of emitting radiations by spontaneous transformation of its atoms. This radioactive substance is placed m a container, normally of steel coated with lead (bomb), which has an aperture designed to let the radiations pass in one direction only. Gamma radiations can be used for much the same purpose as X-rays. The following types ma be distinguished, according to the radiations employed and the use for which they are designed? x (1) Therap apparatus, in which the radioactive source is a charge of radium, radio-cobalt or some ot er radioactive isotope. (2) Apparatus for radiological examinations, used mainly in industry for checking metal parts, etc., without damaging their structure. (4) Fire alarms incorporating smoke detectors containing a radioactive substance. The heading does not cover instruments and apparatus which are not designed to incorporate a radioactive source and which mere1 measure or detect radiation even when such instruments are calibrated in arbitrary terms (heading 60.30). (110 X-RAY TUBES AND OTHER X-RAYGENERATORS, HIGH TENSION GENERATORS, CONTROL PANELS AND DESKS, SCREENS, EXAMINATION OR TREATMENT TABLES, CHAIRS AND THE LJKE This group includes : (A) X-ray tubes. These are devices in which electrical energy is transformed into X-rays. The characteristics of such tubes vary according to the use for which they are designed. They consist essentially of a cathode from which the electrons are emitted, and a target: (anti-cathode or anode) on which the electrons impinge, thus causing it to emit X-rays. In some cases, the tubes also have a number of intermediate electrodes for accelerating the stream of electrons. The electrodes are mounted in a tube or container, usually of glass, with the appropriate electrical contacts. The tube is often mounted in an electrically insulated metal container filled with oil. Sometimes the tube is gas filled, but more usually it is maintained at a high degree of vacuum. The heading excludes glass envelopes for X-ray tubes (heading 70.11). (B) Other X-ray producing ap aratus, e-g., apparatus incorporatin a betatron which greatly accelerates the stream of e ectrons and so produces X-rays o a very high penetrating power. Betatrons and other electron accelerators not adapted for the production of X-rays nor incorporated in X-ray apparatus are excluded (heading 85.43). P F (C) X-ray screens. Radioscopic screens are fluorescent surfaces on which the radiations are received. The active surface usual1 consists of barium cyanoplatinate, cadmium sulphide or cadmium tungstate. They are ofren also coated with a lead-glass facin . Some screens, known as intensifymg screens, produce an image which consists of actinic ight that adds to the density of the photographic image formed purely by the X-rays. f (D) X-ray high tension generators. These incorporate a transformer and rectifying valves mounted inside an insulatin screen; they also have detachable high tension contacts for making connections to the g r a tube. It should be noted that this heading is restricted to generators which are specialise for use with X-ray apparatus. i? (E) X-ray control panels and desks. These inco orate devices for controlling the exposure 3' time and voltage, and often also include a osirneter forming an integral part of the apparatus. It should be noted that this heading is restricted to panels and desks which are specialised for use with X-ray apparatus. (F) Examination or treatment tables, chairs and the like specialised for X-ray work, whether designed to be incorporated in the X-ray a paratus or to form separate articles. Provided they are excIusively or rimaril designe for use with X-ray ap aratus, such tables, chairs, etc., remain classifie in h s eading even if presented separate y; but tables, chairs, etc., not specialised for X-ray work are excluded (usually heading 94.02). 8- - E ?i' f This heading also includes lightning arresters based on the principle of radioactivity. PARTS AND ACCESSORIES Subject to the provisions of Notes 1 and 2 to this Chapter (see the General Explanatory Note), parts and accessories identifiable as bein solely or principally for use with X-ray apparatus, etc., are also classified in this heading. Suc parts and accessories include : % (I) Applicators, usually lead-lined, for fitting to the X-ray tube port or radioactive " bomb "; they are sometimes called " localisers ". (2) Electric incandescent centring devices, used particularly in radiotherapy to check the area treated, by direct si ting on the skin. Like the previous accessories, these devices are usually mounted on tf' e outlet port of the X-ray tube or of the " bomb ". (3) Protective casings of lead-glass or of other substances based on certain salts opaque to X-rays. These casings are placed around the X-ray tubes to protect operators against h& radiations. (4) Lead covered o r lead-glass protective screens o r shields for placing between the operator and the X-ray tubes. The heading does not, however, cover protective devices designed to be worn by the o erator, such as overalls or gloves oflead-filled rubber (heading 40.15), or lead-glass goggles (heading 96104). The heading also excludes : (a) Radium needles, and tubes, needles and the like containing other radioactive materials (Chapter 28). (b) Photographic plates and film (Chapter 37). (c) Kenotrons and other rectifjring tubes or valves, used in power supply units for X-ray apparatus (heading 85.40). (d) Apfaratus for examining .radiophotographs (including image projectors) (heading 90.08 or 90.10), an apparatus for developing radiographc or radiophotographic photographs (headlug 90.10). (e) Medical apparatus for application of ultra-violet or infia-red rays (actinotherapy) (heading 90.18). (f) Instruments for measuring or detecting alpha, beta, gamma or X-radiations; these fall in heading 90.30, unless incorporated in radiology apparatus.

Subheading Explanatory Note. Subheading 9022.12 This subheading includes so-called whole-body computed These are radiodiagnosis systems The regions of the for wholebody examination by electron~cbody-section attenuation of the body are scanned by an X-ray beam in individual X-rays in the body 1s measured by hundreds of detectors arranged annularly around the tunnel in which the patient lies on a table. The system's own automatic data processin machine converts the data fkom the sensors into an image which is displayed on the system monitor. Ti? e tomographic images are usually photographed by a special camera incorporated in the system and if necessary they are stored electromagnetically.