US2793296A

US2793296A - Rotational radiation therapy system and unit

Info

Publication number: US2793296A
Application number: US325547A
Authority: US
Inventors: Jr Oscar S Peterson
Original assignee: Individual
Current assignee: Individual
Priority date: 1952-12-12
Filing date: 1952-12-12
Publication date: 1957-05-21
Anticipated expiration: 1974-05-21

Description

May 21, 1957 o. s. PETERSON, JR

ROTATIONAL. RADIATION THERAPY SYSTEM AND UNIT Filed Dec. 12. fl952 2 Sheets-Sheet 1 Oscar 8. Pefersbn, Jr.

IN VEN TOR.

May 21, 1957 o. s. PETERSON, JR

'ROTATIONAL RADIATION THERAPY SYSTEM AND UNIT 2 Sheets-Sheet 2 Filed Dec.

Wm M n m WW 9 m 3, a n m l W F r a v. C B S 4 o 0 E s u w a. M Z w 0 2 0 m United States Patent ROTATIONAL RADIATION THERAPY SYSTEM AND UNIT Oscar S. Peterson, in, Burlington, Vt.

Application December 12, 1952, Serial N 0. 325,547

18 Claims. (Cl. 25061.5)

This invention relates to radiotherapeutic or radiographic apparatus and it has for its primary object to so improve transradiation equipment for irradiating diseased or affected tissues or organs located at a certain depth after having passed other unafiected tissues or organs that the doses received by said last named unaffected tissues or organs are smaller than those received by the diseased or affected tissue or organ. It is more specifically a main object of the invention to irradiate diseased or otherwise affected tissues or organs with a dose which is normally harmful to the normal cellular structure of tissues and organs while at the same time keeping such harmful dose from those tissues or organs which are closer to the surface and therefore are closer to the source of radiation or which surrounds the spot to be treated and are located in the path of the rays with which the .aifectedtissues or organs are irradiated.

As is well known, radiation of all kinds, including X-ray radiation, may be harmful, to the tissues of the body and the treatment of a spot within the body with a dosage which is destructive to certain cells is limited by the amount of dosage which can be tolerated by the intervening tissues or organs located between the diseased or affected tissue or organs and the source of radiation. These intervening tissues or organs have to be considered mainly because of the smaller distance from the source of radiation, the radiation received, as well known, increasing inversely with the decrease of the distance according to a square law. Thus the tissues which are not under treatment but which are at less distance from the source of radiation than the treated tissues receive a considerably higher dosage than the deeper tissue. The dosage tolerated by these tissues thus limits the dosage which can be applied.

As it is clear to the therapist that this is a very serious limitation preventing in some cases effective treatment several proposals have been made to overcome this limitation, one of these ways consisting in the use of a plurality of X-ray sources, for instance, located at different points, but all focussed on the same spot for irradiating the spot to be treated alternatively. This method has been termed the multiportal method. Another proposal made is to rotate the patient during the treatment. As in order to produce an eflicient treatment the relative position of the spot to be treated and of the source :of radiation must be absolutely fixed, this is only possible if the patient is very securely lashed to the supporting structure. This is however a very disagreeable and frightening experience for the patient and moreover it is not satisfactory for the therapist in the desired degree, because, under the influence of the gravitational pull, the position of the inner organs of the human body changes somewhat when the body is brought into different positions, and the change is sufficiently marked to impair the result.

It has further been proposed in a rather theoretical way to cause the source of radiation to perform revolutions around the patient, but no equipment has so far been proposed to carry such a method into effect in a practical manner. The equipment as far as considered is not only extremely complex and cumbersome, but has so many disadvantages that this type of equipment was never actually used. The equipment which has been proposed also precludes adjustment of the source of radiation which runs on fixed tracks around the patient and it requires very special devices for supporting the patient on account of these tracks. Moreover the treatment is essentially limited at any one session to a single plane.

The invention essentially consists in providing means for producing a movement of the source of radiation while keeping a collimated beam centered on a single spot within a patient stretched out in a horizontal position on an ordinary stretcher, bed or table.

Further the invention consists in equipment of this type which does not encumber or restrict the use of the floor space below the patient so that the latters position may be adjusted relatively to the source of radiation much in the same way in which the patients position is adjusted at the present time.

The invention further consists in providing equipment which is itself easily adjustable in all directions, including the radial direction, and in adjusting the distance of the source of radiation from the spot to be treated, said adjustment also including the direction at right angles to the plane of rotational movement of the source of radiation and further including the angular inclination of the beam relatively to said plane.

These adjustments greatly facilitate the pointing of the beam towards the exact point to be treated and they also permit to treat an area which is larger than the collimated beam. Moreover they do not interfere with the normally provided mechanism for straight line adjustment of the source of radiation in three directions at right angles to each other.

According to the invention the rotational movement has essentially the character of an oscillation covering an are which is smaller than 360 and in most cases approximating only 180 and the movement around the spot to be irradiated is produced by simultaneously subjecting the support of the source of radiation to a plurality of movements at varying speeds in two directions in a plane intersecting the longitudinal axis of the support carrying the patient.

This movement, according to the invention, may further be supplemented by a movement at right angles to the aforesaid two directions.

Further, according to the invention, the distance between the spot to be irradiated and the source of radiation may be changed during the rotational or oscillatory movement in order to compensate for the different thickness of intervening tissues or organs in different directions so as to produce isodosage, or equal doses per time unit, during the rotational movement of the source of radiation around the spot to be radiated, or so as to produce any other desired variations in dosage which may be required during such rotational movement.

It is also an object of the invention to adapt the mechanism in such a way that it may be used in connection with existing equipment with the least possible change in this equipment and without interference with the normally provided functions of this equipment.

Further features and objects of the invention connected with said features will be stated in the detailed specification.

The invention is illustrated in the accompanying drawings showing one embodiment thereof by way of example. It is however to be understood that the showing is purely diagrammatical and that :the drawing essentially intends to illustrate the principle of the invention and the best mode of applying said principle. The diagrammatic illustration of the invention is largely based on existing equipment and it will be clear to the expert skilled in this art that this equipment is changeable and that therefore the illustration which has been provided may be changed without essentially departing from the principle of the invention.

In the drawings:

Figure 1 is a diagrammatic elevational view of an X- ray equipment to which certain parts have been added in order to operate the equipment in accordance with the invention.

Figure 2 is a diagrammatic illustration of the movement of the X-ray tube around the marked spot the circle in dots and dashes indicating the position of the center of the X-ray tube in the event that the movement of the tube around the spot to be irradiated is a circle.

Figure 3 is an elevational sectional side view of the equipment illustrated in Figure 1 the section being taken along the line 3--3 of Figure l.

Figure 4 is a fragmentary perspective view of the X-ray supporting equipment.

Figure 5 is an elevational diagrammatic view of the control apparatus used for controlling the movement of the X-ray tube.

Figure 6 is a plan view of the controller.

Figure 7 is an elevational sectional view of the controlling apparatus, the section being taken along line 77 of Figure 5.

Figure 8 is a perspective view of a detail.

Figure 9 is a diagram of the connectionsbetween the synchro or Selsyn units.

As above explained the invention consists in providing means for moving the X-ray tube or other source of radiation during a therapeutic treatment in order to treat the desired spot with the maximum dose which can be applied to it, while maintaining the dose on other spots which are incidentally radiated together with the treat ment spot, especially the spots which are closer to the source of radiation than the treatment spot, at relatively low levels. The mechanical principle which is applied includes means adapted to fulfill the above explained conditions and it consists in moving the X-ray tube or other source of radiation constantly around the treatment spot, which has been established by medical diagnosis and which therefore receives radiation during the entire treatment period, with a definite velocity, while those irradiated tissues or organs which surround the treatment spot and especially those which are located between the source of radiation and the treated spot change continuously during such movement. The tissue or organ on the treated point therefore receives the full dosage intended for it, while the surrounding and especially the intervening tissues or organs located in the path of the rays receive a much smaller dosage which is a mere fraction of the full dosage applied to the treatment point.

It has further been explained that while the simplest form of the arrangement thus obtained calls for a circular movement of the source of radiation around the treatment spot during which the distance between the point of treatment and the source of radiation is maintained at a constant value, conditions may be such that it is preferable to change the distance between the source of radiation and the point of treatment during the movement of the former to maintain an equal intensity of radiation or isodosage, notwithstanding the unequal thickness and absorptive properties of the tissues or organs which have to be passed by the rays. Such an unequal distance may also be desirable for other physiological or pathological reasons connected with the particular treatment.

The particular path along which the source of radiation should move is preferably selected individually by providing guiding means which produce the guiding of the source of radiation alongthe path and its movement s along said path with a speed which is defined by the above conditions.

The general arrangement has been shown in a diagrammatic manner and in its simplest form in Figure 1, which arrangement will best illustrate the principle on which the invention is based.

The patient to be treated is stretched out on an ordinary stretcher or bed 10 or on a movable table, the position of the patient being indicated at P. The cross marked S indicates the spot within the patients body which is to be treated by means of radiation.

The treatment is carried out by means of the source of radiation which in this case is a rotatably mounted X-ray tube 15 the ray exit window and ray exit cone or funnel 16 of which is turned towards the spot S to be treated.

The source of radiation indicated at 15 by way of example as an X-ray tube, may of course be of a quite difierent type and may consist of a radioactive substance or of any other source for therapeutically active rays which may damage nonaffected tissues or organs.

The source of radiation is mounted on a slide plate 20 which is provided with guiding bores 28 through which pass the guide bars 31, 32 fastened on the cylindrical

vertical slide members

35, 36. These vertical slide members are slidable along the two

cylindrical columns

38, 40 which may be fixed as indicated or which may be mounted on a carriage or movable platform. The particular arrangement of the radiation source is to be considered as known by itself, the guide bars being usually used for the adjustment of source of radiation. According to the invention this arrangement is however provided with further means producing an automatic movement of the source of radiation so that the guide bars and the slide plate perform in addition quite different functions.

Each of the

cylindrical slide members

35, 36 is provided with a projecting lug 42 having a threaded bore. In the illustration shown in Figure 1 only one of the two slides shows such a lug 42. Through the bore of the lug 42 a threaded vertical spindle 44 passes, engaging the threads of the bore. The spindle is journaled in the two bearing

members

48, 49 and carries a gear wheel 52 meshing with a further gear wheel 53 driven by an electric motor 50.

The electric motor 50 is a synchronous unit which is driven in absolute synchronism with another unit and therefore forms part of a system of synchro-units, Selsyn or Autosyn units. The motor therefore is part of a followup system and moves in exact synchronism with a transmitter unit or generator which will be described below.

The motor 50 is mounted on a base plate 51 fixed to or forming part of the bearing member 49.

When operated the synchro-unit, Selsyn or Autosyn motor will move the cylindrical slide members upwardly or downwardly along the

columns

38, 40 by means of the spindle 44 which is rotated by the motor thus carrying with them thecross'bars 31, 32. Each of the cylindriea-

l slide members

35, 36 is *further provided with a lug or

projection

45, 47 respectively, provided with bearings rotatably holding a threaded horizontal spindle 55. The spindle 55 engages the threads of a threaded bore 29 piercing a lug 23 projecting from the sliding plate 20.

The projection or iug 47 of the cylindrical slide member 36 may have the shape of a plate and may serve as a mounting plate for a second synchro or Selsyn unit 60, which by means of a gear 62 drives a gear wheel 63 fixedly mounted on the spindle 55.

As the two synchro or

Selsyn units

50, 60 thus move the slide plate 20 in two directions at right angles to each other the source of radiation may be moved along any .path which corresponds to a resultant of the two motions produced along the two spindles in a vertical plane which motion is generally performed at varying speeds,

Obviously, the exit window for the rays andthe cone or funnel 16 must be rotated when the source of radia tion is shifted lengthwise in a horizontal direction or in a vertical direction in order to maintain the correct position of the source of radiation relatively to the target area. The X-ray tube 15 is therefore rotatably mounted on a spindle 13 or stud axle which is surrounded by a sleeve 19 tixedly connected with the sleeve 22 supporting and holding the tube 15. Within the sleeve 22 the tube is so arranged that it may be rotated around its longitudinal axis in order to enable the exit window and the cone 16 to swing through an are around said longitudinal axis of the tube which is larger than 180.

The last named movement is performed by hand as it is mainly used to bring the source of radiation into a desired position in which the radiation emanating from the tube may hit the target at an angle. This movement of the X-ray tube 15 and of its exit window and exit cone serves mainly the purpose of irradiating a spot which cannot be easily reached by a beam acting in a vertical plane or which is shielded behind some radiation absorbing body portion or behind some part which the surgeon wants to shield.

The spindle or stub axle 18 is supported by a small platform 24 which is held at the end of two guiding

rods

25, 26. These guiding rods pass through suitable guide holes 33 in the slide plate 20 and they are adjustable therein. By sliding the guiding rods forwardly or backwardly the position of the tube 15 may be adjusted.

However, as shown in Figure 3, one of the guiding rods may be provided with a rack 65 driven by a gear mechanism by means of a motor 66. The motor 66 may also be a synchro or Se'lsyn unit which is operated by a transmitter unit (not shown) which may be turned by hand or the transmitter may be operated automatically so that the motor 66 slides the platform 24 and the tube 15 forwardly and backwardly while the tube and the slide plate perform their motion along the two

spindles

55 and 44. The trajectory of the tube 15 may thus be a curve lying in a plane inclined towards the .plane passing through the axis of the

pillars

38, 40 or it may lie in a curved surface.

The synchro or Selsyn receiver units are operated by means of synchro or Selsyn transmitters the movements of which are controlled by a special control apparatus. It will be clear that the movement of the synchro or

Selsyn units

50, 60, 70 must be coordinated. The unit 66 may however be controlled independently as it is rarely used. The adjustment of

rods

25 and 26 at the start is essentially used for the purpose of bringing the X-ray "tube or other source of radiation accurately into the position relatively to the patient which is desired.

The patient who, as seen in Figures 1 and 2, lies on a stretcher, table or bed which is movable may be brought as nearly as possible into a correct position under the tube 15 and the latter is then finally adjusted in accord ance with the exact relative position desired by the radiologist.

In Figure 2 the case has been illustrated that the patient who remains in his place and who is stretched out on the bed 10 is irradiated by an X-ray tube which performs an oscillatory movement around the spot to be irradiated through an angle of 150 to 160 along an arc which, in the example shown in Figure 2, differs from the arc .of a circle and brings the tube closer to the patient on the side on which the rays must penetrate through a thicker layer of tissue in order :to reach the irradiated spot. To perform such a movement the two synchro or

Selsyn units

50 and 60 must rotate at speeds which are coordinated and which vary in such a way that the desired trajectory of the tube results. Simultaneously however, the motor '70 must rotate the tube to an extent which is directly proportional to the angularmovement of the tube around a center which is the spot to be irradiated. These three movements must therefore be exactly coordinated as seen in Figure 2.

Preferably the trajectory of the tube is so chosen that equal irradiation doses are administered during the movement of the tube within equal time intervals. To obtain such an isodosage the distances of the irradiating tube from the parts treated must vary in an irregular manner in order to obtain compensation -for the differences of the absorption of the rays when passing through tissues of different thickness or different absorptive properties. .This irregular trajectory must also be selected individually for each type of treatment and for various types of patients.

The control apparatus is therefore so constructed that any kind of correlated movement may :be obtained by means of suitably selected exchangeable means for operatin g the synchro or Selsyn units.

An example of a control apparatus providing this type of individually adjustable correlation is diagrammatically shown in Figures 5, 6 and 7. The control apparatus comprises a baseboard 71 which, by means of two parallel undercut and dovetailed guiding grooves 72, acts as a gui-deway for a slotted sliding board 75 provided with dovetailed guiding ledges 74 projecting from the sliding board. The latter is therefore freely movable along the baseboard 71 in the direction of the grooves 72. The position of the baseboard in most cases will be a vertical position. The sliding board is provided with a longitudinal slot 76 at right angles to the direction of motion of the said board on the baseboard. At one end a lug 78 projects from the sliding board which is attached to a cable 82 which may be reeled on a spring tensioned reel 84 which pays out as much cable as is necessary when the sliding board is moved but which reels the cable automatically to the extent necessary to keep the cable under a certain tension. The spring tension is so selected that it is counteracted by the weight of the board so that the spring cannot move the board, while the elastic tension and the weight just counterbalance each other. The cable is thus automatically payed out when the sliding board moves downwardly and is reeled in when the sliding board moves upwardly. The reel drives the shaft 86 which, in its turn, drives the synchro of Selsyn transmitter unit directly connected with the vertical synchro or Selsyn unit 50.

Mounted on the baseboard 71 by means of screws 88 and distance pieces 91 is a template which has a contour so cut that it represents a path along which the X-ray tube travels during irradiation. The template 85 is mounted in such a manner that it can be easily exchanged in order that different templates may be used in every case of treatment to suit different conditions and to provide an isodosic irradiation under diiferent circumstances. The template 85 has a central cut or opening 89 through which passes a shaft 95 which may be either driven manually or which may be oscillated by means of an electric motor diagrammatically indicated at 99 by means of a suitable gear (not specially shown). This shaft 95 is coupled with the synchro or Selsyn transmitter 100 by means of a fixed coupling and to said shaft a slotted arm 102 is keyed in the slot 104 in which a radially movable stone 105 is slidably mounted. The radially movable stone 105 may be drawn towards the center 0 by means of a spring 106 and it carries a pin projecting outwardly which is guided by the edge of the template 85 when the arm 102 is moved angularly either by hand or by electric motor 99. During suchmovement of the pin 110, the stone 105 is drawn inwardly or is pushed outwardly in accordance with the shape of the template.

A projection of pin 110 or a separate pin moreover connects the radially movable stone 105 of arm 102 with a transversely movable stone 108 which is slidably held within and guided by the slot 76 of the sliding board 75.

The two

stones

105 and 108 may freely rock or oscil-v late around the .pin but they always move together and therefore perform a translatory movement in common while maintaining their .positions within the guiding slots during such movement. The transversely movable stone 108 is attached to a cable 92 which is fixed to a reel under spring tension and which is therefore reeled off and on by the tensioned reel 94. The axle 96 of the reel 94 is connected with a synchro or Selsyn transmitter unit 90 acting as a generator or transmitter unit which controls the receiver unit 60 or the tube moving apparatus over the wires 1 20.

Rotation of the motor 60 will therefore produce rotation of .the horizontal spindle 55 and will move the slide plate 20 by means of the lug 23, thus moving with it the X-ray tube 15.

Stops (not shown) may be provided for the arm 102 in order to indicate to the operator the limits of the movementin the event of a hand operation of the shaft 95.

The power for the synchro-units is supplied from a suitable A. C. network 124.

'When the shaft 95 is driven by an electric motor it is also possible to use a reversible motor and a limit switch in order to obtain an oscillatory movement of the shaft 95.

The operation of the device will be understood from the foregoing description.

The patient is stretched out on a movable bed or stretcher and is first brought into the correct position and the X-ray tube is adjusted, bringing it first into an adjustment position which serves as a starting point for the tube adjustment. The tube is also adjusted with respect to the direction in which the X-rays have to issue relatively to the vertical plane. This adjustment is obtained by turning the tube around its longitudinal axis. The exact spot which is the center is determined and the tube is readjusted with respect to the position of this point.

Radiation by means of the tube may now be started.

The shaft 95 is oscillated during such radiation through an are which has been suitably selected and which, in the example shown, is somewhat smaller than 180 but which may also in some cases be larger by properly adjusting the oscillation of shaft 95. The proper template for the treatment has been inserted previously.

In the example shown the are through which the arm oscillates is approximately 150. During the oscillation of the motor the synchro or

Selsyn units

80, 9t and 100 are continuously moved. The movement of the shaft 95 is directly transmitted to the synchro or Selsyn-transmitter 100. The movement of the two

other units

80 and 90 is produced by means of the arm 102 which oscillates and during this oscillation the arm produces a radial and transverse movement of the stone 105 and pin 110 which is drawn against the template 85 during such movement. The pin will always remain in contact with the edge of the template and will thus determine the radial position of the stone 105. When the stone 105 is moved it changes its angular position and also changes its radial distance from point 0, which is the center around which the arm 102 moves, and its position relatively to the coordinates through the point 0. The change of the position of the stone 135 in the horizontal and vertical direction entails also a change of position of the stone 166 in the same direction and thereby the sliding member 75 is moved upwardly and downwardly, or away from the center and towards the said center. The movement of the sliding board 75 entails also a movement of the cable 94 and thereby a movement of the synchro or Selsyn transmitter unit 90. The movement of the stone 106 entails the movement of the cable 92 and thereby a movement of the synchro or Selsyn transmitter unit 90. The two units produce corresponding movements of the synchro or Selsyn receiver units 50 and 6h. The synchro or Selsyn unit 100 directly operates the synchro or Selsyn unit 70 which therefore keeps the tube exit window and cone '16 always pointed towards the center S.

It will be seen from the above description that the relative position between the point S and the source of radiation changes continuously so that the tissues between the point S and the source of radiation are only irradiated in passing and therefore receive a dosage which is muchsmaller than the dosage received by the point S.

The invention, as seen from the above description, thus provides a simple equipment, usable in connection with existing equipment for irradiation, which permits an individualized irradiation treatment conducted in such a manner that only the treatment area receives the full dosage while other tissues or organs in the vicinity of the treatment area receive a dosage which is much smaller than the dosage received in the treatment .area. Further, the treatment area, through the control apparatus with its individually selectable template, determining the rate at which the irradiation source is moved is irradiated with the same dosage throughout the treatment, if a suitable selection of the template has been made, so that the time necessary for irradiation is as short as possible time and the dosis is the maximum dosage which can be applied to the treatment spot. This dosis, as above explained, is not in any way limited by the dosage tolerated by intervening tissues or organs, but is solely determined by the conditions in the treatment area, as the relatively small fraction of the entire dosis which is re ceived at any single point of the intervening tissues is in all cases below the limit which must be applied in order to avoid damage of the treatment spot itself.

The device is not only simple with respect to construction but is also easy to handle and is not likely to get out of order. The speed with which the source of radiation is moved may be properly selected and in dividually regulated by a proper selection of the gears associated with the units and by a suitable selection of the pitch of the spindle threads.

It is to be understood that changes in the construction of an unessential nature may be made without in any Way departing from the essence of the invention as defined by the annexed claims.

What is claimed is as follows:

1. Radiation therapy means adapted for irradiation of a circumscribed area comprising a source of radiation provided with an exit opening through which a beam produced at a source point emanates, a first means for shifting said source .of radiation substantially in a straight line in one direction, a first power operated means for producing said shifting movement, including a second means for shifting said source of radiation substantially in a straight line in a direction at an angle with respect to the direction in which its source is shifted by the said first means, including a second power operated means for producing the shifting by said second means, a third means for producing a rotation of the source of radiation around a center substantially coincident with the source point of the radiation, including a third power operated means producing said rotational movement, means for coordinating the speed of the three power operated means, the coordination of the first and the second means for shifting the source of radiation producing a preselected curved path of the said source of radiation around the circumscribed area to be irradiated, while the coordination of the third power operated means with the two other power operated means directs the rays emanating through the exit opening towards the circumscribed area to be irradiated during the movement produced by the two first named means.

2. Radiation therapy means adapted for irradiation of a circumscribed area comprising a source of radiation radiating from a source point through an exit opening, means for supporting said source of radiation rotatably with the axis of rotation passing through the source point of radiation and means for rotating the source of radiation, power operated means adapted to move intwo opposite directions and oscillating said source of radiation around the axis of rotation, means for moving said supporting means for the source of radiation in a straight line, said means including a second power operated means, further means for imparting a rectilinear translatory movement to the means for moving the supporting means in a straight line, said further means including a third power operated means, and means for coordinating the speed of movement of the three power operated means in order to produce a reciprocating movement in a curve around the circumscribed area to be irradiated while simultaneously the source of radiation performs an oscillatory movement keeping the exit opening of the source of radiation pointed to the circumscribed area to be irradiated.

3. Radiation therapy means as claimed in claim 2 wherein the source of radiation is supported by a supporting plat-form, comprising means for moving said supporting platform in a direction at right angles to the directions of movement in which the source of radiation is shifted by the two rectilinear movement producing means.

4. Radiation therapy means as claimed in claim 2, wherein the power operated means, operating the means for moving the supporting means in a straight line and the power operated means for operating the means for producing the translatory movement of the source of radiation and the power operated means operating the means for rotating the source of radiation each includes a synchronized power unit, each power unit moving in synchronization with a synchronized power transmitting unit and wherein the means for coordinating the movements imparted to the source of radiation include a controller unit driving the said transmitters.

5. Radiation therapy means as claimed in claim 2 wherein the means for supporting the source of radiation include spaced vertical columns carrying vertically tslidable slide members and horizontal slide rods attached to said slide members.

6. Radiation therapy means as claimed in claim 1, wherein the source of radiation is supported on a supporting platform, carrying a self synchronized motor unit and a rotatable shaft driven by the said self synchronizing motor unit.

7. Radiation therapy means as claimed in claim 5, wherein the oscillatory movement around the circumscribed area to be irradiated is produced by means for moving the supporting means of the source of radiation simultaneously along the said horizontal slide rods and means for moving the vertically slidable slide members along the vertical columns.

8. Radiation therapy means as claimed in claim '2, wherein the power operated means include a self synchronizing receiver unit and the coordinating means include a controller unit provided with synchronizing transmitter units, each of said transmitters being connected with one of the synchronized receiver units, a member guided along a trajectory followed by the supporting means of the source of radiation, and means for driving each of the transmitter units in proportion to a component of such movement in a given direction identical with one direction of translatory movement performed by the supporting means.

9. Radiation therapy means as claimed in claim 8,

comprising an additional transmitter unit driven directly prising a source of'radiation, a supporting means for-the same, means for rotating said source of radiation relatively to said supporting means, means for supporting the patient, an area of which is to be irradiated, means for oscillating the supporting means of the source of radiation along an arcuate path while keping the radiation on the area to be irradiated, said means including guide means in two directions at right angles to each other, and means for moving the supporting means along one of said guide means and for moving the last named guide means along guide means running in a direction at right angles to the first named guide means, a syn chronized motor unit, operable in synchronization with transmitter units for moving the said support in one direction along the guide means, and further synchronized motor units for moving the said last named guide means in a direction at right angles thereto along other guide means, means for rotating said source of radiation on its support including a further synchronized motor unit operable by a transmitter unit in synchronism therewith, a controller means for coordinating the movements of the supporting means of the radiation source and the rotational movement of the later, said controller including synchronizing transmitter units for producing a synchronized movement of the synchronous motor units, means for driving said transmitters, said means including a member guided along a trajectory similar to the trajectory described by the supporting member of the source of radiation and also performing an angular movement around a center, at a distance which is proportional to the distance of the source of radiation from the area to be irradiated, said trajectory being so chosen that the said transmitter unit produces a synchronized movement of the motor units which changes the distance of the source of radiation from the area to be irradiated during the oscillation of the source of radiation around this area.

11. A system as claimed in claim 10, wherein the trajectory is so chosen as to produce equal dosage during oscillation of the source of radiation around the irradiated spot.

12. A system as claimed in claim 10, wherein the trajectory member consists in a pin sliding along and kept in contact with a template.

13. A system as claimed in claim 10, wherein the pin member also describes an arcuate path around a center, with a varying distance from said center.

14. A system as claimed in claim 13, wherein the pin is carried by a stone sliding in a slotted arm swingable around the aforesaid center.

15. A system as claimed in claim 10, wherein the controller includes a slotted slide board guided in guides in one direction with a slot arranged in a direction at right angles to the direction of movement, a rockable shaft, a slotted arm keyed to the shaft and swingable around the axis of said shaft, a stone movable in the slotted arm and pivotally connected with the stone moving in the slot of the slide board, a pin projecting from one of the stones, a template for guiding the movement of the pin, a synchronizing transmitter unit being driven by the shaft, and further synchronizing transmitter units being driven by the movement of the slide board and by the movement of the stone within the slide board respectively produced during the rocking of the arm.

16. A system as claimed in claim 15, wherein the slide board is guided on a baseboard and is attached to a cable, a spring tensioned reel attached to the cable, moved by the movement of the slide board, said reel driving one of the synchronizing transmitter units.

17. A system as claimed in claim 15, wherein the stone guided in the slot of the slide board is attached to a cable moved by the movement of the stone within the slot of the slide board, said cable being attached to a spring tensioned reel, which drives one of the synchronizing transmitter units.

1 1 118. A system as claimed in claim '15, wherein one 'of the synchronized transmitter units is coupled {co-the rockable shaft.

References Cited in the file of this patent 5 UNITED STATES PATENTS 1,573,571 Pohl 'Feb. 16, 1926 12 'Iacobson MarmS, 1-929 (Idle Nov. 15, 1932 Augustin et al Apr. 25, 1939 Bartow et-al May 12, 1953 Ger-neth May 26, 1953