US 3866050 A
A method and apparatus is provided whereby a point or elongate radioactive source is introduced into the body of a patient and a source is subsequently oscillated whereby the spacial distribution of radioactivity can be varied to give spherical, oblate spheroidal or cigar-shaped configuration. The invention further contemplates arcuate oscillation in addition to linear oscillation.
Description (OCR text may contain errors)
United States Patent 1191 Whitfield Feb. 11, 1975 I REMOTELY CONTROLLED  References Cited BRACHYTHERAPY UNIT UNITED STATES PATENTS  In e tor: ouglas Whitfield, S e, 3,426,196 2/1969 OShea et al. 250/308 Ontario, Canada 3,669,093 6/1972 Sauerwein et a]. 250/496  Assignee: Atomic Energy of Canada Limited, I
Ottawa, Ontario Canada Primary Examiner-Archie R. Borchelt Attorney, Agent, or FirmCushman, Darby & [22} Filed: Nov. 9, 1973 Cushman [2!] Appl. No.: 414,436
Related US. Application Data  ABSTRACT [63} Continuation of Ser. N0. 266,507, June 26, 1972, 1 A method and apparatus is provided whereby a point abandoned. or elongate radioactive source is introduced into the body of a patient and a source is subsequently oscil-  Foreign Application Priority Data Iated whereby the spacial distribution of radioactivity May 15, 1972 Canada 142103 can be varied to give Spherical, oblate spheroidal or cigar-shaped configuration. The invention further con- 52 11.5. C1. 250/497, 250/496 templates arcuate Oscillation in addition t9 linear 51 1111. C1. c2111 5/00, G2lk 1/00 9111mm- Fleld of Search C i 8 Drawing gu es REMOTELY CONTROLLED BRACHYTI-IERAPY UNIT This is a continuation, of application Ser. No. 266,507 filed June 26, 1972, now abandoned.
This invention is related to a method and apparatus for accurately locating a source of radioactive emmission in relation to and operable upon a volume of material to be irradiated and to the subsequent oscillation of the source whereby the distribution of the irradiation is non-spherical. The invention has particular, but not exclusive, application in brachytherapy. The word brachytherapy is derived from brachys (Gk) meaning short and therepauein (Gklmeaning take care of. Thus, in the present context, the word brachytherapy means treatment in close. The present invention,
however, envisages brachytherapy by remote control in order to protect hospital personnel against radiation hazards.
For years doctors have had to place, by hand, small radioactive sources inside the patient often through the natural openings of the body. This type of procedure has many drawbacks. It is not always positive or precise. It is extremely dangerous to the medical staff, uncomfortable for the patient and it entails extremely long treatment time. Because of these factors, it was not possible to employ powerful radiation sources such as Cobalt 60. The present invention overcomes the above factors by providing a method and an apparatus which places the source in close to the tissue, for example, a tumour, by remote control with precision and safety. The present invention further provides for considerable variation in the shape of the distribution or isodose curves. A single homogeneous source pellet of substantially spherical shape has, of course, spherical distribution if stationary. The same source, if oscillated along a straight line, will provide oblate spheroidal distribution. If a string of similar pellets in juxtaposition is oscillated, along a straight line, the distribution will'be cigar-shaped, that is, substantiallly cylindrical with hemispherical ends. The use ofa string of source pellets has a distinct advantage in that it is not essential that the individual source-strengths of the pellets be equal. (Equality of source strength is difficult and impractical to obtain). The effect of variations between the individual sources is nullified when the string is oscillated and the net distribution can be quickly established by a calibration technique.
The invention will now be described with reference to the accompany drawings, in which:
FIG. 1 is a side view of aunit assembly comprising a control unit and source container.
FIG. 2 shows a catheter, in part section, and a catheter coupling.
FIG. 3 shows a brachtherapy control panel.
FIG. 4 shows a screw mechanism for effecting movement and oscillation of the catheter drive cable.
FIGS. 5 and 6 are right and left hand views of the screw mechanism.
FIG. 7 shows a source position control.
FIG. 8 shows a source container lock switch assembly, (disconnect coupling).
Referring to FIG. 1, there is shown a control unit assembly l, a source container stand assembly 8, flexible hose and disconnect coupling assemblies 13 which extend between the control unit assembly 1 and the source container stand assembly 8. Additional cable 2 guide hose assembly flexible tubes extend from the source container stand assembly 8 to catheter coupling assemblies 10 and hence to the catheter assemblies 11.
Referring to FIG. 2, there is shown a catheter coupling 10 which terminates flexible hose 14 and which receives-catheter assembly 11. The catheter I10 is shown partly in section to disclose a source capsule 112, in the fully out position and movable by means of the drive cable attached thereto. Electrical cables 144, 146 are used in conjunction with contacts, not shown, within the coupling 10 which contacts are connected to and operable upon a Catheter Secured warning light 607 on FIG. 3.
The drive cable 140, which slides within the flexible hose 14 passes through the source container assembly 8, through a disconnect coupling assembly at 800 and through the hose assembly 13 wherein the cable .enters the control unit assembly 1. The drive cable is of the type that has a flexible core around which is formed a spaced apart helical winding for co-operation with a drive member. Such a drive cable is known in the trade under the trademark Teleflex. The drive cable, after entering the control unit assembly, passes through a cable drive assembly 200 where it turns through about 90 to continue upwardly to and around a pulley 210 and downwards to be terminated with a counter weight 220. As shown in FIG. 1, the weight 220 is at its lowest position corresponding to withdrawal of the source capsule 112 into the source container stand assembly 8. The weight 220 slides within a tube 230 and both the weight and the tube are of non-circular cross-section, for example square, to prevent rotation of the weight with consequential slight variation in the effective length thereof. Referring again to FIG. 1, that portion of the drive tube vertically disposed above the cable drive assembly 200 passes through a source position control assembly which will now be discussed in detail with reference to FIG. 7. The tube is longitudinally slotted as at 240 between a top plate 242 and bottom plate 244. The plates 242 and 244 support vertical bearing shafts 246 upon which slide saddles 248, 250. The slide saddlesv 248, 250 carry micro-switches 260, 262 and 258, respectively, having actuator wheels 266, 26 and 264. The actuator wheels are selectively depressed by a micro-switch actuator 270 which is also indicated in FIG. 1. The top saddle 248 can be lowered until mechanically prevented by a stop 272 which may also be used for setting an indicator on the control panel to zero in a manner to be described.
The actual setting of the top and bottom saddles is effected by means of limit switch control cables, one of which is shown at 281 in FIG. 1. The cables extend between the saddles and control knobs to be described. Referring to FIG. 3 there is shown a control console 300 which is mounted on the front of the control unit assembly 1 in FIG. 1. The console shown is intended for controlling the movement and oscillatin of three catheters. The controls on the right hand side will be described. Knobs 310, 320 control individual control box assemblies, 312 on FIG. 1. Rotation of the knob 310 moves the lower saddle 250 up or down by cable 281. Similarly, rotation of the knob 320 moves the upper saddle 248. Each of the limit switch control cables 281, 283 are extended upwards from the control box assemblies 312 to move upper and lower position indicators 330, 340, which co-operate with a scale 350. The 0" mark, at the bottom of the scale, corresponds to the source capsule 112 being fully extended into the catheter 110 as shown in FIG. 2, and occurs when the microswitch actuator 270 depresses the lower micro-switch 258 in FIG. 5. The scale is marked up to 16 cms. If the upper indicator 330 is opposite the 16 mark, upper micro-switch 260, in FIG. 5, will be depressed by actuator 270. As stated previously, the drive cable 130 is moved by a cable drive assembly 200 which is driven by motor 400 in FIG. 1. The cable drive assembly 200 is fitted with sprocket 402 having roller chain 404 thereon which, in turn, drives sprocket 406 on a screw mechanism now to be described with reference to FIGS. 4, 5, and 6. The torque from the motor 400 is transmitted through electromagnetic clutches, now shown.
The screw mechanism assembly, generally indicated at 500, comprises a base 502, bearings 504, 506 which support an actuating screw 508.
A nut 512, having an internal thread of size and pitch to cooperate with the screw 508, is longitudinally movable in response to rotation of the screw 508. In order to prevent the nut 512 from rotating, a circular rod 514 extends from end-to-end of the screw 508 and is restricted against longitudinal movement by a set screw 516 in bearing 504.
Adjacent to the left-hand end of the screw 508 is an upstanding rib 516 to which micro-switches 522, 524 and 526 having actuating plungers 528, 532, and 534 respectively. Longitudinal adjustment, and clamping of the micro-switches is effective by a set-screw 536 and micrometer screw 537.
Adjacent to the right-hand end of the screw 508 is an upstanding flange 542 to which are fastened microswitches 544, 546 having actuators 548, 522 respectively. These switches are adjustably mounted and positioned by micrometer screw 555 and clamped by screw 554.
The nut 512 carries upper and lower micro-switch depressors 562, 564 which are vertically aligned to cooperate with micro-switches 524 and 546' or 526 and 544 respectively. The nut 512 also includes an extension 560 which operates solely upon micro-switch 522.
The number of teeth on sprockets 402 and 406, which are interconnected by chain 404 are selected so that, together with the pitch of the screw 508, the nut 512 moves the entire operational length of the screw while the source capsule moves from its fully extended position, as shown in FIG. 2, to its stored position within the source container stand 8. In the present embodiment there is an 8:1 reduction of the linear movement between the cable and the screw. The motor 400 in FIG. 1 which effects movement of both the catheter and the screw 508 is connected so that limit switch 524 disconnects the power supply to the motor when the nut 512 is near the left hand extremity of its movement. Similarly, microswitch 544, effects disconnection of the motor near the right hand extremity of the movement of the nut.
Operation of the micro-switches will now be described in greater detail.
The right hand end screw corresponds to the SOURCE SAFE or withdrawn condition of the source capsule from the catheter. At the SOURCE SAFE end of the screw mechanism, micro-switch 546 controls a SOURCE SAFE indicator lamp 600 in FIG. 3. Microswitch 544 controls a SOURCE OVERTRAVEL indicator lamp 602 in FIG. 3. At the SOURCE EXPOSED end of the screw mechanism, micro-switch 526 controls the SOURCE OVERTRAVEL indicator lamp 603. At the same end, micro-switch 522 locks in a slowspeed reduction when the source is to be oscillated. Mi-
5 cro-switch 522 is also used in connection with a dummy source for set up purposes.
Once a source has been transferred from the storage position, the lamp 600 is extinguished and lamp 606 is turned on (by micro-switch 526). The source may then be maintained stationary or oscillated by suitably setting switch 604. I
Referring now to FIG. 8 there is shown a source con tainer lock switch and a cable disconnect assembly generally indicated at 800. The assembly is fastened to the source container stand 8, shown in FIG. 1, a portion of which stand is indicated at 81. A portion of the drive cable 130 between the control unit and source container and the catheter end of the drive cable 140 between the control unit assembly 1 are shown. A source lock 802 is provided to prevent unauthorized or accidental withdrawal of the source from the container 8. When the body of the lock is withdrawn, by operation of a key, not shown a micro-switch 804 is depressed and the switch is connected to and operable upon a warning light 608 on FIG. 3. In order to disconnect the drive cable 130 from the source cable 140, asleeve 806 is provided. The sleeve is fastened to the body of the switch by means of set screws 810. When the set screws are withdrawn, the sleeve 806 may be withdrawn to the left in the drawing to expose a split collar 808. Removal of the two halves of the split collar 808 enables withdrawal of a roll pin 812 which joins the drive cable 130 to the source cable 140.
In operation, the catheter 11 is placed in the desired irradiating location before the source is advanced into the catheter. This is accomplished without hazard to the medical staff as the source is safe within the source container. The catheter 11 is then coupled to the catheter coupling whereupon indicator lamp 607 on the control console is activated.
The source may consist of a single pellet of radioactive material, for example, Cobalt 60, or it may comprise a number of pellets arranged in line formation.
The single pellet may be used in a fixed position or oscillated along the axis of the catheter. The line of pellets may be oscillated in a similar manner. A single stationary pellet gives a substantially spherical distribution where a single pellet, when oscillated, gives oblate spheroidal distribution. A line of juxtaposed pellets, when oscillated, gives s substantially cigar-shaped distribution.
While the catheter shown is straight, bent catheters have been used with equal success.
1. A method of selectively distributing the radioactive emission from a source disposed to irradiate a given volume of material in a predetermined pattern in the body of a patient, comprising the steps of:
disposing a source in a selected position in the body of a patient,
oscillating said source about said selected position for a selected period of time, and
enclosing the source ina container which is fixed relative to said body of said patient wherein the distribution of radioactive emission is non-spherical.
2. The method of claim 1 further including the step of automatically withdrawing said source away from said body of said patient to a non-radiation positin immediately following cessation of the oscillation.
3. The method of claim 1 further including the step of utilizing the force of gravity to automatically withdraw said source away from said body to a nonirradiation position immediately following cessation of the oscillation.
4. The method of claim 1 wherein said distribution of emission is substantially oblate spheroidal.
5. The method of claim 1 wherein said distribution of emission is substantially cigar-shaped.
6. The method of claim 1 wherein said source comprises a single pellet.
7. The method of claim 1 wherein said source comprises a plurality of pellets of substantially equal source-strength.
8. The method of claim 1 wherein said source comprises a plurality of pellets of diffusing sourcestrengths.
9. A method of selectively distributing the radioactive emission from a source disposed to irradiate a given volume of material, comprising the steps of:
disposing a source in a selected position relative to a volume, oscillating said source about said selected position for a selected period of time, and enclosing the source in a container which is fixed relative to said volume wherein the distribution of radioactive emission is non-spherical.
10. A method as in claim 9, including the additional step of automatically withdrawing said source away from said volume to a non-irradiation position immediately following cessation of the oscillation.
11. A method as in claim 9, including the additional step of utilizing the force of gravity to automatically withdraw said source away from said volume to a nonirradiation position immediately following cessation of the oscillation. position immediately following cessation of the oscillation.
12. A method as in claim 9, wherein said distribution of emission is substantially oblate spheroidal.
13. A method as in claim 9, wherein said distribution of emission is substantially cigar-shaped.
14. A method as in claim 9, wherein said source comprises a single pellet.
15. A method as in claim 9, wherein said source comprises a plurality of pellets of substantially equal source-strength.
16. A method as in claim 9, wherein said source comprises a plurality of pellets of diffusing sourcestrengths.