WO2002027630A1

WO2002027630A1 - Fast photon counting assay system and method

Info

Publication number: WO2002027630A1
Application number: PCT/US2001/041899
Authority: WO
Inventors: Ira L. Morgan; Michael L. Vinson; William J. Courtney; Michael J. Doke
Original assignee: Isostar Texas, Inc.
Priority date: 2000-09-28
Filing date: 2001-08-27
Publication date: 2002-04-04
Also published as: AU2001295014A1

Abstract

An automated system and method are disclosed for use in assaying radiation emitted by radiotherapeutic products such as brachytherapy seeds. The system and method include an enclosure containing a SCARA robot that is selectively positionable at a plurality of work stations, a calibration seed holder, a vibratory feeder, a radiation detector and an array of storage vials. Pulses from the radiation detector are directed to a fast coincidence counter and CPU, which computes the radiation dosimetry and signals the robot to deposit the assayed product in a particular storage vial within the array.

Description

FAST PHOTON COUNTING ASSAY SYSTEM AND METHOD

Background of the Invention Field of the Invention

[0001] This invention relates to radiation dosimetry, and more particularly, to an automated system useful for assaying, classifying and binning brachytherapy seeds, or other products used in radiotherapy, according to the intensity of the emitted radiation. More broadly characterized, the invention has applicability in pollution analysis and industrial process control as well as for monitoring biological function and in the production of products used in cancer therapy. Description of the Related Art [0002] In the past, products used in radiotherapy have been assayed using manually operated devices for handling the radioactive products and ionization chambers with low level scintillation counters for determining the radiation intensity. The radioactive products are typically manipulated into and out of well counters in the devices by an operator positioned behind a radiation shield. Once the product is assayed, it is stored, packaged and labeled according to the half life and dose rate for that particular radionuclide and product, respectively. In some prior art systems, a pneumatic device is used in combination with a rotary table to deposit an assayed product into the correct storage bin.

[0003] Dose calibrators that are currently commercially available include several marketed by

Capintec, Inc. of Ramsey, New Jersey, including some models said to be particularly useful for determining the radiation intensity of brachytherapy seeds. Such devices can be adapted to provide readouts in Ci, Bq or Air Kerma strength; readouts of quality control functions such as constancy, accuracy and calibration numbers; and can comprise a pressurized chamber to avoid the need for temperature and pressure corrections.

[0004] A system, apparatus and method are needed, however, that will enable manufacturers to assay products used in radiotherapy more rapidly and efficiently, with greater analytical reliability and with improved operator safety when compared to prior art devices and methods. Summary of the Invention

[0005] The invention disclosed herein, when reduced to simplest terms, is the provision and use of a robot within a protective enclosure together with an automated feeder assembly, a radiation detector operatively coupled with counter, an array of storage receptacles and a computerized control system, all of which are cooperatively adapted to assay the radiation intensity of radioactive products and classify the products accordingly. [0006] The subject invention utilizes robotics to achieve greater speed, efficiency, precision and safety in handling, assaying and binning radiotherapeutic products than has previously been achievable with commercially available assay systems. The system of the invention preferably comprises a plurality of discrete modules or subassemblies serviced by a SCARA robot mounted on a stationary base, all housed inside a protective enclosure. "SCARA" is an acronym commonly used to refer to a robot having a "Selectively Compliant Articulated Robot Arm." SCARA robots have a cylindrical work envelope, and the articulated support arm permits access to work locations disposed at virtually all locations within the envelope.

[0007] The discrete modules contained inside the enclosure of the system and serviced by the robot preferably include a calibration module, a vibratory seed feeder, a photon detector module and a vial array. Other elements of the system, including without limitation a power supply, amplifiers, a fast coincidence counter, a CPU, display and printer, are located outside the enclosure. The subject system is desirably automated and operated by programmable electronic controllers that cause the various modules to perform functions as disclosed herein, sometimes receiving input from, and sometimes directing signals to, a plurality of sensors and transducers. One primary control computer preferably receives feed back from the robot and various other sensing devices to control the motion of the robot according to the method of the invention.

[0008] During operation of the system of the invention, and following calibration, the robot desirably picks up a therapeutic product to be assayed, such as a brachytherapy seed, from the vibratory seed feeder and rotates to a position over an upwardly opening receptacle in the photon detector module. The photon detector module has photomultiplier tubes disposed on opposite sides of a seed well in a scintillator. The photo ultiplier tubes sense fluorescence in the scintillator that is produced by interaction with photons emitted by the seed. The output pulses from the photomultiplier tubes are amplified and directed to a fast-coincidence counter, and from there to a computer, display and printer. Once the computer has determined the radiation intensity from the data received from the fast- coincidence counter, a signal is generated and sent to the SCARA robot that causes the robot to deposit the seed, now withdrawn from the photon detector module, into one of an array of bins that is preselected for use as a repository for seeds having that nuclide and intensity.

Brief Description of the Drawings [0009] The apparatus of the invention is further described and explained in relation to the following figures of the drawings wherein:

[0010] Figure 1 is a simplified top perspective view of the fast photon counting assay system of the invention;

[0011] Figure 2 is a simplified front elevation view of the system of Figure 1;

[0012] Figure 3 is a simplified rear elevation view of the system of Figure 1 ;

[0013] Figure 4 is a simplified top plan view of the system of Figure 1 ;

[0014] Figure 5 is a cross-sectional detail view taken along line 5-5 of Figure 4; and - [0015] Figure 6 is a simplified diagram showing the principal elements of the photon detector/counter apparatus of the invention.

[0016] Like reference numerals are used to indicate like parts in all figures of the drawings. Electrical and pneumatic lines are not shown in the drawings to avoid cluttering the views, although points of attachment are disclosed and described herein where needed in order to make the disclosure enabling to those of ordinary skill in the art. Description of the Preferred Embodiments

[0017] Referring to Figures 1-4, automated assay system 10 preferably comprises stand 12, which serves as a base for enclosure 14 and also, if desired, as a support structure for other equipment such as robot controller 26 and electrical junction box 28 that need not be contained within enclosure 14. Enclosure 14 preferably comprises sidewalls 13, 15 having transparent panels mounted in extruded aluminum frame members and front and rear doors 30, 32, respectively, providing convenient access to the interior of enclosure 14. Mounted inside enclosure

14 are robot 16, calibration seed holder 18, automated product feeder 20, storage receptacle array 22 and radiation detector 24.

[0018] Robot 16, preferably a SCARA robot, and the other devices mounted inside enclosure 14, are desirably positioned so that the robot can perform its functions can be performed by moving support arm 19 relative to stationary base 21. Support arm 19 is preferably articulated, with two segments independently rotatable in a horizontal plane and capable of positioning a specimen such as a brachytherapy seed at any desired point within the working zone inside enclosure 14. Robot 16 preferably comprises pneumatically or electrically operated gripping inserts disposed on adjustable fingers, well known to those of skill in the art, that are positioned and controlled by instructions received from programmed controller 26 so as to grip and support a radioactive product, like brachytherapy seed 40 shown in Figure 5, and then subsequently release it at an appropriate time.

[0019] Calibration seed holder 18 is desirably disposed nearby robot 16 and is desirably adapted to hold one or more radioactive products of the type to be assayed, which products have a known radioactivity and can be used as standards in system 10 to calibrate radiation detector 24 at the start of each product assay run. [0020] Automated product feeder 20 can take many different forms, depending upon the type and geometry of the particular radioactive product to be assayed by system 10. Likewise, automated product feeder 20 can be designed to operate in either a continuous or batch/continuous mode, depending upon its mechanical structure and how radioactive parts are fed into system 10. Automated product feeder 20 is desirably capable of sequentially presenting and orienting a new radioactive product to be assayed in such a position that robot 16 can readily grasp and move the product to a different work station within enclosure 14.

[0021] As shown in the accompanying drawings, automated product feeder 20 is preferably a vibratory bowl feeder into which a batch of up to about 500 or more brachytherapy seeds 40, as shown in Figure 5, can be loaded at one time through doors 30, 32 by an operator positioned outside enclosure 14. Vibratory bowl feeders are commercially available and, when activated, desirably cause brachytherapy seeds 40 to migrate upwardly along the sides of the bowl to a track that positions them in longitudinal sequence for pick-up by robot 16. According to one particularly effective embodiment, a pneumatically controlled, flip-tube receiver disposed adjacent to the track at the top of the vibratory bowl sequentially receives a brachytherapy seed 40 from the track and rotates it from horizontal to an upright position where it can be easily grasped by the gripping inserts of robot 16. A vibratory bowl feeder and flip-tube receiver as used herein are further shown, described and explained, for example, in copending United States patent application Ser. Mo. 09/569,536, filed May 12, 2000, which disclosure is incorporated by reference herein. Automated product feeder 20 is desirably provided with a radiation shield 66, which normally covers the radioactive products inside the vibratory bowl but is preferably rotatable to the position shown in Figure 4 to permit refilling of the vibratory bowl.

[0022] For use in assaying the radiation dosimetry of products such as brachytherapy seeds 40, radiation detector 24 and its ancillary equipment are further described and explained, primarily with reference to Figures 4-6. Radiation detector 24 preferably comprises a well 42 in scintillator 45 between oppositely directed photomultiplier tubes 34, 36. Scintillator 45 fluoresces in response to photons emitted by a brachytherapy seed 40 or other product specimen that is inserted into well 42 by robot 16. This fluorescence is then sensed by photomultiplier tubes 34, 36. Referring to Figure 5, well 42 preferably further comprises a vertically oriented sleeve 44 having an inside diameter slightly greater than the outside diameter of brachytherapy seed 40 and a crimp 46 or other similarly effective means for properly positioning seed 40 inside detector 24 following insertion by robot 16.

[0023] Photomultiplier tubes 34, 36 are well known, commercially available devices that are suitable for detecting low level light emitted by a scintillator. Referring to Figure 6, pulses from each of photomultiplier tubes 34, 36 are preferably conducted to interface block 48, where they are energized by high voltage power supplies 50, 52 respectively, amplified by amplifiers 54, 56 and fed into fast coincidence analyzer 58. The coincidence circuit inside analyzer 58 is preferably designed so that only those pulses arriving within very close intervals, such as about 10 nanoseconds or less, can complete the circuit to counter 60. Each quantum of radiation recognized by fast coincidence analyzer 58 generates an electronic signal that is counted by counter 60 and is then further communicated to central processing unit (CPU) 62 and display 64 for recordation and storage. The CPU calculates the radiation dosimetry from the measured data and other preprogrammed information such as the identity and half-life of the particular radionuclide(s) utilized in the product.

[0024] Referring again to Figures 1-4, storage receptacle array 22 preferably comprises a plurality of vials suitable for use in storing radioactive products such as brachytherapy seeds 40. Within array 22, the storage receptacles or vials or preferably arranged in a predetermined order corresponding to a particular radiation dosimetry as determined by the assay. The position of each receptacle and the dosimetry of the products it should contain are preferably mapped into a data base maintained in or otherwise accessible to CPU 62 (Figure 6) of system 10 so that, following analysis of the dosimetry of a particular product specimen, robot controller 26 and robot 16 can be instructed to deposit the assayed product into an appropriate receptacle.

[0025] While the automated system and method of the invention are principally described herein in relation to the preferred embodiment of assaying products for their radiation dosimetry, it will be understood and appreciated by those of ordinary skill in the art upon reading this disclosure that other product assay features can likewise be performed through adaptation of the apparatus and method disclosed herein. Thus, for example, other product inspect stations and equipment can be provided within enclosure 14 and mapped into the control sequence for robot 16 that will enable system 10 to likewise assay products according to geometry, weld integrity, or the like. Products failing to meet predetermined benchmarks for any standard can likewise be assigned to particular receptacles into which they are deposited by robot 16 for further processing or disposal, as appropriate.

[0026] Other alterations and modifications of the invention will likewise become apparent to those of ordinary skill in the art upon reading the present disclosure, and it is intended that the scope of the invention disclosed herein be limited only by the broadest interpretation of the appended claims to which the inventors are legally entitled.

Claims

WHAT IS CLAIMED IS:

1. An automated assay system useful for determining the radiation dosimetry of radiotherapeutic products, the system comprising: a robot selectively positionable at a plurality of work stations; an automated product feeder; a radiation detector; a central processing unit; and an array of product receptacles.

2. The automated assay system of Claim 1, wherein the radiation detector comprises a plurality of photomultiplier tubes.

3. The automated assay system of Claim 2, further comprising a fast coincidence counter, wherein each photomultiplier tube is electronically linked to the fast coincidence counter.

4. The automated assay system of Claim 3, further comprising an amplifier disposed in the electronic link between each photomultiplier tube and the fast coincidence counter.

5. The automated assay system of Claim 3, wherein the fast coincidence counter is actuated by receipt of a pulse from each photomultiplier not more than ten nanoseconds apart.

6. The automated assay system of Claim 1, further comprising a calibration seed holder.

7. The automated assay system of Claim 1, wherein the robot is a SCARA robot.

8. The automated assay system of Claim 1, wherein the automated product feeder comprises a vibratory bowl feeder.

9. The automated assay system of Claim 8, wherein the automated product feeder comprises a radiation shield.

10. The automated assay system of Claim 1, wherein the robot is positionable over a single receptacle in the array in response to a signal generated by the CPU.

11. The automated assay system of Claim 3, wherein the robot is selectively positionable over a single receptacle in the array in response to a signal generated by the CPU, which signal corresponds to a radiation level determined by the CPU with input from the radiation detector and fast coincidence counter.

12. The automated assay system of Claim 1, wherein the robot is controllable by a controller that is electronically linked to the CPU.

13. The automated assay system of Claim 2, wherein the radiation detector comprises two photomultiplier tubes that are oppositely disposed relative to a scintillator and specimen well positioned therebetween.

14. An automated method for assaying the radiation dosimetry of radiotherapeutic products, the system comprising the steps of: providing within an enclosed work space a calibration sample, a continuous batch product feeder containing a plurality of radiotherapeutic products, a radiation detector, an array of product storage receptacles, and a SCARA robot selectively positionable over the calibration sample, feeder, radiation detector and array; providing a fast coincidence counter and CPU electronically linked to the radiation detector, a robot controller electronically linked to the CPU, a data storage device and a display; calibrating the radiation detector and counter using the calibration sample; controlling the robot to remove a radiotherapeutic product from the feeder; controlling the robot to insert the product into the radiation detector, where electrical pulses are generated according to the radiation dosimetry of the therapeutic product; determining the radiation dosimetry of the radiotherapeutic product from electrical pulses transmitted to the CPU from the radiation detector; classifying the radiotherapeutic product according to the radiation dosimetry; and controlling the robot to deposit the radiotherapeutic product in a receptacle within the array that corresponds to the radiation dosimetry.

15. The method of Claim 14, wherein the product feeder is a vibratory bowl feeder.

16. The method of Claim 14, wherein the radiation detector comprises at least two oppositely disposed photomultiplier tubes having the radiotherapeutic product disposed therebetween.

17. The method of Claim 16, wherein the photomultiplier tubes generate electrical signals that correspond to the radiation dosimetry of the radiotherapeutic product.

18. The method of Claim 17, wherein the electrical signals generated by the photomultiplier tubes are amplified and then directed to the fast coincidence counter.

19. The method of Claim 18, wherein the fast coincidence counter relays electrical signals corresponding to those received from the photomultiplier tubes within a predetermined interval to the CPU.

20. The method of Claim 14, wherein the radiotherapeutic product is a brachytherapy seed.