Radioactive material billing system and method

Abstract

Quantities of radioactive material are dispersed at a user location. Billing is accomplished by monitoring the decay of material and the degree of activity following each user withdrawal.

Claims

What is claimed is:

1. A system for billing based on the usage of radioactive material held in a dispensing container comprising:

a radiation shielded chamber adapted to receive the container,

a sensor for providing a signal each time the chamber is accessed,

a detector means for detecting radiation emitted from the container while in the chamber,

a control unit responsive to the sensor and detector means for measuring the level of radiation in the container (a) periodically and (b) each time the chamber is accessed,

memory means responsive to the control unit for storing each of the radiation measurements together with the time of the access event, and

means responsive to the control unit and memory means for calculating the radioactive material actually removed from the container based on the periodic and access measurements.

2. A system for billing as set forth in claim 1 which includes an identification member for each container holding information as to the type of material and shipped radiation level of that container, reader means for ascertaining the information in such member, means responsive to the reader means for transferring such information to the control unit to determine if the initial radiation level in the container is appropriate based on the shipped radiation level.

3. A system as set forth in claim 2 where the detector means includes an activity means for measuring the radiation emitted from the lower portion of the chamber, and dilution means for measuring the radiation emitted from the upper portion of the chamber, the control unit responsive to the radiation emitted from the upper portion of the chamber being greater than a predetermined level to signal a spent container and discontinue measuring radiation emitted from the container.

4. A system as set forth in claim 3 wherein the chamber has a lid that can be opened to provide access to the chamber, the sensor detecting the opening of the lid.

5. A system as set forth in claim 3 wherein the chamber is a cylindrical cavity defined by a block and the radiation detector is located in the lower portion of the block, the block defining first and second bores communicating with different portions of the chamber and the radiation detector, a drum means positioned in the path of the bores and being selectively rotatable to close one end or the other of the first and second bores.

6. A system as set forth in claim 5 wherein the first bore communicates with the bottom of the chamber and the second bore communicates with a portion of the chamber above the bottom.

7. A system as set forth in claim 6 wherein the drum also defines a cavity containing an internal calibration source.

8. A system as set forth in claim 2 which also includes computer means for billing and means for transmitting such information as to material actually removed to the computer means for billing users for material actually used.

9. A system as set forth in claim 8 where the detector means includes an activity means for measuring the radiation emitted from the lower portion of the chamber, and dilution means for measuring the radiation emitted from the upper portion of the chamber, the control unit responsive to the radiation emitted from the upper portion of the chamber being greater than a predetermined level to signal a spent container and discontinue measuring radiation emitted from the container.

10. A system as set forth in claim 2 where the detector means includes an activity means for measuring the radiation emitted from the lower portion of the chamber.

11. A system as set forth in claim 1 wherein the chamber is a cylindrical cavity defined by a block and the radiation detector is located in the lower portion of the block, the block defining first and second bores communicating with different portions of the chamber and the radiation detector, a drum means positioned in the path of the bores and being selectively rotatable to close one or the other of the first and second bores.

12. A system as set forth in claim 11 wherein the first bore communicates with the bottom of the chamber and the second bore communicates with a portion of the chamber above the bottom.

13. A system as set forth in claim 12 which also includes first sensors for detecting the rotating position of the drum and second sensors for detecting the opening of the chamber all coupled to the control unit.

14. A method of measuring dispensed doses of a radioactive material from a dispensing container adapted to be held in a shielded chamber with a removable access lid using a radiation detector to measure radioactivity in the chamber comprising the steps of:

first measuring the radioactivity in the chamber when a dispensing container is first loaded into the chamber,

recording the first measurement and its time and date,

second measuring the radioactivity in the chamber each time the lid is removed,

recording each second measurement and its time and date,

third measuring the radioactivity in the chamber each time the lid restored on the chamber,

recording each third measurement and its time and date, and

calculating the radioactive material actually used based on such measurements.

15. A method set forth in claim 14 which includes the additional step of periodically measuring the radioactivity in the chamber,

recording each such measurement and its time and date, and

comparing such periodic measurements with the anticipated radioactive decay of the material to insure against unauthorized usage of the material.

16. A method set forth in claim 15 which includes the initial step of injecting a dilution fluid into the dispensing container at the end of the materials useful life until the detector senses the dilution fluid having reached a predetermined level in the dispensing container indicating a useless concentration for medical purposes.

17. A method set forth in claim 14 which includes the initial step of injecting a dilution fluid into the dispensing container at the end of the materials useful life until the detector senses the dilution fluid having reached a predetermined level in the dispensing container indicating a useless concentration for medical purposes.

18. A method set forth in claim 17 which includes the additional step of transmitting the recorded measurements, time and dates to a billing location, and preparing a billing based on radioactive material actually withdrawn from the dispensing container.

19. A method set forth in claim 14 which includes the additional step of transmitting the recorded measurements, time and dates to a billing location, and preparing a billing based on radioactive material actually withdrawn from the dispensing container.

Description

BACKGROUND OF THE INVENTION

Radioisotopes, as radiopharmaceuticals, have come into widespread usage in hospitals and the like for diagnostic and other purposes. Once the radioactive material is manufactured it is shipped in multidose containers to the using or distributing site, such as a radio pharmacy, for later dispensing and shipment of prescribed single doses to the ultimate user. This procedure presents little problem except in the case of those isotopes such as thallium, gallium, and technitium which have relatively short half-lives. In the case of thallium-201, for example, which is used in heart imaging, the half-life is in the order of 73 hours. Thus this radioisotope while having a high value in use, i.e., heart studies, is perishable and after manufacture must be shipped quickly to the user before its strength decays below that needed for heart imaging. This necessitates, in many cases, shipment by air which is relatively expensive and does not permit the user to maintain a supply on hand for unanticipated needs. This can create unacceptable delays in performing often urgently needed diagnostic tests.

The radioactive materials could be shipped in larger quantities and stored until the user is ready for them. This presents a problem, however, since one does know how much is used of the material and how the user should be billed for such material used.

SUMMARY OF THE INVENTION

According to the method of this invention, quantities of radioactive material in a container are supplied to a dispenser at a user location together with information on a label card as to the type of radioactive material, calibration date, concentration and total quantity in the container. The user places the container of radioactive material in a shielded chamber attached to a usage recorder in the dispenser. This recorder includes a real time clock, calendar and a radiation detector. The detector measures the received radioactivity of the container and checks it against the label quantity and the information is recorded in a nonvolatile computer memory. Every time the lid of the chamber is opened or closed for the dispensing of the radioactive material, the time and radiation level of the radioactive material in the container is recorded and stored in the nonvolatile memory. At the end of the useful life of the radioactive material, a dilution fluid is injected into the container until the radiation detector means senses that the diluted level of the fluid is now at a useless concentration for medical purposes. The spent radioactive material container may then be removed from the chamber and disposed of in a proper manner. The dispenser then communicates with a billing location to send back information as to actual radioisotope usage for billing the user and the user is billed.

In this manner, the larger quantities of radioactive material may be sent, thereby lowering the transportation costs which is significant particularly with short half-life radioactive materials. Thus the user may be charged on a timely basis only for the quantity of isotope or radioactive material they actually used.

The invention also provides a system for effecting billing from a billing location based on the actual usage of radioactive material held in a dispensing container at a user location. The system comprises a radiation-shielded chamber adapted to receive the container at a user location, a sensor for providing a signal each time the chamber is accessed, a detector means for detecting radiation emitted from the container while in the chamber, a control unit responsive to the sensor and detector means for measuring the level of radiation emitted from the container (a) periodically and (b) each time the chamber is accessed, memory means responsive to the control unit for storing each of the radiation measurements together with the time of the access event, and billing means responsive to the control unit and memory means for calculating the radioactive material actually removed from the container based on the periodic and access measurements.

The system also includes an identification member for each container holding information as to the type of material and shipped radiation level of that container, reader means for ascertaining the information in such member, and means responsive to the reader means for transferring such information to the control unit to determine if the initial radiation level in the container is appropriate based on the shipped radiation level. The detector means includes means for measuring the radiation emitted from the lower portion of the chamber and means for measuring the radiation emitted from the upper portion of the chamber, the control unit being responsive to the radiation emitted from the upper portion of the chamber being greater than a predetermined level to signal a spent container and discontinue measuring radiation emitted from the container.

The user is prevented from cheating--he must dilute and render the radioactive material useless for medical purposes or be billed for the material. Both user and supplier save since the high transportation costs are reduced and the user benefits by always having a supply of material on hand.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed operation of the method and system described briefly above can be best understood by reference to the following drawings in which:

FIG. 1 is a block diagram of the system of this invention constructed in accordance with a preferred embodiment of this invention;

FIGS. 2 through 6 are various views of the dispensing unit constructed in accordance with this invention;

FIG. 7 is an elevation view partially cut away of the complete dispenser including a housing for the I/O board;

FIG. 7A is a plan view of the CAL CARD used with the I/O board;

FIGS. 8 through 10 are plan, elevation of and end views of the drum used in the dispensing unit of FIGS. 2-6;

FIG. 11A and 11B are block schematic diagrams of the I/O board depicted in FIG. 1;

FIGS. 12 through 19 are flow charts depicting the various sequences of operation by which the system of this invention functions to record the usage of radioactive materials at user locations; and

FIGS. 20A & B are flow charts depicting the billing sequence at the billing computer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Thus the system includes as may be seen in FIG. 1, a radioactive material container and sensors 20, a radiation detector 22 located immediately below the container 20, as is seen more clearly in FIGS. 2-6, and a calibration card designated CAL-CARD 24. The output of the radiation detector 22 which is an analog signal together with digital outputs CA28 to 32 from the isotope containers and sensor and digital outputs CA1 to 27 from the CAL-CARD are all coupled to the I/O circuit board 26. The I/O circuit board, as will be more particularly described, contains a 6-K PROM automatic start program, a 2-K CMOS RAM data storage, a real time clock, an 8-BIT analog to digital converter, a 32-BIT input and an 8-BIT output, and provides digital output signals, E.sub.1, E.sub.2, D.sub.0 -D.sub.7, and LCD-R/W and R5 signals to a liquid crystal display (LCD) and sound output device 36. In addition it provides a number of digital signals including reset, I/03, A.sub.0 -A.sub.15, D.sub.0 -D.sub.7, CR/W, VR/W and BLK5 to a computer 28. Although any computer may be used for this purpose, a VIC 20 computer has been found entirely satisfactory. The output of the computer is also coupled to the LCD display 36 and to a modem 30 which of course may be plugged to a telephone 32 for transmittal back through a receiving end modem 33 to a billing location 34.

The isotope container and sensors 20 are best illustrated in FIGS. 2-6.

The dispenser is seen in an elevation view partially cut away most clearly in FIG. 7. In this figure the dispenser is seen to include a base member 40 in which is housed the I/O board 26 (shown in FIGS. 11A & 11B) a slot 42 into which the CAL-CARD 24 may be inserted to be plugged into the I/O board 26. A cavity 44 is provided for a photomultiplier tube 46. The photomultiplier tube 46 extends upwardly out of the base member 40 and into the lower portion of a shielded chamber 48. The shielded chamber is shielded by a shield 50 which is held by a set screw 52 in a cavity 54 formed in a dispenser block 56. A sodium iodide or similar crystal 58 is positioned in the upper portion of the cavity 48. The top of the shield 50 is open and communicates with two bores 60 and 62. The bores 60 and 62 are interrupted by a rotary drum 64. The bores 60 and 62 extend respectively into the lower portion of a shielded cavity 66 adapted to receive a container 68 of radioactive material. The first bore 60 extends into the bottom of that cavity and the second bore 62 extends upward to a point along the side wall of the cavity. The cavity itself is defined by a shield member 70 and a lid 72 which pivots at 74 so that it may be opened easily by a finger indentation 76. The inside of the lid 72 also has a shield member 78 to prevent radiation from the material in the dispenser 68 from harming users. As seen in FIG. 9, the drum 64 is mounted on a shaft 80, one end of which has a single detent dimple 82 (FIGS. 8-10) adapted to engage any one of three microswitches 84, 86, 88 (FIG. 3). Microswitch 84 provides a CA29 signal to the I/O board; microswitch 86 provides the normal signal CA28 to the I/O board; and microswitch 88 provides a CA30 signal denoting CALIBRATE to the I/O board. A fourth microswitch 90 is connected to be operated by a sensing rod 92.

The other end of the shaft 80 has three detent dimples 93 adapted to engage detent 94 (FIG. 4). The three locations correspond to positions on a KNOB 96 (FIG. 4), connected to the other end of the shaft 80, of calibrate, dilute and normal. The shaft 80 is mounted by sleeve bearings 98 (FIG. 6) and a sleeve 100 held by screws to the block 56 which forms the dispensing unit housing. The microswitches are accessed by a rmovable panel 104 held by a screw 106 (FIG. 6). The drum 64 has an offset bore 110 which is in alignment with one of the bores 62, as seen in FIG. 7, and upon rotation of shaft 80, 180.degree. is in alignment with the remaining bore 60. Positioned at approximately 90.degree. around the shaft from the bore 110 is a receptacle holding a calibration source 112 of radioactive material such as 195Au. This internal calibration source when the KNOB is rotated into the "calibrate" position, will then be directly above the sodium iodide crystal 58.

In the operation of this dispenser, when it is desired to introduce a dispensing container 68 into the cavity 66, one merely lifts the lid 72, inserts the container 68, closes the lid 72, inserts the CAL-CARD in the slot 42 and rotates the KNOB 96 to the "normal" position. The "normal" position is such that the bore 110 is in alignment with base 60 to sense the radiation level in the bottom of the cavity 66. Likewise in the "dilute" position bore 110 is in alignment with bore 62 to measure the radiation level in the mid portion of the chamber, i.e., the portion where the diluted fluid in the container will be. The CAL-CARD itself (FIG. 7A) is simply an edge-board 120 having fusible links 124 connected to ground 126 from edge-board connector contacts 122 on both the top and bottom of one edge of the edge-board. The fusible links are broken as needed to provide "1" or "0" inputs CA1-28 to the I/O circuit 26. The program now takes over, as will be described hereinafter, to make the periodic measurements and calculations as are necessary to the operation of this automatic billing system.

The I/O board may be best seen in FIGS. 11A and 11/B. The board includes a number of integrated logic circuits and gates including memory devices, analog digital converters, storage registers and the like. In particular, the chip IC1 is a TTL logic, chip 74 LS 245 Octal Bus Transceiver which is a bidirectional buffer and signal conditioner for eight data lines. Chip IC2 is a National Semi-Conductor, MM58167 microprocessor compatible real time clock and calendar which provides time and data information so that the expected decay of radioactivity can be calculated. This integrated circuit chip also provides the time and data information of actual material usage. Associated with this chip is a crystal used with the invention that is a 32,768 Hz crystal-controlled oscillator, capacitor C.sub.1 is an adjustable capacitor for the crystal, resistor R14 and capacitor C.sub.3 are signal filters, resistor R13 and capacitor C.sub.2 is a power down sensing circuit, resistor R19 is a pull up resistor for another integrated circuit to maintain a logic "1" for IC2 in a power down condition and BUP input is a backup power from battery B.sub.1 to keep the clock IC2 running in a power down condition.

IC3 is a National Semi-Conductor ADC0804 8-bit analog to digital converter which functions to convert the analog signal from the radiation detecting circuit to an 8-bit digital signal accessible by the host computer 28. A reference potential of 2.5 volts is provided by R.sub.15 and a zener diode. Integrated circuit chips IC4, IC5 and IC6 are Motorola MCM2716 2048.times.8-Bit UV erasable programmable read only memory (PROM) chips that provide 6-K bytes of software program for the recorder. A CMOS RAM 6516 chip IC7 provides 2-K bytes of data storage for machine identification, and up to 254 files of isotope usage data. This chip is powered by BUP which will retain the data in this chip during power down. This chip will also be deselected by connecting R.sub.4 to BUP during power down.

A TTL logic 74 LS 156 with an open collector address decoder decodes signals from A.sub.11 and A.sub.12 and memory block select line BLK5 for integrated circuit chips IC4, 5, 6 and 7.

Chips IC9, 10, 11 and 12 are tri-state octal bus transceivers for 32-bits of digital input data from the CAL-CARD and lid condition sensor lines in FIGS. 2 through 6.

A TTL 74 LS 373 octal D-type latch is used for IC13 and provides 8 bits of digital output signal to drive the LED indicators and automatic reset circuit (IC16).

The chip IC14 is a TTL 74 LS 156 address decoder and functions to decode A.sub.0, A.sub.6, A.sub.7, A.sub.8 and I/O 3 lines for the chips IC9, 10, 11, 12, 13, 2 and 3.

A TTL 74 LS 221 monostable multivibrator is used for IC15 and functions to provide proper timing signal for the LCD display circuits.

Chip IC16 is a timer NE 555 configured as a "Missing Pulse Detector". R.sub.16, R.sub.19 and C.sub.7 set up this IC as a multivibrator with a 2 minute off-time and a 30 second on-time. Capacitor C.sub.7 is in parallel with transistor T.sub.1. In a normal operating cycle, a pulse is commanded by software to be sent from IC13 to the base of T.sub.1. This pulse will cause the charge built up in C.sub.7 to discharge via the emitter and collector of T.sub.1. In a normal operating cycle, one pulse per minute is expected from IC13 and will keep C.sub.7 from building up charge to 2/3 of Vcc. In case of momentary software or hardware failure which cause the normal program cycle to stop, T.sub.1 will not receive pulse from IC13 and within 2 minutes, C.sub.7 will build up charges to 2/3 Vcc level and cause the output from pin 3 of 555 to go low. This output pulse (from pin 3) will couple via C.sub.12 to reset the host computer and re-initiate the main program.

An Intersil 7660 voltage converter forms the chip IC17 and converts +5 volts to -5 volts for the viewing adjustment circuit of the LCD.

A TTL 74 LS 00 quadruple 2-input positive--NAND GATES constitutes the chip IC18.

The chip IC19 is a TTL 74 LS 04 hex inverter, chip IC20 is a TTL 74 LS 02 quadruple 2-input positive--NOR GATES.

I/O BOARD FUNCTION

This board is connected to a host computer 20 with 16 address lines (A0 to A15) and 8 data lines (D0 to D7) both with positive logic (high--1, low--0). It is also connected to read/write lines CR/W and VR/W which will go "low" when data are sent from host computer to the board and go "high" when data are expected from the board. Furthermore, it is connected to I/03 line and BLK5 line which will address 9C00-9DFF and A000-BFFF memory locations respectively when the line goes low. This board is also connected to the PHASE-2 clock signal and the RESET line of the computer.

The data transfer direction of IC1 is controlled by the signal at pin 1 which is connected to the read/write line. In write mode, data D0-D7 from the computer are transferred to D0'-D7' DATA BUS which are connected to on-board memories IC4, IC5, IC6, IC.sub.7, clock IC2, ADC IC3, Digital Input Devices IC9, IC10, IC11, IC12, Output Device IC13, and LCD. In read mode, data in the DATA BUS will be transferred to the computer BUS D0-D7. IC1 is active only when address groups between A000-BFFF or 9C00-9DFF are called, i.e. when either BLK5 line or I/03 lines goes low which will cause the output (pin 3) of inverter IC18a to go high and in turn causes output (pin 6) of inverter IC19c to go low. When IC1 is not active, (pin 19 high), all data lines of IC1 are in high impedance state and will have no effect on the computer DATA BUS or on any devices on the I/O BOARD.

All devices in the I/O BOARD can be regarded as memory locations to the computer. IC8 decodes A11, A12, and BLK5 lines in the following ways:

    ______________________________________
    . . . BLK5 . . . A11 . . . A12 . . . L0 . . . L1 . . . L2 . . . L3
    . . . . .L . . . . .L .. . . .L .. . .L . . . .H. . .H. . .H
    . . . . .L . . . . .H .. . . .L .. . .H .. . .L. . .H. . .H
    . . . . .L . . . . .L .. . . .H .. . .H . . . .H. . .L. . .H
    . . . . .L . . . . .H .. . . .H .. . .H . . . .H. . .H. .
    ______________________________________
    .L

    __________________________________________________________________________
    . . . A0 . . . I/03 . . . A6 . . . A7 . . . A8 . . . V0 . . . V1 . . . V2
    . . . V3 . . . V4 . . . V5 . . . V6 . . . V7
    . . .L. . .X. . .X. . .X. . .X. . .H. . .H. . .H. . .H. . .H. . .H. . .H.
    . .H
    . . .H. . .H. . .X. . .X. . .H. . .H. . .H. . .H. . .H. . .H. . .H. . .H.
    . .H
    . . .H. . .L. . .L. . .L. . .L. . .L. . .H. . .H. . .H. . .H. . .H. . .H.
    . .H
    . . .H. . .L. . .H. . .L. . .L. . .H. . .L. . .H. . .H. . .H. . .H. . .H.
    . .H
    . . .H. . .L. . .L. . .H. . .L. . .H. . .H. . .L. . .H. . .H. . .H. . .H.
    . .H
    . . .H. . .L. . .H. . .H. . .L. . .H. . .H. . .H. . .L. . .H. . .H. . .H.
    . .H
    . . .H. . .L. . .L. . .L. . .H. . .H. . .H. . .H. . .H. . .L. . .H. . .H.
    . .H
    . . .H. . .L. . .H. . .L. . .H. . .H. . .H. . .H. . .H. . .H. . .L. . .H.
    . .H
    . . .H. . .L. . .L. . .H. . .H. . .H. . .H. . .H. . .H. . .H. . .H. . .L.
    . .H
    . . .H. . .L. . .H. . .H. . .H. . .H. . .H. . .H. . .H. . .H. . .H. . .H.
    . .L
    __________________________________________________________________________

    ______________________________________
    IC9 V0 ADDRESS: 9C00-9C3F
                       DIGITAL INPUT
                         FROM CA1-CA8
                       IC10 V1 ADDRESS: 9C40-9C7F
                        DIGITAL INPUT
                         FROM CA9-CA16
                       IC11 V2 ADDRESS: 9C80-9CBF
                        DIGITAL INPUT
                         FROM CA17-CA24
                       IC12 V3 ADDRESS: 9CC0-9CFF
                        DIGITAL INPUT
                         FROM CA25-CA32
                       IC13 V4 ADDRESS: 9D00-9D3F
                        DIGITAL OUTPUT
                         TO CA33-CA39
                         AND Q8
                       LCD V5 ADDRESS: 9D40-9D7F
                        LIQUID CRYSTAL
                         DISPLAY --
                         SEE NOTE A
                       IC3 V6 ADDRESS: 9D80-9DBF
                        ANALOG TO
                         DIGITAL
                         CONVERTER -
                         SEE NOTE B
                       IC2 V7 ADDRESS: 9DC0-9DFF
                        REAL TIME
                         CLOCK -- SEE
                         NOTE C
    ______________________________________

    ______________________________________
    . . . A1 . . . A2 . . . A3
    . . .L. . .L. . .L. . .
                        SECOND
    . . .H. . .L. . .L. . .
                        MINUTE
    . . .L. . .H. . .L. . .
                        HOUR
    . . .H. . .H. . .L. . .
                        DAY OF WEEK
    . . .L. . .L. . .H. . .
                        DAY OF MONTH
    . . .H. . .L. . .H. . .
                        MONTH
    ______________________________________

• Inventors
  Lee, Denny L. Y.;
• Assignee
  E.I. du Pont de Nemours and Company (Wilmington, DE)
• Published
  Jul-7-1987
• Current US Classes:
  250/328
  250/432PD
  340/825
  340/870.07
  379/106.01
  705/34
  902/24
• Application #
  627867
• International Classes
  G01R 021/00; G06F 015/20; G06F 015/24
• Field of Search
  250/328 250/361 364/406 364/413 364/414 364/446 340/825 340/31-34 340/870.07
• Examiner
  Smith; Jerry
• US Patent References:
  4291375