On-line treatment monitoring for radiation teletherapy

• US 4,365,341 A
• Filed: 06/09/1980
• Issued: 12/21/1982
• Est. Priority Date: 06/09/1980
• Status: Expired due to Term

• Current Assignee: Johns Hopkins University
• Original Assignee: Johns Hopkins University
• Inventors: Lam, Wing-Chee
• Primary Examiner(s): Smith, Alfred E.
• Assistant Examiner(s): FIELDS, CAROLYN
• Application Number:
  US06/157,843
• Time in Patent Office: 925 Days
• Field of Search: 250/491, 250/492 R, 250/416 TV, 250/369, 250/370, 364/414
• US Class Current: 378/65
• CPC Class Codes: A61N 2005/1054 using a portal imaging system
• CPC Class Codes: A61N 5/1049 for verifying the position of the patient with respect to the radiation beam

Abstract

A method and apparatus are provided for the on-line treatment monitoring of patients during radiation teletherapy. A patient is positioned in the irradiation portal of the radiation teletherapy machine in a supposed effective treatment position, and operation of the machine is effected to provide several pulses of high energy x-rays. The pulses are detected by a plurality of solid-state detectors disposed on the opposite side of the patient as the teletherapy machine, and the pulses are transformed to electrical signals. Lead covers the detectors to screen out low energy radiation. The electrical signals are immediately automatically converted to a readable display providing the landmarks of the irradiation portal, and the patient'"'"'s position as defined by the landmarks is compared to a predetermined desired position for effective treatment. In case of misalignment, treatment is halted, the patient'"'"'s position is then immediately adjusted with respect to the irradiation portal so that it is proper for effective treatment, and the radiation teletherapy machine is then actuated to deliver the desired dosage of radiation to the patient for therapy. The digital data of the image can be stored on magnetic disk or tape for later review.

Claims

1. A method of treating a patient with radiation therapy utilizing a radiation teletherapy machine capable of emitting high-energy x-rays, comprising the steps of:

(a) positioning the patient in the irradiation portal of the radiation teletherapy machine in a supposed effective treatment position;

(b) effecting operation of the machine to emit a therapy beam, and only a therapy beam, of high-energy pulses for effective patient treatment;

(c) automatically detecting only the high-energy pulses and transforming the radiation detected during the pulses to electrical signals, by providing at least one linear array of solid-state detectors in a position on the opposte side of the patient as the fixed beam radiation teletherapy machine, and stepping the at least one linear array over at least a portion of the irradiation portal in sync with the pulses from the radiation teletherapy machine;

(d) immediately converting the electrical signals to a readable display providing the landmarks of the irradiation portal;

(e) comparing the patient'"'"'s position as defined by the landmarks to a predetermined desired position for effective treatment;

(f) immediately halting irradiation if the portal is outside the acceptable margin;

(g) adjusting the patient'"'"'s position with respect to the irradiation portal so that it is proper for effective treatment; and

(h) continuing radiation therapy to deliver the desired dosage of radiation to the patient.

2. A method as recited in claim 1 wherein step (c) is further practiced by positioning filtering means over the detectors to prevent low energy scattered radiation from reaching the detectors.

3. A method as recited in claim 1 comprising the further step (i) of, repeating steps (b) through (g) until the patient'"'"'s position corresponds exactly to that desired.

4. The method of claim 1 wherein the readable display of step (d) is recorded.

5. A method as recited in claim 1 wherein step (d) is practiced by automatically processing and digitizing the electrical signals in synchronization with the radiation teletherapy machine pulses, and summing the electrical signals from each detector.

6. A method as recited in claim 5 wherein step (d) is further practiced by automatically converting the summed signals to analog information, and converting the analog information to a video display.

7. A method as recited in claim 5 wherein step (d) comprises the further step of feeding the summed digitized information to a microprocessor.

8. A method as recited in claim 1 wherein step (d) is practiced by amplifying the electrical signals, and sampling and holding the signals in sync with the radiation teletherapy machine pulses.

9. A method as recited in claim 8 wherein step (d) is further practiced by reading the signals from the sample and holds with a multiplexer, converting the signals to digital information, summing the digital information from each detector for a plurality of pulses, feeding the information to a microprocessor, and feeding the information from the microprocessor to an ultimate display station.

10. A method as recited in claim 8 comprising the further step of isolating grounds for the solid-state detectors and the radiation teletherapy machine utilizing an opto-coupler.

11. A method as recited in claim 1 wherein step (d) is practiced in part by scanning all detectors after each pulse.

12. A method as recited in claims 1 or 2 consisting essentially of said steps.

13. Apparatus for on-line treatment monitoring for radiation teletherapy, comprising

a radiation teletherapy machine for emitting high-energy x-ray pulses in a therapy beam, and only a therapy beam, in an irradiation portal;

a patient treatment couch;

detecting means for detecting only the high-energy x-rays emitted from said radiation teletherapy machine and transforming the x-rays detected to electrical signals, said means located on the opposite side of said patient treatment couch as said radiation teletherapy machine, said detecting means comprising a plurality of solid-state detectors disposed in a two-dimensional matrix operatively covering the irradiation portal;

filtering means covering said detecting means for preventing low energy scattered radiation from reaching said detecting means; and

means for converting the electrical signals produced by said detecting means to a readable display providing patient landmarks of the irradiation portal.

14. Apparatus as recited in claim 13 wherein said solid-state detectors are composed of materials selected from the group consisting essentially of silicon, cadmium telluride, and mercuric iodide.

15. Apparatus as recited in claim 13 wherein said solid-state detectors are detectors operable at room temperature having an effective atomic number Z greater than or equal to about 14.

16. Apparatus as recited in claim 13 wherein said means for converting the electrical signals produced by said detecting means to a readable display comprise an amplifier associated with each detector;

a sample and hold means associated with each detector; and

means for connecting said sample and hold means to said radiation teletherapy machine through a pulse shaping and time delay for controlling said sample and hold means.

17. Apparatus as recited in claim 16 further comprising an opto-coupler for isolating the ground of said radation teletherapy machine from the ground of said detectors.

18. Apparatus as recited in claim 16 wherein said means for converting the electrical signals produced by said detecting means to a readable display further comprise analog/digital converter means operatively attached to the output from said sample and hold means;

adding means operatively attached to the output from said analog/digital converter means for summing the electrical signals from each detector; and

a microprocessor operatively connected to said adding means.

19. Apparatus as recited in claim 16 wherein said means for converting the electrical signals produced by said detecting means to a readable display further comprise a multiplexer connected to the output from said sample and hold means, and an analog/digital converter operatively connected to said multiplexer.

20. Apparatus as recited in claims 13, or 16 consisting of the recited components.

21. Apparatus as recited in claim 13 wherein said detectors are arranged in at least one horizontal line, and in parallel in vertical stacks, a metal sheet being provided between the detectors in each vertical stack to thereby increase detection efficiency.

22. Apparatus as recited in claim 13 wherein a single conductor is connected to each row of detectors, and a single conductor to each column of detectors, in said matrix.

23. Apparatus as recited in claim 13 wherein said solid-state detectors comprise silicon diodes.

24. Apparatus as recited in claim 23 wherein the anodes of said diodes are connected to a reverse bias voltage source.

25. Apparatus as recited in claim 23 wherein said diodes are horizontally spaced from each other in a grouping disposed in the irradiation portal.