Patient positioning and monitoring system

• US 5,446,548 A
• Filed: 10/08/1993
• Issued: 08/29/1995
• Est. Priority Date: 10/08/1993
• Status: Expired due to Term

• Current Assignee: Siemens Medical Systems, Inc. (Siemens AG)
• Original Assignee: Siemens Medical Systems, Inc. (Siemens AG)
• Inventors: Gerig, Lee H., El-Hakim, Sabry F.
• Primary Examiner(s): Evans, F. L.
• Application Number:
  US08/134,362
• Time in Patent Office: 690 Days
• Field of Search: 356/373, 356/375, 250/458.1, 250/462.1, 250/491.1, 378/20, 378/65, 378/68, 378/69, 378/96-97, 378/108, 378/205, 378/206, 359/516, 359/517, 359/519, 364/413.26, 128/653.1, 606/130, 601/2, 607/88
• US Class Current: 356/620
• CPC Class Codes: A61B 2090/101 for stereotaxic radiosurgery
• CPC Class Codes: A61B 2090/3937 Visible markers
• CPC Class Codes: A61B 6/08 Auxiliary means for directing the radiation beam to a particular spot, e.g. using light beams
• CPC Class Codes: A61N 2005/1059 using cameras imaging the patient
• CPC Class Codes: A61N 2005/1076 using a dummy object placed in the radiation field, e.g. phantom
• CPC Class Codes: A61N 5/1049 for verifying the position of the patient with respect to the radiation beam
• CPC Class Codes: A61N 5/1069 Target adjustment, e.g. moving the patient support
• CPC Class Codes: G01B 11/002 for measuring two or more coordinates

Abstract

The present invention is a remote sensing system for real time monitoring of patient position which can report variations in patient setup from day to day as well as motion during individual treatments. In particular, an embodiment of the present invention includes: (a) a source of radiation for applying radiation to a patient; (b) targets affixed to the patient for reflecting radiation impinging thereon; (c) two cameras and a computer for detecting the reflected radiation and for determining the current position of the targets in three-dimensional space; (d) a data store for storing the position of the targets; (e) the computer also serving to compare the current position of the targets with positions stored in the data store; and (f) a display for displaying indicators whenever differences between the current position and the stored position exceed tolerances stored in the data store.

Claims

1. Apparatus for monitoring and sensing changes in position of a patient from a prior position at a prior time to a current position at a current time, which apparatus comprises:

a source of radiation for applying radiation to a patient;

a plurality of individual targets adapted to be releasably affixed at both a current time and a prior time to the patient, for reflecting radiation impinging thereon;

camera and computer means for detecting the reflected radiation from individual ones of the targets, uniquely identifying individual ones of said targets from which radiation was detected, and for individually determining current and prior positions of the uniquely identified targets in three-dimensional space, based on the target fixation to the patient at the current and prior times, respectively;

data storage means for storing data representative of at least the prior position of the uniquely identified targets;

computer means for comparing the current position of the uniquely identified targets with the prior position data stored in the data storage means for those identified targets, and developing from said comparing position signals representative of a difference in position of said identified targets, and therefore said patient from said prior time to said current time; and

display means responsive to said position signals for displaying indicators representative of said difference in position of said patient.

2. The apparatus of claim 1 which further comprises means for user interaction for receiving and storing data from the user, the data comprising user-set tolerances;

and wherein the display means displays the indicators so that they have a size which is proportional to the magnitude of the difference, and a color which is dependent upon the magnitude that the difference exceeds a percentage of the tolerance stored in the data storage means.

3. The apparatus of claim 2 which further comprises means for sending a position signal to a table means which supports the patient, wherein

the table means, in response to the position signal, comprises means for moving the patient so that the differences do not exceed the tolerances.

4. The apparatus of claim 2 wherein the display means comprises means for displaying an indicator in a first color if the difference exceeds a first limit and in a second color if the difference exceeds a second limit.

5. The apparatus of claim 2 wherein the display means further comprises means for displaying the differences in a predetermined color if the differences do not exceed the tolerance.

6. The apparatus of claim 1 wherein the data further comprises a treatment fraction requirement for a user defined modality of treatment and wherein the computer means further comprises means for comparing the treatment fraction with a time of application of radiation and means for signaling the operator that the time of treatment for the fraction has expired.

7. The apparatus of claim 1 wherein the data further comprises a treatment fraction requirement for a user defined modality of treatment and wherein the apparatus further comprises means for signaling that a radiation therapy machine is active and the computer means further comprises:

means for receiving the signal and determining a time of radiation;

means for comparing the treatment fraction with the time of radiation and means for signaling the operator that the time of treatment for the fraction has expired.

8. The apparatus of claim 7 which further comprises means for sending a turnoff signal to the radiation therapy machine for causing the radiation therapy machine to cease being active.

10. The apparatus of claim 5 wherein the predetermined color is green.

11. The apparatus of claim 4 wherein the first color is orange and the second color is red.

12. The apparatus of claim 4 wherein the first limit comprises a first percentage of the tolerance and the second limit comprises a second percentage of the tolerance.

13. The apparatus of claim 1 wherein the source of radiation comprises a source of infrared radiation.

14. The apparatus of claim 1 wherein the camera means comprises CCD camera means.

15. The apparatus of claim 14 wherein the camera means further comprises infrared filter means.

16. The apparatus of claim 1 wherein the target means comprises retroreflective reflector means.

17. The apparatus of claim 16 wherein the retroflector means comprises at least one reflector, the reflector being comprised of a first portion which is retroreflective and a second portion which is not retroreflective.

18. The apparatus of claim 17 wherein the first portion has a first predetermined shape and the second portion has an aperture, wherein the aperture is large enough so that a mark placed the surface of the patient may be seen when the target is affixed to the patient.

19. The apparatus of claim 1, wherein a target comprises:

a body of substantially flat material;

means disposed on one side of the body for releasably affixing the body to a patient; and

means disposed on the other side of the body for retroreflecting radiation;

wherein;

the retroreflecting means comprises a first portion which is retroreflective and a second portion which is not retroreflective.

20. The target of claim 19 wherein the first portion has a first predetermined shape and the second portion has an aperture, wherein the aperture is large enough so that a mark placed on the surface of the patient may be seen when the target is affixed to the patient.

21. The apparatus of claim 2 wherein the targets comprises at least three reflectors and wherein the computer means further comprises means for determining a position of a plane of at least three of the at least three reflectors.

22. The apparatus of claim 21 wherein the targets comprises more than three reflectors and the computer means further comprises means for determining a plane by a least squares fit between planes determined by groups of three reflectors.

23. The apparatus of claim 2 wherein the computer means further comprises means for determining a position of the patient as a center of mass of the Positions of the targets.

9. The apparatus of 6 wherein the computer means for comparing further comprises:

means for storing the fraction of treatments provided for a patient in the storage means for each treatment along with an indicator of the data of the treatment;

means for displaying the stored treatment fractions and sums of the treatment fractions.

24. Apparatus for monitoring and sensing changes in position of a patient from a prior position at a prior time to current position at a current time, which apparatus comprises:

a plurality of individual phosphorescent targets adapted to be releasably affixed to the patient at both the current time and the prior time, for generating radiation;

camera and computer means for detecting the radiation from individual ones of the targets, uniquely identifying individual ones of said targets from which radiation was detected, and for individually determining current and prior positions of the uniquely identified targets in three-dimensional space, based on the target fixation at the current and prior times;

data storage means for storing data representative of at least the prior position of the uniquely identified targets;

computer means for comparing the current position of the uniquely identified targets with the prior position stored in the data storage means for those identified targets, and developing from said comparing position signals representative of a difference in position of said identified targets, and therefore said patient, from said prior time to said current time; and

display means responsive to said position signals for displaying indicators representative of said difference in the position of said patient.

26. The apparatus of claim 24 wherein the phosphorescent means comprises at least one generator, the generator being comprised of a first portion which is phosphorescent and a second portion which is not phosphorescent.

27. The apparatus of claim 24, further comprising:

means for user interaction for receiving and storing data from the user, the data comprising a user-set tolerance; and

wherein the display means displays the indicators so that they have a size which is proportional to the magnitude of the difference, and a color which is dependent upon the magnitude that the difference exceeds a percentage of the user-set tolerance stored in the data storage means.

25. The apparatus of 24 wherein the camera means further comprises filter means for passing radiation substantially in the range of wavelengths emitted by the targets.

28. Apparatus for monitoring and sensing changes in position of a patient from a prior position at a prior time to a current position at a current time, which apparatus comprises:

a source of radiation for applying radiation to a patient;

a plurality of targets adapted to be releasably affixed at both a current time and a prior time to the patient, for reflecting radiation impinging thereon;

camera and computer means for detecting the reflected radiation from the targets and for determining current and prior positions of the targets in three-dimensional space, based on the target fixation at the current and prior times, respectively;

data storage means for storing data representative of at least the prior position of the targets;

computer means for comparing the current position of the targets with the stored prior position data for those targets, and developing from said comparing position signals representative of a difference in position of said patient from said prior time to said current time;

user means for causing input to and storage by said data storage means of user-set tolerances; and

display means responsive to said position signals for displaying indicators which are representative of said difference in position of said patient by causing the indicators to have a size which is proportional to the magnitude of the difference, and a color which is dependent upon the magnitude that the difference exceeds a percentage of the user-set tolerance stored in the data storage means.

29. The apparatus of claim 28 wherein the display means further comprises means for displaying an indicator in a first color if the difference exceeds a first limit and in a second color if the difference exceeds a second limit.

30. The apparatus of claim 28 wherein the display means further comprises means for displaying the differences in a predetermined color if the differences do not exceed the percentage of the user-set tolerance.

31. The apparatus of claim 29 wherein the first color is orange and the second color is red.

32. The apparatus of claim 29 wherein the first limit comprises a first percentage of the user-set tolerance and the second limit comprises a second percentage of the user-set tolerance.

33. The apparatus of claim 30 wherein the predetermined color is green.

34. Apparatus for monitoring and sensing changes in the position of a patient from a prior position at a prior time to a current position at a current time, which apparatus comprises:

a source of radiation for directing a predetermined narrow spectral bandwidth of radiation towards a patient;

a plurality of targets adapted to be releasably affixed at both a current time and a prior time to the patient, said targets having a reflecting surface thereon for reflecting the predetermined narrow spectral bandwidth of radiation directed to the patient and impinging thereon;

camera means having an optical bandpass filter at its optical input which passes substantially only said predetermined narrow bandwidth, and which is directed to said targets for detecting the reflected radiation from the targets and providing at an output an image signal representative of said detection;

position determining means coupled to said camera means and responsive to said image signal for determining current and prior positions of the targets in three-dimensional space, based on the target fixation at the current and prior times, respectively;

data storage means for storing at least the prior position data of the targets;

computer means for comparing the current position of individual ones of the uniquely identified targets with the prior position data stored in the data storage means for those targets, and developing from said comparing position signals representative of a difference in position of said patient from said prior time to said current time; and

display means responsive to said position signals for displaying indicators which are representative of said difference in position of said patient.

35. The apparatus of claim 34, wherein said source of radiation comprises an infrared light source, and said optical filter comprises a infrared light filter.

36. A method for monitoring and sensing changes in the position of a patient from a prior time to a current time, said method comprising the following steps:

applying a plurality of indicating marks to a surface portion of a patient whose position is to be monitored, said applying being done before the prior time;

releasably affixing a plurality of individual radiation reflecting targets to the patient so that each target of said plurality is aligned with an indicating mark at the current time and prior time;

directing radiation towards the patient;

detecting radiation reflected from individual ones of the targets at the current time and prior times, uniquely identifying individual ones of said targets from which radiation was detected, and determining current and prior positions for individual ones of the uniquely identified targets in three-dimensional space, based on the target fixation at the current and prior times, respectively;

storing data representative of at least the prior position of the targets;

comparing the current position of the targets with the prior data stored for those identified targets, and developing from said comparing position signals representative of a difference in position of said patient from said prior time to said current time; and

displaying said position signals as an indication of the difference in position of the patient from said prior time to said current time, thereby monitoring the position of the patient.

37. The method of claim 36, wherein:

said displaying step comprises displaying indicators in a three-dimensional coordinate system, which indicators have a size which is proportional to the magnitude of the difference, and a color which is dependent upon the magnitude that the difference exceeds a percentage of the tolerance stored in the data storage means.

38. The method of claim 36, wherein said affixing step comprises:

affixing individual radiation reflecting targets to the patient at the current time and prior time, each target comprising a body of substantially flat material having affixing means disposed on one side of the body for affixing the body to the patient, and retroreflecting means disposed on the other side of the body for retroreflecting radiation, the retroreflector means comprising a first portion which is retroreflective and a second portion which is not retroreflective and allows said indicating marks to be visible therethrough, so that during this affixing step said second portion of each of said targets is aligned with said indicating marks on said surface of said patient.

39. The method of claim 36, wherein:

said comparing step comprises comparing a center of mass calculated for the current position of said targets to a center of mass calculated for the prior position of said targets.

40. The method of claim 36, wherein said detecting step comprises:

calculating position vectors between each one of a plurality of said target, and a relative angular relationship between each one of said vectors at both of the current and prior times, and comparing the calculated vectors and their relative angular relationship at said current time to the calculated vectors and their angular relationship at said prior time, for uniquely identifying a plurality of said targets and their current position, and therefor said patient, in three-dimensional space.

41. The method of claim 40, wherein:

said comparing step comprises individually comparing the current position of individual ones of said uniquely identified targets to the prior position of those identified targets; and

said displaying step comprises displaying magnitudes in a three-dimensional coordinate system, said magnitudes being representative of the difference between the current three-dimensional position and a prior three-dimensional position of the patient, thereby monitoring the position of the patient.