Method and apparatus for diagnostic imaging in radiation therapy

• US 5,233,990 A
• Filed: 01/13/1992
• Issued: 08/10/1993
• Est. Priority Date: 01/13/1992
• Status: Expired due to Fees

• Current Assignee: Gideon Barnea
• Original Assignee: Gideon Barnea
• Inventors: Barnea, Gideon
• Primary Examiner(s): Cohen, Lee S.
• Assistant Examiner(s): GILBERT, SAMUEL G
• Application Number:
  US07/819,957
• Time in Patent Office: 575 Days
• Field of Search: 128/653.1, 378/65
• US Class Current: 600/427
• CPC Class Codes: A61B 6/00 Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment instruments measuring radiation intensity for application in the field of nuclear medicine, e.g. in vivo counting, G01T1/161; apparatus for taking X-ray photographs G03B42/02
• CPC Class Codes: A61N 2005/1054 using a portal imaging system
• CPC Class Codes: A61N 2005/1061 using an x-ray imaging system having a separate imaging source
• CPC Class Codes: A61N 5/1049 for verifying the position of the patient with respect to the radiation beam

Abstract

An apparatus for diagnostic and verification imaging in radiation therapy that consists of attachments for standard radiotherapy equipment comprising an x-ray tube and an x-ray detector placed on opposite sides of a patient along the main axis of the beam produced by the treatment unit. The detector is placed on a plane orthogonal to the axis of the treatment beam and between the beam source and the patient, while the x-ray tube is placed on the other side of the patient, coaxially with the treatment beam and facing the detector. As a result of this configuration, the radiographic view of the x-ray beam, as seen on the detector, is equivalent to the view produced on the same detector by the therapeutic beam, varied only by parallax deviations that can be corrected by geometrical calculations. Accordingly, x-ray exposures and real-time verification of the position of a patient can be obtained with the same unit used for treatment and without requiring movement of either patient or equipment. In addition, the apparatus enables a user to produce diagnostic images that can be used directly to manufacture shielding blocks in conventional shielding-block cutters.

Claims

1. An imaging apparatus in combination with conventional radiation therapy equipment consisting of a gantry having a high-energy radiation source capable of emitting a high-energy radiation beam and having shielding blocks, said gantry being disposed for irradiation of a stationary patient positioned on a gurney at a fixed distance from the high-energy radiation source, said apparatus comprising the following components:

a low-energy radiation source capable of emitting a low-energy radiation beam and mounted on a side of the gantry opposite to the high-energy radiation source, such that the beam from said low-energy radiation source is coaxial with the beam from the high-energy radiation source; and

a radiation detector mounted between the high-energy radiation source and the low-energy radiation source so as to be between the high-energy radiation source and the patient'"'"'s gurney, said detector being positioned so that it can be exposed to both the high-energy beam and the low-energy beam;

wherein said low-energy radiation source and said detector are used to irradiate the patient and obtain diagnostic images of the patient before treatment with the high-energy beam and to obtain verification images of the patient'"'"'s position for proper therapeutic irradiation during treatment.

2. The apparatus described in claim 1, wherein said low-energy radiation source consists of an x-ray tube.

3. The apparatus described in claim 1, wherein said radiation detector consists of a fluorescent screen.

4. The apparatus described in claim 1, further comprising a mirror positioned to receive the verification images formed on said radiation detector thereby forming corresponding images on said mirror and comprising a video camera positioned to receive the corresponding images formed on said mirror, so that the verification images created on the radiation detector are received by the video camera during a treatment session.

5. A method for producing corrected verification images of anatomical portions of a patient being treated with conventional radiation therapy equipment consisting of a gantry having a high-energy radiation source capable of emitting a high-energy radiation beam along a high-energy beam axis and having shielding blocks, said gantry being disposed for irradiation of a stationary patient positioned on a gurney at a fixed distance from the high-energy radiation source, a simulator of the radiation therapy equipment, and a shielding-block cutter, said method comprising the following steps:

(a) using the simulator of the radiation therapy equipment to produce diagnostic images of the patient from a field of view equal to the field of view of the high-energy radiation source;

(b) delineating the anatomical portions of the patient requiring treatment on said diagnostic images;

(c) using said shielding-block cutter to adapt the shielding blocks so that the high-energy source has a field of view limited to an area corresponding to the anatomical portions delineated on said diagnostic images;

(d) providing a low-energy radiation source mounted on a side of the gantry opposite to the high-energy radiation source, said low-energy radiation source being capable of emitting of low-energy radiation beam along a low-energy beam axis coaxial with the axis of the beam from the high-energy radiation source;

(e) providing a radiation detector mounted between the high-energy radiation source and the patient'"'"'s gurney, said detector being positioned so that it can be exposed to both the high-energy beam and the low-energy beam;

(f) irradiating the patient with said coaxial low-energy radiation source during treatment to form verification images on said radiation detector;

(g) performing parallax corrections to the verification images so produced in order to obtain corrected verification images that are directly comparable to the diagnostic images produced during step (a); and

(h) comparing the corrected verification images with the diagnostic images during treatment to ensure that the anatomical portions of the patient being irradiated by high-energy radiation treatment correspond to the anatomical portions delineated on the diagnostic images.

6. The method described in claim 5, wherein said parallax corrections are performed using the following relationship:

space="preserve" listing-type="equation">X.sub.d =X.sub.t (1+d/S.sub.t)/(1-d/S.sub.d),

where S_t and S_d are the distances of the high-energy radiation source and the low-energy radiation source, respectively, from the detector;

X_t is a distance between the axis of the high-energy beam and an image of an anatomatical point back-projected by the high-energy beam on the radiation detector, and X_d is a distance between the axis of the low-energy beam and the image of the same anatomical point projected by the low-energy beam on the radiation detector; and

d is the distance between the anatomical point and the radiation detector.

7. The method described in claim 5, further comprising the steps of:

providing a mirror positioned to receive the verification images formed on said radiation detector thereby forming corresponding images on the mirror and providing a video camera positioned to receive the corresponding images formed on said mirror, so that the verification images created on the radiation detector are received by the video camera; and

irradiating the patient during a treatment session to provide real-time verification of the patient'"'"'s position to ensure that the anatomical portions being irradiated by high-energy radiation treatment correspond to the anatomical portions delineated on the diagnostic images.

8. A method for producing diagnostic and verification images of anatomical portions of a patient being treated with conventional radiation therapy equipment consisting of a gantry having a high-energy radiation source capable of emitting a high-energy radiation beam along a high-energy beam axis and having shielding blocks, said gantry being disposed for irradiation of a stationary patient positioned on a gurney at a fixed distance from the high-energy radiation source, and a shielding-block cutter, said method comprising the following steps:

(a) providing a low-energy radiation source mounted on a side of the gantry opposite to the high-energy radiation source, said low-energy radiation source being capable of emitting a low-energy radiation beam along a low-energy beam axis coaxial with the axis of the beam from the high-energy radiation source;

(b) providing a radiation detector mounted between the high-energy radiation source and the patient'"'"'s gurney, said detector being positioned so that it can be exposed to both the high-energy beam and the low-energy beam;

(c) irradiating the patient with said coaxial low-energy radiation source to form diagnostic images of the patient on said radiation detector from a field of view corresponding to the low-energy radiation source;

(d) delineating the anatomical portions of the patient requiring treatment on said diagnostic images;

(e) using said shielding-block cutter to adapt the shielding blocks so that the high-energy source has a field of view limited to an area corresponding to the anatomical portions delineated on said diagnostic images;

(f) irradiating the patient with said coaxial low-energy radiation source during treatment to form corresponding verification images on said radiation detector; and

(g) comparing the verification images with the diagnostic images during treatment to ensure that the anatomical portions of the patient being irradiated by high-energy radiation treatment correspond to the anatomical portions delineated on the diagnostic images.

9. The method described in claim 8, wherein said shielding block cutter comprises a high-energy radiation source simulator, a shielding blocks simulator and a radiation detector simulator, and wherein said step of adapting the shielding blocks so that the high-energy source has a field of view limited to an area corresponding to the anatomical portions delinated on the diagnostic images consists of positioning the high-energy radiation source simulator, the shielding blocks simulator and the radiation detector simulator exactly as the high-energy radiation source, the shielding blocks and the radiation detector are positioned in the radiation therapy equipment, and further consists of positioning the diagnostic images at a distance Y from the high-energy radiation source simulator in the shielding-block cutter given by the following equation:

space="preserve" listing-type="equation">Y=S.sub.t (1+d/S.sub.t)/(1-d/S.sub.d),

where S_t and S_d are the distances of the high-energy radiation source and the low-energy radiation source, respectively, from the detector; and

d is the distance between the anatomical portions and the radiation detector.

10. The method described in claim 8, further comprising the steps of:

providing a mirror positioned to receive the verification images formed on said radiation detector thereby forming corresponding images on the mirror and providing a video camera positioned to receive the corresponding images formed on said mirror, so that the verification images created on the radiation detector are received by the video camera; and

irradiating the patient during a treatment session to provide real-time verification of the patient'"'"'s position to ensure that the anatomical portions being irradiated by high-energy radiation treatment correspond to the anatomical portions delineated on the diagnostic images.