CCD X-ray microdensitometer system

• US 5,623,139 A
• Filed: 08/05/1994
• Issued: 04/22/1997
• Est. Priority Date: 08/05/1994
• Status: Expired due to Term

• Current Assignee: Carl Zeiss AG (Carl-Zeiss-Stiftung)
• Original Assignee: Photoelectron Corporation
• Inventors: Sliski, Alan P.
• Primary Examiner(s): ALLEN, STEPHONE B
• Application Number:
  US08/286,285
• Time in Patent Office: 991 Days
• Field of Search: 250/552, 250/553, 250/555, 250/556, 250/559, 250/566, 250/571, 250/370.07, 250/341.7, 250/208.1, 250/205, 250/578.1
• US Class Current: 250/205
• CPC Class Codes: A61N 2005/1076 using a dummy object placed in the radiation field, e.g. phantom
• CPC Class Codes: A61N 5/1048 Monitoring, verifying, controlling systems and methods
• CPC Class Codes: H01L 27/148 Charge coupled imagers individual charge coupled devices H01L29/765

Abstract

A system is disclosed for producing images representing radiation dose distributions in order to verify the radiation dose applied to a target area. The system uses a phantom assembly constructed of material that is the radiological equivalent of live tissue. The phantom assembly has slits where radiation sensitive film can be inserted and can include a channel for an insertable radiation generating device. The treatment dose is then applied to the phantom and the radiation sensitive film records the dose. A CCD camera microdensitometer is then used to read the exposed radiation sensitive film. The CCD camera microdensitometer includes a computer system which processes the image to remove artifacts and generates isodose contours for the radiation treatment applied. In addition, several pieces of radiation sensitive film in different planes can be exposed and processed in order to produce images representing the radiation dose distribution in three dimensions.

Claims

1. An microdensitometer system for reading an image recorded on radiation sensitive film, said microdensitometer system comprising:

camera means, directed along an imaging axis, for producing image signals representative of said image, said camera means including a planar array of CCD sensing elements extending transverse to said imaging axis,

illumination means for producing light uniformly across an imaging plane extending transverse to said imaging axis, said illumination means including an array of light producing elements, a stable voltage reference and a light control means coupled to said array of light producing elements and said stable voltage reference, said light control means including means for sensing the light output of at least one of said light producing elements and means for controlling a level of current to each of said light producing elements in response to said sensed light output,

alignment means for adjustably aligning said camera means with respect to said illumination means along said imaging axis.

2. A microdensitometer system according to claim 1 wherein the wavelength of the light producing elements is substantially the same as the peak absorption wavelength of said radiation sensitive film.

3. A microdensitometer system according to claim 2 wherein the wavelength of the light producing elements is 660 nanometers.

4. A microdensitometer system according to claim 1 wherein said illumination means includes a plurality of groups of light producing elements arranged in an array, and said light control means controls the current level applied to each group of light producing elements.

5. A microdensitometer system according to claim 4 wherein each of said groups are annular groups with respect to a central location of said array and the current level applied to at least one group is different from the current level applied to any other group.

6. A microdensitometer system according to claim 5 wherein at least one of said groups is further arranged into two or more subgroups and the same current level is applied to each of said subgroups in said group.

7. A microdensitometer system according to claim 5 comprising three annular groups of light producing elements, an inner group adjacent to said central location of said array, a middle group substantially surrounding said inner group and an outer group substantially surrounding said middle group, and said light control means controls the current level applied to each group, and the current level applied to at least one group is different from the current level applied to any other group,

said outer group is further arranged into at least four subgroups and the same current level is applied to each of said subgroups in said outer group,

said middle group is further arranged into at least four subgroups and the same current level is applied to each of said subgroups in said middle group, and

said inner group is further arranged into at least two subgroups and the same current level is applied to each of said subgroups in said inner group.

8. A microdensitometer system according to claim 1 wherein said light producing elements are arranged in a circular array.

9. A microdensitometer system according to claim 1 wherein said light control means comprises photosensing means for monitoring the intensity of at least one light producing element and for generating an intensity signal representative of the intensity of at least one light producing element, and current control means for regulating the current to at least one of the light producing elements in response to said intensity signal to maintain constant intensity.

10. A microdensitometer system according to claim 9 wherein said illumination means further comprises illumination intensity control means for uniformly adjusting the intensity of each of light producing elements, said intensity control means including means for uniformly adjusting the current supplied to each of said light producing elements.

11. A microdensitometer system according to claim 1 wherein said illumination means includes means for maintaining said stable voltage reference irrespective of ambient temperature.

12. A microdensitometer system according to claim 1 wherein said alignment means includes an optical rail means, extending parallel to said imaging axis, for aligning said camera means along said imaging axis and baseplate means for supporting said optical rail means,

said camera means includes means for adjustably positioning said camera means along said optical rail means and

said illumination means is moveable in a direction transverse to said imaging axis and includes means for removably securing said illumination means to said baseplate means.

13. A microdensitometer system according to claim 12 wherein said means for removably securing said illumination means to said baseplate means includes a removable magnetic clamp.