AUTOMATIC SYSTEM FOR PRECISE COLLIMATION OF RADIATION

• US 3,863,073 A
• Filed: 04/26/1973
• Issued: 01/28/1975
• Est. Priority Date: 04/26/1973
• Status: Expired due to Term

• Current Assignee: Varian Associates, Inc.
• Original Assignee: Howard G. Wagner
• Inventors: Wagner, Howard G.
• Primary Examiner(s): Borchelt, Archie R.
• Assistant Examiner(s): Church, C. E.
• Application Number:
  US05/354,826
• Time in Patent Office: 642 Days
• Field of Search: 250/511,512,513,514,402,416
• US Class Current: 378/91
• CPC Class Codes: A61B 6/06 Diaphragms
• CPC Class Codes: A61B 6/548 Remote control of the apparatus or devices
• CPC Class Codes: G05D 3/20 using a digital comparing device

Abstract

A radiographic system comprising a radiation source disposed to direct a beam of radiation through an adjustable aperture in an aligned beam-limiting device and onto an image receptor located at a selected distance from the source, and automatic means for making a unidirectional final adjustment of the aperture to provide the beam with a cross-sectional area which conforms to the size of the image receptor at the selected distance from the source.

Claims

1. A radiographic system comprising:

means for directing a beam of radiation from a source through an adjustable shutter aperture and onto an image receptor installed at a selected distance from the source; and

automatic means for adjusting the size of the aperture in accordance with the size of the receptor and the source-toimage receptor distance, said automatic means including mechanical drive means for adjusting the shutter aperture and electronic means for removing hysteresis from the drive means.

2. A radiographic system as set forth in claim 1 wherein the automatic means includes receptor detecting means for producing an electrical signal indicative of an installed image receptor and source-to-image receptor detecting means for producing an electrical signal indicative of a selected source-to-image receptor distance.

3. A radiographic system as set forth in claim 2 wherein the automatic means also includes sensing means for producing electrical signals corresponding to the size of the image receptor, the source-to-image receptor distance, and the size of the shutter aperture.

4. A radiographic system as set forth in claim 3 wherein the automatic means includes electrical means for combining the source-to-image receptor distance signal with the shutter aperture signal, and producing an output signal corresponding to the radiation field size at the plane of the image receptor.

5. A radiographic system as set forth in claim 4 wHerein the automatic means includes collimator monitoring means for electrically controlling the mechanical drive means and comprising a detector monitoring circuit means for receiving the electrical indicating signals from the receptor detecting means and the source-to-image receptor detecting means and for indicating system readiness for automatic operation.

6. A radiographic system as set forth in claim 5 wherein the detector monitoring circuit means includes gating means for producing an output signal indicative of an installed image receptor and a selected source-to-image receptor distance.

7. A radiographic system as set forth in claim 6 wherein the output of the gating means is electrically connected to monostable multivibrating means for producing an electrical pulsed output signal indicative of changes in image receptor sizes and in source-to-image receptor distances.

8. A radiographic system as set forth in claim 7 wherein the collimator monitoring means also comprises sensor monitoring circuit means for receiving the field size signal from the electrical combining means, and the receptor size signal from the receptor sensing means, in addition to the output signal from the gating means and the output signal from the monostable multivibrating means in the detector monitoring circuit, nd producing an electrical drive signal for operating the mechanical drive means.

9. A radiographic system as set forth in claim 8 wherein the sensor monitoring circuit means includes an electrical comparator having respective input terminals connected to the electrical combining means and to the receptor size means and means for producing an electrical signal indicative of the difference between the radiation field size and the image receptor size.

10. A radiographic system as set forth in claim 9 wherein the sensor monitoring circuit means includes a flip-flop device having respective terminals connected to the output of the comparator, the output of said gating means, the output of said monostable multivibrating means and having means for latching the flip-flop in a particular mode of operation.

11. A radiographic system as set forth in claim 10 wherein the sensor monitoring circuit means includes a transient protection gating means for producing an electrical signal indicative of the output of the flip-flop device and the gating means in the detector monitoring circuit.

12. A radiographic system as set forth in claim 11 wherein the sensor monitoring circuit means includes the means for removing hysteresis and comprises a one-shot multivibrating means connected to the output of the transient protection gating means.