GRAPHIC RECORDING APPARATUS AND METHOD

• US 3,767,850 A
• Filed: 02/22/1972
• Issued: 10/23/1973
• Est. Priority Date: 02/22/1972
• Status: Expired due to Term

• Current Assignee: Arthur H. Hutchison, Leslie H. Gard, Lonnie S. Mcmillian
• Original Assignee: Arthur H. Hutchison, Leslie H. Gard, Lonnie S. Mcmillian
• Inventors: McMillian, Lonnie S., Hutchison, Arthur H., Gard, Leslie H.
• Primary Examiner(s): Moffit, James W.
• Application Number:
  US05/228,173
• Time in Patent Office: 609 Days
• Field of Search: 178/6.6R,6.7R 250/52,71.5S,83R,234
• US Class Current: 358/474
• CPC Class Codes: G01T 1/166 involving relative movement between detector and subject scanners in general without using scintigraphy G01T1/2964
• CPC Class Codes: G01T 1/1663 Processing methods of scan data, e.g. involving contrast enhancement, background reduction, smoothing, motion correction, dual radio-isotope scanning, computer processing for measuring spatial distribution of radiation G01T1/2992; general purpose image data processing G06T1/00; computerized tomography G06T11/003; Ancillary equipment colour printers G01T1/1666

Abstract

The disclosure describes apparatus for preventing scalloping the photographic film image produced by a scintillation scanner. The described scanner comprises a detector which can be scanned along parallel paths over an area of interest in a patient. The detector is directly coupled to a light-emitting tube that simultaneously is scanned in a similar manner over a photographic film. Gamma rays emitted by the patient are received by the detector and are converted into corresponding electrical event pulses and bits of event information which are sequentially shifted through shift registers in response to periodic clock pulses. A stepping motor moves the detector and light-producing tube a predetermined distance in response to the receipt of each clock pulse so that the concentration of gamma ray events occuring along any particular segment of the detector scan path can be precisely determined. An individual event pulse is transmitted to the light-producing tube after is has been shifted halfway through the shift register, so that the information stored in the shift register represents gamma ray events occurring before and after the gamma ray event resulting in the event pulse. A counter continuously analyzes the information flowing into and out of the shift register so that an accurate count of the information bits stored in the shift register is continuously available. Additional means are provided for controlling the intensity of the light produced by the tube in response to the value of the information stored in the shift register. As a result, the light intensity produced in response to any single gamma ray event depends on the concentration of gamma ray events occurring on either side of the single event along the detector scan path.

Claims

1. In a scintillation scanner comprising detection means for detecting a predetermined class of events, improved apparatus for controlling the recording of individual events on a recording medium in response to the concentration of other such events in the class occurring in the areas adjacent the individual events, comprising in combination:

recording means for recording the occurrence of an individual event in the class on the recording medium;

scanning means for moving the detection means in a first direction along a first scan path and for moving the detection means along a second scan path parallel to the first scan path;

coupling means for coupling the detection means to the recording means whereby the detection means and the recording means are moved simultaneously;

storage means for storing individual event information representing an individual event in the class occurring at an arbitrary first location along the first scan path and for storing information representing other events in the class occurring before and after the individual event in segments of the first scan path lying on both sides of the first location;

operating means for transmitting information representing events in the class from the detection means to the storage means and for operating the storage means;

transmitting means for transmitting the individual event information from the storage means to the recording means;

control means for analyzing the information stored in the storage means and for controlling the recording means so that the individual event information is recorded in response to the value of the stored information; and

means for maintaining the recording means and the recording medium in a first relative position while the detection means is moving along the first scan path and for maintaining the recording means and the recording medium in a second relative position while the detection means is moving along the second scan path, whereby events occurring in adjacent locations of the first and second scan paths are recorded in adjacent locations on the recording medium.

2. Apparatus, as claimed in claim 1 wherein the recording means comprises a beam of light and means for generating the beam of light.

3. Apparatus, as claimed in claim 2, wherein the means for generating comprises a glow modulator tube.

4. Apparatus as claimed in claim 1, wherein the scanning means comprises stepping motor means adapted to receive a clock pulse for moving the detection means a predetermined distance in response to each clock pulse.

5. Apparatus, as claimed in claim 1, wherein the coupling means comprises a boom on which the detection means and the recording means are mounted.

6. Apparatus, as claimed in claim 1, wherein the storage means comprises:

first storage meanS for storing said individual event information and for storing information representing events occurring in a first segment of the first scan path extending from the first location in the first direction;

second storage means for storing information representing events occurring in a second segment of the first scan path extending from the first location in a second direction opposite the first direction; and

means for transferring information between the first and second storage means.

7. Apparatus, as claimed in claim 6, wherein the first storage means comprises a first shift register means for storing digital information and wherein the second storage means comprises a second shift register means for storing digital information.

8. Apparatus, as claimed in claim 1, wherein the operating means comprises means for retaining the individual event information in the storage means until the information representing said other events occurring before and after the individual event has been stored in the storage means.

9. Apparatus, as claimed in claim 7, wherein the scanning means comprises stepping motor means adapted to receive a clock pulse for moving the detection means a predetermined distance in response to each clock pulse and wherein the operating means comprises:

clock means for generating clock pulses at a predetermined rate;

means for transmitting the clock pulses to the stepping motor means;

buffer means for temporarily storing information corresponding to one of said events and for transferring the information into one of the shift register means in response to a clock pulse; and

means for transmitting the clock pulses to the first and second shift register means, whereby information is advanced through the first and second shift register means in response to the clock pulses.

10. Apparatus, as claimed in claim 9, wherein the transmitting means is connected between the first shift register means and the second shift register means, whereby information is transmitted by the transmitting means to the recording means as it is shifted from one of the shift register means to the other shift register means.

11. Apparatus, as claimed in claim 1, wherein the control means comprises:

accounting means for analyzing the information stored in the storage means;

generating means for generating a control signal having a value corresponding to the value of the information analyzed by the accounting means; and

driving means for controlling the recording means in a non-linear manner in proportion to the value of the control signal, whereby the contrast with which the event information is recorded is enhanced.

12. Apparatus, as claimed in claim 1, wherein the control means comprises means for disabling the recording means if the value of the stored information is below a preset threshold level.

13. Apparatus, as claimed in claim 11, wherein the accounting means comprises means for determining the total number of bits of information held in the storage means and wherein the generating means comprises a digital-to-analog converter.

14. Apparatus, as claimed in claim 13, wherein the means for determining comprises:

a counter capable of counting up and counting down; and

gate means comprising first means for enabling the counter to count up when the value of information entering the storage means is greater than the value of information leaving the storage means, second means for enabling the counter to count down when the value of information entering the storage means is less than the value of information leaving the storage means, and the third means for disabling the counter when the value of information entering the storage means is equal to the value of information leaving the storage means.

15. Apparatus, as claimed in claim 2, wherein the means for maintaining comprises means for deflecting the beam of light.

16. Apparatus, as claimed in claim 15, wherein the means for deflecting comprises:

A prism;

means for positioning the prism in the beam of light; and

means for maintaining the prism in a first position relative to the beam of light when the detection means is moving along the first scan path and for maintaining the prism in a second position relative to the beam of light when the detection means is moving along the second scan path.

17. A method of controlling the manner in which a predetermined class of events is recorded in a scintillation scanner on a recording medium by a recording means having a variable output value capable of altering a predetermined characteristic of the recording medium, said method comprising the steps of:

detecting events in the class occurring along a first path segment having a predetermined length and having first and second end points;

detecting events along a second path segment parallel to the first path segment;

storing information representing said events occurring along the first path segment;

determining the value of the stored information;

recording the occurrence of an event located in the first path segment at a location other than at the first or second end points by varying the predetermined characteristic of the recording medium in proportion to the value of the stored information; and

altering the relative positions at which events are recorded on the recording medium in the first scan path as compared with the second scan path, whereby events occurring in adjacent locations of the first and second scan paths are recorded in adjacent locations of the recording medium.

18. A method, as claimed in claim 17, wherein the step of storing comprises the steps of:

converting the occurrence of an event into stored information during spaced intervals of time occurring at a constant rate, and shifting the storage location of the information at said constant rate.

19. A method, as claimed in claim 17, wherein the step of determining the value comprises the step of determining the total number of bits of information stored.

20. A method, as claimed in claim 17, wherein the steps of recording comprises the steps of:

generating a beam of radiant energy;

transmitting the beam toward the recording medium;

regulating the intensity of the beam in proportion to the value of the stored information.

21. A method, as claimed in claim 20, wherein the step of altering comprises the step of directing the beam along a first path when events are being detected in the first path segment and directing the beam along a second path when events are being detected in the second path.