Medical imaging apparatus

• US 4,437,161 A
• Filed: 06/29/1981
• Issued: 03/13/1984
• Est. Priority Date: 06/29/1981
• Status: Expired due to Fees

• Current Assignee: Siemens Gammasonics Incorporated
• Original Assignee: Siemens Gammasonics Incorporated
• Inventors: Anderson, William
• Primary Examiner(s): Krass, Errol A.
• Application Number:
  US06/278,481
• Time in Patent Office: 988 Days
• Field of Search: 364/414, 364/415, 382/6, 382/54, 358/93, 358/105, 358/111, 378/901, 377/1, 377/2, 377/17, 377/39
• US Class Current: 600/425
• CPC Class Codes: H04N 5/3205 using subtraction imaging techniques
• CPC Class Codes: Y10S 128/922 including image analysis
• CPC Class Codes: Y10S 378/901 Computer tomography program or processor

Abstract

The apparatus contains a detector for detecting radiation emitted from an object under examination, and a device associated therewith for forming an imaging signal. The imaging signal is composed of a sequence of individual image signals each of which represents an individual radiation image of the object under examination. The imaging signal comprises a first individual image signal and second individual image signals following the first individual image signal. The apparatus also contains a signal processing circuit for processing the imaging signal and for forming a display signal thereof, and a display device for receiving the display signal and for displaying a sequence of images of the object under examination. In particular, the signal processing device basically contains three functional elements, that is a storage device, a subtractor, and an evaluation circuit. The storage device is provided for storing the first individual image signal, thereby forming a reference image signal. The subtractor subtracts the reference image signal from each of the second individual image signals. Thereby it forms a difference imaging signal composed of a sequence of individual difference image signals. The monitoring device receives the difference imaging signal. It determines whether a portion of each of the second individual image signals is different from the reference image signal. If so, it issues a change-of-image signal which is indicative of a change of image intensity distribution. In X-ray examinations of a patient, for instance, where a contrast medium is applied to the patient, such change may be caused by the appearance of the contrast medium in the radiation image.

Claims

1. In a medical imaging apparatus containing

means for detecting radiation emitted from an object under examination,

means associated with said detecting means for forming an imaging signal from said radiation, said imaging signal being composed of a sequence of individual image signals each representing an individual radiation image of said object under examination and said imaging signal containing a first individual image signal and second individual image signals following said first individual image signal;

signal processing means for processing said imaging signal and for forming a display signal thereof, and

display means for receiving said display signal and for displaying a sequence of images of said object under examination,

the improvement wherein said signal processing means comprises

storage means for storing said first individual image signal, thereby forming a reference image signal;

subtracting means for subtracting said reference image signal from each of said second individual image signals, thereby forming a difference imaging signal composed of a sequence of individual difference image signals; and

monitoring means receiving said difference image signal for determining whether a portion of each of said second individual image signals is different from said reference image signal, said monitoring means issuing a change-of-image signal indicative of a change of image intensity distribution.

2. The improvement according to claim 1, further comprising

(a) additional storage means for storing said second individual image signals;

and

(b) means for initiating the storage of said second individual image signals in said additional storage means, said initiating means being controlled by said change-of-image signal.

3. The improvement according to claim 1, wherein said monitoring means comprises

(a) a comparator having a predetermined threshold for comparing said difference image signal with said threshold and producing an output pulse if said threshold is exceeded;

and

(b) means associated with said comparator for counting said output pulses and for forming a corresponding count rate.

4. The improvement according to claim 3, wherein said counting means has a predetermined count value for comparing said count rate therewith.

5. The improvement according to claim 3, wherein said monitoring means has associated with it, evaluation circuitry associated with said counting means, said evaluation circuitry comparing said count rate at the end of each different image signal with a predetermined count rate, and said evaluation circuitry delivering said change-off-image signal when said count rate exceeds said predetermined count rate.

6. The improvement according to claim 1, wherein said monitoring means has associated with it,

a summation device fed by said difference image signal for integration of said individual difference image signals, said summation device having a predetermined integration value and issuing an integral signal after each individual difference image signal, and

a comparator connected to said summation device for comparing said integral signal with said predetermined integration value.

7. The improvement according to claim 6, wherein said predetermined integration value defines predetermined window.

8. The improvement according to claim 1, wherein said imaging signal is a digital imaging signal, and wherein said additional storage means is a digital memory.

9. The improvement according to claim 1, wherein said radiation is nuclear radiation received from a tracer which is applied to a patient.

10. The improvement according to claim 1, further comprising connecting means for applying said difference imaging signal to said display means.

11. In a medical imaging apparatus containing,

(a) means for detecting radiation emitted from an object under examination;

(b) means associated with said detecting means for forming an imaging signal from said radiation, said imaging signal being composed of a sequence of individual image signals each representing an individual radiation image of said object under examination and said imaging signal containing a first individual image signal and second individual image signals following said first individual image signal;

(c) signal processing means for processing said imaging signal and for forming a display signal thereof; and

(d) display means for receiving said display signal and for displaying a sequence of images of said object under examination,

the improvement wherein said signal processing means comprises,

(a) storage means for storing said first individual image signal, thereby forming a reference image signal;

(b) subtracting means for subtracting said reference image signal from each of said second individual image signals, thereby forming a difference imaging signal composed of a sequence of individual difference image signals;

(c) monitoring means receiving said difference imaging signal for determining whether a portion of each of said second individual image signals is different from said reference image signal, said monitoring means issuing a change-of-image signal indicative of a change of image intensity distribution;

(d) additional storage means for storing said second individual image signals; and

(e) means for initiating the storage of said second individual image signals in said additional storage means, said initiating means being controlled by said change-of-image signal, wherein said initiating means comprises a gate associated with said additional storage means for controlling the recording of said individual image signals in said additional storage means.

12. The improvement according to claim 11, wherein means for manually starting the storage of said second individual image signals are connected to said gate.

13. The improvement according to claim 12, wherein said starting means comprises a switch.

14. The improvement according to claim 12, wherein said starting means comprises a flip-flop.