Vision system to calculate a fluid volume in a container

• US 20060178578A1
• Filed: 02/10/2005
• Published: 08/10/2006
• Est. Priority Date: 02/10/2005
• Status: Active Grant

• Current Assignee: Baxter Corporation Englewood (Baxter International Inc.)
• Original Assignee: FHT, Inc.
• Inventors: Tribble, Dennis, Khan, Abdul Wahid, Adams, John A.
• Granted Patent: US 7,499,581 B2
• Time in Patent Office: Days
• US Class Current: 600/432
• CPC Class Codes: A61M 2205/3306 Optical measuring means
• CPC Class Codes: A61M 2205/3389 Continuous level detection A61M2205/3393 takes precedence
• CPC Class Codes: A61M 5/1684 by detecting the amount of infusate remaining, e.g. signalling end of infusion
• CPC Class Codes: A61M 5/31568 Means keeping track of the total dose administered, e.g. since the cartridge was inserted
• CPC Class Codes: B65B 3/003 Filling medical containers such as ampoules, vials, syringes or the like
• CPC Class Codes: B65B 3/30 by volumetric measurement
• CPC Class Codes: G01B 11/00 Measuring arrangements characterised by the use of optical techniques
• CPC Class Codes: G01F 22/00 Methods or apparatus for measuring volume of fluids or fluent solid material, not otherwise provided for
• CPC Class Codes: G01F 25/0092 for metering by volume
• CPC Class Codes: G06T 2207/30004 Biomedical image processing
• CPC Class Codes: G06T 7/0006 using a design-rule based approach
• CPC Class Codes: G06T 7/62 of area, perimeter, diameter or volume

Abstract

Broadly speaking the present invention is directed to a system for calculating a volume of fluid that is disposed within a container. The system includes (1) an imaging device that captures and stores an image of at least the volume of fluid in the container; (2) a background disposed behind the container so that at least the volume of fluid in the container is disposed in front of the background; and (3) a processor that performs at least one operation on the stored image to calculate the volume of the fluid within the container.

Claims

1. A system for calculating a volume of liquid that is disposed within a container comprising:

an imaging device that captures and stores an image of at least the volume of liquid in the container;

a background disposed behind the container so that at least the volume of liquid in the container is disposed in front of the background; and

a processor that performs at least one operation on the stored image to calculate the volume of the liquid within the container.

2. The system of claim 1, wherein the fluid is a unit dose of medication and the container is a syringe including a plunger slidably received within a barrel of the syringe.

3. The system of claim 2, wherein the barrel includes graduations formed along a length of the barrel for indicating the volume of the liquid.

4. The system of claim 1, wherein the imaging device comprises a digital camera.

5. The system of claim 1, wherein the container is disposed between the digital camera and the background, the stored image being defined by a set of vertical pixel numbers and a set of horizontal pixel numbers, and wherein the background is defined by a first region that has a first color contrast and a second region that has a second color contrast.

6. The system of claim 5, wherein the first region is one half the entire area of the background, while the second region is the other half of the entire area of the background.

7. The system of claim 5, wherein the first color contrast is darker than the second color contrast.

8. The system of claim 5, wherein the first region has a black color and the second region has a white color and the first region is in the form of a first vertical stripe and the second region is in the form of a second vertical stripe that is adjacent the first vertical stripe so that a vertical interface is formed between the first and second vertical stripes.

9. The system of claim 1, wherein the controller is configured to divide the image into a black-side and an adjacent white-side and dispose a graphic overlay on the stored image with the overlay dividing the image into a plurality of measurement areas, where each measurement area disposed in the black-side has a complementary measurement area disposed in the white-side.

10. The system of claim 1, wherein the plurality of measurement areas comprise a first syringe body zone, a first funnel zone and a first cannula zone all located on the black-side as well as a second syringe body zone, a second funnel zone and a second cannula zone all located on the opposing white-side.

11. The system of claim 9, wherein the controller is configured to perform a scan of any complementary measurement areas found in the black and white-sides, the scan measuring a gray-scale value of a medium detected along a length of the container.

12. The system of claim 11, wherein the controller is configured to plot feature vectors of the white-side scan and the black-side scan and then low-pass filters the feature vectors to form a low-pass filter scan, wherein the low-pass filtered feature vectors of the black-side and the white-side intersect one another at a point that represents an air-liquid interface of the liquid in the container.

13. The system of claim 12, wherein the controller is configured to calculate the white-side low-pass filtered vector divided by the black-side low-pass filtered vector in the form a ratio vector that can be plotted on a plot having ascending gray-scale values along an x-axis and ascending pixel numbers along a y-axis, wherein a point at which the ratio vector crosses 1 as measured on the x-axis represents the air-liquid interface for the liquid, whereby a liquid level representing the pixel numbers of boundaries of the volume of liquid is calculated.

14. The system of claim 12, wherein the controller is configured to locate and calculate a position of a plunger that is associated with the container by detecting a backside of the plunger and correcting the plunger position by subtracting an offset that corresponds to an actual thickness of the plunger, whereby the volume of the liquid in the container is calculated as being the difference between the plunger position and the liquid level in the container.

15. The system of claim 1, further including a calibration feature that processes an image of an empty container that includes a plurality of graduations that indicate the volume in the container so as to determine and record pixel locations for the graduations, thereby permitting pixel data to be converted to volumetric data.

16. The system of claim 1, further including:

a light source that directs light on at least a section of the background.

17. The system of claim 16, wherein the light source comprises a light tower having a plurality of lights that extend along a height of the light tower, wherein the light tower emits light that is directed at a white colored half of the background, with the other half of the background has a black color.

18. The system of claim 16, wherein the light source comprises a light that is provided behind a substantially translucent panel that forms a part of the background so as to define a bright colored panel when actuated.

19. The system of claim 1, wherein the system is incorporated into an automated medication preparation system including preparation and dispensing of medication to the container, the preparation system includes an automated device for preparing and dispensing a prescribed unit dose of medication, wherein the imaging device is located downstream of the automated device.

20. The system of claim 19, wherein the automated device comprises an automated syringe preparation that includes reconstitution of the medication and delivery of the unit dose of the reconstituted medication to a syringe from a drug vial, the automated device includes a fluid delivery device for delivering the prescribed unit dose of medication to the syringe in a just-in-time for use manner, wherein the fluid delivery device is adapted to aspirate the reconstituted medication into a main fluid conduit and later discharging reconstituted medication from the drug vial into the syringe.

21. The system of claim 1, wherein the liquid is substantially clear.

22. A method for calculating a volume of liquid that is disposed within a container comprising the steps of:

providing a background in front of which the container is placed so that at least the volume of liquid is disposed in front of the background;

operating an imaging device to capture and store an image of at least the volume of liquid; and

performing at least one operation on the stored image to calculate the volume of the liquid contained within the container.

23. The method of claim 22, wherein the imaging device is a digital camera and the stored image is a digital image and the background is defined by a first region that a first color contrast and a second region that has a second color contrast, the first color contrast being substantially darker than the second color contrast.

24. The method of claim 22, wherein the step of capturing the image comprises the steps of:

placing the container in front of the background that is defined by a black-colored region and an adjacent white-colored region; and

illuminating the white-colored region with a light source.

25. The method of claim 24, wherein the step of illuminating the white-colored region comprises the steps of:

providing a light tower that represents the light source; and

emitting light from the light tower onto the white-colored region of the background;

wherein the light tower is located either behind the white-colored region to provide backlighting of the white-colored region or in front of the background with the container being located between the light tower and the background.

26. The method of claim 22, wherein the step of performing at least one operation on the stored image comprises the steps of:

dividing the stored image into a black-side and a white-side that correspond to black and white-sides, respectively, of the background;

disposing a graphic overlay on the stored image within the overlay dividing the image into a plurality of measurement areas, where each measurement area disposed in the black-side has a complementary measurement area disposed in the white-side; and

scanning complementary measurement areas found in the black and white-sides of the stored image, the scan measuring a gray-scale value of scanned medium detected along a length of the container.

27. The method of claim 26, wherein the container is a syringe and the step of dividing the image into measurement areas comprises the steps of:

dividing a barrel of the syringe into first and second syringe body zones formed respectively on the black-side and the white-side;

dividing a funnel section of the syringe into first and second syringe funnel zones formed respectively on the black-side and the white-side; and

dividing a cannula section of the syringe into first and second cannula zones formed respectively on the black-side and the white-side.

28. The method of claim 27, wherein the step of performing at least one operation on the stored image comprises the steps of:

plotting feature vectors of the white-side scan and the black-side scan, the plot having ascending gray-scale values along an x-axis and ascending pixel numbers along a y-axis that measures from a top to a bottom of the captured image;

low-pass filtering the feature vectors of the white and black-side scans to form a low-pass filtered scan; and

analyzing the low-pass filtered scan for a point where the low-pass filtered vectors of the black-side and the white-side intersect one another, the point representing an air-liquid interface of the fluid in the container.

29. The method of claim 28, wherein the step of performing at least one operation on the stored image comprises the steps of:

dividing the white-side low-pass filtered vector by the black-side low-pass filtered vector to form a ratio vector;

plotting the ratio vector that includes ascending gray-scale values along an x-axis thereof and ascending pixel numbers along a y-axis thereof; and

analyzing the ratio vector plot for a point at which the ratio vector crosses 1 as measured on the x-axis represents the air-liquid interface for the liquid in the container.

30. The method of claim 29, further including the step of:

determining a first pixel number of the air-liquid interface of the fluid in the container;

determining a second pixel number that can be used to calculate the volume of the liquid in the container;

converting the first and second pixel numbers to volumetric measurement units; and

calculating the volume of the liquid in the container by performing an operation on the volumetric measurement units.

31. The method of claim 22, wherein the container is a syringe with a slideable plunger and the step of performing at least one operation on the stored image comprises the steps of

calculating a position of the plunger by performing the step of:

detecting a backside of the plunger;

correcting the plunger position by subtracting an offset that corresponds to an actual thickness of the plunger; and

calculating the volume of the liquid in the syringe as being a difference between the plunger position and a liquid level calculation in the syringe.

32. The method of claim 22, further including the steps of:

performing a calibration of the container by;

capturing an image of an empty container that includes graduations for indicating a volume of a content of the container;

determining and recording pixel locations of each graduations on the container so as to equate each pixel location of the captured image with a corresponding volumetric measurement.

33. The method of claim 32, wherein the step of determining and recording pixel locations of each graduations on the container comprises the steps of:

recording pixel data from the captured image; and

fitting the pixel data to a 2^nd degree polynomial and determining associated coefficients to generate a curve that calibrates pixel position to plunger position in milliliter units.

34. The method of claim 22, wherein the step of performing at least one operation comprises the steps of:

dividing the stored image into a black-side and a white-side that correspond to the black and white-sides, respectively, of the background;

scanning the black and white-sides of the stored image, the scan measuring a gray-scale value of scanned medium detected along a length of the syringe to generate feature vectors of the white-side scan and the black-side scan;

low-pass filtering the feature vectors of the white and black-side scans to form a low-pass filtered scan; and

analyzing a change in slope of the white-side scan, which represents a top scan line, for a point where the slope change exceeds a predetermine threshold, the point representing the air-liquid interface for the liquid in the container.

35. The method of claim 34, where the at least one operation further includes:

calculating a position of the plunger by performing the steps of;

detecting a backside of the plunger;

correcting the plunger position by subtracting an offset that corresponds to an actual thickness of the plunger; and

calculating the volume of the liquid in the syringe based on the position of the air-liquid interface and the plunger position.

36. A system for calculating a volume of liquid that is disposed within a container comprising:

an imaging device that captures and stores an image of at least the volume of liquid in the container;

a background disposed behind the container so that at least the volume of liquid in the container is disposed in front of the background, wherein the container is constructed so that optical properties thereof and the liquid filled therein serve to define a liquid lens causing a portion of the background that lies behind the liquid in the container to be inverted in the captured and stored image; and

a processor that performs at least one operation on the stored image to calculate the volume of the liquid within the container.

37. The system of claim 36, wherein the at least one operation includes:

dividing the stored image into a black-side and a white-side that correspond to the black and white-sides, respectively, of the background;

scanning the black and white-sides of the stored image, the scan measuring a gray-scale value of scanned medium detected along a length of the syringe to generate feature vectors of the white-side scan and the black-side scan;

low-pass filtering the feature vectors of the white and black-side scans to form a low-pass filtered scan; and

analyzing a change in slope of the white-side scan, which represents a top scan line, for a point where the slope change exceeds a predetermine threshold, the point representing the air-liquid interface for the liquid in the container.

38. The system of claim 37, where the at least one operation further includes:

calculating a position of the plunger by performing the steps of;

detecting a backside of the plunger;

correcting the plunger position by subtracting an offset that corresponds to an actual thickness of the plunger; and

calculating the volume of the liquid in the syringe based on the position of the air-liquid interface and the plunger position.

39. The system of claim 36, wherein the imaging device comprises a digital camera.

40. The system of claim 36, wherein the container is disposed between the digital camera and the background that is defined by a first region that has a first color contrast and a second region that has a second color contrast, with the first color contrast being substantially darker than the second color contrast, the stored image being defined by a set of vertical pixel numbers and a set of horizontal pixel numbers.