Digital flow cytometer and method

• US 6,221,671 B1
• Filed: 08/14/2000
• Issued: 04/24/2001
• Est. Priority Date: 12/12/1997
• Status: Expired due to Term

• Current Assignee: Chemunex
• Original Assignee: Chemunex
• Inventors: Sanghera, Jaspal, Desfetes, Patrick, Groner, Warren
• Primary Examiner(s): SNAY, JEFFREY R
• Application Number:
  US09/581,156
• Time in Patent Office: 253 Days
• Field of Search: 422/82.08, 436/63, 436/172, 356/72, 356/73
• US Class Current: 436/63
• CPC Class Codes: G01N 15/1456 without spatial resolution of the texture or inner structure of the particle, e.g. processing of pulse signals
• CPC Class Codes: G01N 2021/6439 with indicators, stains, dyes, tags, labels, marks

Abstract

A system and method for testing for microbial contamination using a digital flow cytometer comprising an illumination source, a fluorescence detector, a digitizing device, and a digitized signal transferring device.

Claims

1. An apparatus for detecting and counting fluorescent particles, comprising:

an illuminating source providing a fluorescence stimulating beam;

means for supplying a suspension containing fluorescently labeled particles to pass through said beam at a high velocity;

means for detecting fluorescence of said particles and converting said fluorescence into electrical signals;

means for digitizing said electrical signals wherein said digitizing occurs at a rate sufficient to reproduce an intensity profile of an individual fluorescent particle passing said stimulating beam;

means for transferring said digitized signals and means for providing interruptions of said transferred digitized signals and outputting digitized data to a digital signal processor, wherein a duration of each of said interruptions is a function of the operating speed of said digital signal processor in order to facilitate the transfer of digital information whereby the interruptions cause transfer and processing of data to be matched with the digital sampling rate of the digitizing means;

means for analyzing digitized data output from said signal processor whereby particles are distinguished from background noise.

2. The apparatus according to claim 1, wherein said means for detecting fluorescence and converting said fluorescence includes at least two photomultiplier tubes.

3. The apparatus according to claim 1, wherein said means for transferring includes a storage buffer for continuous storage at high rates for a predetermined measurement interval.

4. The apparatus according to claim 1, wherein said means for analyzing includes a moving threshold discrimination means for discriminating fluorescence features which functions to provide a discriminative fluorescence feature when a fluorescence intensity level exceeds a local average value.

5. The apparatus according to claim 2, further including a means for providing a comparison ratio of outputs of said at least two photodetectors.

6. A method for detecting and counting fluorescent particles, comprising the steps of:

providing a suspension containing fluorescently labeled particles at a high velocity;

providing a fluorescence stimulating beam;

detecting resulting fluorescence of said particles and converting said fluorescence into electrical signals;

digitizing said electric signals at a digitizing rate sufficient to reproduce an intensity profile of an individual particle in said suspension as it passes said stimulating beam at high velocity and outputting digitized signals;

transferring said outputted digitized signals and intermittently interrupting said digitized signals to provide digital data;

performing a digital signal processing on said digital data wherein the interrupting of said digitized signals occurs for a period of time which is a function of a speed of operation of said digital signal processing in order to facilitate the transfer of digital information whereby the interruptions cause transfer and processing of data to be matched with the digital sampling rate of the digitizing of said electric signals;

analyzing data output from said digital signal processing whereby particles are distinguished from background noise.

7. Method according to claim 6 wherein said step of detecting fluorescence and converting said fluorescence into electrical signals include the use of at least two photomultiplier tubes to provide two different wave lengths.

8. The method according to claim 6 wherein said step of transferring includes the step of storing at high rates for a predetermined measurement interval.

9. The method according to claim 6 wherein said step of analyzing includes a step of discriminating fluorescent features by moving threshold which functions to provide a discriminating fluorescent feature whenever a fluorescent intensity level exceeds a local average value.

10. Method according to claim 7 further including the step of providing a comparison of outputs of said at least two photodetectors.