Real time detection of aspiration short shots using pressure signal

Patent metadata

Field	Value
Publication number	US-2016157704-A1
Application number	US-201314404408-A
Country	US
Kind code	A1
Filing date	May 30, 2013
Priority date	May 31, 2012
Publication date	Jun 9, 2016
Grant date	—

Abstract

Embodiments relate to detecting insufficient volume of a fluid aspiration. During aspiration of fluids, a pressure trace is obtained using a pressure transducer. An algorithm is applied to detect short shot (i.e., insufficient aspiration) instances utilizing characteristics of the pressure trace. In addition, the fluid probe geometry may be optimized to improve the accuracy of the detection, and temperature may be obtained to correct the pressure trace to account for fluid viscosity and thereby further improve the accuracy.

First claim

We claim:

1 . A method for detecting insufficient volume of a fluid aspiration, the method comprising:
utilizing a pressure transducer to obtain a pressure signal of the fluid aspiration over a period of time during and after aspiration of the fluid aspiration; obtaining, from the pressure signal, a value for:
start time, wherein the start time comprises an initial time when pressure of the fluid aspiration falls below a reference start pressure level; and
stop time, wherein the stop time comprises an initial time from a minimum pressure point when pressure of the fluid aspiration exceeds or equals a reference stop pressure level;
computing, based on characteristics of the pressure signal, a value for:
pressure transition time, wherein the pressure transition time comprises a time when pressure of the fluid aspiration begins to rapidly increase;
duration of overshoot, wherein the duration of overshoot comprises a time interval of a first pressure overshoot period; and
a transition time, wherein the transition time comprises the difference between the pressure transition time and the start time;
comparing each of the transition time and the duration of overshoot to respective limit values; and identifying the volume of the fluid aspiration as erroneous if one or more of the comparisons differ from the respective limit values by a predetermined amount.

2 . The method of claim 1 , wherein the time when pressure of the fluid aspiration begins to rapidly increase comprises a first time, preceding backwards from a peak pressure point, when the first derivative of the pressure signal is less than a threshold value, and when the pressure is less than a pressure threshold value.

3 . The method of claim 2 , wherein the threshold value is dependent on a volume of the fluid aspiration.

4 . The method of claim 1 , wherein the pressure transition time further comprises a time following a plateau pressure period that occurs during aspiration.

5 . The method of claim 1 , wherein the first pressure overshoot period is determined by:
calculating an average pressure of the pressure signal after aspiration of the fluid aspiration; determining a first time point and a second time point after the pressure transition time when the pressure signal equals the average pressure after aspiration; and determining the difference between the second time point and the first time point after the pressure transition time.

6 . The method of claim 1 , wherein the predetermined amount comprises +/−2.5 standard deviation points.

7 . The method of claim 1 , wherein the fluid aspiration is identified as a short shot if one or more of the transition time and the duration of overshoot is less than the respective limit values by the predetermined amount.

8 . The method of claim 1 , further comprising:
filtering the pressure signal prior to obtaining the start time, pressure transition time, and duration of overshoot values.

9 . The method of claim 1 , further comprising:
determining a baseline pressure signal on which the obtained and computed values are based.

10 . The method of claim 1 , wherein identifying the volume of the fluid aspiration as erroneous occurs in real-time with respect to the comparisons of the transition time and the duration of overshoot.

11 . The method of claim 1 , further comprising:
utilizing a thermistor to obtain a temperature reading of the fluid aspiration; correcting the pressure signal to reflect viscosity of the fluid aspiration, the viscosity based on the temperature reading; obtaining, from the corrected pressure signal, a value for pressure overshoot, wherein pressure overshoot comprises a maximum pressure of the fluid aspiration; and identifying the volume of the fluid aspiration as a short shot if the pressure overshoot value differs from a pressure overshoot limit value by a predetermined amount.

12 . A system for detecting insufficient volume of a fluid aspiration in a diagnostic instrument, the system comprising:
a conduit connecting a pump and a probe for aspirating the fluid aspiration; a pressure transducer located upstream of the probe, the pressure transducer configured to obtain a pressure signal of the fluid aspiration over a period of time during and after aspiration of the fluid aspiration; a signal converter configured to transform the pressure signal to a digitized pressure signal; and a processing unit in communication with the signal converter and configured to receive the digitized pressure signal, the processing unit further configured to:
obtain, from the digitized pressure signal, a value for:
start time, wherein the start time comprises an initial time when pressure of the fluid aspiration falls below a reference start pressure level; and
stop time, wherein the stop time comprises an initial time from a minimum pressure point when pressure of the fluid aspiration exceeds or equals a reference stop pressure level;

compute, based on characteristics of the digitized pressure signal, a value for:
pressure transition time, wherein the pressure transition time comprises a time when pressure of the fluid aspiration begins to rapidly increase;
duration of overshoot, wherein the duration of overshoot comprises a time interval of a first pressure overshoot period; and
a transition time, wherein the transition time comprises the difference between the pressure transition time and the start time;

compare each of the transition time and the duration of overshoot to respective limit values; and
identify the volume of the fluid aspiration as erroneous if one or more of the comparisons differ from the respective limit values by a predetermined amount.

13 . The system of claim 12 , wherein the processing unit identifies the volume of the fluid aspiration as erroneous in real-time with respect to the comparisons of the transition time and the duration of overshoot.

14 . The system of claim 12 , wherein the pressure transducer is located in the conduit upstream of the probe at a distance greater than a distance associated with a maximum liquid aspiration volume, and wherein no fluid is pulled past the pressure transducer.

15 . The system of claim 12 , wherein a geometry of the probe comprises a small internal diameter at a tip of the probe, wherein the internal diameter of the probe increases beyond the tip of the probe.

16 . The system of claim 12 , wherein the system for detecting volume of a fluid aspiration in a diagnostic instrument is part of a liquid delivery system, wherein the liquid is a reagent, and wherein the diagnostic instrument is a high throughput diagnostic instrument.

17 . The system of claim 12 , further comprising:
a thermistor positioned in the conduit to obtain a real-time temperature reading of the fluid aspiration.

18 . The system of claim 17 , wherein the processing unit is further configured to:
correct the pressure signal to reflect viscosity of the fluid aspiration, the viscosity based on the temperature reading of the fluid aspiration; determine, from the corrected pressure signal, a value for pressure overshoot, wherein pressure overshoot comprises a maximum pressure of the fluid aspiration; and identify the volume of the fluid aspiration as a short shot if the pressure overshoot value differs from a pressure overshoot limit value by a predetermined amount.

19 . The system of claim 12 , further comprising:
a user interface configured to display an indication relating to an erroneous volume of the fluid aspiration.

Assignees

• Hsieh Pei-Ying
• Huang Qiang
• Siemens Healthcare Diagnostics

Inventors

• Hsieh Pei-Ying
• Huang Qiang

Classifications

• G01F22/02

  involving measurement of pressure · CPC title

• A61B1/012 Primary

  characterised by internal passages or accessories therefor · CPC title

• G01F25/0084 Primary

  for measuring volume · CPC title

• G01N35/1016

  Control of the volume dispensed or introduced · CPC title