Cerebral spinal fluid shunt evaluation system Number:7,520,862 from the United States Patent and Trademark Office (PTO) owispatent

Title: Cerebral spinal fluid shunt evaluation system

Abstract: A method for evaluating cerebrospinal fluid (CSF) flow rate in a CSF shunt applied to a patient for transmitting the CSF between first and second locations of the patient includes applying temperature sensors to the CSF shunt for determining a flow rate of the CSF through the shunt to provide a determined CSF flow rate and applying an error correction sensor to the patient for providing an error correction signal. The determined CSF flow rate is adjusted in accordance with the error correction signal to provide a corrected CSF flow rate. The sensor can be a temperature sensor such as a thermistor. The CSF is cooled and a temperature value of the CSF is measured in accordance with the cooling. A time value is determined in accordance with the temperature value and the CSF flow rate is determined in accordance with the time value.

Patent Number: 7,520,862 Issued on 04/21/2009 to Neff

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Inventors:	Neff; Samuel (Haddon Heights, NJ)
Assignee:	Neuro Diagnostic Devices, Inc. (Philadelphia, PA)
Appl. No.:	10/770,754
Filed:	February 3, 2004

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Current U.S. Class:	600/549 ; 604/290; 604/6.13
Current International Class:	A61B 5/00 (20060101); A61M 3/00 (20060101); A61M 37/00 (20060101)
Field of Search:	600/549 604/6.13,290

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References Cited [Referenced By]

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U.S. Patent Documents

3623473	November 1971	Anderson
RE28686	January 1976	Coulthard
3933045	January 1976	Fox et al.
4206762	June 1980	Cosman
4210029	July 1980	Porter
4246908	January 1981	Inagakl et al.
4255968	March 1981	Harpster
4265252	May 1981	Chubback et al.
4281666	August 1981	Cosman
4281667	August 1981	Cosman
4307097	December 1981	Kanno et al.
4340038	July 1982	McKean
4354504	October 1982	Bro
4354506	October 1982	Sakaguchi et al.
4385636	May 1983	Cosman
4393878	July 1983	Kahn
4441357	April 1984	Kahn et al.
4471786	September 1984	Inagaki et al.
4494411	January 1985	Koschke et al.
4519401	May 1985	Ko et al.
4548516	October 1985	Helenowski
4564022	January 1986	Rosenfeld et al.
4576182	March 1986	Normann
4600013	July 1986	Landy et al.
4608992	September 1986	Hakim et al.
4621647	November 1986	Loveland
4627832	December 1986	Hooven et al.
4646752	March 1987	Swann et al.
4648868	March 1987	Hardwick et al.
4653508	March 1987	Cosman
4660568	April 1987	Cosman
4677985	July 1987	Bro et al.
4684367	August 1987	Schaffer et al.
4688577	August 1987	Bro
4714459	December 1987	Hooven
4738267	April 1988	Lazorthes et al.
4858619	August 1989	Toth
4971061	November 1990	Kageyama et al.
4984567	January 1991	Kageyama et al.
4993425	February 1991	Kronberg
4995401	February 1991	Bunegin et al.
5054497	October 1991	Kapp et al.
5074310	December 1991	Mick
5117835	June 1992	Mick
5117836	June 1992	Millar
5189018	February 1993	Goldman et al.
5191898	March 1993	Millar
5257630	November 1993	Broitman et al.
5291899	March 1994	Watanabe et al.
5325865	July 1994	Beckman et al.
5409005	April 1995	Blssonnette et al.
5494822	February 1996	Sadri
5579774	December 1996	Miller et al.
5617873	April 1997	Yost et al.
5682899	November 1997	Nashef et al.
5683357	November 1997	Magram
5692514	December 1997	Bowman
5716386	February 1998	Ward et al.
5873840	February 1999	Neff
5919144	July 1999	Bridger et al.
5951477	September 1999	Ragauskas et al.
5993398	November 1999	Alperin
6030358	February 2000	Odland
6033366	March 2000	Brockway et al.
6086533	July 2000	Madsen et al.
6113553	September 2000	Chubbuck
6117089	September 2000	Sinha
6210346	April 2001	Hall et al.
6231509	May 2001	Johnson et al.
6245027	June 2001	Alperin
6248080	June 2001	Miesel et al.
6260968	July 2001	Stark et al.
6283934	September 2001	Borgesen
6296654	October 2001	Ward
6309354	October 2001	Madsen et al.
6328694	December 2001	Michaeli
6364899	April 2002	Dobak, III
6379308	April 2002	Brockway et al.
6379331	April 2002	Barbut et al.
6383159	May 2002	Saul et al.
6390989	May 2002	Denninghoff
6410537	June 2002	Tortella et al.
6413227	July 2002	Yost et al.
6413233	July 2002	Sites et al.
6475147	November 2002	Yost et al.
6492407	December 2002	Brenner et al.
6500809	December 2002	Frazer
6527798	March 2003	Ginsburg et al.
6533733	March 2003	Ericson et al.
6537232	March 2003	Kucharczyk et al.
6547734	April 2003	Madsen et al.
6558336	May 2003	Collins
6575928	June 2003	Saul et al.
6585677	July 2003	Cowan, Jr. et al.
6589189	July 2003	Meyerson et al.
6620188	September 2003	Ginsburg et al.
6669661	December 2003	Yee
6682491	January 2004	Johnson
6683530	January 2004	Wang
6699269	March 2004	Khanna
6702743	March 2004	Michaeli
6740048	May 2004	Yost et al.
6746410	June 2004	Yost et al.
6758832	July 2004	Barbut et al.
6761695	July 2004	Yost et al.
6773407	August 2004	Yost et al.
6849072	February 2005	Lee et al.
6875176	April 2005	Mourad et al.
6875192	April 2005	Saul et al.
6905474	June 2005	Borgesen
6923799	August 2005	Asfora
6932787	August 2005	Cowan et al.
7004961	February 2006	Wong et al.
7014624	March 2006	Meythaler et al.
7025727	April 2006	Brockway et al.
7025739	April 2006	Saul
2001/0020159	September 2001	Barbut et al.
2001/0027335	October 2001	Meyerson et al.
2001/0039386	November 2001	Johnson
2002/0035331	March 2002	Brockway et al.
2002/0052550	May 2002	Madsen et al.
2002/0095087	July 2002	Mourad et al.
2002/0128569	September 2002	Collins
2002/0161304	October 2002	Eide
2002/0183650	December 2002	Johnson
2002/0198579	December 2002	Khanna
2003/0004495	January 2003	Saul
2003/0013956	January 2003	Michaeli
2003/0032915	February 2003	Saul
2003/0044055	March 2003	Park et al.
2003/0060711	March 2003	Michaeli
2003/0100845	May 2003	Eide
2003/0171693	September 2003	Yost et al.
2003/0191409	October 2003	Yost et al.
2003/0191410	October 2003	Yost et al.
2003/0191411	October 2003	Yost et al.
2003/0199784	October 2003	Lenhardt
2003/0216666	November 2003	Ericson et al.
2004/0010208	January 2004	Ayad
2004/0024358	February 2004	Meythaler et al.
2004/0030278	February 2004	Cowan, Jr. et al.
2004/0049105	March 2004	Crutchfield et al.
2004/0057901	March 2004	Morita
2004/0068201	April 2004	Saul
2004/0081949	April 2004	Lakin et al.
2004/0082900	April 2004	Luttich
2004/0087871	May 2004	Ragaukas
2004/0092908	May 2004	Harper et al.
2004/0092909	May 2004	Harper et al.
2004/0102761	May 2004	Ahmed
2004/0127813	July 2004	Schwamm
2004/0138728	July 2004	Wong et al.
2004/0142905	July 2004	Wang
2004/0158161	August 2004	Lemaire
2004/0211415	October 2004	Lurie
2004/0211416	October 2004	Lurie
2004/0230124	November 2004	Querfurth
2004/0243058	December 2004	Barbut et al.
2004/0243145	December 2004	Bobo, Sr. et al.
2004/0246441	December 2004	Stark et al.
2005/0015009	January 2005	Mourad et al.
2005/0033171	February 2005	Stergiopoulos et al.
2005/0038342	February 2005	Mozayeni et al.
2005/0090761	April 2005	Carney
2005/0119602	June 2005	Murphy et al.
2005/0171452	August 2005	Neff
2005/0187488	August 2005	Wolf
2006/0020224	January 2006	Geiger
2006/0020239	January 2006	Geiger et al.
2006/0034730	February 2006	Beyette, Jr. et al.
2006/0052737	March 2006	Bertrand et al.
2006/0057065	March 2006	Wang
2006/0079773	April 2006	Mourad et al.

Other References

Sep. 1980, Go et al., "A Thermosensitive Device for the Evaluation of the Patency of Ventriculo-atrial Shunts in Hydrocephalus", Acta Neurochirurgica, vol. 19, pp. 209-216, Fasc. 4. cited by other . Stein et al., "A Noninvasive Approach to Quantitative Measurement of Flow through CSF Shunts", Journal of Neurosurgery, Apr. 1981; 54(4):556-558. cited by other . Dec. 1979, Stein et al., "Noninvasive Test of Cerebrospinal Shunt Function", Surgical Forum, 30:442-442, 1979. cited by other . Stein, "Testing Cerebrospinal Fluid Shunt Function: A Noninvasive Technique", Neurosurgery, Jun. 1980 6(6):649-651. cited by other.

Primary Examiner: Hindenburg; Max
Assistant Examiner: Hoekstra; Jeffrey G
Attorney, Agent or Firm: Caesar, Rivise, Bernstein, Cohen & Pokotilow, Ltd

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Claims

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What is claimed is:

1. A method for evaluating an internal cerebrospinal fluid (CSF) flow rate using external measurements, said CSF flow rate occurring in a CSF shunt within a body of a patient, and said CSF shunt transmitting said CSF between differing locations of said body, the method comprising: (a) applying a plurality of temperature sensors to said body over said CSF shunt at exterior locations on said body to determine an externally determined CSF flow rate signal representative of said CSF flow rate to provide an externally determined CSF flow rate; (b) applying a background temperature sensor to said body at an exterior location on said body to determine an externally measured background induced error correction signal representative of a temperature of said exterior of said body simultaneously with said evaluating of said CSF flow rate for correcting a measurement error induced in said externally determined CSF flow rate signal by a background condition; (c) adjusting said CSF flow rate determination in accordance with said externally measured background induced error correction signal to provide a more accurate representation of said externally determined CSF flow rate, whereby said more accurate representation of said CSF flow rate determination is determined independently of any internally determined temperature signals provided in accordance with any temperature sensors located in the interior of said body, and whereby said CSF flow rate determination is (i) provided only according to external measurement and (ii) corrected only according to external measurement performed simultaneously with said evaluating of said externally determined CSF flow rate; and (d) whereby said CSF flow rate determination is provided according to a comparison of temperature values that are measured simultaneously with said evaluating of said externally determined CSF flow rate only and independently of any comparison with a predetermined control value of temperature for controlling a temperature of a fluid to make said temperature of a fluid equal to said predetermined control value of temperature.

2. A method for evaluating internal CSF flow rate in a CSF shunt applied to the body of a patient of claim 1, further comprising determining a zero CSF flow rate.

3. A method for evaluating internal CSF flow rate in a CSF shunt applied to the body of a patient of claim 1, further comprising determining a non-zero CSF flow rate.

4. A method for evaluating internal CSF flow rate in a CSF shunt applied to the body of a patient of claim 1, further comprising determining that said CSF flow rate exceeds a predetermined threshold.

5. A method for evaluating internal CSF flow rate in a CSF shunt applied to the body of a patient of claim 1, wherein said at least one temperature sensor of said plurality of temperature sensors comprises a thermistor.

6. A method for evaluating internal CSF flow rate in a CSF shunt applied to the body of a patient of claim 1, further comprising cooling said CSF.

7. A method for evaluating internal CSF flow rate in a CSF shunt applied to the body of a patient of claim 6, further comprising measuring a temperature value of said CSF in accordance with said cooling.

8. A method for evaluating internal CSF flow rate in a CSF shunt applied to the body of a patient of claim 7, further comprising determining a time value in accordance with said temperature value.

9. A method for evaluating internal CSF flow rate in a CSF shunt applied to the body of a patient of claim 8, further comprising determining said externally determined CSF flow rate in accordance with said time value.

10. A method for evaluating internal CSF flow rate in a CSF shunt applied to the body of a patient of claim 9, further comprising determining said externally determined CSF flow rate in accordance with a plurality of temperature values.

11. A method for evaluating internal CSF flow rate in a CSF shunt applied to the body of a patient of claim 7, further comprising providing a frequency signal in accordance with said measured temperature value.

12. A method for evaluating internal CSF flow rate in a CSF shunt applied to the body of a patient of claim 11, further comprising providing said frequency signal in accordance with a temperature sensor resistance.

13. A method for evaluating internal CSF flow rate in a CSF shunt applied to the body of a patient of claim 12, further comprising providing said frequency signal using an oscillator having an oscillation frequency dependent upon said temperature sensor resistance.

14. A method for evaluating internal CSF flow rate in a CSF shunt applied to the body of a patient of claim 13, wherein said oscillator comprises a relaxation oscillator.

15. A method for evaluating internal CSF flow rate in a CSF shunt applied to the body of a patient of claim 11, further comprising determining a frequency oscillation value in accordance with a measured frequency of said frequency signal.

16. A method for evaluating internal CSF flow rate in a CSF shunt applied to the body of a patient of claim 15, further comprising providing said corrected CSF flow rate in accordance with said frequency oscillation value.

17. A method for evaluating internal CSF flow rate in a CSF shunt applied to the body of a patient of claim 1, further comprising: applying a further background temperature sensor at an exterior location on said body for providing a further externally determined background temperature correction signal; and providing said corrected CSF flow rate in accordance with said further externally determined background temperature correction signal.

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Description

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BACKGROUND OF THE INVENTION

1. Field of Invention

This invention relates to cerebrospinal fluid shunts and, more particularly, to apparatus and methods for quantitatively detecting the flow of cerebrospinal fluid in such shunts noninvasively.

2. Description of Related Art

A cerebrospinal fluid (CSF)shunt includes a system of tubing that allows CSF to flow from a patient's brain to another part of the body (e.g., abdomen to relieve pressure in the spinal column). As a result, it is desirable to know, periodically, that the pathway of the CSF shunt remains unobstructed to permit CSF flow and what the flow rate is. It is also desirable to make these determinations non-invasively when quantifying the CSF flow.

The following describe different apparatus and methodologies that have been used to monitor, determine or treat body fluid flow, including CSF flow through a shunt.

"A Thermosensitive Device for the Evaluation of the Patency of Ventriculo-atrial Shunts in Hydrocephalus", by Go et al. (Acta Neurochirurgica, Vol. 19, pages 209-216, Fasc. 4) discloses the detection of the existence of flow in a shunt by placement of a thermistor and detecting means proximate the location of the shunt and the placement of cooling means downstream of the thermistor. The downstream thermistor detects the cooled portion of the CSF fluid as it passes from the region of the cooling means to the vicinity of the thermistor, thereby verifying CSF flow. However, among other things, the apparatus and method disclosed therein fails to teach or suggest an apparatus/method for quantifying the flow of the fluid through the shunt.

In "A Noninvasive Approach to Quantitative Measurement of Flow through CSF Shunts" by Stein et al., Journal of Neurosurgery, 1981, April; 54(4):556-558, a method for quantifying the CSF flow rate is disclosed. In particular, a pair of series-arranged thermistors is positioned on the skin over the CSF shunt, whereby the thermistors independently detect the passage of a cooled portion of the CSF fluid. The time required for this cooled portion to travel between the thermistors is used, along with the shunt diameter, to calculate the CSF flow rate. See also "Noninvasive Test of Cerebrospinal Shunt Function," by Stein et al., Surgical Forum 30:442-442, 1979; and "Testing Cerebropspinal Fluid Shunt Function: A Noninvasive Technique," by S. Stein, Neurosurgery, 1980 Jun. 6(6): 649-651. However, the apparatus/method disclosed therein suffers from, among other things, variations in thermistor signal due to environmental changes.

U.S. Pat. No. 4,548,516 (Helenowski) discloses an apparatus for indicating fluid flow through implanted shunts by means of temperature sensing. In particular, the apparatus taught by Helenowski comprises a plurality of thermistors mounted on a flexible substrate coupled to a rigid base. The assembly is placed on the skin over the implanted shunt and a portion of the fluid in the shunt is cooled upstream of the assembly. The thermistors detect the cooled portion of the fluid as it passes the thermistor assembly and the output of the thermistor is applied to an analog-to-digital converter for processing by a computer to determine the flow rate of the shunt fluid.

U.S. Pat. No. 6,413,233 (Sites et al.) discloses several embodiments that utilize a plurality of temperature sensors on a patient wherein a body fluid (blood, saline, etc.) flow is removed from the patient and treated, e.g., heated or cooled, and then returned to the patient. See also U.S. Pat. No. 5,494,822 (Sadri). U.S. Pat. No. 6,527,798 (Ginsburg et al.) discloses an apparatus/method for controlling body fluid temperature and utilizing temperature sensors located inside the patient's body.

U.S. Pat. No. 5,692,514 (Bowman) discloses a method and apparatus for measuring continuous blood flow by inserting a catheter into the heart carrying a pair of temperature sensors and a thermal energy source. See also U.S. Pat. No. 4,576,182 (Normann).

U.S. Pat. No. 4,684,367 (Schaffer et al.) discloses an ambulatory intravenous delivery system that includes a control portion of an intravenous fluid that detects a heat pulse using a thermistor to determine flow rate.

U.S. Pat. No. 4,255,968 (Harpster) discloses a fluid flow indicator which includes a plurality of sensors placed directly upon a thermally-conductive tube through which the flow passes. In Harpster a heater is located adjacent to a first temperature sensor so that the sensor is directly within the sphere of thermal influence of the heater.

U.S. Pat. No. 3,933,045 (Fox et al.) discloses an apparatus for detecting body core temperature utilizing a pair of temperature sensors, one located at the skin surface and another located above the first sensor wherein the output of the two temperature sensors are applied to a differential amplifier heater control circuit. The control circuit activates a heat source in order to drive the temperature gradient between these two sensors to zero and thereby detect the body core temperature.

U.S. Pat. No. 3,623,473 (Andersen) discloses a method for determining the adequacy of blood circulation by measuring the difference in temperature between at least two distinct points and comparing the sum of the detected temperatures to a reference value.

U.S. Pat. No. 3,762,221 (Coulthard) discloses an apparatus and method for measuring the flow rate of a fluid utilizing ultrasonic transmitters and receivers.

U.S. Pat. No. 4,354,504 (Bro) discloses a blood-flow probe that utilizes a pair of thermocouples that respectively detect the temperature of a hot plate and a cold plate (whose temperatures are controlled by a heat pump. The temperature readings are applied to a differential amplifier. Energization of the heat pump is controlled by a comparator that compares a references signal to the differential amplifier output that ensures that the hot plate does not exceed a safety level during use.

All references cited herein are incorporated herein by reference in their entireties.

BRIEF SUMMARY OF THE INVENTION

A method for evaluating cerebrospinal fluid (CSF) flow rate in a CSF shunt applied to the body of a patient for transmitting the CSF between first and second locations of the body includes the steps of applying a plurality of temperature sensors to the CSF shunt for determining a flow rate of the CSF through the shunt to provide a determined CSF flow rate and applying an error correction sensor to the body of the patient for providing an error correction signal. The CSF flow rate determination is adjusted in accordance with the error correction signal to provide a corrected CSF flow rate. The sensor can be a temperature sensor such as a thermistor. The CSF is cooled and a temperature value of the CSF is measured in accordance with the cooling. A time value is determined in accordance with the temperature value and the CSF flow rate is determined in accordance with the time value. The CSF flow rate can be determined in accordance with a plurality of temperature values. A temperature correction value can be determined using the error correction sensor. The temperature correction value can be a background temperature value and the corrected CSF flow rate can be provided in accordance with the temperature correction value.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

The invention will be described in conjunction with the following drawings in which like reference numerals designate like elements and wherein:

FIG. 1 shows a schematic representation of a prior art cerebral spinal fluid shunt evaluation system for monitoring the fluid flow through the shunt.

FIG. 2 shows a schematic representation of a prior cerebral spinal fluid shunt evaluation system for monitoring the fluid flow through the shunt.

FIG. 3 shows a schematic representation of the cerebral spinal fluid shunt evaluation system of the present invention for monitoring the fluid flow through the shunt.

FIG. 4 shows a schematic representation of a circuit suitable for use in the cerebral spinal fluid shunt evaluation system of FIG. 3.

FIG. 5 shows a cerebral spinal fluid flow rate calculation system including the circuit of FIG. 4.

FIG. 6 shows a graphical representation of the response time of two sensors within the cerebral spinal fluid shunt evaluation system of FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIG. 1, there is shown a prior art cerebral spinal fluid (CSF) shunt evaluation system 10. The CSF shunt evaluation system 10 includes a shunt tubing 18 that allows CSF to flow from the brain of a patient to another part of the body of the patient such as the abdomen, e.g., for treatment of a patient with hydroencephalus. The CSF shunt evaluation system 10 monitors the flow of the CSF through the shunt tubing 18 by means of upstream cooling of the CSF and a downstream sensor 14. The sensor 14 can be a temperature sensor, such as a thermistor, a thermocouple or a semiconductor sensor. The downstream sensor 14 is disposed over the shunt tubing 18 in the vicinity where the shunt tubing 18 empties into the abdominal cavity in order to detect changes in temperature as the cooled CSF is transported from the cooled region to the abdominal cavity.

The sensor 14 could be conventional temperature sensitive device wherein the internal resistance of the sensor 14 varies, either directly or inversely, according to the temperature of the sensor 14. Thus, changes in the temperature of the sensor 14 were detected by merely making a determination of its resistance or, equivalently, a measurement of the changes in the amount of current through the sensor 18.

In operation, a user of the shunt evaluation system 10 could place an ice cube on the scalp of the patient over the shunt tubing 18 for about one minute using, for example, forceps. While the safety of using ice m