Nuclear magnetic resonance module for a dialysis machine

• US 9,713,664 B2
• Filed: 03/15/2013
• Issued: 07/25/2017
• Est. Priority Date: 03/15/2013
• Status: Active Grant

• Current Assignee: Fresenius Medical Care Holdings Incorporated (Fresenius Medical Care AG)
• Original Assignee: Fresenius Medical Care Holdings Incorporated (Fresenius Medical Care AG)
• Inventors: Tuckwell, Mark David
• Primary Examiner(s): Bass, Dirk
• Assistant Examiner(s): BREWSTER, HAYDEN R
• Application Number:
  US13/836,875
• Publication Number:
  US 20140262983A1
• Time in Patent Office: 1,593 Days
• Field of Search: 7386111, 210 85, 210646, 210647, 324 7619, 324113, 324313, 324318-322, 32475431, 3408546
• CPC Class Codes: A61B 5/055 involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• CPC Class Codes: A61B 5/145 Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissuemeasuring of blood pressure or blood flow A61B5/02; non-radiation detecting or locating of foreign bodies in blood A61B5/06
• CPC Class Codes: A61M 1/152 Details related to the interface between cassette and machine
• CPC Class Codes: A61M 1/154 with sensing means or components thereof
• CPC Class Codes: A61M 1/1562 Details of incorporated reservoirs
• CPC Class Codes: A61M 1/16 with membranes
• CPC Class Codes: A61M 1/1605 Physical characteristics of the dialysate fluid
• CPC Class Codes: A61M 1/1619 Sampled collection of used dialysate, i.e. obviating the need for recovery of whole dialysate quantity for post-dialysis analysis
• CPC Class Codes: A61M 1/3609 Physical characteristics of the blood, e.g. haematocrit, urea
• CPC Class Codes: A61M 1/36222 Details related to the interface between cassette and machine
• CPC Class Codes: A61M 1/36224 with sensing means or components thereof
• CPC Class Codes: A61M 1/36226 Constructional details of cassettes, e.g. specific details on material or shape
• CPC Class Codes: A61M 2205/3317 Electromagnetic, inductive or dielectric measuring means
• CPC Class Codes: A61M 2205/3324 PH measuring means
• CPC Class Codes: A61M 2205/50 with microprocessors or computers
• CPC Class Codes: G01F 1/586 constructions of coils, magnetic circuits, accessories therefor G01F1/582 takes precedence; magnet; inductances; transformers; selection of materials for their magnetic properties per se H01F
• CPC Class Codes: G01N 27/023 where the material is placed in the field of a coil
• CPC Class Codes: G01N 33/49 Blood chemical methods for determining blood cell populations G01N33/5094; chemical analysis of blood groups or blood types G01N33/80

Abstract

This disclosure relates to medical fluid sensors and related systems and methods. In some aspects, a circuit includes a radio frequency coil tuned to at least one frequency and at least one switching circuit directly connected to the radio frequency coil. The radio frequency coil is characterized by a high impedance.

Claims

1. A dialysis machine comprising:

a blood line set;

a blood pump configured to draw blood from a patient and return the blood to the patient via the blood line set; and

a nuclear magnetic resonance (NMR) module configured to determine a concentration of sodium in a sample of blood flowing through a portion of the blood line set during a dialysis treatment, the NMR module comprising;

an NMR sensor assembly;

an opening formed in a cover plate of the NMR module, the opening configured to accept the portion of the blood line set; and

a circuit board disposed proximate to the opening, the circuit board including circuitry comprising;

at least one switching circuit that includes electronic components, the at least one switching circuit isolating a first subset of the components for transmitting signals from a second subset of the components for receiving signals;

a radio frequency coil tuned to at least one frequency and connected to the at least one switching circuit, the radio frequency coil being characterized by a high impedance relative to impedances of the second subset of the components of the at least one switching circuit when the circuit is operating at the tuned at least one frequency; and

a low noise amplifier connected to the at least one switching circuit, the low noise amplifier being characterized by a high impedance relative to the impedance of the radio frequency coil, the impedance characterizing the low noise amplifier being chosen to limit loss in a signal provided by the radio frequency coil,

wherein no impedance matching circuit is used to match impedance of the low noise amplifier and impedance of the radio frequency coil, and wherein the at least one switching circuit is positioned between the radio frequency coil and the low noise amplifier.

2. The dialysis machine of claim 1 wherein the high impedance by which the radio frequency coil is characterized is an impedance of greater than 10K ohms.

3. The dialysis machine of claim 1 wherein the at least one switching circuit comprises at least one high voltage transistor.

4. The dialysis machine of claim 3 wherein the at least one high voltage transistor comprises a transistor which maintains a switching state when a voltage of at least 100 volts is applied to an input.

5. The dialysis machine of claim 1 wherein the high impedance by which the low noise amplifier is characterized is an impedance that is ten times the impedance of the radio frequency coil.

6. The dialysis machine of claim 1 wherein the radio frequency coil is tuned to both a first frequency and a second frequency, wherein

the first frequency is a frequency of sodium molecules, and

the second frequency is a frequency of hydrogen molecules.

7. The dialysis machine of claim 6 comprising a subset of the components for receiving signals at the first frequency, and a subset of the components for receiving signals at the second frequency.

8. The dialysis machine of claim 6 wherein the first frequency is 6.5 to 11 megahertz and the second frequency is 25 to 42 megahertz.

17. The dialysis machine of claim 1 wherein the dialysis machine is a hemodialysis machine.

18. The dialysis machine of claim 1 wherein the electronic components of the at least one switching circuit include transistors.

19. The dialysis machine of claim 1 wherein the radio frequency coil is directly connected to the at least one switching circuit.

20. The dialysis machine of claim 1 wherein the low noise amplifier is directly connected to the at least one switching circuit.

24. The dialysis machine of claim 1 wherein the dialysis machine is a hemodialysis machine.

9. A hemodialysis machine comprising:

a blood line set that forms a blood circuit;

a blood pump configured to draw blood from a patient, pump the blood through a dialyzer, and return the blood to the patient via the blood line set;

a blood cartridge connected in series with blood lines of the blood line set; and

a nuclear magnetic resonance (NMR) module configured to determine a concentration of sodium in a sample of blood flowing through the blood cartridge during a hemodialysis treatment, the NMR module comprising;

an NMR sensor assembly;

an opening formed in a cover plate of the NMR module, the opening configured to accept the blood cartridge; and

a circuit board disposed proximate to the opening, the circuit board including circuitry comprising;

at least one switching circuit that includes electronic components, the at least one switching circuit isolating a first subset of the components for transmitting signals from a second subset of the components for receiving signals;

a radio frequency coil tuned to at least one frequency and connected to the at least one switching circuit, the radio frequency coil being characterized by a high impedance relative to impedances of the second subset of the components of the at least one switching circuit when the circuit is operating at the tuned at least one frequency; and

a low noise amplifier connected to the at least one switching circuit, the low noise amplifier being characterized by a high impedance relative to the impedance of the radio frequency coil, the impedance characterizing the low noise amplifier being chosen to limit loss in a signal provided by the radio frequency coil,

wherein no impedance matching circuit is used to match impedance of the low noise amplifier and impedance of the radio frequency coil, and wherein the at least one switching circuit is positioned between the radio frequency coil and the low noise amplifier.

10. The hemodialysis machine of claim 9 wherein the high impedance by which the radio frequency coil is characterized is an impedance of greater than 10K ohms.

11. The hemodialysis machine of claim 9 wherein the at least one switching circuit comprises at least one high voltage transistor.

12. The hemodialysis machine of claim 11 wherein the at least one high voltage transistor comprises a transistor which maintains a switching state when a voltage of at least 100 volts is applied to an input.

13. The hemodialysis machine of claim 9 wherein the high impedance by which the low noise amplifier is characterized is an impedance that is ten times the impedance of the radio frequency coil.

14. The hemodialysis machine of claim 9 wherein the radio frequency coil is tuned to both a first frequency and a second frequency, wherein

the first frequency is a frequency of sodium molecules, and

the second frequency is a frequency of hydrogen molecules.

15. The hemodialysis machine of claim 14 comprising a subset of the components for receiving signals at the first frequency, and a subset of the components for receiving signals at the second frequency.

16. The hemodialysis machine of claim 14 wherein the first frequency is 6.5 to 11 megahertz and the second frequency is 25 to 42 megahertz.

21. The hemodialysis machine of claim 9 wherein the electronic components of the at least one switching circuit include transistors.

22. The hemodialysis machine of claim 9 wherein the radio frequency coil is directly connected to the at least one switching circuit.

23. The hemodialysis machine of claim 9 wherein the low noise amplifier is directly connected to the at least one switching circuit.