Medical fluid sensing and concentration determination in a fluid cartridge with multiple passageways, using a radio frequency device situated within a magnetic field

Abstract

This disclosure relates to medical fluid sensors and related systems and methods. In certain aspects, a method includes reading an indicia of a medical fluid cartridge to determine a volume of a fluid passageway of the medical fluid cartridge indicated by the indicia, receiving radio frequency energy generated by excited atoms in medical fluid in the fluid passageway of the medical fluid cartridge, and determining a concentration of a substance in the medical fluid based on the determined volume of the fluid passageway of the medical fluid cartridge indicated by the indicia and the received radio frequency energy generated by the excited atoms in the medical fluid in the fluid passageway of the medical fluid cartridge.

What is claimed is: 
     
         1 . A method comprising:
 measuring a quantity of a first substance in a reference fluid in a reference fluid cartridge;   measuring a quantity of a second substance in the reference fluid in the reference fluid cartridge;   measuring a quantity of the first substance in a medical fluid in a medical fluid cartridge;   measuring a quantity of the second substance in the medical fluid in the medical fluid cartridge; and   determining a concentration of the second substance in the medical fluid based on the measured quantities of the first and second substances in the reference fluid and the medical fluid.   
     
     
         2 . The method of  claim 1 , wherein concentrations of the first and second substances in the reference fluid are known. 
     
     
         3 . The method of  claim 2 , wherein a concentration of the first substance in the medical fluid is known. 
     
     
         4 . The method of  claim 1 , wherein measuring the quantities of the first and second substances in the reference fluid comprises receiving radio frequency energy generated by excited atoms in the reference fluid in the reference fluid cartridge, and measuring the quantities of the first and second substances in the medical fluid comprises receiving radio frequency energy generated by excited atoms in the medical fluid in the medical fluid cartridge. 
     
     
         5 . The method of  claim 4 , further comprising exciting the atoms in the reference fluid by applying radio frequency energy to the reference fluid in the reference fluid cartridge, and exciting the atoms in the medical fluid by applying radio frequency energy to the medical fluid in the medical fluid cartridge. 
     
     
         6 . The method of  claim 4 , wherein the radio frequency energy generated by the excited atoms in the reference fluid in the reference fluid cartridge is received by a radio frequency device surrounding a portion of the reference fluid cartridge, and the radio frequency energy generated by the excited atoms in the medical fluid in the medical fluid cartridge is received by a radio frequency device surrounding a portion of the medical fluid cartridge. 
     
     
         7 . The method of  claim 6 , wherein a single radio frequency device receives the radio frequency energy generated by the excited atoms in the reference fluid in the reference fluid cartridge and the radio frequency energy generated by the excited atoms in the medical fluid in the medical fluid cartridge. 
     
     
         8 . The method of  claim 7 , wherein the single radio frequency device is a radio frequency coil. 
     
     
         9 . The method of  claim 8 , wherein the radio frequency coil is operated at a first frequency to measure the quantities of the first substance in the reference fluid and the medical fluid and is operated at a second frequency to measure the quantities of the second substance in the reference fluid and the medical fluid. 
     
     
         10 . The method of  claim 6 , further comprising exciting the atoms in the reference fluid by applying radio frequency energy to the reference fluid in the reference fluid cartridge by activating the radio frequency device that receives the radio frequency energy generated by the excited atoms in the reference fluid in the reference fluid cartridge, and exciting the atoms in the medical fluid by applying radio frequency energy to the medical fluid in the medical fluid cartridge by activating the radio frequency device that receives the radio frequency energy generated by the excited atoms in the medical fluid in the medical fluid cartridge. 
     
     
         11 . The method of  claim 10 , wherein a single radio frequency device receives the radio frequency energy generated by the excited atoms in the reference fluid in the reference fluid cartridge and the medical fluid in the medical fluid cartridge and applies the radio frequency energy to the reference fluid in the reference fluid cartridge and the medical fluid in the medical fluid cartridge. 
     
     
         12 . The method of  claim 11 , wherein the single radio frequency device is a radio frequency coil. 
     
     
         13 . The method of  claim 12 , wherein the radio frequency coil is operated at a first frequency to measure the quantities of the first substance in the reference fluid and the medical fluid and is operated at a second frequency to measure the quantities of the second substance in the reference fluid and the medical fluid. 
     
     
         14 . The method of  claim 4 , wherein the radio frequency energy generated by the excited atoms in the reference fluid in the reference fluid cartridge and the radio frequency energy generated by the excited atoms in the medical fluid in the medical fluid cartridge is received by a sensor assembly. 
     
     
         15 . The method of  claim 14 , wherein prior to determining the concentration of the second substance in the medical fluid, the sensor assembly is used to determine a concentration of one of the first and second substances in the reference fluid in the reference fluid cartridge and the sensor assembly is calibrated based on the determined concentration of the one of the first and second substances in the reference fluid in the reference fluid cartridge. 
     
     
         16 . The method of  claim 15 , wherein calibrating the sensor assembly comprises comparing the concentration of the one of the first and second substances in the reference fluid in the reference fluid cartridge as determined by the sensor assembly to a known concentration of the one of the first and second substances in the reference fluid in the reference fluid cartridge. 
     
     
         17 . The method of  claim 1 , further comprising adjusting the concentration of the second substance in the medical fluid if the determined concentration of the second substance in the medical fluid falls outside of a desired range. 
     
     
         18 . The method of  claim 1 , wherein the first substance is hydrogen and the second substance is sodium. 
     
     
         19 . The method of  claim 1 , wherein the medical fluid is dialysis fluid.