Diagnostic system for detection of fluid changes

Abstract

A diagnostic system for monitoring changes in a medium is disclosed. The system includes a transmitter configured to generate and transmit a time-varying magnetic field into a medium responsive to a first signal. The system also includes a receiver positioned on an opposite side of the medium from the transmitter and configured to generate a second signal responsive to a received magnetic field at the receiver. The system also includes a processing unit configured to determine a phase shift between the transmitted magnetic field and the received magnetic field for a plurality of frequencies of the transmitted time-varying magnetic field.

What is claimed is: 
     
         1 . A method for determining changes in a fluid in a patient's head and treating the patient, the method comprising:
 transmitting a time-varying magnetic field from at least one transmitter on or near the patient's head through the fluid;   receiving the magnetic field with at least one receiver on or near the patient's head;   generating, with the at least one receiver, a signal responsive to the received magnetic field;   determining, using a processing unit coupled with the at least one receiver, a first phase shift between the transmitted magnetic field and the received magnetic field for multiple frequencies of the transmitted time-varying magnetic field;   repeating the transmitting, receiving, generating and determining steps, to determine a second phase shift;   determining a change in the fluid in the patient's head over time, based on the determined first and second phase shifts; and   administering a therapeutic agent to the patient, based at least in part on the determined change in the fluid in the patient's head.   
     
     
         2 . The method of  claim 1 , further comprising:
 repeating the steps of transmitting, receiving, generating and determining a phase shift, to determine a third phase shift;   determining a new change in the fluid in the patient's head; and   determining whether to again administer the therapeutic agent to the patient, based at least in part on the determined new change in the fluid.   
     
     
         3 . The method of  claim 1 , wherein the at least one of the transmitter and the at least one receiver comprise shielded transmission lines, each of which comprises a strip line on a printed circuit board coupled between two grounded planes, wherein the shielded transmission lines have a loop shape, and wherein at least one of the transmitter or the receiver has a lowest natural resonant frequency above 200 MHz. 
     
     
         4 . The method of  claim 3 , wherein each of the transmission lines comprises a first conductor as a shield that at least partially encloses a second conductor, and the second conductor provides a signal responsive to a varying magnetic field. 
     
     
         5 . The method of  claim 1 , wherein administering the therapeutic agent comprises administering an agent selected from the group consisting of mannitol, blood pressure medication, hypertonic saline, hypotonic saline, electrolytes, and electrolyte regulating medication. 
     
     
         6 . The method of  claim 1 , further comprising, before the transmitting step:
 taking an air scan, using the transmitter and the receiver;   placing a headset on the patient's head, wherein the at least one transmitter and the at least one receiver are attached to the headset; and   performing an initialization step, using the processing unit, responsive to the air scan.   
     
     
         7 . The method of  claim 1 , wherein the at least one transmitter comprises multiple transmitters, wherein the at least one receiver comprises multiple receivers, and wherein the method comprises transmitting and receiving multiple time-varying magnetic fields and generating multiple signals with the at least one transmitter and the at least one receiver. 
     
     
         8 . The method of  claim 7 , further comprising:
 averaging, with the processing unit, a plurality of respective samples of the transmitted and received magnetic fields; and   determining a phase shift between the averaged transmitted magnetic fields and the averaged received magnetic fields.   
     
     
         9 . The method of  claim 1 , further comprising converting the signal from an analog signal to a digital signal using an analog to digital converter coupled to the receiver. 
     
     
         10 . The method of  claim 1 , further comprising converting the signal from an analog signal to a digital signal using an analog to digital converter mounted to a headset positioned on the patient's head, wherein the method further comprises positioning the headset on the patient's head. 
     
     
         11 . The method of  claim 1 , further comprising generating a sampling signal, using a sampling signal generator, the sampling signal having a frequency to under-sample the transmitted and received magnetic fields. 
     
     
         12 . The method of  claim 1 , further comprising using the processing unit to reduce errors in the determined phase shift resulting from movement of the transmitter, the receiver, or the patient. 
     
     
         13 . The method of  claim 12 , further comprising:
 detecting motion of the transmitter or the receiver, using an accelerometer coupled to the transmitter or the receiver; and   excluding data, using the processing unit, corresponding to periods of time wherein the accelerometer detects significant motion of the transmitter or receiver.   
     
     
         14 . The method of  claim 1 , further comprising using the processing unit to exclude data corresponding to periods of time during which the determined phase shift between the transmitted magnetic field and the received magnetic field is such that it is unlikely the result of biological changes within the medium. 
     
     
         15 . A method for treating a patient, the method comprising:
 placing a headset on the patient's head, wherein the headset holds multiple transmitters and multiple receivers;   transmitting a first time-varying magnetic field from the multiple transmitters toward the multiple receivers;   receiving the first magnetic field with the multiple receivers;   determining a first phase shift between the transmitted magnetic field and the received magnetic field;   transmitting, at some time after determining the baseline phase shift, a second time-varying magnetic field from the transmitter toward the receiver;   receiving the second magnetic field with the receiver;   determining a second phase shift between the transmitted magnetic field and the received magnetic field;   comparing, with a processor coupled with the headset, the first and second phase shifts;   determining, using the processor and based on the comparison between the first and second phase shifts, whether a clinically significant change in intracranial fluid has occurred; and   administering a therapeutic agent to the patient, based at least in part on the change in intracranial fluid.   
     
     
         16 . The method of  claim 15 , wherein each of the transmitters is positioned in a fixed position relative to one of the receivers. 
     
     
         17 . The method of  claim 15 , wherein the headset further holds multiple spacers disposed along the headset such that one of the spacers is positioned between the patient's head and each of the transmitters and receivers. 
     
     
         18 . The method of  claim 15 , wherein each of the time-varying magnetic fields comprises a plurality of frequencies. 
     
     
         19 . The method of  claim 15 , wherein each of the time-varying magnetic fields comprises a plurality of frequencies that are harmonics of a fundamental frequency, wherein all of the plurality of frequencies are simultaneously transmitted for each time-varying magnetic field, and wherein the phase shifts are determined and compared for at least one of the plurality of frequencies of the transmitted time-varying magnetic fields. 
     
     
         20 . The method of  claim 15 , further comprising converting signals for at least one of the transmitters or the receivers with an analog to digital converter mounted on the headset at or near at least one of the transmitters or the receivers. 
     
     
         21 . The method of  claim 15 , further comprising converting the transmitted magnetic fields with an analog to digital converter coupled directly with the headset at or near the transmitter. 
     
     
         22 . The method of  claim 15 , further comprising generating a signal, via the processor, if it is determined that the clinically significant change has occurred. 
     
     
         23 . The method of  claim 15 , wherein the first and second magnetic fields are in a frequency range of 1 KHz to 10 GHz. 
     
     
         24 . The method of  claim 15 , further comprising, before transmitting the first time-varying magnetic field, initiating the headset by transmitting a calibration magnetic field from the transmitters to the receivers while the headset is not coupled with the patient. 
     
     
         25 . The method of  claim 15 , further comprising:
 detecting motion of the patient with a motion detection member;   transmitting a signal to the processor based on the detected motion; and   distinguishing, using the processor, the comparison of the first and second phase shifts from the detected motion of the patient.   
     
     
         26 . The method of  claim 15 , further comprising:
 calculating, with the processor, a Fourier transform of samples of the transmitted and received magnetic fields; and   determining the first and second phase shifts by comparing phase components of the calculated respective Fourier transforms.   
     
     
         27 . The method of  claim 15 , wherein coupling the headset with the patient's head comprises positioning an elastic headband on the head. 
     
     
         28 . The method of  claim 15 , wherein the therapeutic agent is selected from the group consisting of mannitol, blood pressure medication, hypertonic saline, hypotonic saline, electrolytes, and electrolyte regulating medication. 
     
     
         29 . The method of  claim 15 , further comprising repeating the steps to monitor and treat the patient over time. 
     
     
         30 . The method of  claim 15 , further comprising determining, using the processor and based on the determination of whether a clinically significant change in intracranial fluid has occurred, whether to administer more of the therapeutic agent.