Patent EA-001007-B1 (EA)
Title: Improving radio frequency spectral analysis for in vitro or in vivo environments
Inventor: FULLER MILTON E
IPC: A61B5/00
Filed: 1997-04-15
Abstract: 1. A method for determining in vivo concentration of a first chemical in the presence of a second substance in a specimen, the method including the following steps: (a) subjecting said specimen to radio frequency signals having a frequency regime ranging from about 0.1 MHz to about 5 GHz; (b) at a first frequency regime, using at least some of said radio frequency signals to obtain data proportional to magnitude of concentration of said second substance in said specimen; (c) at a second frequency regime, using at least some of said radio frequency signals to obtain data proportional to combined concentration in said specimen of said first chemical and said second substance; and (d) using data from said first frequency regime and data from said second frequency regime to obtain a measure of concentration of said first chemical in said specimen. 2. The method of claim 1, wherein said specimen includes blood. 3. The method of claim 1, wherein said specimen includes blood, said first chemical includes glucose, and said second substance includes NaCl. 4. The method of claim 1, wherein at step (a), at least some of said frequencies are presented sequentially. 5. The method of claim 1, wherein at step (a), at least some of said frequencies are presented simultaneously. 6. The method of claim 1, wherein at step (b), said first frequency regime ranges from about 1 GHz to about 3 GHz. 7. The method of claim 1, wherein at step (b), said data proportional to magnitude is obtained by measuring phase shift between radio frequency signals input to said specimen and radio frequency signals returned from said specimen. 8. The method of claim 1, wherein at step (c), said second frequency regime ranges from about 0.11 MHz to about 3 GHz. 9. The method of claim 1, wherein at step (c), said second frequency regime ranges from about 800 MHz to about 900 MHz, in which regime temperature effects upon data are minimized. 10. The method of claim 1, wherein at step (c), said data proportional to combined concentration is obtained by measuring magnitude of impedance at said specimen. 11. The method of claim 1, wherein at step (d) a concentration value determined in step (b) is subtracted from a combined concentration determined in step (c) to provide said measure of concentration of said first chemical. 12. The method of claim 1, in which said method is carried out non-invasively on a human subject, and wherein step (a) includes coupling said radio frequency signals via at least one probe that contacts a distal portion of said subject's body. 13. A method for determining in vivo concentration of a first chemical in the presence of a second substance in a specimen, the method including the following steps: (a) subjecting said specimen to radio frequency signals at a cross-over frequency at which frequency concentration effects of said second substance are essentially nulled-out; and (b) determining from data taken at said cross-over frequency concentration of said first chemical. 14. The method of claim 13, wherein said specimen includes blood, said first chemical includes glucose, and said second substance includes NaiCl. 15. The method of claim 14, wherein said cross-over frequency is about 2.5 GHz. 16. The method of claim 13, wherein at step (b), said data is impedance data. 17. The method of claim 13, wherein step (a) is carried out non-invasively on a human subject by coupling said cross-over frequency via at least one probe that contacts a distal portion of said subject's body. 18. A system for determining in vivoconcentration of a first chemical in the presence of a second substance in a specimen, including: a transmitter outputting radio frequency signals having a frequency regime ranging from about 0.1 MHz to about 5 GHz; at least one probe. coupling to said transmitter, contacting a portion of said specimen; and a receiver-signal processor system, coupled to said at least one probe, that analyzes at least some of said radio frequency signals present at said probe; said receiver-signal processor system providing data including at least impedance and/or phase shift present at an interface between said specimen and said at least one probe; wherein data provided by said receiver-signal processor system is used to determine said concentration of said first chemical in said specimen. 19. The system of claim 18, wherein said transmitter outputs signals suitable for said specimen which is human subject, for said first chemical which is glucose, for said second chemical which includes NaCl, and wherein transmitter includes a network analyzer. 20. The system of claim 18, wherein: said specimen is a human subject including said subject's blood; said first chemical is glucose; said second chemical includes NaCI; and said at least one probe contacts an exterior portion of a finger of said subject such that non-invasive data is provided by said system. 21. A non-invasive method for determining concentration of at least a first constituent in the presence of a second constituent in a specimen, the method including the following steps: (a) subjecting said specimen to radio frequency signals having a frequency regime ranging from about 0.1 MHz to about 5 GHz; (b) at a first frequency regime, using at least some of said radio frequency signals to obtain data proportional to magnitude of concentration of said second constituent in said specimen; (c) at a second frequency regime, using at least some of said radio frequency signals to obtain data proportional to combined concentration in said specimen of said first constituent and said second constituent; and (d) using data from said first frequency regime and data from said second frequency regime to obtain a measure of concentration of said first constituent in said specimen. 22. The method of claim 21, wherein said sample includes in vivo blood, wherein said first constituent is hematocrit in said in vivo blood; and wherein said second constituent includes at least one chemical whose concentration in said in vivo blood can affect a measured concentration of said first constituent in said specimen.