Sensor system using fluorometric decay measurements

A measurement system for analysis of fluid concentration of a component inside a body, comprising:

• pulse generator means for generating a number of time related pulses;
• a fiber-optic equipped catheter for measuring a fluid component concentration;
• said catheter having a length to extend to a region of interest within a body while a proximal end portion of said catheter remains outside the body and including at least one fluorometric sensor in communication with one or more fiber optic light pipes within said catheter, said fluorometric sensor producing a fluorescent output in response to a light input, said fluorescent output having a fluorescent decay indicative of said fluid concentration in an environment of said fluorometric sensor;
• temperature sensing means for monitoring a temperature in the vicinity of the body and producing a temperature signal;
• light source means responsive to one or more of said pulses to generate pulses of output light, and for directing a portion of said light into said proximal end portion of said fiber-optic light pipe-equipped catheter;
• a photosensor positioned relative the proximal end portion for sensing the fluorescent output of said fluorometric sensor conveyed to the proximal end portion by one of said fiber optic light pipes;
• sampling means for sampling an output of the photosensor at two or more predetermined times after initiation of a pulse of said output light to provide two or more fluorescent decay signals;
• and
• analysis means for analyzing said fluorescent decay signals of said sampling means to obtain a lifetime signal related to the fluid concentration of the component in the environment of the fluorometric sensor;
• and
• processing means for presenting a visual indication of the fluid component concentration by using the lifetime signal in a relation correlating the lifetime signal to component concentration of the form:
• ##EQU6## where:
• T.sub.o =lifetime in absence of fluid component
• T=measured lifetime in the presence of a given concentration [Q] of fluid component
• K.sub.g =bimolecular quenching factor
• [Q]=fluid component concentration
• N=linearizing factor
• and wherein the processing means includes temperature compensation means responsive to the temperature signal to adjust values of T.sub.o, K.sub.g and N used in the relation with changes in the temperature in the vicinity of the body sensed by the temperature sensing means.

A method for analyzing fluid component levels in a body comprising the steps of:

• positioning a probe that fluoresces in response to incident light near a distal end of a fiber optic light pipe equipped catheter, said probe emitting a diminished fluorescent signal in the presence of the fluid component;
• sensing a temperature in the vicinity of the body;
• inserting the catheter into the body to position the probe in a body region of interest,
• sending a pulse of light through the catheter to excite the probe;
• monitoring light returning from the probe to determine a fluorescent lifetime of the probe by sampling light output at multiple times subsequent to exciting the probe, ascribing an exponential decay to said light output, and determining from said multiple samples a sensed fluorescent lifetime;
• correlating the sensed fluorescent lifetime with a fluid component concentration by using the sensed fluorescent lifetime in a relation correlating the sensed fluorescent lifetime with fluid component concentration of the form:
• ##EQU7## where:
• T.sub.o =lifetime in absence of fluid component
• T=sensed lifetime in the presence of a given concentration [Q] of fluid component
• K.sub.g =bimolecular quenching factor
• [Q]=fluid component concentration
• while adjusting one or more of the values of T.sub.o, and K.sub.g used in the relation as the temperature of the body changes.

A method for analyzing fluid component levels in a body comprising the steps of:

• positioning a probe that fluoresces in response to incident light near a distal end of a fiber optic light pipe equipped catheter, said probe emitting a diminished fluorescent signal in the presence of the fluid component;
• sensing a temperature in the vicinity of the body;
• inserting the catheter into the body to position the probe in a body region of interest;
• sensing a pulse of light through the catheter to excite the probe;
• monitoring light returning from the probe to determine a fluorescent lifetime of the probe by sampling light output at multiple times subsequent to exciting the probe, ascribing an exponential decay to said light output, and determining from said multiple samples a sensed fluorescent lifetime;
• correlating the sensed fluorescent lifetime with a fluid component concentration by using the sensed fluorescent lifetime in a relation correlating the sensed fluorescent lifetime with fluid component concentration of the form:
• ##EQU8## where:
• T.sub.o =lifetime in absence of fluid component
• T=sensed lifetime in the presence of a given concentration [Q] of fluid component
• K.sub.g =bimolecular quenching factor
• [Q]=fluid component concentration
• N=linearizing factor
• while adjusting one or more of the values of T.sub.o, N, and K.sub.g used in the relation as the temperature of the body changes.