Method for Correcting Medical Fluid Injection Pressures Based on Usage
Certain embodiments of the invention are directed to a medical fluid injector of the type that uses a motor to drive fluid from a fluid container by receiving electrical energy from a power source. The medical fluid injector has a motor drive control that delivers electrical energy to the motor. The motor drive control measures electrical energy delivered to the motor and computes a pressure value of the fluid delivered based upon the measured electrical energy. This pressure value is computed utilizing a calibrated relationship between the electrical energy delivered to the motor and resulting fluid pressure from the fluid delivered. The control further tracks a time factor over an operative life of the motor and alters the calibrated relationship based upon the time factor.
1 . A medical fluid injector, comprising:
a fluid container;
a motor for driving fluid from the fluid container; and
a motor drive control that:
delivers electrical energy to the motor;
measures the electrical energy delivered to the motor;
computes a pressure value of the fluid delivered from the fluid container based upon the electrical energy that is measured, wherein the pressure value is computed utilizing a calibrated relationship between the electrical energy delivered and fluid pressure;
tracks a time factor over an operative life of the motor; and
alters the calibrated relationship based upon the time factor.
2 . The injector of claim 1 , wherein the time factor is a count of a number of injections performed by the injector.
3 . The injector of claim 1 , wherein the time factor is a measure of elapsed time since the injector or one or more particular components thereof were placed into service.
4 . The injector of claim 1 , wherein the calibrated relationship is altered to reflect an increase, over time, in fluid pressure for a given amount of electrical energy delivered.
5 . The injector of claim 1 , wherein the calibrated relationship is altered to reflect a decrease, over time, in fluid pressure for a given amount of electrical energy delivered.
6 . The injector of claim 1 , wherein the time factor comprises one or more of:
a measure of elapsed time since the injector or one or more particular components thereof were placed into service;
a count of a number of injections performed by the injector; and
a cumulative duration of injections performed.
7 . A method of adjusting a motor feedback current-verses-pressure relationship for a medical fluid injector, the method comprising:
studying a sample size of individual specimens of a medical fluid injector type, the injector type comprising a motor drive control and a motor controlled by the motor drive control to inject fluid from a fluid container;
forming a model of usage-related changes in efficiency of the injector type based upon parameters-of-usage;
calibrating a motor drive control of a specific injector of the injector type, to compute injection pressure from electrical energy delivered to the motor;
monitoring the parameters-of-usage of the specific injector; and
recomputing the calibration of the motor drive control of the specific injector based upon the monitored parameters-of-usage utilizing the model formed for the injector type.
8 . The method of claim 7 , wherein the parameters-of-usage comprise a count of the number of injections completed by the specific injector.
9 . The method of claim 7 , wherein the parameters-of-usage comprise a count of the number of injections performed by the specific injector.
10 . The method of claim 7 , wherein the parameters-of-usage comprise a cumulative duration of injections performed by the specific injector.
11 . The method of claim 7 , wherein the parameters-of-usage comprise one or more pressures reached during medical fluid injections by the specific injector.
12 . The method of claim 7 , wherein the motor is a rotary electrical motor, and the electrical energy delivered to the motor and measured by the control is an electrical current, the drive motor producing an output torque in approximately proportional relation to the electrical current.
13 . The method of claim 7 , further comprising:
altering the calibration to reflect an increase, over time, in fluid pressure for a given amount of electrical energy delivered.
14 . The injector of claim 7 , further comprising:
altering the calibration to reflect an increase, over time, in fluid pressure for a given amount of electrical energy delivered.
15 . The method of claim 7 , wherein the motor is a rotary electrical motor, and electrical energy delivered to the motor and measured by the motor drive control is an electrical current, the motor producing an output torque in approximately proportional relation to the electrical current.
16 . The method of claim 7 , wherein the fluid container comprises a syringe.
17 . The method of claim 7 , wherein the fluid container comprises a fluid-containing bag.
18 . The injector of claim 1 , wherein the motor is a rotary electrical motor, and electrical energy delivered to the motor and measured by the motor drive control is an electrical current, the motor producing an output torque in approximately proportional relation to the electrical current.
19 . The injector of claim 1 , wherein the fluid container comprises a syringe.
20 . The injector of claim 1 , wherein the fluid container comprises a fluid-containing bag.