RF/MRI compatible in-vivo temperature sensing

Diagnostic instruments are the tools physicians use to acquire data about the patient. Important parameter is the body temperature, both externally on the skin and in-vivo. Especially during Hyperthermia, the in-vivo body temperature is a parameter that needs continuous monitoring.

Disadvantage of electrical temperature senors is the fundamental use of electric current, and the sensitivity to RF-sources (e.g. MRI). Fiber Bragg Gratings (FBG) are sensors written in an optical fiber and insensitive to RF-sources. Therefore they are ideally to be used during in-vivo temperature monitoring in RF environment (e.g. Hyperthermia and MRI). 

The T-gator is an absolute temperature sensing system using FBGs. It can interrogate up to 7 optical fibers with 8 FBGs in each. The FBGs are integrated in an optical fiber with a typical diameter of 0.25 mm allowing for easy integration into a catheter or needle. 

Experiment T-gator

A benchmark experiment has been performed with an fiber optic sensor inserted into a temperature controlled environment. The temperature setpoint started at 37 oC, increased to 47oC over an hour and kept stable. A calibrated high resolution thermometer was used (TTI-10, Isotech, Merseyside, England) as reference with an absolute accuracy of 0.01oC. 

In conclusion, The T-gator is considered a highly accurate absolute temperature sensing device applicable within an RF-environment. The error between the FBG sensor and TTI-10 reference demonstrates a standard deviation of less than 0.03 oC over a period of 4 hours.