The purpose of this study is to develop a circuit that can be placed inside a deep brain stimulator (DBS) and enable real-time temperature monitoring of tip of the implant during MRI examination, and show temperature increase during MRI examination a few days after implantation eliminating hyperacute effects of the surgery.RF tissue heating of metallic implants is a well-known problem shown with many phantom experiments^1,2. It is well-known that the amount of temperature rise depends on both electrical and thermal properties of the body of interest. In vivo experiments are needed to accurately predict the temperature rise because the tissue properties cannot be simulated even with complex phantoms. In limited number of in-vivo studies3 RF heating tests were performed with placing temperature probes into the tissue with surgery. Unfortunately, both electrical and thermal tissue properties change acutely. Additionally, traumatic hyperacute symptoms can disturb the perfusion system which can mislead the temperature measurements while location sensitive temperature probe measurements can also lapse the localized RF heating of the electrode and tissue. Here, we demonstrate an in vivo study of RF heating of an Active Implantable Medical Device (AIMD) with enhanced version of Temperature Sensor implant (TSI) which we proposed earlier⁴ having very similar electrical properties with commercial AIMDs but measures its own temperature allowing a closer approach to subacute surgery effects to the RF tissue heating problem.The enhanced version of TSI proposed earlier is used for the experiment. Unlike the early prototype, the case is changed to a circular shape of 5x4x1cm titanium alloy covered with Polydimethylsiloxane. 1.5cm2 of surface is left uncovered for tissue connection. Furthermore, additional functionalities are added to the implant circuit illustrated in Figure 1 such as capability of measuring the electrode impedance and case temperature upon request. In addition to an Android phone connection, real-time communication software with TSI is implemented using a BLED112 dongle (Bluegiga Technologies Inc.) It collects the Bluetooth data inside the MRI room and sends it to an external computer via USB connection. The real-time implant monitoring with a computer software interface (Figure 2) under MRI scan eliminates memory size limitation. TSI was tested with a sheep experiment. The implant was inserted into the sheep following 1 hour medical surgery. The case was placed near the neck of the animal. Under the skin, the lead was sent straight toward to the top of skull. With assistance of prior MR images, the electrode was sent to interior of the brain (see Figure 3). After surgery, a rapid MRI heating test implemented with a Siemens 3T TrimTrio scanner. Then, for partially eliminating surgery’s traumatic effect on tissue, the animal was kept alive for 3 days and RF heating experiment was repeated. Maximum possible power was given by scanner for 10 min continuously. The tip temperature was monitored in real-time. Furthermore, the case temperature and the electrode impedance recorded as reference.In Figure 4a, tip temperature of rapid RF heating experiment, immediately after surgery, is shown. Note that the glitches at data are due to thermistor filtering. The temperature measurements for this result were post-processed with a median filter. Maximum of 2^oC difference due to local RF heating was observed at the tip. Case temperature remained almost the same. The electrode impedance was approximately 1.7kΩ having 100Ω difference at maximum temperature. However, tissue impedance was the same when temperature is back to its reference. In the 3^rd day experiment, animal scars due to the surgery were healed partially. Maximum of 3^oC temperature change at the tip was observed as it is shown in Figure 4b. However, after tip temperature saturated at its maximum around 40^oC, case temperature gradually increased up to 40^oC while tip temperature slightly decreased as RF proceeds. Electrode impedance behavior was not changed compared with previous experiment. Lastly, no tissue damage due to the RF heating observed on post experiment MRI images.In this study, RF heating was demonstrated with TSI in vivo. Although it is only one animal experiment, electrode heating can be easily observed in contrast to other techniques, because the localized heating was measured at the most possible heating source. Additionally, the tissue property and perfusion change due to the hyperacute surgery were tried to be reduced. Future studies should consider longer tissue recovery time, and more heating tests must be performed to confirm the animal’s physiological response to the heating.