Aiming at miniaturization, wireless power transfer (WPT) is frequently used in biomedical electronic implants as an alternative to batteries. However, WPT methods in use still require integrating bulky parts within the receiver, thus hindering the development of devices implantable by minimally invasive procedures, particularly when powers above 1 mW are required in deep locations. In this regard, WPT based on volume conduction of high frequency currents is an advantageous alternative relatively unexplored, and never demonstrated in humans. We describe an experimental study in which ac and dc electric powers in the order of milliwatts are obtained from pairs of needle electrodes (diameter = 0.4 mm, separation = 30 mm) inserted into the arms or lower legs of five healthy participants while innocuous and imperceptible high frequency (6.78 MHz) currents are delivered through two textile electrodes strapped around the considered limb. In addition, we demonstrate a procedure to model WPT based on volume conduction which characterizes coupling between the transmitters and the receivers by means of two-port impedance models which are generated from participants' medical images.

Aiming at miniaturization, wireless power transfer (WPT) is frequently used in biomedical electronic implants as an alternative to batteries. However, WPT methods in use still require integrating bulky parts within the receiver, thus hindering the development of devices implantable by minimally invasive procedures, particularly when powers above 1 mW are required in deep locations. In this regard, WPT based on volume conduction of high frequency currents is an advantageous alternative relatively unexplored, and never demonstrated in humans. We describe an experimental study in which ac and dc electric powers in the order of milliwatts are obtained from pairs of needle electrodes (diameter = 0.4 mm, separation = 30 mm) inserted into the arms or lower legs of five healthy participants while innocuous and imperceptible high frequency (6.78 MHz) currents are delivered through two textile electrodes strapped around the considered limb. In addition, we demonstrate a procedure to model WPT based on volume conduction which characterizes coupling between the transmitters and the receivers by means of two-port impedance models which are generated from participants' medical images.

Purpose: Twin-to-Twin Transfusion Syndrome (TTTS) is a serious condition that occurs in about 10-15% of monochorionic twin pregnancies. In most instances, the blood flow is unevenly distributed throughout the placenta anastomoses leading to the death of both fetuses if no surgical procedure is performed. Fetoscopic laser coagulation is the optimal therapy to considerably improve co-twin prognosis by clogging the abnormal anastomoses. Notwithstanding progress in recent years, TTTS surgery is highly risky. Computer assisted planning of the intervention can thus improve the outcome. Methods:In this work, we implement a GPU-accelerated random walker (RW) algorithm to detect the placenta, both umbilical cord insertions and the placental vasculature from Doppler ultrasound (US). Placenta and background seeds are manually initialized in 10-20 slices (out of 245). Vessels are automatically initialized in the same slices by means of Otsu thresholding. The RW finds the boundaries of the placenta and reconstructs the vasculature. Results:We evaluate our semi-automatic method in 5 monochorionic and 24 singleton pregnancies. Although satisfactory performance is achieved on placenta segmentation (Dice ≥ 84.0%), some vascular connections are still neglected due to the presence of US reverberation artifacts (Dice ≥ 56.9%). We also compared inter-user variability and obtained Dice coefficients of ≥ 76.8% and ≥ 97.42% for placenta and vasculature, respectively. After a threeminute manual initialization, our GPU approach speeds the computation 10.6 times compared to the CPU. Conclusions:Our semi-automatic method provides a near real-time user experience and requires short training without compromising the segmentation accuracy. A powerful approach is thus presented to rapidly plan the fetoscope insertion point ahead of TTTS surgery.

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