Simultaneous Control of Venous Reservoir Level and Arterial Flow Rate in Cardiopulmonary Bypass With a Centrifugal Pump.

Cardiopulmonary bypass (CPB) is an indispensable technique in cardiac surgery, providing the ability to temporarily replace cardiopulmonary function and create a bloodless surgical field. Traditionally, the operation of CPB systems has depended on the expertise and experience of skilled perfusionists. In particular, simultaneously controlling the arterial and venous occluders is difficult because the blood flow rate and reservoir level both change, and failure may put the patient's life at risk. This study proposes an automatic control system with a two-degree-of-freedom model matching controller nested in an I-PD feedback controller to simultaneously regulate the blood flow rate and reservoir level. CPB operations were performed using glycerin and bovine blood as perfusate to simulate flow-up and flow-down phases. The results confirmed that the arterial blood flow rate followed the manually adjusted target venous blood flow rate, with an error of less than 5.32%, and the reservoir level was maintained, with an error of less than 3.44% from the target reservoir level. Then, we assessed the robustness of the control system against disturbances caused by venting/suction of blood. The resulting flow rate error was 5.95%, and the reservoir level error 2.02%. The accuracy of the proposed system is clinically satisfactory and within the allowable error range of 10% or less, meeting the standards set for perfusionists. Moreover, because of the system's simple configuration, consisting of a camera and notebook PC, the system can easily be integrated with general CPB equipment. This practical design enables seamless adoption in clinical settings. With these advancements, the proposed system represents a significant step towards the automation of CPB.

Frequency-fixed motion compensation system for in-vivo electron paramagnetic resonance tooth dosimetry.

This article describes the design process for a motion compensation system that can suppress the spectral distortion caused by human motion and breathing during in-vivo electron paramagnetic resonance (EPR) spectroscopy on an intact incisor. The developed system consists of two elements: an electronically controlled tunable resonator and an automatic control circuit (ACC). The resonator can modify the resonant frequency and impedance by tuning and matching the voltage, while the ACC can generate a feedback signal using phase-sensitive detection (PSD). The signal is transferred into the resonator to maintain the critical coupling state. The tunable frequency range of the resonator was measured at over 10 MHz, offering approximately eight times the required range. The bandwidth of the resonator fluctuated in a negligible range (0.14% relative standard error) following the resonant frequency. With the feedback signal on, in-vivo EPR measurements were demonstrated to be a stable baseline with 35% higher signal-to-noise ratio (SNR). When one incisor sample was irradiated by an X-ray instrument, the EPR signal responses to the absorbed doses of 0-10 Gy exhibited high linearity (R2 = 0.994). In addition, the standard error of inverse prediction was estimated to be 0.35 Gy. The developed system achieved a discrimination ability of 2 Gy, which is required for triage in large-scale radiation accidents. Moreover, the compensation is fully automated, meaning that the system can be operated with simple training in an emergency.

Design and testing of a 750MHz CW-EPR digital console for small animal imaging.

This paper describes the development of a digital console for three-dimensional (3D) continuous wave electron paramagnetic resonance (CW-EPR) imaging of a small animal to improve the signal-to-noise ratio and lower the cost of the EPR imaging system. A RF generation board, an RF acquisition board and a digital signal processing (DSP) & control board were built for the digital EPR detection. Direct sampling of the reflected RF signal from a resonator (approximately 750MHz), which contains the EPR signal, was carried out using a band-pass subsampling method. A direct automatic control system to reduce the reflection from the resonator was proposed and implemented in the digital EPR detection scheme. All DSP tasks were carried out in field programmable gate array ICs. In vivo 3D imaging of nitroxyl radicals in a mouse's head was successfully performed.