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The kVp setting is one of the major factors affecting the image quality in X-ray imaging and should be annually measured and calibrated if necessary. In this work, a kVp-meter is designed around the ATmega16 (Atmel) microcontroller, based on the physical principle that the linear attenuation coefficient of materials, namely copper has a smooth dependence on the energy level of the X-ray photons. Based on the logarithm of the ratio of the radiation intensities through 0.5mm and 1mm thick copper filters, a look-up table is generated in the range 60-120kVp. Logarithmic operation increased the precision at higher kVp values. Since sampling is performed over the exposure period in a continuous manner, the measurement is not affected by the X-ray waveform. A prototype unit was built and the performance was tested in terms of accuracy, precision and reliability.

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In this work, a fully optical Complementary Metal Oxide Semiconductor (CMOS) based catheter tracking system designed for 3 T Magnetic Resonance Imaging (MRI) environment is presented. The system aims to solve the Radio Frequency (RF) induced heating problem present in conventional wired catheter tracking systems used in MRI. It is based on an integrated circuit, consisting of a receiver and an optical power supply unit. The optical power supply unit includes a single on-chip photodiode and a DC-DC converter that boosts the low photodiode voltage output to voltages greater than 1.5 V. Through an optically driven switch, the accumulated charge on an a storage capacitor is transferred to the rest of the system. This operation is novel in the way that it is fully optical and the switch control is done through modulation of the applied light. An on-chip local oscillator signal for the receiver is avoided by application of an RF signal that is generated by the MRI machine at the receiving period. The signals received by a micro-coil antenna are processed by the on-chip direct conversion receiver. The processed signal is then transferred, also optically, to the outside world for tracking purposes. The frequency encoding method is used for MRI tracking. Operation with various levels of external optical power does not generate noticeble temperature increase in the system. The overall system is successfully tested in a 3 T MRI machine to demonstrate its full operation.

Measurement of complex impedance of biological systems is gaining wide popularity in determining the pathological and physiological status of tissues in research areas such as; body fat content, blood freshness, tissue ischemia, skin hydration, and etc. In this paper, we designed a fourprobe, multi-frequency impedance meter for quick assessment of the viability of erythrocyte suspensions under storage conditions. Impedance measurements are based on magnitude-ratio and phase-difference detection principles. The system is built around a sine-wave generator, a voltage controlled current source, a phasegain detector and a microcontroller unit. Device accuracy is checked against the HP 4284A LCR meter under different RC test loads that simulate physiological measurements. As a novelty, Cole-Cole parameters namely R 0 , R ∞ , f c , α and the extracellular fluid and intracellular fluid resistances, R e and R i are directly displayed in the same device, for the ease of use.