Uncertainties in radiofrequency dielectric measurements of biological substances

Capacitive sample holders and an automatic network analyzer are used to measure dielectric properties of biological tissues in vivo and in vitro at a controlled temperature in the frequency range of 10 kHz-100 MHz. An analysis of uncertainty is performed leading to the optimization of the sensor and the measurement system. Under optimized conditions, one sample holder can be used over the entire frequency range, and uncertainties below ±3% in the dielectric constant and ±1% in the loss factor are achieved for high water content tissues (blood, muscle, brain, liver, kidney, and spleen).