Fractal geometry in urodynamics of lower urinary tract.

The physiological signals are usually extremely complicated and difficult to analyze. Recently, investigators have tried the fractal dimension that can characterize roughness and self-similarity of them. It turns out that it is also suitable for obtaining the modalities of lower urinary tract during normal micturition. In this investigation, the external urethral sphincter electromyogram (EUS EMG) and the cystometrogram (CMG) of the Wistar rats under both room temperature and cold water stimulation of the bladder are studied. The modified relative differential box-counting (RDBC) method is used to calculate the fractal dimensions of EMG and CMG time series. According to the experimental results, the modalities of micturition for the Wistar rats can be characterized as normal if both the fractal dimensions of EMG and CMG are of low values during voiding. Furthermore, the technique is validated in identifying the dyssynergia of the bladder and EUS under cold water stimulation.