[en] Temporal Fourier analysis on a time series on images concentrates on the change in information contained in each picture element as a function of time. A TFT limited to the first Fourier coefficients, will yield two functional images, the amplitude and the phase, respectively. In the case of periodic phenomena such as the beating of the heart or the breathing of the lungs amplitude and phase are the most characteristic parameters available for functional imaging. In gated cardiac blood pool studies, count rate derived functional images allow a great accuracy in the detection and localisation of asynergy. Any transient function f(x) wich is not periodic but defined within an internal (-T,T) can be made periodically by defining f(t + 2T) = f(t). TFT can then be applied to study such phenomena as first pass blood flow. The amplitude image corresponds to the changes in counts within the image series, the phase images to the time of transit. The two functional images will permit a rapid and sensitive assessment of the vascularisation of various structures or lesions. As a rule, the information content in a dynamic series of images is used with maximal efficiency. This highly increases the resolution in time and space of studies limited by poor count rate statistics as compared with other functional imaging techniques