Biomedical Engineers Blog

Fast Fourier Transforms for Fast Fourier Transforms Signal Types—Deterministic Biosignals (with or without Noise). Fast Fourier transform (FFT) is commonly used in analyzing the spectral content of any deterministic biosignal (with or without noise). I will discuss the issue of estimating the spectrum of the signal under noisy conditions in the following subsections. Discrete Fourier transform (DFT) allows the decomposition of discrete time signals into sinusoidal components whose frequencies are multiples of a fundamental frequency. The amplitudes and phases of the sinusoidal components can be estimated using the DFT and is represented mathematically as for a given biosignal x(n) whose sampling period is T with N number of total samples (NT is therefore the total duration of the signal segment). The spectrum X(k) is estimated at multiples of fs /N,  where fs is the sampling frequency. Fast Fourier transform (FFT) is an elegant numerical...

The image intensifier  is the detector used in fluoroscopy, where an  X-ray beam is continually applied to visualize movement in a real-time manner.  X rays that interact with the input phosphor (usually CsI) release visible light  photons. CsI crystals are grown as tiny pins, which, when arranged in the  phosphor, provide very high resolution. Released photons from the input  phosphor interact with the photocathode by a process called photoemission,  which results in the release of electrons. These electrons are pulled toward the  anode by 20 kV at the other end of the tube, and guided by electrostatic lenses to  be focused on the output phosphor. Visible light photons released by the output  phosphor may be recorded by a video camera or charge-coupled device (CCD) camera. Working Principle X rays that hit the input phosphor of an image-intensifier tube release visible light. Light photons react with the photocathode to produce elect...