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Deconvolution01:20

Deconvolution

Deconvolution, also known as inverse filtering, is the process of extracting the impulse response from known input and output signals. This technique is vital in scenarios where the system's characteristics are unknown, and they must be inferred from the observable signals.
Deconvolution involves several mathematical techniques to derive the impulse response. One common approach is polynomial division. In this method, the input and output sequences are treated as coefficients of...
Upsampling01:22

Upsampling

Managing signal sampling rates is essential in digital signal processing to maintain signal integrity. A decimated signal, characterized by a reduced frequency range due to its lower sampling rate, can be upsampled by inserting zeros between each sample. This upsampling process expands the original spectrum and introduces repeated spectral replicas at intervals dictated by the new Nyquist frequency. To refine this zero-inserted sequence, it is passed through a lowpass filter with a cutoff...
Linear Approximation in Frequency Domain01:26

Linear Approximation in Frequency Domain

Linear systems are characterized by two main properties: superposition and homogeneity. Superposition allows the response to multiple inputs to be the sum of the responses to each individual input. Homogeneity ensures that scaling an input by a scalar results in the response being scaled by the same scalar.
In contrast, nonlinear systems do not inherently possess these properties. However, for small deviations around an operating point, a nonlinear system can often be approximated as linear.
Discrete Fourier Transform01:15

Discrete Fourier Transform

The Discrete Fourier Transform (DFT) is a fundamental tool in signal processing, extending the discrete-time Fourier transform by evaluating discrete signals at uniformly spaced frequency intervals. This transformation converts a finite sequence of time-domain samples into frequency components, each representing complex sinusoids ordered by frequency. The DFT translates these sequences into the frequency domain, effectively indicating the magnitude and phase of each frequency component present...

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Related Experiment Video

Updated: May 14, 2026

Optical Scatter Microscopy Based on Two-Dimensional Gabor Filters
14:58

Optical Scatter Microscopy Based on Two-Dimensional Gabor Filters

Published on: June 2, 2010

Nonlinear spatio-temporal filtering of dynamic PET data using a four-dimensional Gaussian filter and

J M Floberg1, J E Holden

  • 1Department of Medical Physics, University of Wisconsin-Madison, 1111 Highland Avenue, Madison, WI 53705 USA. jfloberg@wisc.edu

Physics in Medicine and Biology
|February 2, 2013
PubMed
Summary

Spatio-temporal expectation-maximization (STEM) filtering effectively denoises dynamic positron emission tomography (PET) data. This novel method significantly reduces noise in PET images and kinetic parameters, offering a valuable tool for various dynamic PET applications.

Related Experiment Videos

Last Updated: May 14, 2026

Optical Scatter Microscopy Based on Two-Dimensional Gabor Filters
14:58

Optical Scatter Microscopy Based on Two-Dimensional Gabor Filters

Published on: June 2, 2010

Area of Science:

  • Medical Imaging
  • Nuclear Medicine
  • Signal Processing

Background:

  • Dynamic Positron Emission Tomography (PET) imaging generates complex spatio-temporal data.
  • Noise reduction is crucial for accurate quantitative analysis and interpretation of dynamic PET studies.
  • Existing denoising methods have limitations in balancing noise suppression and signal preservation.

Purpose of the Study:

  • To introduce and evaluate a novel denoising technique for dynamic PET data called Spatio-Temporal Expectation-Maximization (STEM) filtering.
  • To assess the efficacy of STEM filtering in reducing variance in individual time frames and parametric images.
  • To compare STEM filtering against established 3D and 4D denoising methods.

Main Methods:

  • STEM filtering combines four-dimensional Gaussian filtering with Expectation-Maximization (EM) deconvolution.
  • Gaussian filtering reduces noise across spatial and temporal frequencies.
  • EM deconvolution rapidly restores signal-relevant frequencies.

Main Results:

  • STEM filtering demonstrated substantial improvements in variance for individual PET time frames and parametric images.
  • The method showed minimal bias, with early frame bias not impacting quantitative parameter estimates.
  • STEM filtering outperformed other evaluated simple denoising techniques in dynamic phantom, simulated, and human PET studies.

Conclusions:

  • STEM filtering is a simple yet effective method for denoising dynamic PET data.
  • The technique offers significant advantages in reducing noise and improving quantitative accuracy in PET imaging.
  • STEM filtering holds potential value for a broad spectrum of dynamic PET applications, including those using tracers with reversible and irreversible binding behaviors.