Image Processing , Substraction and Averaging

May 26 • Notes • 6765 Views • 3 Comments on Image Processing , Substraction and Averaging

Image processing:

It is the operation typically defines a new image g in terms of an  f existing image. We can transform either the range    or the domain of f.

Image subtraction:

To study this impact of image  processing or subtraction of registered images on the detection of this change in pulmonary ground glass nodules is identified on the chest CT.

Materials and Methods:

A cohort of 33 individuals (25 men, 8 women; age range 51–75 years) with 37 focal ground glass opacities (GGO) were recruited from a lung cancer of screening trial. For every of the participant, 1 to 3 follow up scans were available  84 which is the total number of pairs  . Pairs of scans of the same nodule were registered non-rigidly and then subtracted to enhance differences in density and size. Four observers rated  density and size change of the GGO between pairs of scans by visual comparison alone and with additional availability of indicated their overconfidence  a subtraction image . The independent experienced chest radiologist served as the arbiter having all the clinical data, reader data,  and follow up availability of   examinations . Nodule pairs due to which the arbiter would not establish definite  regression, progression, or stability were excluded from the

further evaluation. This left 59 and 58 pairs for evaluation of density and size change respectively. Weighted kappa statistics (w) were used to assess inter observer agreement and agreement with  arbiter. Statistical significance was tested by a  z test.


When the subtraction image or image processing were available, the average inter observer  improved to 0.66 from 0.52  for size change and  to 0.57  from 0.47 for density change. Average agreement with the arbiter improved to 0.76 from 0.61  for size change and to 0.64 from 0.53  for density change. The effect was more pronounced when observer confidence without the subtraction image was low: agreement improved to 0.57 from 0.26  and to 0.47 from 0.19  in those cases.


Image subtraction improves that evaluation of subtle changes in pulmonary ground glass opticities and decreases inter-observer variability.

Image averaging:

Frame Averaging provides a way to average multiple video frames to create a  stable image. This module can be used to eliminate pixel vibrations or high frequency image changes.

The frame averaging works by adding each frame into frames of a moving average . This can effectively creates the same effect of averaging many frames without the significant memory and time that averaging hundreds of frames would take. Random noise is a problem that often arises in fluorescence microscopy due to the extremely low light levels experienced with this technique, It’s presence may seriously degrade the spatial resolution of a image digitization . For  remedy the situation, an image averaging algorithm can often be applied in order to enhance spatial resolution  to digital images while sacrificing a small degree of temporal resolution.

The averaging effect can be used to remove fast moving objects from frames when a high frame averaging are used. when fewer frames are averaged the effect creates a washing or strobe like effect. This interactive tutorial explores various aspects of the image processing or averaging algorithm, that is widely utilized from digital images for removing random noise .


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3 Responses to Image Processing , Substraction and Averaging

  1. Anonymous says:
  2. Prabhat Saxena says:

    image processing is any form of signal processing for which the input is an image, such as a photograph or video frame; the output of image processing may be either an image or a set of characteristics or parameters related to the image. This article also gives the idea about image subtraction and averaging.

  3. Rajeev Ranjan says:

    The most requirements for image processing of images is that the images be available in digitized form, that is, arrays of finite length binary words. For digitization, the given Image is sampled on a discrete grid and each sample or pixel is quantized using a finite number of bits. The digitized image is processed by a computer. To display a digital image, it is first converted into analog signal, which is scanned onto a display.
    DIP is very helpful in cameras 🙂

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