The Effect Of Digital And Physical Filters On Image Quality For Quantitative Tc-99m Single Photon Emission Computed Tomography (Spect)

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Date
2010-05
Authors
A. Latiff, Rukiah
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Publisher
Universiti Sains Malaysia
Abstract
An absolute quantitation can be made on SPECT data to accurately measure the volume and estimate total radionuclide activity in the organ or lesion. The major problem to produce an accurate quantitation is the contamination of SPECT images by scattered photons. The aim of the study is to investigate the effect of physical filters on image quality in quantitative SPECT imaging. Two types of material filters viz copper (Cu) with 0.05 cm thickness and aluminium (Al) with 0.04 cm (aluminium A) and 0.06 cm thickness (aluminium B) were applied as scattered radiation correction method. Six different mathematical filters such as Ramp, Parzen, Hanning, Hamming, Butterworth and Gaussian filter with different order and cut-off frequency (cof) were used to reconstruct the images. The image for each phantom was acquired by using low-energy-high-resolution (LEHR) collimator, symmetrical window of 126 to 154 keV (centered at 140 keV), 64 views over 3600 and 30 seconds/projection. The radius of rotation was 30 cm from the phantom with 64 x 64 x 16 matrix. The image count difference between before and after reconstruction using Ramp (76 to 78 %), Gaussian and Butterworth filters were independent of the size of the phantoms. Parzen, Hanning and Hamming showed an image count dependency on size for small phantom sizes (10 ml, 20 ml, 30 ml and 40 ml). As cof increased the image count reduction increased. Contrast and signal-noise ratio (SNR) increased when the sizes of phantoms and cof increased for all mathematical filters. Using specific physical filter does not suit different sizes of phantom for contrasts and SNR improvement.
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Keywords
Digital And Physical Filters , Tc-99m Single Photon Emission Computed Tomography (Spect)
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