Background: In nuclear medicine,
phantoms are mainly used to evaluate the overall performance of the imaging
systems and practically there is no phantom exclusively designed for the
evaluation of the software performance. In this study the Hoffman brain phantom
was used for quantitative evaluation of reconstruction techniques. The phantom
is modified to acquire tomographic and planar image of the same structure. The
planar image may be used as the reference image to evaluate the quality of
reconstructed slices using the companion software developed in MATLAB.
Methods and Materials: The designed
phantom is composed of 4 independent 2D slices that may be placed juxtapose to
form the 3D phantom. Each slice is composedof objects of different size
and shape e.g. circle, triangle, and rectangle. Each 2D slice was imaged at the
distances from 0 to 15 cm from the collimator surface. The phantom in 3D
configuration was imaged acquiring 128 views of 128×128 matrix size.
Reconstruction was performed using different filtering condition and the
reconstructed images were compared to the corresponding planar images. The
modulation transfer function, scatter fraction and attenuation map were
calculated for each reconstructed image
Results: Since all the parameters of the
acquisition were identical for the 2D and the 3D imaging. It was assumed that
the difference in the quality of the images was exclusively due to
reconstruction condition. The planar images were assumed to be the most perfect
images that could be obtained with the system. Comparing the reconstructed
slices to the corresponding planar images yielded the optimum reconstruction
condition. The results clearly showed that Wiener
filter yields superior quality image among the entire filter tested. The extent
of the improvement has been quantified in terms of universal image quality
index.
Conclusion: The
phantom and the accompanying software were evaluated and found to be quite
useful in determining the optimum filtering condition and mathematical
evaluation of the scatter and attenuation in tomographic images.
Raeisi E, Rajabi H, Aghamiri S. A New Approach for Quantitative Evaluation of Reconstruction Algorithms in SPECT . Int J Radiat Res 2006; 4 (2) :77-80 URL: http://ijrr.com/article-1-226-en.html