Abstract
In order to investigate the effect of the number of projections on digital tomosynthesis image quality, images were acquired over a 40 degree arc and sampled into sets of 2 to 41 projections used as input to three different reconstruction algorithms: the shift‐and‐add, the Feldkamp‐Davis‐Kress filtered back projection algorithms, and the simultaneous algebraic reconstruction technique. The variation of several image characteristics, such as in‐plane resolution, contrast to noise ratio, artifact spread, volumetric accuracy, and dose, are investigated based on the reconstruction algorithms used and also the number of projections used as source data. The results suggest that only 11 projections are required since the various parameters checked do not improve much past that number. As a reconstruction algorithm, SART did best but took much longer to reconstruct images. Thus, if reconstruction time is a determining factor, filtered back‐projection looks like a better compromise.PACS number: 87.57.C‐, 87.57.nf, 87.57.Q‐, 87.59.‐e
Highlights
IntroductionThe technique of tomosynthesis was first introduced in 1932 by Ziedses des Plantes.[12] Its main advantage is that it uses only a subset of the projections required for computed tomography (CT) reconstruction to retroactively produce any number of tomograms
156 Sarkar et al.: Study of number of projections and algorithm on tomosynthesis data each image can be acquired using the minimum of one monitor unit (MU)
If one MU is needed for each image, the dose that would be given to the patient for the acquisition of the approximately 100-200 projection images required for a full computed tomography (CT) reconstruction becomes too large to be acceptable
Summary
The technique of tomosynthesis was first introduced in 1932 by Ziedses des Plantes.[12] Its main advantage is that it uses only a subset of the projections required for CT reconstruction to retroactively produce any number of tomograms. The three techniques investigated are: (a) the shift-and-add (SAA) algorithm,(19) (b) the simultaneous algebraic reconstruction technique (SART),(20) and (c) the FDK algorithm Such comparisons have been done previously[21,22] for kV images, the inherent low contrast of MV images warrants this investigation since the results may change due to the quality of the source images. Whereas the present work repeats a small part of the investigation by Descovich et al,(16) it investigates three algorithms and looks at the effect of the number of projections used for a given tomosynthesis angle (40°) on the quality of the data sets produced by each algorithm
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