Open AccessImpact of a novel exponential weighted 4 DCT reconstruction algorithm
Author(s) -
Morris Eric D.,
Kim Joshua P.,
Klahr Paul,
GlideHurst Carri K.
Publication year - 2018
Publication title -
journal of applied clinical medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.83
H-Index - 48
ISSN - 1526-9914
DOI - 10.1002/acm2.12423
Subject(s) - discrete cosine transform , full width at half maximum , image quality , mathematics , iterative reconstruction , weighting , algorithm , imaging phantom , trellis quantization , computer vision , artificial intelligence , computer science , image processing , nuclear medicine , image (mathematics) , physics , optics , medicine , image compression , acoustics
Purpose This work characterizes a novel exponential 4 DCT reconstruction algorithm ( EXPO ), in phantom and patient, to determine its impact on image quality as compared to the standard cosine‐squared weighted 4 DCT reconstruction. Methods A motion platform translated objects in the superior–inferior (S‐I) direction at varied breathing rates (8–20 bpm) and couch pitches (0.06–0.1) to evaluate interplay between parameters. Ten‐phase 4 DCT s were acquired and data were reconstructed with cosine squared and EXPO weighting. To quantify the magnitude of image blur, objects were translated in the anterior–posterior (A‐P) and S‐I directions for full‐width half maximum ( FWHM ) analysis between both 4 DCT algorithms and a static case. 4 DCT sinogram data for 10 patients were retrospectively reconstructed using both weighting factors. Image subtractions elucidated intensity and boundary differences. Subjective image quality grading (presence of image artifacts, noise, spatial resolution (i.e., lung/liver boundary sharpness), and overall image quality) was conducted yielding 200 evaluations. Results After taking static object size into account, the FWHM of EXPO reconstructions in the A‐P direction was 3.3 ± 1.7 mm (range: 0–4.9) as compared to cosine squared 9.8 ± 4.0 mm (range: 2.6–14.4). The FWHM of objects translated in the S‐I direction reconstructed with EXPO agreed better with the static FWHM than the cosine‐squared reconstructions. Slower breathing periods, faster couch pitches, and intermediate 4 DCT phases had the largest reductions of blurring with EXPO . 18 of 60 comparisons of artifacts were improved with EXPO reconstruction, whereas no appreciable changes were observed in image quality scores. In 18 of 20 cases, EXPO provided sharper images although the reduced projections also increased baseline noise. Conclusion Exponential weighted 4 DCT offers potential for reducing image blur (i.e., improving image sharpness) in 4 DCT with a tendency to reduce artifacts. Future work will involve evaluating the impact on treatment planning including delineation ability and dose calculation.