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Partial scan artifact reduction (PSAR) for the assessment of cardiac perfusion in dynamic phase‐correlated CT
Author(s) -
Stenner Philip,
Schmidt Bernhard,
Bruder Herbert,
Allmendinger Thomas,
Haberland Ulrike,
Flohr Thomas,
Kachelrieß Marc
Publication year - 2009
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.3259734
Subject(s) - imaging phantom , artifact (error) , partial volume , medical imaging , myocardial perfusion imaging , cardiac imaging , image resolution , dynamic range , perfusion scanning , dynamic imaging , image quality , computer science , nuclear medicine , image processing , artificial intelligence , perfusion , computer vision , image (mathematics) , medicine , radiology , digital image processing
Purpose: Cardiac CT achieves its high temporal resolution by lowering the scan range from 2 π to π plus fan angle (partial scan). This, however, introduces CT‐value variations, depending on the angular position of the π range. These partial scan artifacts are of the order of a few HU and prevent the quantitative evaluation of perfusion measurements. The authors present the new algorithm partial scan artifact reduction (PSAR) that corrects a dynamic phase‐correlated scan without a priori information. Methods: In general, a full scan does not suffer from partial scan artifacts since all projections in [0, 2 π ] contribute to the data. To maintain the optimum temporal resolution and the phase correlation, PSAR creates an artificial full scan p n AF by projectionwise averaging a set of neighboring partial scans p n P from the same perfusion examination (typically N ≈ 30 phase‐correlated partial scans distributed over 20 s and n = 1 , … , N ). Corresponding to the angular range of each partial scan, the authors extract virtual partial scans p n V from the artificial full scan p n AF . A standard reconstruction yields the corresponding images f n P , f n AF , and f n V . Subtracting the virtual partial scan image f n V from the artificial full scan image f n AF yields an artifact image that can be used to correct the original partial scan image:f n C = f n P − f n V + f n AF , where f n C is the corrected image. Results: The authors evaluated the effects of scattered radiation on the partial scan artifacts using simulated and measured water phantoms and found a strong correlation. The PSAR algorithm has been validated with a simulated semianthropomorphic heart phantom and with measurements of a dynamic biological perfusion phantom. For the stationary phantoms, real full scans have been performed to provide theoretical reference values. The improvement in the root mean square errors between the full and the partial scans with respect to the errors between the full and the corrected scans is up to 54% for the simulations and 90% for the measurements. Conclusions: The phase‐correlated data now appear accurate enough for a quantitative analysis of cardiac perfusion.