Filtered‐backprojection reconstruction for a cone‐beam computed tomography scanner with independent source and detector rotations. Issue 5 (13th April 2016)

• Record Type: Journal Article
• Authors: Rit, Simon; Clackdoyle, Rolf; Keuschnigg, Peter; Steininger, Philipp
• Is Part Of: Medical physics. Volume 43:Issue 5(2016)
• Page Start: 2344
• Page End: 2352
• Publication Date: 2016-04-13
• Subjects: computerised tomography -- image reconstruction -- medical image processing -- phantoms -- radiation therapy; Computed tomography; Computerised tomographs -- Radiation therapy -- Biological material, e.g. blood, urine; Haemocytometers -- Digital computing or data processing equipment or methods, specially adapted for specific applications -- Image data processing or generation, in general; image‐guided radiotherapy (IGRT) -- three‐dimensional (3D) imaging -- cone‐beam computed tomography (CT) -- tomographic reconstruction -- filtered‐backprojection algorithm -- offset field‐of‐view; Image sensors -- Medical image reconstruction -- Cone beam computed tomography -- Position sensitive detectors -- X‐ray detectors -- Medical X‐ray imaging -- Image detection systems -- Medical image quality; Medical physics -- Periodicals; Medical physics; Geneeskunde; Natuurkunde; Toepassingen; Biophysics; Periodicals; Periodicals; Electronic journals; 610.153
• DOI: 10.1118/1.4945418
• Languages: English
• ISSNs: 0094-2405

Abstract

Abstract : Purpose: A new cone‐beam CT scanner for image‐guided radiotherapy (IGRT) can independently rotate the source and the detector along circular trajectories. Existing reconstruction algorithms are not suitable for this scanning geometry. The authors propose and evaluate a three‐dimensional (3D) filtered‐backprojection reconstruction for this situation. Methods: The source and the detector trajectories are tuned to image a field‐of‐view (FOV) that is offset with respect to the center‐of‐rotation. The new reconstruction formula is derived from the Feldkamp algorithm and results in a similar three‐step algorithm: projection weighting, ramp filtering, and weighted backprojection. Simulations of a Shepp Logan digital phantom were used to evaluate the new algorithm with a 10 cm‐offset FOV. A real cone‐beam CT image with an 8.5 cm‐offset FOV was also obtained from projections of an anthropomorphic head phantom. Results: The quality of the cone‐beam CT images reconstructed using the new algorithm was similar to those using the Feldkamp algorithm which is used in conventional cone‐beam CT. The real image of the head phantom exhibited comparable image quality to that of existing systems. Conclusions: The authors have proposed a 3D filtered‐backprojection reconstruction for scanners with independent source and detector rotations that is practical and effective. This algorithm forms the basis for exploiting the scanner's unique capabilities in IGRT protocols.