Affiliations: [a] Laboratoire de recherche en imagerie et orthopédie, Centre de recherche du Centre hospitalier de l’Université de Montréal, Montréal, QC, Canada
| [b] Département de génie des systèmes, École de technologie supérieure, Montréal, QC, Canada
| [c] Faculté de médecine dentaire, Université de Montréal, Montréal, QC, Canada
| [d] Département de physique, Université de Montréal, Montréal, QC, Canada
| [e] Département de radio-oncologie, Centre hospitalier de l’Université de Montréal (CHUM), Montréal, QC, Canada
| [f] Département de physique, de génie physique et d’optique and Centre de recherche sur le cancer, Université Laval, Québec, QC, Canada
| [g] Département de radio-oncologie and Centre de recherche du CHU de Québec, Québec (QC) G1R 2J6, Canada
Correspondence:
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Corresponding author: Dmitri Matenine, Laboratoire de recherche en imagerie et orthopédie, Centre de recherche du Centre hospitalier de l’Université de Montréal, 900, rue Saint-Denis, Montréal, QC, H2X 0A9, Canada. Tel.: +1 514 890 8000/Ext. 30294; E-mail: dmitri.matenine@etsmtl.ca.
Abstract: BACKGROUND:Iterative reconstruction is well-established in diagnostic multidetector computed tomography (MDCT) for dose reduction and image quality enhancement. Its application to diagnostic cone beam computed tomography (CBCT) is only emerging and warrants a quantitative evaluation. METHODS:Several phantoms and a canine head specimen were imaged using a commercially available small-field CBCT scanner. Raw projection data were reconstructed using the Feldkamp-Davis-Kress (FDK) method with different filters, including denoising via total variation (TV) minimization (FDK-TV). Iterative reconstruction was carried out using the TV-regularized ordered subsets convex technique (OSC-TV). Signal-to-noise ratio (SNR), noise power spectrum (NPS) and spatial resolution of images were estimated. Dose levels were measured via the weighted computed tomography dose index, while low-dose image quality degradation was estimated via structural similarity (SSIM). RESULTS:OSC-TV and FDK-TV were shown to significantly improve image signal-to-noise ratio (SNR) compared to FDK with a standard filter, 5.8 and 4.0 times, respectively. Spatial resolution attained with different algorithms varied moderately across different experiments. For low-dose acquisitions, image quality decreased dramatically for FDK but not for FDK-TV nor OSC-TV. For low-dose canine head images acquired using about 1/5 of the dose compared to a reference image, SSIM dropped to about 0.3 for FDK, while remaining at 0.92 for FDK-TV and 0.96 for OSC-TV. CONCLUSION:OSC-TV was shown to improve image quality compared to FDK and FDK-TV. Moreover, this iterative approach allowed for significant dose reduction while maintaining image quality.
