Effect of ultra-low doses, ASIR and MBIR on density and noise levels of MDCT images of dental implant sites
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Differences in noise and density values in MDCT images obtained using ultra-low doses with FBP, ASIR, and MBIR may possibly affect implant site density analysis. The aim of this study was to compare density and noise measurements recorded from dental implant sites using ultra-low doses combined with FBP, ASIR, and MBIR.
Cadavers were scanned using a standard protocol and four low-dose protocols. Scans were reconstructed using FBP, ASIR-50, ASIR-100, and MBIR, and either a bone or standard reconstruction kernel. Density (mean Hounsfield units [HUs]) of alveolar bone and noise levels (mean standard deviation of HUs) was recorded from all datasets and measurements were compared by paired t tests and two-way ANOVA with repeated measures.
Significant differences in density and noise were found between the reference dose/FBP protocol and almost all test combinations. Maximum mean differences in HU were 178.35 (bone kernel) and 273.74 (standard kernel), and in noise, were 243.73 (bone kernel) and 153.88 (standard kernel).
Decreasing radiation dose increased density and noise regardless of reconstruction technique and kernel. The effect of reconstruction technique on density and noise depends on the reconstruction kernel used.
• Ultra-low-dose MDCT protocols allowed more than 90 % reductions in dose.
• Decreasing the dose generally increased density and noise.
• Effect of IRT on density and noise varies with reconstruction kernel.
• Accuracy of low-dose protocols for interpretation of bony anatomy not known.
• Effect of low doses on accuracy of computer-aided design models unknown.
KeywordsAlgorithms Dental implants Image processing, computer-assisted Multidetector computed tomography Radiation dosage
Adaptive statistical iterative reconstruction
Model-based iterative reconstruction
The authors wish to thank individuals who donated their bodies and tissues for the advancement of education and research. The scientific guarantor of this publication is Dr. Gerlig Widmann. The authors of this manuscript declare no relationships with any companies whose products or services may be related to the subject matter of the article. The authors state that this work has not received any funding. Amal Ahmed Gaber Abd-Alhafez, MSc (private consultant) and Eidah Alenazi, MSc (Assistant Researcher, Statistics & Operations Research Department, Kind Saud University) kindly provided statistical advice for this manuscript. Institutional review board approval was not required because the bodies used in the study were donated by people who had given their informed consent for their use for scientific and educational purposes prior to death and the study fulfilled all requirements necessary for studies on human cadavers according to the regulations of the Division of Clinical and Functional Anatomy, Medical University of Innsbruck. Written informed consent was obtained from all subjects (patients) in this study. Some study subjects or cohorts have been previously reported in the following experimental studies: Widmann G. et al., Ultralow-dose computed tomography imaging for surgery of midfacial and orbital fractures using ASIR and MBIR. International Journal of Oral and Maxillofacial Surgery. 2015. 44(4): p. 441–446, and Widmann, G. et al., Ultralow-Dose CT of the Craniofacial Bone for Navigated Surgery Using Adaptive Statistical Iterative Reconstruction and Model-Based Iterative Reconstruction: 2D and 3D Image Quality. American Journal of Roentgenology, 2015. 204(3): p. 563–569. Methodology: retrospective, experimental, multicenter study.
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