R Pauwels1,2, L Seynaeve2, J C G Henriques2, C de Oliveira-Santos3, P C Souza4, F H Westphalen4, I R F Rubira-Bullen5, R F Ribeiro-Rotta6, M I B Rockenbach7, F Haiter-Neto8, P Pittayapat1,2, H Bosmans9, R Bogaerts10, R Jacobs1. 1. 1 Department of Radiology, Faculty of Dentistry, Chulalongkorn University, Bangkok, Thailand. 2. 2 OMFS-IMPATH Research Group, Oral Imaging Center, Department of Imaging and Pathology, Biomedical Sciences Group, University of Leuven, Leuven, Belgium. 3. 3 Department of Stomatology, Public Health and Forensic Dentistry, University of São Paulo, School of Dentistry of Ribeirão Preto of Dentistry, São Paulo, Brazil. 4. 4 School of Dentistry, Pontifical Catholic University of Paraná, Curitiba, Brazil. 5. 5 Stomatology Department, Bauru School of Dentistry, University of São Paulo, São Paulo, Brazil. 6. 6 Department of Oral Medicine, School of Dentistry, Federal University of Goiás, Goiás, Brazil. 7. 7 Department of Surgery, Faculty of Dentistry, Pontifical Catholic University of Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil. 8. 8 Department of Oral Diagnosis, Piracicaba Dental School, University of Campinas, Piracicaba, Brazil. 9. 9 Department of Radiology, University Hospitals Leuven, Leuven, Belgium. 10. 10 Department of Experimental Radiotherapy, University Hospitals Leuven, Leuven, Belgium.
Abstract
OBJECTIVES: To investigate the effect of tube current-exposure time (mAs) reduction on clinical and technical image quality for different CBCT scanners, and to determine preliminary minimally acceptable values for the mAs and contrast-to-noise ratio (CNR) in CBCT. METHODS: A polymethyl methacrylate (PMMA) phantom and an anthropomorphic skull phantom, containing a human skeleton embedded in polyurethane, were scanned using four CBCT devices, including seven exposure protocols. For all protocols, the mAs was varied within the selectable range. Using the PMMA phantom, the CNRAIR was measured and corrected for voxel size. Eight axial slices and one coronal slice showing various anatomical landmarks were selected for each CBCT scan of the skull phantom. The slices were presented to six dentomaxillofacial radiologists, providing scores for various anatomical and diagnostic parameters. RESULTS: A hyperbolic relationship was seen between CNRAIR and mAs. Similarly, a gradual reduction in clinical image quality was seen at lower mAs values; however, for several protocols, image quality remained acceptable for a moderate or large mAs reduction compared with the standard exposure setting, depending on the clinical application. The relationship between mAs, CNRAIR and observer scores was different for each CBCT device. Minimally acceptable values for mAs were between 9 and 70, depending on the criterion and clinical application. CONCLUSIONS: Although noise increased at a lower mAs, clinical image quality often remained acceptable at exposure levels below the manufacturer's recommended setting, for certain patient groups. Currently, it is not possible to determine minimally acceptable values for image quality that are applicable to multiple CBCT models.
OBJECTIVES: To investigate the effect of tube current-exposure time (mAs) reduction on clinical and technical image quality for different CBCT scanners, and to determine preliminary minimally acceptable values for the mAs and contrast-to-noise ratio (CNR) in CBCT. METHODS: A polymethyl methacrylate (PMMA) phantom and an anthropomorphic skull phantom, containing a human skeleton embedded in polyurethane, were scanned using four CBCT devices, including seven exposure protocols. For all protocols, the mAs was varied within the selectable range. Using the PMMA phantom, the CNRAIR was measured and corrected for voxel size. Eight axial slices and one coronal slice showing various anatomical landmarks were selected for each CBCT scan of the skull phantom. The slices were presented to six dentomaxillofacial radiologists, providing scores for various anatomical and diagnostic parameters. RESULTS: A hyperbolic relationship was seen between CNRAIR and mAs. Similarly, a gradual reduction in clinical image quality was seen at lower mAs values; however, for several protocols, image quality remained acceptable for a moderate or large mAs reduction compared with the standard exposure setting, depending on the clinical application. The relationship between mAs, CNRAIR and observer scores was different for each CBCT device. Minimally acceptable values for mAs were between 9 and 70, depending on the criterion and clinical application. CONCLUSIONS: Although noise increased at a lower mAs, clinical image quality often remained acceptable at exposure levels below the manufacturer's recommended setting, for certain patient groups. Currently, it is not possible to determine minimally acceptable values for image quality that are applicable to multiple CBCT models.
Authors: Miet Loubele; Frederik Maes; Filip Schutyser; Guy Marchal; Reinhilde Jacobs; Paul Suetens Journal: Oral Surg Oral Med Oral Pathol Oral Radiol Endod Date: 2006-04-21
Authors: R Spin-Neto; J Mudrak; L H Matzen; J Christensen; E Gotfredsen; A Wenzel Journal: Dentomaxillofac Radiol Date: 2012-07-27 Impact factor: 2.419