| 1. |
- Economopoulos, T, et al.
(author)
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Automatic correspondence using the enhanced hexagonal center-based inner search algorithm for point-based dental image registration
- 2006
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In: Conf Proc IEEE Eng Med Biol Soc. ; 1, s. 1421-1424
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Journal article (peer-reviewed)abstract
- In this paper a modified version of the center-based inner search algorithm, the enhanced hexagonal center-based inner search algorithm, for automatic point correspondence is proposed towards dental registration. The modified algorithm is incorporated within a general registration scheme which is based on extracting a set of candidate points on the reference image, finding their corresponding points in the other image (float image) using the proposed algorithm and applying an affine geometrical transformation towards automatic registration. The performance of the proposed algorithm is evaluated against a well-known method for automatic correspondence, in terms of the registration accuracy. Qualitative and quantitative results on registering 24 dental pairs showed that the proposed algorithm outperforms the other method for automatic correspondence.
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| 2. |
- Economopoulos, T, et al.
(author)
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Automatic correspondence using the enhanced hexagonal centre-based inner search algorithm for point-based dental image registration
- 2008
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In: Dentomaxillofacial Radiology. - : British Institute of Radiology. - 0250-832X .- 1476-542X. ; 37, s. 185-204
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Journal article (peer-reviewed)abstract
- Objectives: In this paper, the enhanced hexagonal centre-based inner search (EHCBIS) algorithm, for automatic point correspondence, is proposed for dental image registration. Methods: The presented algorithm is incorporated within a general registration scheme, which is based on extracting a set of candidate points on the reference image, finding their corresponding points in the image to be transformed (float image) using the proposed algorithm and applying a suitable geometrical transformation towards automatic registration. The performance of the proposed algorithm is evaluated against three well-known methods for automatic correspondence, the self-organizing maps, the automatic extraction of corresponding points and the trimmed iterative closest point method, in terms of registration accuracy. Results: Qualitative and quantitative results on registering 123 dental pairs show that the proposed algorithm outperforms the other methods for automatic correspondence with or without the presence of noise. Conclusions: The EHCBIS method is capable of defining automatically corresponding points in dental image pairs. It can be incorporated within a general scheme for point-based registration of dental radiographs acquired with or without rigorous a priori standardization. The applied projective transformation provides a reliable model for registering intraoral radiographs. The methodology does not require any segmentation prior to alignment providing subtraction radiographs and fused images for clinical evaluation regarding the evolution of a disease or the response to a therapeutic scheme.
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| 3. |
- Ekestubbe, Annika, 1953, et al.
(author)
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Oral radiologi
- 2005
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Book (other academic/artistic)
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| 4. |
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| 5. |
- Gröndahl, Hans-Göran, 1940, et al.
(author)
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Radiographic examination of the implant patient
- 2008
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In: In: Lindhe J, Lang NP, Karring T (eds.). Clinical Periodontology and Implant Dentistry (vol 2), fifth edition. PA: Wiley-Blackwell.
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Book chapter (other academic/artistic)
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| 6. |
- Gröndahl, Hans-Göran, 1940, et al.
(author)
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Titta på dina bitewingbilder-andra gör det inte!
- 2005
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In: Tandläkartidningen. ; 97:7, s. 60-66
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Journal article (other academic/artistic)abstract
- De vanligaste röntgenbilder som tandläkare tar är utan tvivel bitewingbilder. Bitewingbilder kan också tas av en tandhygienist vid uppföljning av revisionspatienter. Bilder som tas av hygienister ska dock lämnas till en tandläkare för diagnostik av annat än karies och benförlust som orsakats av parodontit. Varje år tas flera miljoner bitewingbilder i Sverige. De har huvudsakligen två syften: 1) att vara till hjälp vid kariesdiagnostik och 2) för bedömning av det marginala benet. I den stora mängd bilder som tas dyker det då och då upp tecken på patologiska tillstånd av annan och ibland allvarligare art. Det är viktigt att vara medveten om den risken. Det ökar möjligheten att i ett tidigt stadium uppmärksamma sådana processer. Till en specialistklinik för odontologisk radiologi remitteras huvudsakligen patienter som kräver undersökningar som inte kan utföras i allmänpraktik. Hittar specialisterna en större patologisk process som troligen utvecklats under flera år letar de sig alltid bakåt i tiden. De gör det av två skäl: 1) det underlättar diagnostiken och 2) det ökar kunskaperna om på vilket sätt, och hur snabbt, olika typer av patologiska förändringar utvecklas. Tidigare tagna röntgenbilder och journalanteckningar kan berätta något om symtom eller kliniska tecken. När röntgenbilderna granskas kan specialisterna ibland se att det patologiska tillståndet funnits med i bilden men inte uppmärksammats. På följande sidor presenteras några sådana fall. Författarna spekulerar i varför upptäckterna inte gjordes tidigare och föreslår åtgärder som förhoppningsvis innebär att fler upptäckter kan göras i tidigare sjukdomsstadier. På så sätt kan behandlingen bli enklare och resultatet bättre.
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| 7. |
- Lofthag-Hansen, Sara, 1956, et al.
(author)
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Limited cone-beam CT and intraoral radiography for the diagnosis of periapical pathology
- 2007
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In: Oral Surg Oral Med Oral Pathol Oral Radiol Endod. ; 103:1, s. 114-119
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Journal article (peer-reviewed)abstract
- Objective To compare intraoral periapical radiography with 3D images for the diagnosis of periapical pathology. Study design Maxillary molars and premolars and mandibular molars with endodontic problems and examined with periapical radiographs and a 3D technique (3D Accuitomo) were retrospectively selected and evaluated by 3 oral radiologists. Numbers of roots and root canals, presence and location of periapical lesions, and their relation to neighboring structures were studied. Results Among 46 teeth, both techniques demonstrated lesions in 32 teeth, and an additional 10 teeth were found in the Accuitomo images. As regards individual roots, 53 lesions were found in both techniques, and 33 more roots were found to have lesions in Accuitomo images. Artefacts were sometimes a problem in Accuitomo images. In 32 of the 46 cases, all observers agreed that additional clinically relevant information was obtained with Accuitomo images. Conclusions A high-resolution 3D technique can be of value for diagnosis of periapical problems.
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| 8. |
- Lund, Henrik, 1975, et al.
(author)
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Accuracy and precision of linear measurements in cone beam computed tomography Accuitomo tomograms obtained with different reconstruction techniques
- 2009
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In: Dentomaxillofacial Radiology. - 0250-832X. ; 38:6, s. 379-86
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Journal article (peer-reviewed)abstract
- Objectives: To assess the accuracy and precision of linear measurements, the influence of different object positions in cone beam CT (CBCT) images and the effect of different systems for reformatting and viewing the tomograms on measurement values. Methods: An object consisting of Plexiglas® plates with metal spheres was radiographically examined in three positions using the CBCT unit Accuitomo®. Tomograms were reformatted using the i-Dixel software and Sectra® picture archiving and communication system (PACS) multiplanar reformatting (MPR). Two observers measured 20 linear distances in axial, frontal and sagittal planes. Physical measurements of actual distances by means of a digital caliper served as the gold standard. Results: For measurements performed on the Accuitomo and Sectra PACS workstations, the mean differences between repeated measurements were below 0.13 mm (standard deviation (SD) 0.13 mm) and 0.21 mm (SD 0.18 mm), respectively. Mean differences between the two observers were below 0.11 mm (SD 0.07 mm) and 0.15 mm (SD 0.09 mm). The mean difference between the gold standard and the basic position when using the Accuitomo workstation, was –0.08 mm (SD 0.21 mm) and for a deviated/rotated position –0.08 mm (SD 0.23 mm) and –0.09 mm (SD 0.20 mm). None was statistically significant (P > 0.05). For measurement performed on MPR tomograms using the Sectra PACS workstation, mean differences were –0.09 mm (SD 0.17 mm) for basic position, and –0.08 mm (SD 0.19 mm) and –0.13 mm (SD 0.15 mm) for deviated and rotated positions, respectively. The mean difference between gold standard and basic/rotated positions was statistically significant, with P = 0.032 and P = 0.002. Conclusions: Our study confirms previous findings indicating that measurements in 3DX Accuitomo FPD (flat panel detector) tomograms show a high level of agreement with actual distances. Our findings suggest the possibility of minor distortion in tomograms reformatted by means of Sectra PACS MPR.
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| 9. |
- Matsopoulos, GK, et al.
(author)
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Image registration based on lifting process: an application to digital subtraction radiography
- 2006
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In: IEEE Trans Inf Technol Biomed. ; 10:4, s. 763-774
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Journal article (peer-reviewed)abstract
- In this paper, a digital subtraction radiology scheme is presented based on a new method for the automatic registration of dental radiographs acquired with or without rigorous a priori standardization. The scheme is comprised of an automatic registration method and a subtraction process. The proposed registration method can be considered as an object-based registration method without imposing the prerequisite of image segmentation in order to detect the boundary of the objects of interest or the automatic detection of matching landmarks. This is achieved by augmenting the dimensionality of the problem from two-dimensional gray-level matching to three-dimensional surface matching using the process of lifting in combination with a surface-matching technique. The pseudo three-dimensional affine transformation that matches the lifted images incorporates advantageous characteristics including spatial alignment of the surfaces, anisotropic correction of brightness/contrast differences, and stable convergence of the similarity function to its optimal value. The performance of the proposed automatic registration method is assessed against a manual method based on the projective transformation. The qualitative and quantitative assessments of the experiments have shown advantageous performance of the proposed automatic registration method against the manual one. Finally, the proposed registration method has been further improved in terms of execution time by the implementation of a surface decimation process.
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| 10. |
- Sundén Pikner, Solweig, 1948, et al.
(author)
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Marginal Bone Loss at Implants: A Retrospective, Long-Term Follow-Up of Turned Branemark System (R) Implants
- 2009
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In: CLINICAL IMPLANT DENTISTRY AND RELATED RESEARCH. - : Wiley. - 1523-0899 .- 1708-8208. ; 11:1, s. 11-23
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Journal article (peer-reviewed)abstract
- Background: Lately, presence of progressive bone loss around oral implants has been discussed. Purpose: The aim of this study was to report in a large patient group with different prosthetic restorations marginal bone level and its change as measured in radiographs obtained from prosthesis insertion up to a maximum 20 years in service. Further, it also aimed to study the impact of gender, age, jaw, prosthetic restoration, and calendar year of surgery. Materials and Methods: Out of 1,716 patients recorded for clinical examination during 1999, 1,346 patients (78.4%) could be identified. A total of 640 patients (3,462 originally installed Brånemark System® implants, Nobel Biocare, Göteborg, Sweden) with a follow-up of ≥5 years were included in the study, while patients with continuous overdentures and augmentation procedures were not. Distance between the fixture/abutment junction (FAJ) and the marginal bone level was recorded. Results: The number of implants with a mean bone level of ≥3 mm below FAJ increased from 2.8% at prosthesis insertion to 5.6% at year 1, and 10.8% after 5 years. Corresponding values after 10, 15, and 20 years were 15.2, 17.2, and 23.5%, respectively. Implant-based bone loss was as a mean 0.8 mm (SD 0.8) after 5 years, followed by only minor average changes. Mean bone loss on patient level followed a similar pattern. Disregarding follow-up time, altogether 183 implants (107 patients) showed a bone loss ≥3 mm from prosthesis insertion to last examination. Significantly larger bone loss was found the older the patient was at surgery and for lower jaw implants. Conclusions: Marginal bone support at Brånemark implants was with few exceptions stable over years.
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