| 1. |
- Zacharaki, E I, et al.
(författare)
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A digital subtraction radiography scheme based on automatic multiresolution registration.
- 2004
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Ingår i: Dento maxillo facial radiology. - : British Institute of Radiology. - 0250-832X. ; 33:6, s. 379-90
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: To establish a digital subtraction radiography scheme for aligning clinical in vivo radiographs based on the implementations of an automatic geometric registration method and a contrast correction technique. METHODS: Thirty-five pairs of in vivo dental radiographs from four clinical studies were used in this work. First, each image pair was automatically aligned by applying a multiresolution registration strategy using the affine transformation followed by the implementation of the projective transformation at full resolution. Then, a contrast correction technique was applied in order to produce subtraction radiographs and fused images for further clinical evaluation. The performance of the proposed registration method was assessed against a manual method based on the projective transformation. RESULTS: The qualitative assessment of the experiments based on visual inspection has shown advantageous performance of the proposed automatic registration method against the manual method. Furthermore, the quantitative analysis showed statistical difference in terms of the root mean square (RMS) error estimated over the whole images and specific regions of interest. CONCLUSIONS: The proposed automatic geometric registration method is capable of aligning radiographs acquired with or without rigorous a priori standardization. The methodology is pixel-based and does not require the application of any segmentation process prior to alignment. The employed projective transformation provides a reliable model for registering intraoral radiographs. The implemented contrast correction technique sequentially applied provides 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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| 2. |
- Ekestubbe, Annika, 1953, et al.
(författare)
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Effective and organ doses from scanography and zonography: a comparison with periapical radiography.
- 2004
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Ingår i: Dento maxillo facial radiology. - : British Institute of Radiology. - 0250-832X. ; 33:2, s. 87-92
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: To compare absorbed and effective doses from scanographic and zonographic examinations performed in the Scanora unit with intraoral periapical radiography. METHODS: Absorbed dose measurements were made on an anthropomorphic phantom head with LiF thermoluminescent dosemeters in the regions of the pituitary gland, eye lenses, parotid glands, submandibular glands, thyroid gland and skin. Energy imparted was calculated from the measurements of air collision kerma and effective doses by using the quotient 24 mSv J-1 between energy imparted and effective dose. The upper and lower third molar region was examined with intraoral radiographs and with ramus scanograms, dental scanograms and dental zonograms. Radiation dose measurements were also performed for Scanora panoramic radiography (jaw and dental). RESULTS: The effective doses for the ramus and dental scanograms were 0.01 mSv, similar or lower than for intraoral radiography. Zonography yielded the highest effective dose (0.03 mSv). Except for the skin doses, the salivary glands received the highest doses. Salivary gland doses were slightly higher from narrow beam than from intraoral radiography. CONCLUSIONS: Detail narrow beam radiography with the Scanora is an alternative to periapical radiography and is preferred, from a radiation dose point of view, over zonography.
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| 3. |
- Ekestubbe, Annika, 1953, et al.
(författare)
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Quality of digital pre-implant tomography: comparison of film-screen images with storage phosphor images at normal and low dose.
- 2003
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Ingår i: Dento maxillo facial radiology. - 0250-832X. ; 32:5, s. 322-6
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: The aim of this pilot study was to compare the image quality of a storage phosphor system with that of conventional film-screen in pre-implant conventional tomography, and to test the influence of radiation dose on image quality in the storage phosphor system. METHODS: Cross-sectional conventional tomographic images (Scanora) technique) were obtained on 11 patients with film-screen and with storage phosphor image plates (Digora) PCT) at normal and low doses. Ten observers graded the visibility of anatomical structures of importance for implant planning. A three-step rating scale was used, where -1 =worse, 0=equal and 1=better than the reference image. RESULTS: Although image quality was graded as equally good in the majority (59%) of images, the storage phosphor system scored significantly lower than film-screen (-0.37 vs 0.00, respectively) for all the images. Low dose storage phosphor images were rated significantly lower (-0.21) than normal dose images (0.00). CONCLUSIONS: In the majority of patients, anatomic structures of importance for implant planning are visualized equally well on storage phosphor and film-screen images. However, where differences do exist, storage phosphor images score lower than film-screen images. Dose reduction in the storage phosphor system had a negative influence on image quality.
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| 4. |
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| 5. |
- Molander, Björn, 1949, et al.
(författare)
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Quality of film-based and digital panoramic radiography.
- 2004
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Ingår i: Dento maxillo facial radiology. - : British Institute of Radiology. - 0250-832X. ; 33:1, s. 32-6
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: To compare the image quality of panoramic radiographs obtained with storage phosphor plate and screen-film systems. METHODS: Panoramic radiographs were taken in 60 patients both with film and with a storage phosphor plate system (30 with DenOptix (Dentsply/Gendex) and 30 with Digora PCT). The images were obtained with either the Cranex Tome or the Scanora multimodal X-ray unit. The screen-film combination was Lanex medium/Curix Ortho HT-G. The digital images were displayed as 8-bit images with a 300 dpi resolution on a 19" monitor and the film images were placed on a light box adjacent to the screen. Ten observers evaluated diagnostic image quality by means of visual grading analysis of different anatomical structures. The structures were scored as being visualized much better (5), better (4), equal (3), worse (2) or much worse (1) in the digital images than in the film images. The mean number of patients receiving the different scores was calculated. Statistical methods used were Wilcoxon sign rank test and Mann-Whitney test. RESULTS: On average, visualization was equal in 19 of the 30 patients imaged using Digora PCT; in 10 it was worse. The corresponding values for DenOptix were 20 and 9. The difference between the film-based and the digital images was small but statistically significant (P<0.0001). The difference between the two image plate systems was not statistically significant (P>/=0.17). CONCLUSIONS: It was concluded that digital panoramic radiographs are equivalent to film-based images for most purposes.
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