Article

The reproducibility and accuracy of cephalometric analysis using different digital imaging modalities and image compression [microform] /

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Thesis (M. Sc.)--University of Toronto, 2001. Includes bibliographical references.

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... Cziraki et al.,[22] reported loss of diagnostic accuracy on digital lateral cephalograms with a CR of 25:1, whereas 12:1 was similar to the image without compression. Duarte et al.,[12] reported that JPEG images of lateral cephalograms with QFs 100, 80, and 60, resulting in CRs of 3.4:1-4.2:1,17:1-26:1, ...
... We chose the landmarks based on previous researches including the points which did not show good reproducibility.[1112] The location of cephalometric points by the x-y coordinate system was used because this is an adequate methodology, previously tested and employed by different authors.[11122223] ...
Article
With increase of digital imaging, the need for storage space and transmission speed also increases. Compressed images need less storage space and decrease the transmission time. However, compression could compromise image quality. The aim of this study was to evaluate the influence of image compression on the identification of cephalometric points on direct digital lateral cephalogram images, compared with the digital imaging and communications in medicine (DICOM) format. In this analytical-descriptive study, 19 direct digital lateral cephalograms saved in DICOM format were used. They were converted to joint photographic experts group (JPEG) 2000 format with quality factors 85, 75, and 60 adding up to 76 images (DICOM, JPEG 85, 75, and 60). The images were randomized and eight cephalometric points were identified on each image by a professional, using the x-y coordinate system. Analysis of variance (ANOVA) was applied to investigate if there was a statistically significant difference in the location of cephalometric points between each group of images. All tests were applied at a significance level of 5%. The results did not demonstrate any statistically significant difference in the identification of the eight cephalometric points between the DICOM images and the JPEG2000 quality factors 85, 75, and 60. JPEG2000 images of lateral cephalograms with quality factors 85, 75, and 60 did not demonstrate any alterations in the identification of cephalometric points compared with the DICOM format. JPEG2000 is a reliable file format for the compression of digital lateral cephalograms.
... The results in this study showed that there were no statistically significant differences among the three types of the digital image compressions for all the liner cephalometric measurements when the lossless compression was used and this comes in agreement with Cziraki study (21) who stated that the JPEG lossless compression did not affect the reproducibility and accuracy of identification for a few landmarks, also did not impact on the accuracy of cephalometric measurement. Furthermore, it may be acceptable to use this compression level in individual cases to assess dentofacial proportions. ...
Article
Full-text available
This study compared the accuracy of linear cephalometric measurements between the com-pressed and non-compressed digital cephalometric images. Materials and Methods: The adult sample consisted of (60) Iraqi subjects (30 females and 30 males) with age ranged 18 – 25 years old, the sam-ples satisfied the criteria of this study. Eight linear cephalometric measurements were recorded from lateral digital cephalometric radiographs, the ACDsee photo manger software used to compress and resaved the original images in 80% and 60% from their original size. The data were analyzed using descriptive statistic and ANOVA & Duncan test. Results: No significant differences were found be-tween the accuracy of the compressed and non-compressed digital cephalometric measurements. Con-clusions: The results of this study indicated that image compression up to 60% of their original size will not effect on the accuracy of routine cephalometric analysis and reduce the size of image storage and facilitates the easier and faster image transmission.
... The results in this study showed that there were no statistically significant differences among the three types of the digital image compressions for all the liner cephalometric measurements when the lossless compression was used and this comes in agreement with Cziraki study (21) who stated that the JPEG lossless compression did not affect the reproducibility and accuracy of identification for a few landmarks, also did not impact on the accuracy of cephalometric measurement. Furthermore, it may be acceptable to use this compression level in individual cases to assess dentofacial proportions. ...
Article
Aims: This study compared the accuracy of linear cephalometric measurements between the compressed and non-compressed digital cephalometric images. Materials and Methods: The adult sample consisted of (60) Iraqi subjects (30 females and 30 males) with age ranged 18-25 years old, the samples satisfied the criteria of this study. Eight linear cephalometric measurements were recorded from lateral digital cephalometric radiographs, the ACDSee photo manager software used to compress and resaved the original images in 80% and 60% from their original size. The data were analyzed using descriptive statistic and ANOVA & Duncan test. Results: No significant differences were found between the accuracy of the compressed and non-compressed digital cephalometric measurements. Conclusions: The results of this study indicated that image compression up to 60% of their original size will not effect on the accuracy of routine cephalometric analysis and reduce the size of image storage and facilitates the easier and faster image transmission.
... Digital radiography images that have been enhanced by brightness and contrast adjustment can only increase the accuracy of some limited landmark identifications. Therefore, brightness and contrast adjustment must be considered very carefully, based on the radiograph image quality, prior to the enhancement [3,8]. However, the progression in the development of digital radiography in this era had led to overuse of image enhancement, especially brightness and contrast, by many operators. ...
Article
Full-text available
Image enhancement brightness and contrast can be adjusted on lateral cephalometric digital radiographs to improve image quality and anatomic landmarks for measurement by Steiner analysis. To determine the limit value for adjustments of image enhancement brightness and contrast in lateral cephalometric digital radiography for Steiner analysis. Image enhancement brightness and contrast were adjusted on 100 lateral cephalometric radiography in 10-point increments (−30, −20, −10, 0, +10, +20, +30). Steiner analysis measurements were then performed by two observers. Reliabilities were tested by the Interclass Correlation Coefficient (ICC) and significance tested by ANOVA or the Kruskal Wallis test. No significant differences were detected in lateral cephalometric analysis measurements following adjustment of the image enhancement brightness and contrast. The limit value of adjustments of the image enhancement brightness and contrast associated with incremental 10-point changes (−30, −20, −10, 0, +10, +20, +30) does not affect the results of Steiner analysis.
Article
Objectives To evaluate the influence of DICOM and JPEG formats on the reproducibility of identification of cephalometric landmarks on posteroanterior digital radiographs. Methods The sample consisted of digital images of posteroanterior radiographs saved in DICOM format; they were subsequently converted into JPEG format with quality factors of 100, 80, and 60. After sample blinding, 18 cephalometric points were identified on each image by three calibrated orthodontists using a system of x- and y-axis Cartesian coordinates. The intraclass correlation test was applied to analyze the occurrence of systematic errors, and Dahlberg’s formula was used to calculate casual errors. The reproducibility between the DICOM and JPEG formats was compared by analysis of variance. All tests were conducted with a significance level of 5 %. Results Each examiner repeated the procedure 30 days after the initial test with 20 % of the images, which were randomly selected, in each file format. We found that the cephalometric landmarks in the posteroanterior digital radiographs presented intraexaminer and interexaminer reproducibility; the exceptions were points ZL, ZR, AZ, JR, NC, and CN in the y-axis and A6 in the x-axis, which were due to intraclass correlations under 0.90 and casual error over 1.0 mm, irrespective of file format (DICOM or JPEG). Conclusions The DICOM and JPEG file formats and quality factors of 100, 80, and 60 did not affect the intraexaminer and interexaminer reproducibility of cephalometric landmarks.
Article
To test the hypothesis that there is no significant difference in the detectability of chemically-induced periapical lesions between a non-compressed image and one subjected to a Joint Photographic Experts Group (JPEG) lossy compression technique at a ratio of 23:1 or less. Chemically-induced periapical lesions were created by placing a solution of 70% perchloric acid at the apex of extracted teeth in 13 human jaw cadaver specimens. Acid was applied in seven incremental time periods from 0-32 h. Extracted teeth were replaced in the socket and images were made using the Schick CDR digital sensor. Using a JPEG lossy compression algorithm, five compression ratios of 2:1, 14:1, 23:1, 28:1 and 47:1 were applied to the images. Images were viewed three times by three observers who ranked the presence or absence of a lesion at three sites, the mesial area, distal area and apex of the tooth, on a 5-point confidence scale. Intraobserver and interobserver agreement and agreement between the compressed and the original images were assessed with intraclass correlation coefficients (ICCs). Overall ICCs for measuring intraobserver agreement using all images were 0.77, 0.84, and 0.50 for the three observers, respectively. The overall ICC for assessing agreement between observers was 0.57. There was no significant difference (P>0.05) between compressed and original images for any site at compression ratios of 2:1, 23:1 and 28:1. There were significant differences for a compression ratio of 47:1. JPEG compression does not impact detectability of artificial periapical lesions at low and moderate compression ratios up to and including 28:1.
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