Imaging Sci Dent.  2013 Mar;43(1):7-15. 10.5624/isd.2013.43.1.7.

Reference line-pair values of panoramic radiographs using an arch-form phantom stand to assess clinical image quality

• Choi DH
• Choi BR
• Choi JW
• Huh KH
• Yi WJ
• Heo MS
• Choi SC
• Lee SS

• KMID: 2167441
• DOI: http://doi.org/10.5624/isd.2013.43.1.7

Abstract

PURPOSE
This study was performed to suggest reference line-pair values of panoramic images with clinically desirable qualities using an arch-form phantom stand.
MATERIALS AND METHODS
The line-pair test phantom was chosen. A real skull model was selected for setting the arch-form model of the phantom stand. The phantom stand had slits in four regions (incisor, premolar, molar, TMJ). Four raw images of the test phantom in each region and one raw image of the real skull were converted into 50 test phantom images and 50 skull phantom images with various line-pair values. 50 post-processed real skull phantom images were divided into 4 groups and were randomly submitted to 14 evaluators. Image quality was graded on a 4 point scale (1. good, 2. normal, 3. poor but interpretable, and 4. not interpretable). The reference line pair was determined as the first line-pair value scored less than 2 points. RESULT: The mean scores tended to decrease as the line-pair values increased. The reference line-pair values were 3.19 LP/mm in the incisor, 2.32 LP/mm in the premolar and TMJ, and 1.88 LP/mm in the molar region.
CONCLUSION
Image quality evaluation methods and criteria should be able to assess various regions considering the characteristics of panoramic systems. This study suggested overall and regional reference line-pair values and established a set of standard values for them.

Keyword

Radiography, Panoramic; Quality Assurance; Phantom, Imaging

MeSH Terms

Bicuspid
Incisor
Molar
Phantoms, Imaging
Radiography, Panoramic
Skull
Temporomandibular Joint

Figure

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  Fig. 1 A. Line-pair test phantom (Nuclear Associates model 07-501 SER. NO.12913). B. The radiographic image of the line-pair test phantom.

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  Fig. 2 A. Transparent real skull X-ray phantom. B. The structural connection of the mandibular condyle with the lower dental arch of the skull phantom is measured on the 3D CT images.

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  Fig. 3 Reference points and associated measurements. The dimensions of the dental arches are determined according to three sagittal and three transverse measurements. (This image is cited from a study by Raberin et al.8)

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  Fig. 4 A. The phantom stand: Slits are prepared in 4 regions including the incisor, right premolar, left molar, and right TMJ regions to hold the test phantoms. B. Positioning the phantom stand for panoramic image acquisition using the tripod connection.

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  Fig. 5 The selected line-pair phantom is inserted in the right TMJ slit of the phantom stand and these are positioned for panoramic image acquisition.

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  Fig. 6 The post-processed test phantom radiographs and corresponding post-processed real skull phantom radiographs, respectively. A. The post-processed image of the test phantom in premolar region showing a 1.11 line-pair value (1.11 LP/mm). B. The post-processed image of the real skull phantom under the same parameter settings for "A" image post-processing. C. The post-processed image of the test phantom in the premolar region showing a 2.87 line-pair value (2.87 LP/mm). D. The post-processed image of the real skull phantom under the same parameter settings for "C" image post-processing.

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  Fig. 7 The mean scores in the incisor group tend to decrease as the line-pair values increased. 3.19 LP/mm is determined to be the reference line-pair value.

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  Fig. 8 The mean scores in the premolar group tend to decrease as the line-pair values increases. 2.32 LP/mm is determined to be the reference line-pair value.

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  Fig. 9 The mean scores in the molar group consistently decrease as the line-pair values increases. 1.88 LP/mm is determined to be the reference line-pair value.

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  Fig. 10 The mean scores in the TMJ group tend to decrease as the line-pair values increases. 2.32 LP/mm is determined to be the reference line-pair value.

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