Imaging Sci Dent.  2018 Dec;48(4):255-259. 10.5624/isd.2018.48.4.255.

Development of a new ball-type phantom for evaluation of the image layer of panoramic radiography

• Yeom HG
• Kim JE
• Huh KH
• Yi WJ
• Heo MS
• Lee SS
• Choi SC

• KMID: 2450165
• DOI: http://doi.org/10.5624/isd.2018.48.4.255

Abstract

PURPOSE
This study proposes a new ball-type phantom for evaluation of the image layer of panoramic radiography.
MATERIALS AND METHODS
The arch shape of an acrylic resin phantom was derived from average data on the lower dental arch in Korean adult males. Metal balls with a 2-mm diameter were placed along the center line of the phantom at a 4-mm mesiodistal interval. Additional metal balls were placed along the 22 arch-shaped lines that ran parallel to the center line at 2-mm buccolingual intervals. The height of each ball in the horizontal plane was spaced by 2.5 mm, and consequently, the balls appeared oblique when viewed from the side. The resulting phantom was named the Panorama phantom. The distortion rate of the balls in the acquired image was measured by automatically calculating the difference between the vertical and horizontal length using MATLAB®. Image layer boundaries were obtained by applying various distortion rate thresholds.
RESULTS
Most areas containing metal balls (91.5%) were included in the image layer with a 50% distortion rate threshold. When a 5% distortion rate threshold was applied, the image layer was formed with a small buccolingual width along the arch-shaped center line. However, it was medially located in the temporomandibular joint region.
CONCLUSION
The Panorama phantom could be used to evaluate the image layer of panoramic radiography, including all mesiodistal areas with large buccolingual width.

Keyword

Phantoms, Imaging; Radiography, Panoramic

MeSH Terms

Adult
Dental Arch
Humans
Male
Phantoms, Imaging
Radiography, Panoramic*
Temporomandibular Joint

Figure

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  Fig. 1 Graph of the adjusted formula. The continuous line obtained from the graph is defined as the center line of the phantom.

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  Fig. 2 A. Final design of the Panorama phantom. The balls appeared oblique when viewed from the side. B. Actual model of the Panorama phantom. It was made of acrylic resin and metal balls with a diameter of 2 mm.

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  Fig. 3 Distortion rate thresholds of the obtained images of metal balls. The balls that satisfied the distortion rate threshold are displayed in red. (A–J) Several image layer boundaries were obtained by applying various distortion rate thresholds, from 50% to 5% with 5% decrements.

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