Imaging Sci Dent.  2016 Sep;46(3):203-210. 10.5624/isd.2016.46.3.203.

Contrast reference values in panoramic radiographic images using an arch-form phantom stand

• Shin JM
• Lee C
• Kim JE
• Huh KH
• Yi WJ
• Heo MS
• Choi SC
• Lee SS

• KMID: 2408252
• DOI: http://doi.org/10.5624/isd.2016.46.3.203

Abstract

PURPOSE
The purpose of this study was to investigate appropriate contrast reference values (CRVs) by comparing the contrast in phantom and clinical images.
MATERIALS AND METHODS
Phantom contrast was measured using two methods: (1) counting the number of visible pits of different depths in an aluminum plate, and (2) obtaining the contrast-to-noise ratio (CNR) for 5 tissue-equivalent materials (porcelain, aluminum, polytetrafluoroethylene [PTFE], polyoxymethylene [POM], and polymethylmethacrylate [PMMA]). Four panoramic radiographs of the contrast phantom, embedded in the 4 different regions of the arch-form stand, and 1 real skull phantom image were obtained, post-processed, and compared. The clinical image quality evaluation chart was used to obtain the cut-off values of the phantom CRV corresponding to the criterion of being adequate for diagnosis.
RESULTS
The CRVs were obtained using 4 aluminum pits in the incisor and premolar region, 5 aluminum pits in the molar region, and 2 aluminum pits in the temporomandibular joint (TMJ) region. The CRVs obtained based on the CNR measured in the anterior region were: porcelain, 13.95; aluminum, 9.68; PTFE, 6.71; and POM, 1.79. The corresponding values in the premolar region were: porcelain, 14.22; aluminum, 8.82; PTFE, 5.95; and POM, 2.30. In the molar region, the following values were obtained: porcelain, 7.40; aluminum, 3.68; PTFE, 1.27; and POM, - 0.18. The CRVs for the TMJ region were: porcelain, 3.60; aluminum, 2.04; PTFE, 0.48; and POM, - 0.43.
CONCLUSION
CRVs were determined for each part of the jaw using the CNR value and the number of pits observed in phantom images.

Keyword

Radiography, Panoramic; Quality Assurance, Health Care; Phantoms, Imaging

MeSH Terms

Aluminum
Bicuspid
Dental Porcelain
Diagnosis
Incisor
Jaw
Molar
Phantoms, Imaging
Polymethyl Methacrylate
Polytetrafluoroethylene
Quality Assurance, Health Care
Radiography, Panoramic
Reference Values*
Skull
Temporomandibular Joint
Aluminum
Dental Porcelain
Polymethyl Methacrylate
Polytetrafluoroethylene

Figure

• 

  Fig. 1 The contrast phantom id composed of 2 parts. Five tissue-equivalent materials are contained in an acrylic block on the top. From the top, the materials are polymethylmethacrylate, polyoxymethylene, polytetrafluoroethylene, aluminum, and porcelain. The bottom contains an aluminum block with pits of various depths.

• 

  Fig. 2 A. X-ray phantom head (transparent, product number 7280; Erler Zimmer Co., Lauf, Germay). B. The reconstructed 3-dimensional computed tomography image of the phantom was used for the central arch curve of the mandible.

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  Fig. 3 A. A fabricated phantom stand for this study. The phantom has slits in the incisor, right premolar, left molar, and right temporomandibular joint regions to insert the contrast phantom. B. The phantom is inserted in the contrast phantom to obtain X-rays.

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  Fig. 4 Contrast phantom images. A. Anterior area. B. Premolar area. C. Molar area. D. Temporomandibular joint area.

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  Fig. 5 Each phantom image obtained was modified into 18 different images with proportionally different contrast values using Aperture (Apple Inc., San Francisco, CA, USA).

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  Fig. 6 A. The skull X-ray phantom head is positioned to take a clinical image. B. The panoramic image of the skull phantom.

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  Fig. 7 The contrast-to-noise ratio (CNR) of the tissue-equivalent material of the phantom in each dental arch region. A. Incisor region. B. Premolar region. C. Molar region. D. Temporomandibular joint region. POM: polyoxymethylene, PTFE: polytetrafluoroethylene.

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