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Change in Image Quality According to the 3D Locations of a CBCT Phantom.

Hwang JJ, Park H, Jeong HG, Han SS - PLoS ONE (2016)

Bottom Line: We evaluated and compared the voxel size, homogeneity, contrast to noise ratio (CNR), and the 10% point of the modulation transfer function (MTF10%) of the center and periphery.Because the CNR, homogeneity, and MTF10% were significantly affected by positional changes of the phantom, an object's position can influence the interpretation of follow up CBCT images.Therefore, efforts to locate the object in the same position are important.

View Article: PubMed Central - PubMed

Affiliation: Department of Oral and Maxillofacial Radiology, College of Dentistry, Yonsei University, Seoul, Korea.

ABSTRACT
A patient's position changes in every CBCT scan despite patient alignment protocols. However, there have been studies to determine image quality differences when an object is located at the center of the field of view (FOV). To evaluate changes in the image quality of the CBCT scan according to different object positions, the image quality indexes of the Alphard 3030 (Alphard Roentgen Ind., Ltd., Kyoto, Japan) and the Rayscan Symphony (RAY Ind., Ltd., Suwon, Korea) were measured using the Quart DVT_AP phantom at the center of the FOV and 6 peripheral positions under four types of exposure conditions. Anterior, posterior, right, left, upper, and lower positions 1 cm offset from the center of the FOV were used for the peripheral positions. We evaluated and compared the voxel size, homogeneity, contrast to noise ratio (CNR), and the 10% point of the modulation transfer function (MTF10%) of the center and periphery. Because the voxel size, which is determined by the Nyquist frequency, was within tolerance, other image quality indexes were not influenced by the voxel size. For the CNR, homogeneity, and MTF10%, there were peripheral positions which showed considerable differences with statistical significance. The average difference between the center and periphery was up to 31.27% (CNR), 70.49% (homogeneity), and 13.64% (MTF10%). Homogeneity was under tolerance at some of the peripheral locations. Because the CNR, homogeneity, and MTF10% were significantly affected by positional changes of the phantom, an object's position can influence the interpretation of follow up CBCT images. Therefore, efforts to locate the object in the same position are important.

No MeSH data available.


Related in: MedlinePlus

3D locations of the phantom.C represent the center of the FOV; A, P, R, L, Up, and Lo represent anterior, posterior, right, left, upper, and lower positions, respectively, 1 cm offset from the FOV center.
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pone.0153884.g002: 3D locations of the phantom.C represent the center of the FOV; A, P, R, L, Up, and Lo represent anterior, posterior, right, left, upper, and lower positions, respectively, 1 cm offset from the FOV center.

Mentions: CBCT data were collected using the Rayscan Symphony (RAY Ind., Ltd., Suwon, Korea) and three exposure protocols from the Alphard 3030 (Alphard Roentgen Ind., Ltd., Kyoto, Japan). The exposure protocols used for each CBCT unit are shown in Table 1. The QUART DVT_AP (QUART GmbH, Zorneding, Germany) is made of polymethyl methacrylate (PMMA) containing all of the required test objects for quality control (Fig 1). The center of the FOV was used as a reference position according to the phantom manual. The center of the Quart DVT_AP phantom was located in the upper, lower, right, left, anterior, and posterior positions 1 cm offset from the center of the FOV (Fig 2). All of the examinations were repeated five times independently. Because there is no ear holder and head rest in the Symphony, these components were removed from the Alphard in order to maintain similar examination conditions. One of the protocols with the smallest FOV of the Alphard was excluded because the images of the test object were partially obtained in the peripheral positions and some indexes could not be obtained.


Change in Image Quality According to the 3D Locations of a CBCT Phantom.

Hwang JJ, Park H, Jeong HG, Han SS - PLoS ONE (2016)

3D locations of the phantom.C represent the center of the FOV; A, P, R, L, Up, and Lo represent anterior, posterior, right, left, upper, and lower positions, respectively, 1 cm offset from the FOV center.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4836729&req=5

pone.0153884.g002: 3D locations of the phantom.C represent the center of the FOV; A, P, R, L, Up, and Lo represent anterior, posterior, right, left, upper, and lower positions, respectively, 1 cm offset from the FOV center.
Mentions: CBCT data were collected using the Rayscan Symphony (RAY Ind., Ltd., Suwon, Korea) and three exposure protocols from the Alphard 3030 (Alphard Roentgen Ind., Ltd., Kyoto, Japan). The exposure protocols used for each CBCT unit are shown in Table 1. The QUART DVT_AP (QUART GmbH, Zorneding, Germany) is made of polymethyl methacrylate (PMMA) containing all of the required test objects for quality control (Fig 1). The center of the FOV was used as a reference position according to the phantom manual. The center of the Quart DVT_AP phantom was located in the upper, lower, right, left, anterior, and posterior positions 1 cm offset from the center of the FOV (Fig 2). All of the examinations were repeated five times independently. Because there is no ear holder and head rest in the Symphony, these components were removed from the Alphard in order to maintain similar examination conditions. One of the protocols with the smallest FOV of the Alphard was excluded because the images of the test object were partially obtained in the peripheral positions and some indexes could not be obtained.

Bottom Line: We evaluated and compared the voxel size, homogeneity, contrast to noise ratio (CNR), and the 10% point of the modulation transfer function (MTF10%) of the center and periphery.Because the CNR, homogeneity, and MTF10% were significantly affected by positional changes of the phantom, an object's position can influence the interpretation of follow up CBCT images.Therefore, efforts to locate the object in the same position are important.

View Article: PubMed Central - PubMed

Affiliation: Department of Oral and Maxillofacial Radiology, College of Dentistry, Yonsei University, Seoul, Korea.

ABSTRACT
A patient's position changes in every CBCT scan despite patient alignment protocols. However, there have been studies to determine image quality differences when an object is located at the center of the field of view (FOV). To evaluate changes in the image quality of the CBCT scan according to different object positions, the image quality indexes of the Alphard 3030 (Alphard Roentgen Ind., Ltd., Kyoto, Japan) and the Rayscan Symphony (RAY Ind., Ltd., Suwon, Korea) were measured using the Quart DVT_AP phantom at the center of the FOV and 6 peripheral positions under four types of exposure conditions. Anterior, posterior, right, left, upper, and lower positions 1 cm offset from the center of the FOV were used for the peripheral positions. We evaluated and compared the voxel size, homogeneity, contrast to noise ratio (CNR), and the 10% point of the modulation transfer function (MTF10%) of the center and periphery. Because the voxel size, which is determined by the Nyquist frequency, was within tolerance, other image quality indexes were not influenced by the voxel size. For the CNR, homogeneity, and MTF10%, there were peripheral positions which showed considerable differences with statistical significance. The average difference between the center and periphery was up to 31.27% (CNR), 70.49% (homogeneity), and 13.64% (MTF10%). Homogeneity was under tolerance at some of the peripheral locations. Because the CNR, homogeneity, and MTF10% were significantly affected by positional changes of the phantom, an object's position can influence the interpretation of follow up CBCT images. Therefore, efforts to locate the object in the same position are important.

No MeSH data available.


Related in: MedlinePlus