Table 1.
Cone beam CT machines and exposure protocols.
Fig 1.
(A) the DVT_AP phantom. (B) disc 1 containing the test objects and disc 2 containing scatter radiation parts.
Fig 2.
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.
Fig 3.
QUART DVT_TEC software for image quality assessment.
(A) Nyquist Frequency. (NF) (B) Contrast to Noise Ratio (CNR). (C) Homogeneity. (D) Modulation Transfer Function (MTF). “Screenshots from QUART DVT_TEC software under a CC BY license, with permission from QUART GmbH, original copyright 2014.”
Table 2.
Definition and tolerance of four image quality indexes.
All tolerance levels are from the phantom manual.
Table 3.
Means and standard deviations (SD) of four indexes.
SD is the standard deviation. CNR = Contrast to Noise Ratio. MTF10% = the 10% point of the modulation transfer function. Upper, Lower, Center, Anterior, Posterior, Right, and Left represent upper, lower, center, anterior, posterior, right, and left positions 1 cm offset from the center of the FOV. Measurements below the tolerance are shown in bold. The CNR, which showed over 20% difference with the center, is also marked in bold.
Table 4.
Statistical analysis of image quality index values.
a represents p<0.05. CNR = Contrast to Noise Ratio. MTF10% = the 10% point of the modulation transfer function. Upper, Lower, Center, Anterior, Posterior, Right, and Left represent upper, lower, center, anterior, posterior, right, and left positions 1 cm offset from the center of the FOV. Measurements below the tolerance are shown in bold. The CNR, which showed over 20% difference with the center, is also marked in bold.
Fig 4.
Statistical analysis of image quality index values.
(A) Voxel size. (B) Contrast to Noise Ratio (CNR). (C) Homogeneity. (D) 10% point of the modulation transfer function (MTF10%). C, P, and I represent cephalo, panorama, and implant modes of the Alphard 3030 CBCT, respectively. Ray is the Ray Symphony CBCT. Gray columns represent the center position, large nodes represent the values with statistically significant difference compared with the center, and black dotted lines represent the tolerance levels.
Table 5.
The mean difference (%) with the center position.
CNR = Contrast to Noise Ratio. MTF10% = the 10% point of the modulation transfer function. Upper, Lower, Center, Anterior, Posterior, Right, and Left represent upper, lower, center, anterior, posterior, right, and left positions 1 cm offset from the center of the FOV. Measurements below the tolerance are shown in bold. The CNR, which showed over 20% difference with the center, is also marked in bold.