*2.1. Ultra-High-Resolution Cone-Beam Computed Tomography System and Imaging Configurations*

A photograph and a specification of a prototype CBCT system are provided in Figure 1 and Table 1. Our system was mounted with an amorphous silicon (aSi)-based thin-film transistor (TFT) array FPD (PaxScan 4030CB, Varian Imaging Products, Palo Alto, CA) and was operated in full and binning acquisition modes. As shown in Table 2, the imaging configuration was categorized into four

subsections according to the two acquisition resolution setups and two reconstructed image resolutions. Each configuration was named depending on the row and column number of the matrix.

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**Figure 1.** Photograph of the prototype cone-beam computed tomography (CBCT) system capable of both standard and ultra-high resolution (UHR) acquisition.


**Table 1.** Specifications of the imaging conditions.

The center of rotation of the system was registered using the calibration phantom while rotating a full 360 ◦ with a 1 ◦ angle step for projection view image acquisition of 361 images. The 0.25 and 0.5 mm slice thicknesses were chosen based on previous studies [2–4]. The readout time of FPD with a 2 × 2 binning mode acquisition was four times faster than that of a full mode acquisition; therefore, a lower total acquisition time and lower radiation exposure were achievable owing to the higher framerate in the binning mode. All FBP reconstruction algorithms were self-programmed and coded in C++ with the CUDA toolkit version 10.0 using a single GPU card (GTX Titan-Xp, NVIDIA Co., Ltd., Santa Clara, CA, USA).


**Table 2.** Each configuration protocol with different resolution settings.
