Factors affecting modulation transfer function measurements in cone-beam computed tomographic images

Abstract

Purpose This study was designed to investigate the effects of voxel size, the oversampling technique, and the direction and area of measurement on modulation transfer function (MTF) values to identify the optimal method of MTF measurement. Materials and Methods Images of the wire inserts of the SedentexCT IQ phantom were acquired, and MTF values were calculated under different conditions (voxel size of 0.1, 0.2, and 0.3 mm; 5 oversampling techniques; simulated pixel location errors; and different directions and areas of measurement). The differences in the MTF values across various conditions were evaluated. Results The MTF 10 values showed smaller standard deviations than the MTF 50 values. Stable and accurate MTF values were obtained in the 0.1-mm voxel images. In the 0.3-mm voxel images, oversampling techniques of 11 lines or more did not show significant differences in MTF values depending on the presence of simulated location errors. MTF 10 values showed significant differences according to the direction and area of the measurement. Conclusion To measure more accurate and stable MTF values, it is better to measure MTF 10 values in small-voxel images. In large-voxel images, the proper oversampling technique is required. MTF values from the radial and tangential directions may be different, and MTF values vary depending on the measured area.

Influence of voxel size on micro-CT analysis of debris after root canal preparation

“…However, larger voxels do not always mean lower diagnostic accuracy. 30,31 Studies that have evaluated the influence of voxel size in diagnoses using cone beam computed tomography images of root fracture are conflicting. 31,32,33 Whereas a previous investigation showed significantly higher detection of vertical root fractures in images with smaller voxel size, 32 Özer 33 reported that there were no significant differences in the diagnostic accuracy of root fracture among cone beam computed tomography images captured with different voxel sizes.…”

How image-processing parameters can influence the assessment of dental materials using micro-CT

“…40 The smallest possible voxel size should preferably be used for scans of small structures in order to maximize the accuracy of the measurements. 18,21,41,42 However, higher-resolution scans require longer acquisition times, because they must collect more projections and generate large datasets. Therefore, the tradeoff between voxel size and scan time should be carefully considered.…”