A study on the reproducibility of the volume in 3-D volume-rendering images for radiation treatment planning

This study examined the effects of a change in the reconstruction cross-section, which depends on the slice thickness and the phantom shape, on the volume changes in a three-dimensional volume-rendering image reconstructed in a computed tomography (CT) simulation. For this, precise phantoms with different shapes and sizes were manufactured, and the three-dimensional volume-rendering images obtained from computed treatment planning for a phantom were measured. The CT simulation, which had been standardized using a phantom, was implemented with slice thicknesses of 1.25, 2.5, 5, and 10 mm. The measurements were performed on the X-axis, the Y-axis and the Z-axis for the accessory phantom to identify the following changes: length, area and volume, measurement deviation between analyzers, and maximum and minimum values. With increasing slice thickness the difference in the visual error range between analyzers increased, the cross section for the scan increased, and the thickness or density in the scan direction became nonuniform. These results are expected to help analyze the cause of the error in digitally-reconstructed radiographs and establish a more precise CT simulation.