[Study of improvement in X-ray computed tomography images with a radiation treatment planning system: image noise and...

In radiotherapy, dose distribution and calculation of dose monitor units (DMU) are generally performed by a radiation treatment planning system using CT images. Therefore, differences in calculation can arise as a result of the quality of the CT image data. The quality of CT images involves contrast resolution, resolution, noise, slice thickness, and other factors. Among these factors, we examined noise and slice thicknesses. Results demonstrated that, even if noise increased, CT value did not change, and, therefore, did not influence DMU. Examination of slice thickness showed that, when the radiation field was rectangular, it was not influenced by slice thickness. However, when a multi-leaf collimator (MLC) was used, if slice thickness was thicker than the size of the MLC, a difference arose in the position of the MLC, and, therefore, some difference arose in dose. Therefore, slice thickness should be thinner than the size of the MLC.