Intensity-modulated radiotherapy (IMRT) involves dose-intensity optimization for inverse planning and creates an ideal dose distribution. Optimization calculation is necessary to avoid iterative calculation, which is time consuming. This study aimed to prove the theoretical possibility of planning IMRT using filtered back projection (FBP). In a previous study, we created an FBP program using Excel. The program was used for image reconstruction to obtain the desired virtual cancer shape, and back projection data were obtained during reconstruction. IMRT dose distribution was achieved by transplanting these back projection data as beam intensity to the treatment planning system. In the previous study, the dose distribution was not evaluated with a quantitative index. Therefore, to evaluate the dose distribution of this method through a quantitative index, the projection angles during image reconstruction were planned in 18 and 36 directions, and the dose-volume histogram (DVH), homogeneity index, and conformity index were compared. The results of the DVH graph of projection in 18 and 36 directions confirmed that the larger the projection angle, the higher the reproducibility of the original image. Creating a dose distribution with high dose concentration was possible. At present, IMRT is planned using an optimization algorithm. However, results of the current study show that the beam intensities of IMRT can also be determined by processing only the image reconstruction using FBP in terms of dose distribution evaluation through quantitative indicators.