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Purpose: To validate the point-A dose and dose distribution of metal and resin applicators in comparison with those of TG-43U1. Methods: The metal and resin applicators consisting of tandem and ovoid were modeled by the egs_brachy. The doses to point A and dose distributions considering each applicator were calculated and compared to those of TG-43U1. Results: The dose to point A considering the metal applicator was 3.2% lower than that of TG-43U1, but there was no difference in the dose to point A considering the resin applicator. The dose distribution considering the metal applicator was lower than that of TG-43U1 at all calculation points, but there was no difference in the dose distribution considering the resin applicator at almost all calculation points. Conclusion: In this study, the dose distribution considering the metal applicator was lower than that of TG-43U1 at all calculation points, but there was no difference in the dose distribution considering the resin applicator at almost all calculation points. Therefore, TG-43U1 can accurately calculate the dose distribution when changing from the metal applicator to the resin applicator.

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This paper proposes a new concept of phantom development, along with the utilization of new materials that can reproduce lung morphology and density. A lung substitute phantom using microspheres was fabricated; then, its dosimetric utility in radiotherapy was investigated, during which the density was adjusted to closely resemble the morphology of the actual human lung. Microspheres were used to reproduce alveoli, which are the main components of the lung. By changing the ratio of urethane, which is commonly used in soft tissue phantoms, to microspheres, we reproduced the density change of the lungs due to respiration. Here, we fabricated two slab-like lung substitutes to emulate commercially used phantoms. Although there is room for improvement in terms of practicality, the substitutes were easy to fabricate. Microscopic observation of the cut surface of the phantoms showed that the morphology of the phantoms mimicked the alveoli more faithfully than commercial phantoms. Furthermore, to compensate for the energy-independent mass attenuation and mass collision inhibition ability required by the tissue substitute phantom, we examined the physical properties of the phantom and confirmed that there was negligible energy dependence.