本研究旨在开发和验证一种用于磁共振引导放射治疗（CCCMR）的坍塌锥卷积。在1.5T横向磁场中，以水为基质生成三维能量沉积核（EDKs）。CCCMR通过参考介质密度和能量沉积点之间的质量密度来校正模拟几何中的不均匀性，并进行密度缩放。使用蒙特卡罗（MC）和CCCMR计算水相体和插入不均匀性的浅板体中的剂量分布。比较百分之一深度剂量（PDD）和离轴比（OAR），并评估伽马通过率（3％/ 2mm）。CCCMR在模拟浅板体中模拟了非对称剂量分布，特别是在水相体中，并且所有的PDD和OAR曲线都与MC的发现一致。伽马通过率对于每个场的大小和整个地区都超过99％。在不均匀性浅板体中，尽管CCCMR低估了低质量密度区域的剂量，但它可以重建质量密度边界处的剂量变化。对于2×2 cm2的场大小，整个区域的伽马通过率大于95％，但对于≥5×5 cm2的场大小，它仅为68.9-86.7％。总之，在水中，CCCMR可以获得与MC相当的剂量分布。尽管它们之间的剂量差异主要存在于不均匀区域中，但有效利用CCCMR在小场大小中的可能性得以证明。©作者（S）2023。由牛津大学出版社代表日本辐射研究学会和日本放射肿瘤学会出版。

This study aimed to develop and validate a collapsed cone convolution for magnetic resonance-guided radiotherapy (CCCMR). The 3D energy deposition kernels (EDKs) were generated in water in a 1.5-T transverse magnetic field. The CCCMR corrects the inhomogeneity in simulation geometry by referring to the EDKs according to the mass density between the interaction and energy deposition points in addition to density scaling. Dose distributions in a water phantom and in slab phantoms with inserted inhomogeneities were calculated using the Monte Carlo (MC) and CCCMR. The percentage depth dose (PDD) and off-axis ratio (OAR) were compared, and the gamma passing rate (3%/2 mm) was evaluated. The CCCMR simulated asymmetric dose distributions in the simulation phantoms, especially the water phantom, and all PDD and OAR profiles were in good agreement with the findings of the MC. The gamma passing rates were >99% for each field size and for the entire region. In the inhomogeneity phantoms, although the CCCMR underestimated dose in the low mass density regions, it could reconstruct dose changes at mass density boundaries. The gamma passing rate for the entire region was >95% for the field size of 2 × 2 cm2, but it was 68.9-86.7% for the field sizes of ≥5 × 5 cm2. Conclusively, in water, the CCCMR can obtain dose distributions comparable to those with the MC. Although the dose differences between them were mainly in inhomogeneity regions, the possibility of the effective use of the CCCMR in small field sizes was demonstrated.© The Author(s) 2023. Published by Oxford University Press on behalf of The Japanese Radiation Research Society and Japanese Society for Radiation Oncology.