This study compared dosimetric outcomes of craniospinal irradiation (CSI) using volumetric-modulated arc therapy (VMAT) from TrueBeam (TB) and Halcyon, and intensity-modulated proton therapy from ProBeam.

Fifteen CSI cases prescribed 2340 cGy in 13 fractions were optimized. Dose coverage of the clinical target volume (CTV), organs at risk (OARs), conformity index (CI), homogeneity index (HI), total normal tissue volume (%TNTV), and beam-on time were evaluated.

Significant differences in D95% were observed among the three techniques. ProBeam plans achieved the best CI, while Halcyon plans demonstrated superior HI. ProBeam resulted in the lowest %TNTV dose, followed by Halcyon and TB. Among 16 evaluated OARs, 10 received significantly lower doses with ProBeam compared to photon techniques. ProBeam also showed the shortest beam-on time (4.2±0.1 minutes) but required the highest total monitor units due to its delivery method. Compared with Halcyon, TB delivered lower doses to 11 OARs, with significant differences in seven. However, Halcyon reduced beam-on time by approximately half (6.1±0.8 vs. 12.1±0.5 minutes).

Although ProBeam provided the best overall dosimetric performance, Halcyon represents an effective alternative for CSI, offering good plan quality, acceptable OAR sparing, improved %TNTV dose, and shorter treatment times compared to TrueBeam, potentially enhancing clinical efficiency.