Objective:To investigate the dose characteristics of the Zeiss INTRABEAM system in air and water, providing dose reference for electronic brachytherapy.Methods:A Monte Carlo program was used to establish a three-dimensional model of a miniature X-ray source vacuum drift tube and a 4 cm spherical applicator. The process of electron beam bombardment on a gold target to generate X-rays was simulated, and parameters such as photon fluence spectrum, percentage depth dose, and half-value layer were calculated. Additionally, the radial dose uniformity in water was measured.Results:The average energy of X-rays at 3 cm in air was 20.8 keV, with a half-value layer of 0.08 mm Al. Under the influence of the applicator, the spectrum becomes hardened, with axial and radial average energies of 28.7 and 29.0 keV, respectively. In water, the percentage depth dose (PDD) curve follows an inverse cubic decay with depth, indicating strong dose concentration and rapid fall-off in near-field irradiation. The radial dose uniformity in water exceeded 99.5%.Conclusions:The INTRABEAM device emits low-energy X-rays characterized by shallow penetration depth, and concentrated dose delivery. Its highly uniform dose distribution ensures comprehensive coverage of the target area, making it particularly suitable for treating superficial tumors and for intraoperative radiotherapy at close range.

Objective:To investigate the dose characteristics of the Zeiss INTRABEAM system in air and water, providing dose reference for electronic brachytherapy.Methods:A Monte Carlo program was used to establish a three-dimensional model of a miniature X-ray source vacuum drift tube and a 4 cm spherical applicator. The process of electron beam bombardment on a gold target to generate X-rays was simulated, and parameters such as photon fluence spectrum, percentage depth dose, and half-value layer were calculated. Additionally, the radial dose uniformity in water was measured.Results:The average energy of X-rays at 3 cm in air was 20.8 keV, with a half-value layer of 0.08 mm Al. Under the influence of the applicator, the spectrum becomes hardened, with axial and radial average energies of 28.7 and 29.0 keV, respectively. In water, the percentage depth dose (PDD) curve follows an inverse cubic decay with depth, indicating strong dose concentration and rapid fall-off in near-field irradiation. The radial dose uniformity in water exceeded 99.5%.Conclusions:The INTRABEAM device emits low-energy X-rays characterized by shallow penetration depth, and concentrated dose delivery. Its highly uniform dose distribution ensures comprehensive coverage of the target area, making it particularly suitable for treating superficial tumors and for intraoperative radiotherapy at close range.