The Institute of Nuclear Medical Physics, School of Nuclear Science and Technology at the University of Science and Technology of China has recently published a research article titled “Dosimetric characterization of a Varex VF-80/μXHP x-ray unit using open-ended applicators for superficial radiotherapy” in the Journal of Applied Clinical Medical Physics. The work is carried out by Muhammad Zeeshan (first author), a doctoral student in the institute, together with colleagues Yikai Wu, Zhongyu Qi, Ning Gao, and Xi Pei, under the supervision of Professor Xie George Xu, who also serves as the corresponding author.

This study provides the first comprehensive dosimetric evaluation of the Varex VF-80/μXHP (80 kV, 100 W) x-ray tube for potential use in superficial radiotherapy. Although the VF-80/μXHP system is primarily designed for fluorescence applications, its compact size and growing use in preclinical irradiation motivated a rigorous assessment of its clinical dosimetric characteristics. The research employs both experimental measurements using a PTW 34013 parallel-plate ionization chamber in a solid-water phantom and Monte Carlo simulations with the TOPAS code to determine absolute depth dose, HVL, applicator effects, and percent-depth-dose (PDD) profiles.

A total of nearly 40 x-ray beams with different energy qualities, filtrations, and applicator diameters and thicknesses were evaluated. The measured and simulated depth-dose data demonstrated excellent agreement with established reference datasets, such as the BJR 25 supplementary tables, with differences within 1.9-1.5% for 50 kV and 0.5-0.2% for 70 kV beams. The study also highlights the dosimetric influence of PMMA and stainless-steel applicators, including their effects on surface dose, beam hardening, and penetration depth. By establishing a validated dosimetric dataset for the VF-80/μXHP system, this work provides an important foundation for its safe adoption in low-kV radiotherapy, radiobiology experiments, and preclinical small-animal irradiation. The findings strengthen the evidence that compact low-energy x-ray units can be reliably characterized for therapeutic and research applications.

Paper link: https://doi.org/10.1002/acm2.70326