Search

Objectives: The present study aimed to compare the tumor growth delay between conventional radiotherapy (CRT) and the spatially fractionated modalities of microbeam radiation therapy (MRT) and minibeam radiation therapy (MBRT). In addition, we also determined the influence of beam width and the peak-to-valley dose ratio (PVDR) on tumor regrowth., Methods: A549, a human non-small-cell lung cancer cell line, was implanted subcutaneously into the hind leg of female CD1 -Foxn1 nu mice. The animals were irradiated with sham, CRT, MRT, or MBRT. The spatially fractionated fields were created using two specially designed multislit collimators with a beam width of 50 μm and a center-to-center distance (CTC) of 400 μm for MRT and a beam width of 500 μm and 2000 μm CTC for MBRT. Additionally, the concept of the equivalent uniform dose (EUD) was chosen in our study. A dose of 20 Gy was applied to all groups with a PVDR of 20 for MBRT and MRT. Tumor growth was recorded until the tumors reached at least a volume that was at least three-fold of their initial value, and the growth delay was calculated., Results: We saw a significant reduction in tumor regrowth following all radiation modalities. A growth delay of 11.1 ± 8 days was observed for CRT compared to the sham, whereas MBRT showed a delay of 20.2 ± 7.3 days. The most pronounced delay was observed in mice irradiated with MRT PVDR 20, with 34.9 ± 26.3 days of delay., Conclusions: The current study highlights the fact that MRT and MBRT modalities show a significant tumor growth delay in comparison to CRT at equivalent uniform doses.

Purpose: Microbeam radiation therapy (MRT) has shown superior healthy tissue sparing at equal tumour control probabilities compared to conventional radiation therapy in many preclinical studies. The limitation to preclinical research arises from a lack of suitable radiation sources for clinical application of MRT due to high demands on beam quality. To overcome these limitations, we developed and built the first prototype of a line-focus X-ray tube (LFXT). During commissioning, characterisation of the X-ray focal spot is necessary. For the generation of microbeams, we require a specially designed collimator adapted to the LFXT., Methods: We present an adapted edge method and a pinhole method for focal spot measurements of the LFXT prototype as well as the design of the microbeam collimator with a slit width of 50μm, spaced by 400μm. Monte Carlo simulations validated the focal spot measurement techniques and the design of the collimator., Results: We showed that the adapted edge method is more complex but superior to the adapted pinhole method in terms of quantitative validity. Simulations for the microbeam collimator showed a sharp microbeam dose profile with a peak-to-valley dose ratio (PVDR) above 23 throughout 50 mm of water., Conclusion: During commissioning, the adapted focal spot visualisation methods will be used to determine the focal spot dimensions and to optimise machine parameters. The LFXT prototype will enable preclinical MRT with significantly higher dose rates than any other compact MRT source and will pave the way for the first clinical trials in a hospital setting., Competing Interests: Declaration of competing interest The authors declare that they have no competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Associazione Italiana di Fisica Medica e Sanitaria. Published by Elsevier Ltd. All rights reserved.)