Enhancing pre-clinical microbeam radiation therapy capabilities at PETRA III beamline P61A through high-precision beam delivery

<i>Objective.</i>Microbeam radiation therapy (MRT) exploits spatially fractionated, micrometer-scale x-ray beam arrays that deliver high-dose (peak) and low-dose (valley) regions. At beamline P61A of the PETRA III synchrotron (DESY, Hamburg, Germany), MRT delivery has been limited to a fixed 2 mm wide field and single-direction irradiation. This study aimed to implement stereotactic multi-port MRT (STX-MRT) with lateral field extension and to quantify the spatial reproducibility of the microbeam arrays during patched and multi-angle delivery.<i>Approach.</i>A custom motorized stage providing vertical and lateral translation and rotation was developed to enable discrete lateral patching and sequential delivery from multiple ports (1-9). Each microbeam array comprised five peaks with a beam width of 50<i>µ</i>m and a center-to-center spacing of 400<i>µ</i>m. Spatial accuracy was assessed with Gafchromic™ HD-V2 film scanned at 7.9<i>µ</i>m resolution. Fifteen films (three per geometry), corresponding to 225 patched arrays, were included to determine the spatial accuracy.<i>Main results.</i>Beam delivery was highly reproducible. In 88% of the microbeam arrays, deviations were below the detection limit (⩽7.9<i>µ</i>m). Detectable displacements occurred in 12% of arrays and ranged from 33 to 258<i>µ</i>m, typically localized to individual patches or ports. The rotational isocenter remained stable across all configurations, and increasing the number of ports and delivery speed did not introduce systematic alignment errors.<i>Significance.</i>Reliable lateral field patching and multi-port MRT delivery with micrometer-scale precision was achieved, extending the usable irradiation field and enabling STX-MRT at beamline P61A. This technical capability broadens the range of irradiation of different target sizes and supports advanced preclinical studies of MRT.