Surface guided radiotherapy (SGRT) is becoming a routine tool for patient positioning for specific clinical sites in many clinics. However, it has not yet gained its full potential in terms of widespread adoption. This vision paper first examines some of the difficulties in transitioning to SGRT before exploring the current and future role of SGRT alongside and in concert with other imaging techniques. Finally, future horizons and innovative ideas that may shape and impact the direction of SGRT going forward are reviewed.

The aim of this study was to evaluate if surface guided radiotherapy (SGRT) can decrease patient positioning time for localized prostate cancer patients compared to the conventional 3-point localization setup method. The patient setup accuracy was also compared between the two setup methods. A total of 40 localized prostate cancer patients were enrolled in this study, where 20 patients were positioned with surface imaging (SI) and 20 patients were positioned with 3-point localization. The setup time was obtained from the system log files of the linear accelerator and compared between the two methods. The patient setup was verified with daily orthogonal kV images which were matched based on the implanted gold fiducial markers. Resulting setup deviations between planned and online positions were compared between SI and 3-point localization. Median setup time was 2:50 min and 3:28 min for SI and 3-point localization, respectively (p < 0.001). The median vector offset was 4.7 mm (range: 0–10.4 mm) for SI and 5.2 mm for 3-point localization (range: 0.41–17.3 mm) (p = 0.01). Median setup deviation in the individual translations for SI and 3-point localization respectively was: 1.1 mm and 1.9 mm in lateral direction (p = 0.02), 1.8 and 1.6 mm in the longitudinal direction (p = 0.41) and 2.2 mm and 2.6 mm in the vertical direction (p = 0.04). Using SGRT for positioning of prostate cancer patients provided a faster and more accurate patient positioning compared to the conventional 3-point localization setup.

Spatially fractionated radiotherapy (SFRT) is emerging as a powerful tool in cancer therapy for patients who are ineligible for treatment with clinically established irradiation techniques. Microbeam radiotherapy (MRT) is characterized by spatial dose fractionation in the micrometre range. This presents challenges in both treatment planning and dosimetry. While a dosimetry system with a spatial resolution of 10 µm and an option for real-time readout already exists, this system can only record dose in a very small volume. Thus, we are exploring dosimetry in an N-isopropylacrylamide (NIPAM) gel as an option for 3D dose visualization and, potentially, also three-dimensional dosimetry in larger volumes. In the current study, we have recorded the geometric patterns of single- and multiport irradiation with microbeam arrays in NIPAM gel. Data for 3D dose distribution was acquired in a 7T small animal MRI scanner. We found that the resolution of the gel is well suited for a detailed 3D visualization of microbeam patterns even in complex multiport geometries, similar to that of radiochromic film, which is well established for recording 2D dose distribution in MRT. The results suggest that a dose–response calibration is required for reliable quantitative dosimetry.

Objective. 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. Approach. 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 µ m and a center-to-center spacing of 400 µ m. Spatial accuracy was assessed with Gafchromic™ HD-V2 film scanned at 7.9 µ m resolution. Fifteen films (three per geometry), corresponding to 225 patched arrays, were included to determine the spatial accuracy. Main results. Beam delivery was highly reproducible. In 88% of the microbeam arrays, deviations were below the detection limit (⩽7.9 µ m). Detectable displacements occurred in 12% of arrays and ranged from 33 to 258 µ 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. Significance. 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.