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. 2025 Sep;52(9):e18100.
doi: 10.1002/mp.18100.

Quality assurance and reporting for FLASH clinical trials: The experience of the FEATHER trial

Isabella Colizzi  1   2 , Robert Schäfer  1 , Jonas Brückner  3 , Gaia Dellepiane  1 , Martin Grossmann  1 , Maximilian Körner  3 , Antony John Lomax  1   2 , David Meer  1 , Benno Rohrer  1 , Carla Rohrer Bley  3 , Michele Togno  1 , Serena Psoroulas  1   4
Affiliations

Quality assurance and reporting for FLASH clinical trials: The experience of the FEATHER trial

Isabella Colizzi et al. Med Phys. 2025 Sep.

Abstract

Background: Research on ultra-high dose rate (UHDR) radiation therapy has indicated its potential to spare normal tissue while maintaining equivalent tumor control compared to conventional treatments. First clinical trials are underway. The randomized phase II/III FEATHER clinical trial at the Paul Scherrer Institute in collaboration with the University of Zurich Animal Hospital is one of the first curative domestic animal trials to be attempted, and it is designed to provide a good example for human trials. However, the lack of standardized quality assurance (QA) guidelines for FLASH clinical trials presents a significant challenge in trial design.

Purpose: This work aims to demonstrate the development and testing of QA and reporting procedures implemented in the FEATHER clinical trial.

Methods: We have expanded the clinical QA program to include UHDR-specific QA and additional patient-specific QA. Furthermore, we have modified the monitor readout to enable time-resolved measurements, allowing delivery log files to be used for dose and dose rate recalculations. Finally, we developed a reporting strategy encompassing relevant parameters for retrospective studies.

Results: We evaluated our QA and reporting procedures with simulated treatments. This testing confirmed that our QA procedures effectively ensure the correct and safe delivery of the planned dose (3%/3 mm gamma criteria, pass > 90%). Additionally, we demonstrated that we could reconstruct the delivered dose and dose rate using the delivery log files.

Conclusion: We developed and used in practice a comprehensive QA and reporting protocol for a FLASH clinical trial at the Paul Scherrer Institute. This work aims to establish guidelines and standardize reporting practices for future advancements in the FLASH-RT field.

Keywords: FLASH; clinical trial; proton therapy; ultra‐high dose rates.

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Conflict of interest statement

The authors have no relevant conflicts of interest to disclose.

Figures

FIGURE 1
FIGURE 1
In‐house QA phantom designed for the QA procedure: CCD mounted to a rotation stage.
FIGURE 2
FIGURE 2
The five‐spot pattern is delivered to evaluate spot positioning and beam size (left). The purple line represents the reference central axis that passes through the center of the cross‐hair laser. The first delivery is used to evaluate the offset. After calculating the offset, a second delivery with the corrected spot position is performed to confirm the results (right).
FIGURE 3
FIGURE 3
2D dose distribution of the reference and test fields, including the dose difference and gamma analysis between the two, along with an evaluation of the gamma index. On the left, we display the PSQA analysis, where the reference represents the dose distribution recalculated in water from the TPS and the test dose distribution, the measured field. On the right, the reference field is the dose delivered on the day of the PSQA. (left) µD detector current readout during a UHDR beam delivery. (right) The cumulative sum of the dose delivered.
FIGURE 4
FIGURE 4
Dose map recalculated from log files (left), measured with the CCD camera (center), and calculated by our TPS (right). The dose measured by the µD detector in the reference point is 10.3 Gy.
FIGURE 5
FIGURE 5
Dose rate map recalculated from log files (left), and calculated by our TPS (right). The dose rate measured by the µD detector in the reference point is 54.3 Gy/s. Additional information are in the Appendix (Figure A1 and A2).
FIGURE 6
FIGURE 6
Screenshot of the delivery report for an example patient.
FIGURE 7
FIGURE 7
Screenshot of the delivery report for an example patient.
See this image and copyright information in PMC

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