## 5 Conclusions  
EBT-XD is a commonly used dosimetry film in UHDR investigations, and within this study it was shown to exhibit a dependence upon DPP, becoming pronounced above 4 Gy. While the film was not designed to be used at either the energies, or the dose rates used within this study and other VHEE studies, with careful consideration and properly applied correction factors, it still provides an adequate response suitable for such measurements. By using it as an independent reference measurement, the MOS_kin_ was able to be investigated for DPP independence, having previously been shown to exhibit a response independent of dose rate in both clinical and UHDR environments. When subjected to increasing DPP at PEER, the linearity of the MOS_kin_ response was retained, demonstrating its applicability for dose measurements within UHDR VHEE fields. While this linearity is a significant result in and of itself, the MOS_kin_ is the only device that is currently utilised clinically, whilst also being suitable for on-patient quality assurance dosimetry as the field of VHEE radiotherapy progresses towards animal and human trials. Conceptualisation, J.C., M.L. and A.R. ; Data curation, J.C. and E.E. ; Formal analysis, J.C. and M.L. ; Funding acquisition, Y.-R.E.T. and M.L. ; Investigation, J.C., E.E., T.C., P.B., M.C., J.P. ([PERSON]), D.B. and Y.-R.E.T. ; Methodology, J.C., E.E., J.P. ([PERSON]) and Y.-R.E.T. ; Project administration, J.C. and Y.-R.E.T. ; Resources, J.P. ([PERSON]), D.H., D.B., D.C., M.P. and Y.-R.E.T. ; Software, P.B. and Y.-R.E.T. ; Supervision, D.C., M.P., A.R., Y.-R.E.T. and M.L. ; Validation, J.C.; Writing--original draft, J.C.; Writing--review and editing, J.C., E.E., T.C., P.B., M.C., J.P. ([PERSON]), D.H., J.P. ([PERSON]), D.B., D.C., M.P., A.R., Y.-R.E.T. and M.L. All authors have read and agreed to the published version of the manuscript. * [1] [PERSON]; [PERSON] Modification of the Oxygen Effect when Bacteria are given Large Pulses of Radiation. _Nature_**1959**, _183_, 1450-1451.. [CrossRef] [PubMed]
* [2] [PERSON]; [PERSON] Effects of Dose-rate on the Radiation Response of Rat Skin. _Int. J. Radiat. Biol. Relat. Stud. Phys. Chem. Med._**1974**, _26_, 259-267. [CrossRef] [PubMed]
* [3] [PERSON]; [PERSON]; [PERSON]; [PERSON] The Constant Low Oxygen Concentration in All the Target Cells for Mouse Tail Radionecrosis. _Radiat. Res._**1982**, _92_, 172-181. [CrossRef] [PubMed]
* [4] [PERSON]; [PERSON] Unexpected Dose-rate Effect in the Killing of Mice by Radiation. _Nature_**1966**, _210_, 212-213. [CrossRef] [PubMed]
* [5] [PERSON] [PERSON]; [PERSON]; [PERSON]; [PERSON] [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] [PERSON]; et al. Ultrahigh dose-rate FLASH irradiation increases the differential response between normal and tumor tissue in mice. _Sci. Transl. Med._**2014**, \(6\), 245 ra93. [CrossRef] [PubMed]
* [6] [PERSON] [PERSON]; [PERSON] [PERSON]; [PERSON]; [PERSON] [PERSON]; [PERSON]; [PERSON] [PERSON]; [PERSON] [PERSON]; [PERSON]; [PERSON]; [PERSON]; et al. Clinical translation of FLASH radiotherapy: Why and how? _Radiother. Oncol._**2019**, _139_, 11-17. [CrossRef] [PubMed]* _[PERSON] et al. (2021)_ [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] [PERSON]; [PERSON]; [PERSON] [PERSON]; [PERSON]; et al. Hypoffractionated FLASH-RT as an Effective Treatment against Glioblastoma that Reduces Neurocognitive Side Effects in Mice. _Clin. Cancer Res._**2021**, _27_, 775-784. [CrossRef] [PubMed]
* _[PERSON] et al. (2021)_ [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; et al. Ultra-high-dose-rate FLASH and Conventional-Dose-Rate Irradiation Differentially Affect Human Acute Lymphoblastic Leukemia and Normal Hematopoiesis. _Int. J. Radiat. Oncol._**2021**, _109_, 819-829. [CrossRef] [PubMed]
* _[PERSON] et al. (2019)_ [PERSON]; [PERSON]; [PERSON]; [PERSON] [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; et al.