Objective. This study aims to design, manufacture, and test 3D printed quality assurance (QA) dosimetry phantoms for synchrotron brain cancer radiation therapy at the Australian synchrotron. Approach. Fabricated 3D printed phantoms from simple slab phantoms, a preclinical rat phantom, and an anthropomorphic head phantom were fabricated and characterized. Attenuation measurements of various polymers, ceramics and metals were acquired using synchrotron monochromatic micro-computed tomography (CT) imaging. Polylactic acid plus, VeroClear, Durable resin, and tricalcium phosphate were used in constructing the phantoms. Furthermore, 3D printed bone equivalent materials were compared relative to ICRU bone and hemihydrate plaster. Homogeneous and heterogeneous rat phantoms were designed and fabricated using tissue-equivalent materials. Geometric accuracy, CT imaging, and consistency were considered. Moreover, synchrotron broad-beam x-rays were delivered using a 3 Tesla superconducting multipole wiggler field for four sets of synchrotron radiation beam qualities. Dose measurements were acquired using a PinPoint ionization chamber and compared relative to a water phantom and a RMI457 Solid Water phantom. Experimental depth doses were compared relative to calculated doses using a Geant4 Monte Carlo simulation. Main results. Polylactic acid (PLA+) shows to have a good match with the attenuation coefficient of ICRU water, while both tricalcium phosphate and hydroxyapatite have good attenuation similarity with ICRU bone cortical. PLA+ material can be used as substitute to RMI457 slabs for reference dosimetry with a maximum difference of 1.84%. Percent depth dose measurement also shows that PLA+ has the best match with water and RMI457 within ±2.2% and ±1.6%, respectively. Overall, PLA+ phantoms match with RMI457 phantoms within ±3%. Significance and conclusion. The fabricated phantoms are excellent tissue equivalent equipment for synchrotron radiation dosimetry QA measurement. Both the rat and the anthropomorphic head phantoms are useful in synchrotron brain cancer radiotherapy dosimetry, experiments, and future clinical translation of synchrotron radiotherapy and imaging.

FLASH radiotherapy, which refers to the delivery of radiation at ultra-high dose-rates (UHDRs), has been demonstrated with various forms of radiation and is the subject of intense research and development recently, including the use of very high-energy electrons (VHEEs) to treat deep-seated tumors. Delivering FLASH radiotherapy in a clinical setting is expected to place high demands on real-time quality assurance and dosimetry systems. Furthermore, very high-energy electron research currently requires the transformation of existing non-medical accelerators into radiotherapy research environments. Accurate dosimetry is crucial for any such transformation. In this article, we assess the response of the MOSkin, developed by the Center for Medical Radiation Physics, which is designed for on-patient, real-time skin dose measurements during radiotherapy, and whether it exhibits dose-rate independence when exposed to 100 MeV electron beams at the Pulsed Energetic Electrons for Research (PEER) end-station. PEER utilizes the electron beam from a 100 MeV linear accelerator when it is not used as the injector for the ANSTO Australian Synchrotron. With the estimated pulse dose-rates ranging from (7.84±0.21)×105 Gy/s to (1.28±0.03)×107 Gy/s and an estimated peak bunch dose-rate of (2.55±0.06)×108 Gy/s, MOSkin measurements were verified against a scintillating screen to confirm that the MOSkin responds proportionally to the charge delivered and, therefore, exhibits dose-rate independence in this irradiation environment.

The sophistication and diversity of radiation medicine modalities continue to increase significantly in both cancer imaging and cancer radiation therapy. With over 50% of cancer patients receiving some form of radiation procedure as part of their cancer management plan, the importance and impact of quantitative radiation detector systems for quality assurance in radiation medicine should not be underestimated. There are numerous challenges faced by silicon‐based detector systems used for dosimetry in radiation therapy that are discussed in this review article, especially considering emerging radiation therapy modalities that incorporate ultra‐high irradiation dose‐rates (e.g., MRT, FLASH‐RT, VHEE‐RT), while others utilize mixed radiation fields (e.g., proton‐RT, heavy ion therapy) or diffusion‐based dose delivery techniques (e.g., Alpha DaRT). Such challenges create exciting opportunities for new radiation detector materials. This concise review paper explores the role of silicon in radiation detection applications and highlights the challenges it faces in achieving optimal performance. Additionally, this review discusses new materials that are emerging as strong candidates for the next generation of radiation detectors, emphasizing both the opportunities and challenges associated with these materials.

Very-high-energy electrons, coupled with ultra-high dose rates, are being explored for their potential use in radiotherapy to treat deep-seated tumours. The dose per pulse needed to achieve ultra-high dose rates far exceeds the limit of current medical linear accelerator capabilities. A high dose per pulse has been observed as the limiting factor for many existing dosimeters, resulting in saturation at doses far below what is required. The MOSkin, an existing clinical quality assurance dosimeter, has previously been demonstrated as dose rate independent but has not been subjected to a high dose per pulse. Within this study, the MOSkins dose-per-pulse response was tested for linearity, with a dose per pulse as high as 23 Gy within 200 ns at the ANSTO Australian Synchrotron’s Pulsed Energetic Electrons for Research facility. While using EBT-XD film as a reference dosimeter, a dose rate dependence of the EBT-XD was discovered. Once confirmed and a correction factor established, EBT-XD was used as an independent reference measurement. This work presents confirmation of the MOSkin suitability for ultra-high dose-rate environments with an electron energy of 100 MeV, and a theoretical discussion of its dose-rate and dose-per-pulse independence; the MOSkin is the only detector suitable for both clinical quality assurance, and ultra-high dose-rate measurements in its standard, unmodified form.

The Pulsed Energetic Electrons for Research (PEER) beamline at the ANSTO Australian Synchrotron comprises a 100 MeV linac injector that is currently being developed for ultra-high dose-rate, very high-energy electron radiotherapy research. Previously, dosimetry studies discovered a lack of reliable charge measurement to the in-air end station, though no change in response was recorded in fast current transformer measurements, the only available diagnostic device for measuring charge. This work describes the process of simulating and then commissioning a purpose-built Faraday cup to ascertain absolute in-air charge measurements at PEER. By combining simulation data with experimental results, the PEER Faraday cup is shown to possess a primary electron capture efficiency of (99.22 ± 0.10)%, with a net capture efficiency due to secondary electron emission of (97.87 ± 0.24)%. These results show the PEER Faraday cup performs as intended and, when scaled against simulations, will be suitable for measuring absolute charge at PEER.

Background/Objectives: The PEER beamline at the ANSTO Australian Synchrotron has been developed to enable VHEE FLASH radiotherapy studies, both dosimetric and biological. Featuring a 100 MeV electron linac, it delivers single or multi-pulse irradiations consisting of 100 ps bunches with a 2 ns spacing, resulting in average dose-rates and instantaneous dose-rates as high as ${10}^8$ Gy/s and ${10}^9$ Gy/s, respectively. Much work has been conducted to realise a stable accelerator facility, complete with the tooling and diagnostics required to undertake such studies. However, to truly confirm its suitability required a successful biological benchmarking. Methods: Three cell lines were irradiated utilising real-time dosimetry to compare linear quadratic cell survival curves with other facilities. Also, mouse cadavers were transported and irradiated, mimicking live animals, to assess the feasibility and logistics of small animal experiments. Results: By comparing the trends of the linear quadratic model, evident in the $\alpha$ and $\beta$ parameters, the PEER cell survival results were shown to be in agreement with VHEE results from the ARES beamline at DESY, Hamburg, Germany. Evident in the survival trends, VHEE produced more cell sparing in all cell lines compared to 2 Gy/s X-rays delivered on the IMBL, another beamline at the Australian Synchrotron. The results of the mouse cadaver irradiations showed that PEER can safely and efficiently irradiate small animals. Conclusions: The PEER beamline is shown to possess suitable capabilities, including real-time dosimetry, repeatable alignment, and linac diagnostics, rendering it suitable for future in vivo VHEE UHDR FLASH radiotherapy investigations.