François Bochud

In low-energy photon fields, such as those encountered during fluoroscopy-guided interventions, the current operational quantity for area dosimetry, ambient dose equivalent H*(10), overestimates effective dose by roughly a factor of two. ICRU Report 95 introduces a revised set of operational quantities intended to better align with protection quantities, replacing H*(10) with ambient dose H* for area monitoring. Experimental data validating these changes in realistic clinical environments remain scarce. This study examines the differences between current and newly proposed operational quantities in scattered radiation fields representative of occupational staff exposure during fluoroscopy-guided procedures. Measurements were performed using a Timepix4 hybrid pixel detector operated simultaneously as an X-ray spectrometer and dosimeter. The detector provides energy-resolved photon fluence measurements convertible into operational dose quantities via published fluence-to-dose conversion coefficients. Measurement campaigns were conducted in a urology theatre and an interventional cardiology (IC) theatre under realistic clinical conditions. Photon spectra were recorded at staff positions representative of standard procedures and converted into current and newly proposed quantities relevant to whole-body, skin, and eye lens exposure. The influence of beam angulation and additional shielding was further investigated in the IC theatre.For whole-body exposure, ratios between H* and H*(10) ranged from 0.52 in urology to 0.59 in IC. Quantities relevant to skin and eye lens exposure remained close to unity, with deviations not exceeding 5% and 8%, respectively. Beam angulation and shielding induced only minor variations in these ratios, below 5%.These results provide the first experimental validation of ICRU Report 95 quantities in interventional workplaces. Whole-body dosimetry is most affected by the transition, while skin and eye lens monitoring should remain largely unchanged. Ambient dosimeters calibrated in H*(10) used in low-energy photon fields may be recalibrated using a single procedure-specific calibration factor, whereas calibration procedures for skin and eye lens dosimeters may remain unchanged.

Background: In radiation therapy, Patient‐Specific Quality Assurance (PSQA) is used to ensure safety and accuracy of treatment deliveries, which is paramount to control the disease while safeguarding healthy tissues. In common clinical practice, this involves comparing the planned dose to a dose measured in a phantom prior to the treatment. However, the emergence of Adaptive Radiation Therapy (ART) modalities challenges the PSQA workflow. This is especially the case in online ART workflow, where the patient is maintained immobilized on the treatment couch during treatment adaptation and delivery. Furthermore, for treatment plans using motion management, the plan is adapted in real time to encounter target motion. In these cases, the traditional phantom‐based pre‐treatment PSQA is impractical, and the development of substitute strategies is needed. Purpose: To validate a PSQA tool for the Radixact® units, which allows phantomless post‐delivery verifications. Methods: In tomotherapy, the dose is optimized by modulating the Leaf Open Times (LOTs) of the Multileaf Collimator (MLC). A metric based on the actual LOTs was developed to verify the accuracy of the dose delivered to the target and to the Organs At Risk (OARs). To validate the metric, treatment plans of prostate and Head and Neck (H&N) patients were modified by introducing errors in the LOT sinogram and subsequently delivered to a phantom. Based on these deliveries, LOT‐based metric indices were calculated and their sensitivity to clinically relevant errors were analyzed and compared to the standard benchmark gamma index metric. The clinically relevant errors included category 1 errors, when measured outputs don't remain within 3% of the established baseline, and category 2 errors, when the clinical goals are not fulfilled. Results: The LOT‐based metric outperforms the gamma index metric in predicting dose deviations and clinical goal deviations. It also demonstrates superior performance in classifying acceptable and unacceptable plans in terms of category 1 error detection for H&N patients, while its performance in category 1 error detection for prostate cases and category 2 error detection for both groups is comparable. The LOT‐based metric, with optimal cutoffs, outperforms the gamma index metric in terms of both sensitivity and specificity for category 1 and 2 error detection in prostate cases, while the gamma index metric outperforms the LOT‐based metric in term of sensitivity for category 2 error detection in H&N cases. Conclusions: This study establishes the LOT‐based metric as a reliable tool for pretreatment PSQA, serving as a substitute for the conventional gamma index metric, while additionally offering the advantage of fraction‐by‐fraction monitoring of treatment delivery quality.

The System of Radiological Protection (the “System”) developed by the International Commission on Radiological Protection (ICRP) is built on nearly a century of efforts of numerous scientists and practitioners working together internationally. It rests on three enduring pillars: science, ethics, and experience. These pillars support the three fundamental principles that shape radiological protection strategies: justification, optimisation, and application of dose limits. Of note, optimisation of protection must be understood as a flexible and context-sensitive process, which allows identification of the appropriate level of protection, not simply the lowest dose, taking into account economic, societal and environmental factors. The System has proven effective in protecting workers, patients, members of the public, and the environment in all exposure situations. Effects of high doses, where acute injuries to healthy tissue occur, are rarely observed, and mostly due to accidental situations except for unavoidable side effects of radiotherapy. At low doses, the System is supported by application of the Linear-No-Threshold (LNT) model. This model enables prudent (that is, carefully considered given existing uncertainties) policy decisions and estimation of risks at low doses by extrapolation from epidemiological data observed at medium and high radiation doses, acknowledging uncertainty without ignoring potential harm.

In 2015 the United Nations issued 17 Sustainable Development Goals (SDGs) addressing a wide range of global social, economic, and environmental challenges. The main goal of this paper is to provide an understanding of how the current System of Radiological Protection relates to these SDGs. In the first part it is proposed that the current System of Radiological Protection is implicitly linked to sustainable development. This is substantiated by analysing the features of the current System as set out by the International Commission on Radiological Protection (ICRP) in its publications. In the second part it is proposed that sustainability should be considered and more explicitly addressed in the next ICRP general recommendations, as part of the currently ongoing review and revision of the current System. A few examples are given of how this could be realised, and it is proposed that this issue should be discussed and developed together with the international community interested in radiological protection.

Ionising radiation has been used for over a century for peaceful purposes, revolutionising health care and promoting well-being through its application in industry, science, and medicine. For almost as long, the International Commission on Radiological Protection (ICRP) has promoted understanding of health and environmental risks of ionising radiation and developed a protection system that enables the safe use of ionising radiation in justified and beneficial practices, providing protection from all sources of radiation. However, we are concerned that a shortage of investment in training, education, research, and infrastructure seen in many sectors and countries may compromise society’s ability to properly manage radiation risks, leading to unjustified exposure to or unwarranted fear of radiation, impacting the physical, mental, and social well-being of our peoples. This could unduly limit the potential for research and development in new radiation technologies (healthcare, energy, and the environment) for beneficial purposes. ICRP therefore calls for action to strengthen expertise in radiological protection worldwide through: (1) National governments and funding agencies strengthening resources for radiological protection research allocated by governments and international organisations, (2) National research laboratories and other institutions launching and sustaining long-term research programmes, (3) Universities developing undergraduate and graduate university programmes and making students aware of job opportunities in radiation-related fields, (4) Using plain language when interacting with the public and decision makers about radiological protection, and (5) Fostering general awareness of proper uses of radiation and radiological protection through education and training of information multipliers. The draft call was discussed with international organisations in formal relations with ICRP in October 2022 at the European Radiation Protection Week in Estoril, Portugal, and the final call announced at the 6th International Symposium on the System of Radiological Protection of ICRP in November 2022 in Vancouver, Canada.

FLASH radiation therapy (RT) is a promising new paradigm in radiation oncology. However, a major question that remains is the robustness and reproducibility of the FLASH effect when different irradiators are used on animals or patients with different genetic backgrounds, diets, and microbiomes, all of which can influence the effects of radiation on normal tissues. To address questions of rigor and reproducibility across different centers, we analyzed independent data sets from The University of Texas MD Anderson Cancer Center and from Lausanne University (CHUV). Both centers investigated acute effects after total abdominal irradiation to C57BL/6 animals delivered by the FLASH Mobetron system. The two centers used similar beam parameters but otherwise conducted the studies independently. The FLASH-enabled animal survival and intestinal crypt regeneration after irradiation were comparable between the two centers. These findings, together with previously published data using a converted linear accelerator, show that a robust and reproducible FLASH effect can be induced as long as the same set of irradiation parameters are used.