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As part of the American Association of Physicists in Medicine Working Group on Stereotactic Body Radiotherapy, tumor control probability (TCP) after stereotactic radiosurgery (SRS) and fractionated stereotactic radiosurgery (fSRS) for brain metastases was modeled based on pooled dosimetric and clinical data from published English-language literature.
Verification of patient position through pretreatment setup imaging is crucial in modern radiation therapy. As treatment complexity increases and technology evolves, physicist-physician collaboration becomes imperative for safe and successful radiation delivery. Despite the importance of both, residency programs lack formal interprofessional education (IPE) activities or structured training for image verification. Here we show the impact of an interprofessional image verification workshop for residents in a multi-institutional setting.
The Anatomy and Radiology Contouring (ARC) Bootcamp was a face-to-face (F2F) intervention providing integrated education for radiation oncology (RO) residents and medical physicists. To increase access, we launched an online offering in 2019. We evaluated the effect of the online course on participants' knowledge acquisition, contouring skills, and self-confidence by comparing it with the F2F course.
It is important to monitor the spatial resolution of a gamma camera on a weekly basis to acquire medical images with accurate quantitative information. A simple and fast computer program with a graphical user interface to analyze spatial resolution was successfully developed using MATLAB. The results were compared with those obtained from the standard processing system available in our gamma camera. The spatial resolution calculated using MATLAB was 1.24% lower than using the standard processing system. The developed program is cost effective, faster, and provides an easy platform for the physicists and technologists to analyze the spatial resolution based on the image of the line source.
Daily volumetric imaging through cone-beam computed tomography (CBCT) has greatly impacted the roles and responsibilities of radiation therapists (RTTs). A CBCT eLearning module was developed at our cancer centre to equip RTTs with critical thinking skills and clinical judgement required in a CBCT guidance environment. This study aims to evaluate the effectiveness of the electronic module and its impact on the learner's outcome from the perspectives of various radiation therapy professions and to assess the applicability of the eLearning module to RTTs, oncologists, and physicists.
This study aimed to investigate the high-dose rate Iridium-192 brachytherapy, including near source dosimetry, of a catheter-based applicator from 0.5 mm to 1 cm along the transverse axis. Radiochromic film and Monte Carlo (MC) simulation were used to generate absolute dose for the catheter-based applicator. Results from radiochromic film and MC simulation were compared directly to the treatment planning system (TPS) based on the American Association of Physicists in Medicine Updated Task Group 43 (TG-43U1) dose calculation formalism. The difference between dose measured using radiochromic film along the transverse plane at 0.5 mm from the surface and the predicted dose by the TPS was 24%±13%. The dose difference between the MC simulation along the transverse plane at 0.5 mm from the surface and the predicted dose by the TPS was 22.1%±3%. For distances from 1.5 mm to 1 cm from the surface, radiochromic film and MC simulation agreed with TPS within an uncertainty of 3%. The TPS under-predicts the dose at the surface of the applicator, i.e., 0.5 mm from the catheter surface, as compared to the measured and MC simulation predicted dose. MC simulation results demonstrated that 15% of this error is due to neglecting the beta particles and discrete electrons emanating from the sources and not considered by the TPS, and 7% of the difference was due to the photon alone, potentially due to the differences in MC dose modeling, photon spectrum, scoring techniques, and effect of the presence of the catheter and the air gap. Beyond 1 mm from the surface, the TPS dose algorithm agrees with the experimental and MC data within 3%.
In a 2-part study, we first examined the results of 71 surveyed physicians who provided responses on how they address the management of patients who maintained either a pacemaker or a defibrillator during radiation treatment. Second, a case review study is presented involving 112 medical records reviewed at 18 institutions to determine whether there was a change in the radiation prescription for the treatment of the target cancer, the method of radiation delivery, or the method of radiation image acquisition. Statistics are provided to illustrate the level of administrative policy; the level of communication between radiation oncologists and heart specialists; American Joint Committee on Cancer (AJCC) staging and classification; National Comprehensive Cancer Network (NCCN) guidelines; tumor site; patient's sex; patient's age; device type; manufacturer; live monitoring; and the reported decisions for planning, delivery, and imaging. This survey revealed that 37% of patient treatments were considered for some sort of change in this regard, whereas 59% of patients were treated without regard to these alternatives when available. Only 3% of all patients were identified with an observable change in the functionality of the device or patient status in comparison with 96% of patients with normal behavior and operating devices. Documented changes in the patient's medical record included 1 device exhibiting failure at 0.3-Gy dose, 1 device exhibiting increased sensor rate during dose delivery, 1 patient having an irregular heartbeat leading to device reprogramming, and 1 patient complained of twinging in the chest wall that resulted in a respiratory arrest. Although policies and procedures should directly involve the qualified medical physicist for technical supervision, their sufficient involvement was typically not requested by most respondents. No treatment options were denied to any patient based on AJCC staging, classification, or NCCN practice standards.
Stereotactic body radiation therapy (SBRT) treatment planning and delivery can be accomplished using a variety of techniques that achieve highly conformal dose distributions. Herein, we describe a template-based automated treatment field approach that enables rapid delivery of more than 20 coplanar fields. A case study is presented to demonstrate how modest adaptations to traditional SBRT planning can be implemented to take clinical advantage of this technology. Treatment was planned for a left-sided lung lesion adjacent to the chest wall using 25 coplanar treatment fields spaced at 11° intervals. The plan spares the contralateral lung and is in compliance with the conformality standards set forth in Radiation Therapy and Oncology Group protocol 0915, and the dose tolerances found in the report of the American Association of Physicists in Medicine Task Group 101. Using a standard template, treatment planning was accomplished in less than 20 minutes, and each 10 Gy fraction was delivered in approximately 5.4 minutes. For those centers equipped with linear accelerators capable of automated treatment field delivery, the use of more than 20 coplanar fields is a viable SBRT planning approach and yields excellent conformality and quality combined with rapid planning and treatment delivery. Although the case study discusses a laterally located lung lesion, this technique can be applied to centrally located tumors with similar results.
Radiation therapy for pediatric patients often includes the use of intravenous anesthesia with supplemental oxygen delivered via the nasal cannula. Here, we describe the use of an adaptive anesthesia technique for electron irradiation of the right naris in a preschool-aged patient treated under anesthesia. The need for an intranasal bolus plug precluded the use of standard oxygen supplementation. This novel technique required the multidisciplinary expertise of anesthesiologists, radiation therapists, medical dosimetrists, medical physicists, and radiation oncologists to ensure a safe and reproducible treatment course.
American Association of Physicists in Medicine (AAPM) Task Group 176 evaluated the dosimetric effects caused by couch tops and immobilization devices. The report analyzed the extensive physics-based literature on couch tops, stereotactic body radiation therapy (SBRT) frames, and body immobilization bags, while noting the scarcity of clinical reports of skin toxicity because of external devices. Here, we present a clinical case report of grade 1 abdominal skin toxicity owing to an abdominal compression device. We discuss the dosimetric implications of the utilized treatment plan as well as post hoc alternative plans and quantify differences in attenuation and skin dose/build-up between the device, a lower-density alternative device, and an open field. The description of the case includes a 66-year-old male with HER2 amplified poorly differentiated distal esophageal adenocarcinoma treated with neoadjuvant chemo-radiation and the use of an abdominal compression device. Radiation was delivered using volumetric modulated arc therapy (VMAT) with 2 arcs using abdominal compression and image guidance. The total dose was 50.4 Gy delivered over 40 elapsed days. With 2 fractions remaining, the patient developed dermatitis in the area of the compression device. The original treatment plan did not include a contour of the device. Alternative post hoc treatment plans were generated, one to contour the device and a second with anterior avoidance. In conclusion, replanning with the device contoured revealed the bolus effect. The skin dose increased from 27 to 36 Gy. planned target volume (PTV) coverage at 45 Gy was reduced to 76.5% from 95.8%. The second VMAT treatment plan with an anterior avoidance sector and more oblique beam angles maintained PTV coverage and spared the anterior wall, however at the expense of substantially increased dose to lung. This case report provides an important reminder of the bolus effect from external devices such as abdominal compression. Special consideration must be given to contour and/or avoiding beam entrance to the device, and to the use of such devices in patients who may have heightened radiosensitivity, such as those who are human immunodeficiency virus (HIV)–positive.
In modern cancer management, treatment planning has progressed as a contemporary tool with all the advances in computing power in recent years. One of the advanced planning tools uses 3-dimensional (3D) data sets for accurate dose distributions in patient prescription. Among these planning processes, brachytherapy has been a very important part of a successful cancer management program, offering clinical benefits with specific or combined treatments with external beam therapy. In this chapter, we mainly discussed the Elekta Oncentra planning system, which is the main treatment planning tool for high-dose rate (HDR) modality in our facility and in many other facilities in the United States. HDR is a technically advanced form of brachytherapy; a high-intensity radiation source (3.6 mm in length) is delivered with step motor in submillimeter precision under computer guidance directly into the tumor areas while minimizing injury to surrounding normal healthy tissue. Oncentra planning is the key component to generate a deliverable brachytherapy procedure, which is executed on the microSelectron V3 remote afterloader treatment system. Creating a highly conformal plan can be a time-consuming task. The development of Oncentra software (version 4.5.3) offers a variety of useful tools that facilitate many of the clinical challenging tasks for planning, such as contouring and image reconstruction, as well as rapid planning calculations with dose and dose volume histogram analysis. Oncentra Brachy module creates workflow and optimizes the planning accuracy for wide varieties of clinical HDR treatments, such as skin, gynecologic (GYN), breast, prostate, and many other applications. The treatment file can also be transferred to the afterloader control station for speedy delivery. The design concept, calculation algorithms, and optimization modules presented some key characteristics to plan and treat the patients effectively and accurately. The dose distribution and accuracy of several clinical sample cases were discussed to illustrate the effectiveness and clinical efficacy. The American Association of Physicists in Medicine brachytherapy reports of TG-43 and TG-186 were also described and compared in evaluations of fundamental calculation methodologies.
The general question of how a beam becomes unstable has been one of the fundamental research topics among beam and accelerator physicists for several decades. In this study, we revisited the general problem of linear beam stability in periodic focusing systems by applying the concepts of Krein signature and band structure. We numerically calculated the eigenvalues and other associated characteristics of one-period maps, and discussed the stability properties of single-particle motions with skew quadrupoles and envelope perturbations in high-intensity beams on an equal footing. In particular, an application of the Krein theory to envelope instability analysis was newly attempted in this study. Finally, the appearance of instabilities is interpreted as the result of the collision between eigenmodes of opposite Krein signatures and the formation of a band gap.
In this contribution to the proceedings of the 182nd Nobel Symposium, I reflect on the concept of “discovery” as it is used by physicists and astronomers. In particular, I comment on how the scientific community distinguishes discoveries from propositions that are supported only by lesser forms of evidence, emphasizing the social nature of this process and remarking on the subjective factors that go into making such judgments. I advocate for an approach that is intentionally Bayesian in nature, in which individuals are encouraged to evaluate and publicly state their priors and to update them systematically. I close by applying these practices to the case example of the Galactic Center Gamma-Ray Excess.
William Allan Bardeen (September 15, 1941 − November 18, 2025) was an American theoretical physicist who worked at the Fermi National Accelerator Laboratory. He is renowned for his foundational work on the chiral anomaly, the Adler-Bardeen theorem, the non-Abelian anomaly and gravitational anomalies. He was instrumental in the development of quantum chromodynamics and its applications, such as semileptonic decays and the Λ $\overline{MS}$ scheme frequently used in perturbative analysis of high energy processes involving strong interactions. Bardeen also played a major role in developing a theory of dynamical breaking of electroweak symmetry via top quark condensates, leading to one of the first composite Brout-Englert-Higgs boson models. His work on the chiral symmetry dynamics of heavy-light quark bound states correctly predicted abnormally long-lived resonances which are chiral symmetry partners of the ground state.
The exploration of the universe has recently entered a new era thanks to the multi-messenger paradigm, characterized by a continuous increase in the quantity and quality of experimental data that is obtained by the detection of the various cosmic messengers (photons, neutrinos, cosmic rays and gravitational waves) from numerous origins. They give us information about their sources in the universe and the properties of the intergalactic medium. Moreover, multi-messenger astronomy opens up the possibility to search for phenomenological signatures of quantum gravity. On the one hand, the most energetic events allow us to test our physical theories at energy regimes which are not directly accessible in accelerators; on the other hand, tiny effects in the propagation of very high energy particles could be amplified by cosmological distances. After decades of merely theoretical investigations, the possibility of obtaining phenomenological indications of Planck-scale effects is a revolutionary step in the quest for a quantum theory of gravity, but it requires cooperation between different communities of physicists (both theoretical and experimental). This review, prepared within the COST Action CA18108 “Quantum gravity phenomenology in the multi-messenger approach”, is aimed at promoting this cooperation by giving a state-of-the art account of the interdisciplinary expertise that is needed in the effective search of quantum gravity footprints in the production, propagation and detection of cosmic messengers.
Neutrinos continue to provide a testing ground for the structure of the standard model of particle physics as well as hints towards the physics beyond the standard model. Neutrinos of energies spanning over several orders of magnitude, originating in many terrestrial and astrophysical processes, have been detected via various decay and interaction mechanisms. At MeV scales, there has been one elusive process, until a few years ago, known as coherent elastic neutrino-nucleus scattering (CEvNS) that was theoretically predicted over five decades ago but was never observed experimentally. The recent experimental observation of the CEvNS process by the COHERENT collaboration at a stopped pion neutrino source has inspired physicists across many subfields. This has vital implications for nuclear physics, high-energy physics, astrophysics, and beyond. CEvNS, being a low-energy process, provides a natural window to study light, weakly-coupled, new physics in the neutrino sector. In this review, we intend to provide the current status of low energy neutrino scattering physics and its implications for the standard and beyond the standard model physics. We discuss the general formalism of calculating the tree-level CEvNS cross section and present estimated theoretical uncertainties on the CEvNS cross section stemming from different sources. We also discuss the inelastic scattering of tens of MeV neutrinos that have implications for supernova detection in future neutrino experiments. We discuss how the CEvNS experiments can be used as a testing ground for the Standard Model (SM) weak physics as well as in searching for the Beyond the Standard Model (BSM) physics signals. Any deviation from the SM predicted event rate either with a change in the total event rate or with a change in the shape of the recoil spectrum, could indicate new contributions to the interaction cross-section. The SM implications include the study of weak nuclear form factor and weak mixing angle. The BSM studies include non-standard interactions, neutrino electromagnetic properties, and sterile neutrino searches. In conclusion, stopped pion facilities are also a copious source of neutral and changed mesons that allow study of several dark sector physics scenarios such as vector portal models, leptophobic dark matter as well as axion-like particle searches.
Considerable attention has recently focused on the vast energy and water demands of supercomputing, namely large-scale data centers that underpin artificial intelligence (AI), one of the great disruptors of contemporary society. Looking ahead some years from now, quantum computing is poised to disrupt established computing paradigms once again. Scientists and engineers are now working intensely to bring this century-old dream of physicists to fruition. Yet, as quantum computers begin to be integrated with classical supercomputing architectures, the implications for energy and physical resource use also need to be understood, especially how they compare to today’s AI data centers. These impacts have not yet been quantified by the research community – a notable gap in the literature, even if commercial-scale deployment of Quantum-Accelerated Computing Infrastructure (QuACI) is not expected for a few more years. This study is the first to conduct such an assessment. Using publicly available information from academic sources and private industry, we characterize multiple configurations of superconducting qubit-based, fault-tolerant quantum computers (FTQC) that could plausibly be deployed at scale in the 2030s and into the 2040s. By parameterizing these FTQC systems at a process level, we conduct a prospective scenario analysis to quantify their energy and physical resource needs. While these estimates are uncertain, given the current state of quantum technologies and their unknown future trajectories, important insights can already be drawn. One key finding is that while the electricity needs for a fleet of FTQCs are within the bounds of previous modeling studies that have explored high electricity demand futures, the needs for certain physical resources, namely water and helium-3, could pose bottlenecks to QuACI scale-up.
The cosmic evolution of the chemical elements from the Big Bang to the present time is driven by nuclear fusion reactions inside stars and stellar explosions. A cycle of matter recurrently re-processes metal-enriched stellar ejecta into the next generation of stars. The study of cosmic nucleosynthesis and this matter cycle requires the understanding of the physics of nuclear reactions, of the conditions at which the nuclear reactions are activated inside the stars and stellar explosions, of the stellar ejection mechanisms through winds and explosions, and of the transport of the ejecta towards the next cycle, from hot plasma to cold, star-forming gas. Due to the long timescales of stellar evolution, and because of the infrequent occurrence of stellar explosions, observational studies are challenging, as they have biases in time and space as well as different sensitivities related to the various astronomical methods. Here, we describe in detail the astrophysical and nuclear-physical processes involved in creating two radioactive isotopes useful in such studies, 26 Al and 60 Fe. Due to their radioactive lifetime of the order of a million years, these isotopes are suitable to characterise simultaneously the processes of nuclear fusion reactions and of interstellar transport. We describe and discuss the nuclear reactions involved in the production and destruction of 26 Al and 60 Fe, the key characteristics of the stellar sites of their nucleosynthesis and their interstellar journey after ejection from the nucleosynthesis sites. This allows us to connect the theoretical astrophysical aspects to the variety of astronomical messengers presented here, from stardust and cosmic-ray composition measurements, through observation of γ rays produced by radioactivity, to material deposited in deep-sea ocean crusts and to the inferred composition of the first solids that have formed in the Solar System. We show that considering measurements of the isotopic ratio of 26 Al to 60 Fe eliminate some of the unknowns when interpreting astronomical results, and discuss the lessons learned from these two isotopes on cosmic chemical evolution. This review paper has emerged from an ISSI-BJ Team project in 2017–2019, bringing together nuclear physicists, astronomers, and astrophysicists in this inter-disciplinary discussion.