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Purpose: Unique characteristics of MRI-linac systems and mutual interactions between their components pose specific challenges for their commissioning and quality assurance. The Australian MRI-linac is a prototype system which explores the inline orientation, with radiation beam parallel to the main magnetic field. The aim of this work was to commission the radiation-related aspects of this system for its application in clinical treatments. Methods: Physical alignment of the radiation beam to the magnetic field was fine-tuned and magnetic shielding of the radiation head was designed to achieve optimal beam characteristics. These steps were guided by investigative measurements of the beam properties. Subsequently, machine performance was benchmarked against the requirements of the IEC60976/77 standards. Finally, the geometric and dosimetric data was acquired, following the AAPM Task Group 106 recommendations, to characterize the beam for modelling in the treatment planning system and with Monte Carlo simulations. The magnetic field effects on the dose deposition and on the detector response have been taken into account and issues specific to the inline design have been highlighted. Results: Alignment of the radiation beam axis and the imaging isocentre within 2 mm tolerance was obtained. The system was commissioned at two source-to-isocentre distances (SIDs): 2.4 m and 1.8 m. Reproducibility and proportionality of the dose monitoring system met IEC criteria at the larger SID but slightly exceeded it at the shorter SID. Profile symmetry remained under 103% for the fields up to ca. 34×34 cm2 and 21×21 cm2 at the larger and shorter SID respectively. No penumbra asymmetry, characteristic for transverse systems, was observed. The electron focusing effect, which results in high entrance doses on central axis, was quantified and methods to minimize it have been investigated. Conclusion: Methods were developed and employed to investigate and quantify the dosimetric properties of an inline MRI-Linac system. The Australian MRI-linac system has been fine-tuned in terms of beam properties and commissioned, constituting a key step towards the application of inline MRI-linacs for patient treatments.

The Neutron Radiography Reactor at Idaho National Laboratory (INL) has two beamlines extending radially outward from the east and north faces of the reactor core. The control rod withdrawal procedure has recently been altered, potentially changing power distribution of the reactor and thus the properties of the neutron beams, calling for characterization of the neutron beams. The characterization of the East Radiography Station involved experiments used to measure the following characteristics: Neutron flux, neutron beam uniformity, cadmium ratio, image quality, and the neutron energy spectrum. The ERS is a Category-I neutron radiography facility signifying it has the highest possible rank a radiography station can achieve. The thermal equivalent neutron flux was measured using gold foil activation and determined to be 9.61 × 106 ± 2.47 × 105 n/cm2-s with a relatively uniform profile across the image plane. The cadmium ratio measurement was performed using bare and cadmium-covered gold foils and measured to be 2.05 ± 2.9%, indicating large epithermal and fast neutron content in the beam. The neutron energy spectrum was measured using foil activation coupled with unfolding algorithms provided by the software package Unfolding with MAXED and GRAVEL (UMG). The Monte-Carlo N-Particle (MCNP6) transport code was used to assist with the unfolding process. UMG, MCNP6, and measured foil activities were used to determine a neutron energy spectrum which was implemented into the MCNP6 model of the east neutron beam to contribute to future studies.

The neutron radiography reactor (NRAD) is a 250 kW Mark-II Training, Research, Isotopes, General Atomics (TRIGA) reactor at Idaho National Laboratory, Idaho Falls, ID, USA. The East Radiography Station (ERS) is one of two neutron beams at the NRAD used for neutron radiography, which sits beneath a large hot cell and is primarily used for neutron radiography of highly radioactive objects. Additional fuel elements were added to the NRAD core in 2013 to increase the excess reactivity of the reactor, and may have changed some characteristics of the neutron beamline. This report discusses characterization of the neutron beamline following the addition of fuel to the NRAD. This work includes determination of the facility category according to the American Society for Testing and Materials (ASTM) standards, and also uses an array of gold foils to determine the neutron beam flux and evaluate the neutron beam profile. The NRAD ERS neutron beam is a Category I neutron radiography facility, the highest possible quality level according to the ASTM. Gold foil activation experiments show that the average neutron flux with length-to-diameter ratio (L/D) = 125 is 5.96 × 106 n/cm2/s with a 2σ standard error of 2.90 × 105 n/cm2/s. The neutron beam profile can be considered flat for qualitative neutron radiographic evaluation purposes. However, the neutron beam profile should be taken into account for quantitative evaluation.

Preliminary results of characterization experiments for the New Neutron Imaging Facility (NIF) that is being developed at the Penn State Breazeale Nuclear reactor are presented in the following sections. The methodology of neutron beam characterization described in the American Society for Testing and Materials (ASTM) documents for the neutron imaging systems have been followed to improve the NIF at Penn State to a Category I facility by ASTM designation of quality. Preliminary results showed that our system is capable of producing images of high quality, corresponding to Category I; however, further experiments are needed for full declaration of our facility as such. Additionally, the effective collimation ratio (L/D ratio) of our current system is ∼110 with the capability of improvement to ∼150. The thermal flux at the exit surface of the neutron beam is equal to 5.4 × 106n cm−2s−1 at 1MWth reactor power, which corresponds to the industry comparable value.

When using Shack-Hartmann wavefront sensors (SH) and Zernike coefficients (Zs) in applications where the position of the measurement and the point of interest are far apart, as it is common practice in ophthalmic optics, problems in the interpretation of the values of the Zs arise, related to how the shape of the wavefront propagates along the beam. One typical example is pupil conjugation where an auxiliary lens is added to match the size of the area of the interest of the beam with the size of the entrance pupil of the SH used for measurements. In the present work, we address this problem in the framework of a numerical scheme for modeling the beam propagation. We calculate the wavefronts with exact ray tracing plus the fitting of the impacts so as to match a rectangular grid. This procedure allows the subsequent calculation of the Zs or, similarly, the pupil function at an arbitrary plane perpendicular to the optical axis. All the numerical methods and procedures have been implemented in MATLAB code and can be illustrated by running the MATLAB script for the setup configuration that is being considered. Several examples are presented to illustrate the previous ideas and to show the real capabilities of our procedures. They will help to clarify the issues actually found in practical setups for beam manipulation, often encountered in ophthalmic optics.

A feasibility study of an experimental setup for the irradiation of biological samples at the cyclotron facility installed at the National Centre of Accelerators (Seville, Spain) is presented. This cyclotron, which counts on an external beam line for interdisciplinary research purposes, produces an 18 MeV proton beam, which is suitable for the irradiation of mono-layer cultures for the measurement of proton cell damages and Relative Biological Effectiveness (RBE) at energies below the beam nominal value. Measurements of this kind are of interest for proton therapy, since the variation of proton RBE at the distal edge of the Bragg curve may have implications in clinical proton therapy treatments. In the following, the characteristics of the beam line and the solutions implemented for the irradiation of biological samples are described. When dealing with the irradiation of cell cultures, low beam intensities and broad homogeneous irradiation fields are required, in order to assure that all the cells receive the same dose with a suitable dose rate. At the cyclotron, these constraints have been achieved by completely defocusing the beam, intercepting the beam path with tungsten scattering foils and varying the exit-window-to-sample distance. The properties of the proton beam thus obtained have been analysed and compared with Monte Carlo simulations. The results of this comparison, as well as the experimental measurement of the lateral dose profiles expected at the position of samples are presented. Meaningful dose rates of about 2–3 Gy/min have been obtained. Homogeneous lateral dose profiles, with maximum deviations of 5%, have been measured at a distance of approximately 50 cm in air from the exit window, placing a tungsten scattering foil of 200 µm in the beam path., This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Grant No. 675265, OMA—Optimization of Medical Accelerators, from the Spanish Ministry of Economy and Competitiveness under Grant No. FPA2016-77689-C2-1-R, and from the Council for Innovation, Science and Commerce of the Andalusian Government under Grant No. P12-FQM-1605.

The IEC 1689 standard specifies: methods of measurement, characterisation of the output performance, requirements for safety due to the ultrasonic field generated, characteristics to be declared by manufacturers and acceptance criteria for aspects of performance. For the characterisation, reference as well as routine testing methods are described. Important parameters such as effective radiating area (AER), beam nonuniformity ratio (RBN) (characterising 'hot-spots': potentially harmful to patients) and beam type have been re-defined. The quality, reproducibility and accuracy of measurements of AER are significantly improved compared to those in IEC 150 (which is now replaced) and the FDA 1050.10 (USA) standards. As a result, values of effective intensity are shown to be significantly higher than those obtained using the FDA 1050.10 (USA) definitions. As it may be expected that the new standard will be implemented worldwide, this problem is just a matter of time. The standard discussed above specifies the need for acoustic power measurement with an accuracy of more than 15%. However, several investigations carried out over the last ten years show a lack of proper facilities to calibrate the acoustic output power at physiotherapy levels. A project to investigate the complications and to produce definitive guidance for therapy-level power measurements is funded by the EC and has been started recently. Future activities will be undertaken to estimate the expected temperature rise in tissue due to the ultrasonic field. Such a figure may result in an improved judgement of the ultrasonic safety aspects of physiotherapy systems. © 1998 Elsevier Science B.V.