Radionuclide-based diagnostics and therapy require proper selection of production nuclear reaction based on knowledge of the production excitation functions and the achievable yields completed with ...data on the formation of possible impurities. In the present work the existing IAEA recommended cross section data database for production of therapeutic isotopes is extended to production of the
47
Sc,
47
Ca(
47
Sc),
58m
Co,
71
As(
71
Ge),
71
Ge,
77
Br,
77
Kr(
77
Br),
80m
Br,
103
Pd,
103
Pd(
103m
Rh),
103
Ru(
103m
Rh),
105
Rh,
117m
Sn,
119
Sb,
119m
Te(
119
Sb),
134
Ce,
135
La,
149g
Tb,
161
Tb,
165
Er,
165
Tm(
165
Er),
167
Tm,
197m
Hg,
197g
Hg,
198g
Au, and
230
Pa(
230
U) radioisotopes. Nearly 60 nuclear reactions are presented and discussed. The new recommended cross-section data and their uncertainties for the production of these 21 radionuclides will be available on the Web page of the IAEA Nuclear Data Section at
https://nds.iaea.org/radionuclides
and also at the IAEA medical portal
https://nds.iaea.org/medportal
.
Purpose: The increased use of small photon fields in stereotactic and intensity modulated radiotherapy has raised the need for standardizing the dosimetry of such fields using procedures consistent ...with those for conventional radiotherapy. An international working group, established by the IAEA in collaboration with AAPM and IPEM, is finalising a Code of Practice for the dosimetry of small static photon fields. Methods: Procedures for reference dosimetry in non‐standard machine specific reference (msr) fields are provided following the formalism of Alfonso et al., Med. Phys. 35 (2008). Recommended correction factors are based on experiment data or Monte Carlo simulated data reported in the literature. They are tabulated for suitable detectors for specific machines such as CyberKnife, GammaKnife and TomoTherapy as well as for generic rectangular fields defined by multi‐leaf collimators and circular fields 4010 defined by cones. Results: Reference dosimetry using ionization chambers in machines that cannot establish a conventional 10 cm × 10 cm reference field is based on either a direct calibration in the msr field traceable to primary standards or a calibration in a reference field and a generic correction factor or the product of a correction factor for a virtual reference field and a correction factor for the difference between the msr and virtual fields. For the latter method, procedures are provided for determining the beam quality in non‐reference conditions. For the measurement of field output factors in small fields, procedures for connecting large field measurements using ionization chambers to small field measurements using high‐resolution detectors such as diodes, diamond, liquid ion chambers, organic scintillators and radiochromic film are given. Conclusions: A new Code of Practice will be published by the IAEA in the near future. Further research to measure or calculate missing data according to well‐defined procedures will be strongly encouraged by the publication of this document.
The need of neutron capture cross section measurements for astrophysics motivates present work, where calculations to generate stellar neutron spectra at different temperatures are performed. The ...accelerator-based (7)Li(p,n)(7)Be reaction is used. Shaping the proton beam energy and the sample covering a specific solid angle, neutron activation for measuring stellar-averaged capture cross section can be done. High-quality Maxwell-Boltzmann neutron spectra are predicted. Assuming a general behavior of the neutron capture cross section a weighted fit of the spectrum to Maxwell-Boltzmann distributions is successfully introduced.
Purpose: An international IAEA/AAPM working group is preparing recommendations for reference dosimetry in small fields and composite fields. A proposed formalism for dosimetry in small and composite ...fields was published that introduces machine specific reference (msr) fields for static small fields and plan‐class specific reference (pcsr) fields for composite fields such as an IMRT sequence. The status of present activities, based on the proposed formalism, will be reviewed. Method and Materials: For msr fields a literature review is conducted and for some modalities experiments and Monte Carlo simulations are performed. For composite fields various routes are explored to arrive at suitable pcsr fields. Some of these start from clinical plans and try to distil most representative reference deliveries, while others start from treatment unit specific features to arrive at relevant modulated plans. Experiments and Monte Carlo simulations are performed as well to determine correction factors for ionisation chambers in pcsr fields and to evaluate their suitability to represent a class of clinical plans. One idea being explored is that for a composite field where full charged particle equilibrium is established, the overall correction factor equals the reciprocal of the gradient correction factor in the conventional reference field. Results: State‐of‐the‐art results on the correction factors for msr and pcsr fields will be reviewed. Experimental work performed on pcsr fields in TomoTherapy and step‐and‐shoot prostate plans indicates that correction factors for suitably sized ion chambers are not more than 1% different from unity. Monte Carlo simulations confirm this. Studies are underway to test the sensitivity of the correction factors to characteristics of the pcsr field. Conclusion: Results indicate that reference dosimetry in msr and pcsr fields is feasible with acceptably small corrections. A working document on static small field dosimetry is aimed for by the end of this year.
Abstract The evaluation and deduction of recommended cross section values allowing extension of the database to monitor energy and intensity parameters of charged particle beams is presented. ...Included are 53 charged particle (p, d, 3 He, 4 He) induced reactions on suited C, Al, Ti, Fe, Ni, Cu, Nb and Au targets. The new data allow more systematic simultaneous use of multiple reactions on the same target and promote the backings of electrodeposited and sedimented targets as monitoring aids. Where possible the energy range is extended to above 100 MeV. Integral yield curves over the studied energy range are derived and compared to experimentally measured yields at specific energy points. A comparison with the theoretical excitation curve prediction of the TALYS-code as available in the TENDL 2021–2023 libraries is shown.
Purpose: Protons and heavy ions loose energy via atomic and nuclear interaction processes. When simulating charged‐particle beam characteristics, for example absorbed dose distributions or secondary ...particle fluences, accurate physics descriptions are required. Sophisticated computing techniques, e.g. Monte Carlo, are applied for high accuracy calculations. However, the availability of high‐quality cross‐section data for the simulation of heavy charged‐particle interactions is far from being satisfactory. For example, the intra‐nuclear cascade models that are employed for cross‐section calculations are strictly valid only at high energies (>200 MeV per nucleon). Data libraries of charged‐particle interactions are needed to validate the calculations using nuclear models and for direct use in calculations. Method and Materials: The new IAEA coordinated research project on heavy charged‐particle interaction data for radiotherapy comprises of a program to compile and evaluate charged‐particle nuclear data for therapeutic applications. Plan is to review data and parameterizations for protons and heavy ions. Sensitivity analysis for different applications will be done with different codes for representative examples. The outcome will be a recommendation of preferred universal parameterization for all applications. Further, the aim is to work with code developers of the Monte Carlo codes FLUKA, Geant4, MCNPX, and SHIELD‐HIT in order to implement reference models for use in charged‐particle therapy simulations. Results: This presentation will discuss the sensitivity of nuclear interaction data for various applications in heavy charged‐particle therapy. We will discuss the nuclear interaction component in patient dose calculations, neutron background estimations, absolute dosimetry, and PET imaging for treatment verification. Based on these examples we will outline the specific aims of the IAEA initiative. Conclusion: The IAEA initiative aims at standardizing the use of charged‐particle nuclear interaction data for Monte Carlo simulations in proton and heavy ion therapy in order to improve the accuracy and compatibility of dosimetric studies.
We have performed a new combined set of evaluations for 90–96Zr, including new resolved resonance parameterizations from Said Mughabghab for 90,91,92,94,96Zr and fast region calculations made with ...EMPIRE-3.1. Because 90Zr is a magic nucleus, stable Zr isotopes are nearly spherical. A new soft-rotor optical model potential is used allowing calculations of the inelastic scattering on low-lying coupled levels of vibrational nature. A soft rotor model describes dynamical deformations of the nucleus around the spherical shape and is implemented in EMPIRE/OPTMAN code. The same potential is used with rigid rotor couplings for odd-A nuclei. This then led to improved elastic angular distributions, helping to resolve improper leakage in the older ENDF/B-VII.1β evaluation in KAPL proprietary, ZPR and TRIGA benchmarks. Another consequence of 90Zr being a magic nucleus is that the level densities in both 90Zr and 91Zr are unusually low causing the (n,el) and (n,tot) cross sections to exhibit large fluctuations above the resolved resonance region. To accommodate these fluctuations, we performed a simultaneous constrained generalized least-square fit to (n,tot) for all isotopic and elemental Zr data in EXFOR, using EMPIRE's TOTRED scaling factor. TOTRED rescales total cross sections so that the optical model calculations are unaltered by the rescaling and the correct competition between channels is maintained. In this fit, all (n,tot) data in EXFOR was used for Ein>100keV, provided the target isotopic makeup could be correctly understood, including spectrum averaged data and data with broad energy resolution. As a result of our fitting procedure, we will have full cross material and cross reaction covariance for all Zr isotopes and reactions.
The EUROMET project 428 examines efficiency transfer results for Ge gamma-ray spectrometers when the efficiency is known for a reference point source geometry. For this, different methods are used, ...such as Monte Carlo simulation or semi-empirical computation. The exercise compares the application of these methods to the same selected experimental cases to determine the usage limitations versus the requested accuracy. For carefully examining these results and trying to derive information for improving the computation codes, this study was limited to a few simple cases. The first part concerns the simplest case of geometry transfer, i.e., using point sources for 3 source-to-detector distances: 2, 5 and 20cm; the second part deals with transfer from point source geometry to cylindrical geometry with three different matrices. The general conclusion is that the deviations between the computed results and the measured efficiencies are within 10% mostly. The quality of the results is rather inhomogeneous and shows that these codes cannot be used directly for metrological purposes. However, most of them are operational for routine measurements when efficiency uncertainties of 5–10% can be sufficient.
The new experimental setup TANGRA (Tagged Neutrons & Gamma Rays), for the investigation of neutron induced nuclear reactions, e.g. (n,xn’), (n,xn’γ), (n,γ), (n,f), on a number of important isotopes ...for nuclear science and engineering (235,238U, 237Np, 239Pu, 244,245,248Cm) is under construction and being tested at the Frank Laboratory of Neutron Physics (FLNP) of the Joint Institute for Nuclear Research (JINR) in Dubna.
The TANGRA setup consists of: a portable neutron generator ING-27, with a 64-pixel Si charge-particle detector incorporated into its vacuum chamber for registering of α-particles formed in the T(d, n)4He reaction, as a source of 14.1 MeV steady-state neutrons radiation with an intensity of ∼5x107n/s; a combined iron (Fe), borated polyethylene (BPE) and lead (Pb) compact shielding-collimator; a reconfigurable multi-detector (neutron plus gamma ray detecting system); a fast computer with 2 (x16 channels) PCI-E 100 MHz ADC cards for data acquisition and hard disk storage; Linux ROOT data acquisition, visualization and analysis software. The signals from the α-particle detector are used to ‘tag’ the neutrons with the coincident α-particles. Counting the coincidences between the α-particle and the reaction-product detectors in a 20ns time-interval improves the effect/background-ratio by a factor of ∼200 as well as the accuracy in the neutron flux determination, which decreases noticeably the overall experimental data uncertainty.
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