F. Sudbrock

Cross sections for the production of residual nuclides by low- and medium-energy protons from the target elements C, N, O, Mg, Al, Si, Ca, Ti, V, Mn, Fe, Co, Ni, Cu, Sr, Y, Zr, Nb, Ba and Au

Abstract Cross sections for residual nuclide production by p-induced reactions were measured from thresholds up to 2.6 GeV using accelerators at CERN/Geneve, IPN/Orsay, KFA/Julich, LANL/Los Alamos, LNS/Saclay, PSI/Villigen, TSL/Uppsala, LUC/Louvain La Neuve. The target elements C, N, O, Mg, Al, Si, Ca, Ti, V, Mn, Fe, Co, Ni, Cu, Sr, Y, Zr, Nb, Ba and Au were investigated. Residual nuclides were measured by X- and γ-spectrometry and by Accelerator Mass Spectrometry (AMS). The measured cross sections were corrected for interfering secondary particles in experiments with primary proton energies above 200 MeV. Our consistent database covers presently ca 550 nuclear reactions and contains nearly 15000 individual cross sections of which about 10000 are reported here for the first time. They provide a basis for model calculations of the production of cosmogenic nuclides in extraterrestrial matter by solar and galactic cosmic ray protons. They are of importance for many other applications in which medium energy nuclear reactions have to be considered ranging from astrophysics over space and environmental sciences to accelerator technology and accelerator-based nuclear waste transmutation and energy amplification. The experimental data are compared with theoretical ones based on calculations using an INC/E model in form of the HETC/KFA2 code and on the hybrid model of preequilibrium reactions in form of the AREL code.

Cross sections for the proton-induced production of He and Ne isotopes from magnesium, aluminum, and silicon

Abstract We measured integral thin target cross sections for the proton-induced production of the rare gas isotopes 3 He, 4 He, 20 Ne, 21 Ne and 22 Ne from Mg, Al, and Si from the respective reaction threshold up to 1.6 GeV. These target elements were chosen since they account for more than 50% and 95% of the cosmogenic He and Ne production in extraterrestrial matter, respectively. In order to minimize the influences of secondary particles on the production of residual nuclides a so-called “mini-stack”-approach was used instead of the well known “stacked-foil-technique” for all irradiation experiments with proton energies above 200 MeV. With this new data base a complete and consistent set of excitation functions for the proton-induced production of He and Ne isotopes is established for all target elements relevant for deciphering the cosmic ray record in extraterrestrial matter.

Production of residual nuclei from irradiation of thin Pb-targets with protons up to 1.6 GeV

Abstract Cross sections for the proton-induced production of residual nuclei from natPb were determined for proton energies between 80 MeV and 1.6 GeV. A comparison with calculated cross sections using an INC/E-model as well as a semiempirical formula has been performed showing that for applications which depend on highly accurate data it is still necessary to measure cross sections.

On the production of 36Cl by high energy protons in thin and thick targets

Abstract Model calculations for the production of cosmogenic nuclides are a versatile tool for the interpretation of the abundances of cosmogenic nuclides, in dependence of the irradiation history in extraterrestrial matter, and the properties of the cosmic particle rays. Such a modelling requires integral excitation functions for the production of these nuclides by the most propagating primary and secondary particles of the cosmic radiation. Although many investigations on 36Cl in meteorites and lunar samples were made, the cross section data base for this nuclide was still insufficient. Here we report on cross section measurements for the proton-induced production of 36Cl from most relevant target elements and on the depth dependent production in thick targets. Our new nuclear data will be applied to the production of 36Cl in a lunar drill core and the meteorite Knyahinya.

Cross Sections for the Production of Radionuclides by Proton-Induced Reactions on W, Ta, Pb and Bi from Thresholds up to 2.6 GeV

Extending our earlier work on cross sections for the production of residual nuclides by proton-induced reactions, the production of radionuclides from the target elements Ta, W, Pb, and Bi was investigated from thresholds up to 2.6 GeV using accelerators at LNS/Saclay, PSI/Villigen, and TSL/Uppsala. Residual nuclides were measured by X- and γ-spectrometry. We obtained more than 5000 new individual cross sections for 402 reactions. Together with the yet not published cross sections for the target elements Rb, Mo, Rh, Ag, In, Te and La and with published results of special investigations of cosmogenic nuclides, our entire consistent data base now covers the target elements C, N, O, Mg, Al, Si, Ca, Ti, V, Mn, Fe, Co, Ni, Cu, Rb, Sr, Y, Zr, Nb, Mo, Rh, Ag, In, Te, Ba, La, Ta, W, Au, Pb and Bi. It contains data for about 1300 nuclear reactions and more than 24000 cross sections. Here, some phenomenological aspects of the residual nuclide production from heavy target elements are described and the capabilities of nuclear models to predict the respective cross sections are discussed.

Development of hypothyroidism during long‐term follow‐up of patients with toxic nodular goitre after radioiodine therapy

Objective  To investigate the cure rate and incidence of hypothyroidism of radioiodine treatment with a calculated dose regimen and an intended thyroid dose of 150 Gy in patients with toxic nodular goitre during long‐term follow‐up.

Cross sections for the proton-induced production of krypton isotopes from Rb, Sr, Y, and Zr for energies up to 1600 MeV

The production by proton-induced reactions of stable and long-lived Kr-isotopes from Rb, Sr, Y, and Zr was investigated by using isotope dilution mass spectrometry of targets irradiated at PSI/CH, TSL/S and LNS/F. Cumulative cross sections were determined for energies between 81 and 1600 MeV, between 15.4 and 1600 MeV, and between 70 and 1600 MeV for the target element Rb, Sr, and Y, respectively. For Zr, three energies of 156, 569 and 1200 MeV were investigated. As a by-product, cross sections for the production of short-lived radionuclides from Rb are reported which were measured by γ-spectrometry prior to mass spectrometry. Flux determination and absolute calibration of cross sections was done by the reaction 27Al(p,3p3n)22Na. The new experimental data are consistent with a large database established during recent years for describing the interactions of cosmic ray protons with matter. They provide a first complete basis for model calculations of cosmogenic krypton in stony meteoroids and planetary surfaces. For the target element Rb we report the first measurements at all. For Sr, only one earlier measurement existed. For Y, our data confirm earlier measurements up to 200 MeV and extend the data set up to 1600 MeV, while for Zr three new energy points complement and check the consistency of the new investigations with earlier work from Bordeaux. The new experimental data are compared with theoretical excitation functions calculated on an a priori basis using the hybrid model of preequilibrium reactions, an intranuclear cascade/evaporation model in form of the HET/KFA2 code and the semi-empirical systematics by Silberberg, Tsao and coworkers. The differences between theories and experiments demonstrate severe shortcomings of the predictive power of existing models and emphasize the importance of experimental determinations if high-quality data are required for applications.

Cellular response on Auger- and Beta-emitting nuclides: Human embryonic stem cells (hESC) vs. keratinocytes

Abstract Purpose: We studied the response of human embryonic stem cells (hESC) to the β-emitter 131I, which affects the entire cell and to the Auger electron emitter 125I-deoxyuridine (125I-dU), primarily affecting the deoxyribonuleic acid (DNA). The effects were also studied in keratinocytes as a prototype for somatic cells. Methods: HESC (H1) and human keratinocytes (HaCaT, human) were exposed to 125I-dU (5 × 10−5 – 5 MBq/ml) and 131I-iodide (5 × 10−5 – 12.5 MBq/ml) and apoptosis was measured by DNA-fragmentation. Cell morphology was studied by light microscopy and electron microscopy. Transcriptional profiling was done on the Agilent oligonucleotide microarray platform. Results: Auger-process induced no apoptosis but a strong transcriptional response in hESC. In contrast, HaCaT cells showed a pronounced induction of apoptosis but only a moderate transcriptional response. Transcriptional response of hESC was similar after 125I-dU and 131I treatments, whereas HaCaT cells expressed a much more pronounced response to 125I-dU than to 131I. A striking radiation-induced down-regulation of pluripotency genes was observed in hESC whereas in keratinocytes the enriched gene annotations were related primarily to apoptosis, cell division and proliferation. Conclusions: Human embryonic stem cells respond to ionizing radiation by 125I-dU and 131I in a different way compared to keratinocytes. Transcriptional response and gene expression appear to facilitate an escape from programmed cell death by striking a new path which probably leads to cell differentiation.

Neuroblastoma: Dosimetry for MIBG Therapies

Radiation dosimetry is a basic requirement when using radioactive substances for targeted therapies (targeted radionuclide therapy, TRT). The objective of dosimetry is, in simple terms, taking a closer look at the effects of ionizing radiation. In order to do this it is most common to start with dedicated assessments of the distribution of the radioactive substance in the patient over time. In the case of 131I-MIBG the radionuclide can easily be measured using counting techniques and quantitative imaging. From a series of measurements an individual function is obtained that can be converted into a quantity describing the amount of nuclear disintegrations in a defined region. From this quantity the absorbed radiation dose can be derived. It is obvious that the absorbed radiation dose representing the degree of energy deposited by nuclear transformations in a defined region should correlate with the therapeutic efficacy in a tumor, in an organ or in the whole body. But knowledge concerning the absorbed doses and the relationship between dose and therapeutic outcome needs more detailed clarification than is accessible at present. This contribution provides a survey on the different techniques and related findings concerning MIBG therapies. The authors first of all want to lay focus on the basic knowledge required for understanding the interaction of radiation with matter and, consequently, the impact of radiopharmaceuticals on biological material. Experiences with targeted therapies using 131I-MIBG have been conveyed by many studies since the 1980s. Although dosimetry is still only sporadically reported there are some assumptions concerning dose-effect relationships for 131I-MIBG that are vindicated by many authors.