Decay data evaluation project : Evaluation of 52 Mn and 52 mMn nuclear decay data

All nuclear decay data within the 52Fe-52m,52Mn-52Cr decay chain have been evaluated at IFINHH, Romania, as part of an IAEA coordinated research project (F41029) and incorporated into the Decay Data Evaluation Project (DDEP). Both 52Fe and daughter 52Mn are two potentially promising radionuclides to be incorporated into suitable radiopharmaceuticals for PET and SPECT imaging. The decay data evaluation of 52Fe has previously been published and reported to the IAEA Nuclear Data Section. Equivalent DDEP evaluations for 52Mn and 52mMn have also been completed recently, and are presented in summary form below. These improved decay data sets have also been reported to the IAEA in detail, and are highly suitable in dose rate calculations for their application in nuclear medicine.


Introduction
Established in 1995, the Decay Data Evaluation Project (DDEP) is an international initiative with the main objective "to provide carefully produced recommended data for applied research and detector calibrations", www.nucleide.org/DDEP.htm.This is achieved by performing peer-review evaluations for the following nuclear decay data of the radionuclides of interest: halflife, decay energy, decay modes and branching fractions, and radiation energies and emission probabilities.The complete DDEP database is hosted by the Laboratoire National Henri Becquerel (CEA/LNE-LNHB) from France. 52Mn and 52m Mn are two radionuclides with potential to be used in PET and SPECT medical applications.While 52m Mn has been used to monitor myocardial perfusion by PET, 52 Mn can also be applied to dual modality manganese-enhanced magnetic resonance imaging (MEMRI) applications, such as neural tractography and stem-cell tracking, [1,2].The aim of the present work was a complete characterization of the 52 Fe-52m,52 Mn-52 Cr decay chain.The presently reported results complement the evaluation of the 52 Fe nuclear decay data which was recently published [3].The work was done under the IAEA Coordinated Research Project "Nuclear Data for Charged-particle Monitor Reactions and Medical Isotope Production".

Evaluation steps and tools
The most recent ENSDF evaluation for the mass chain A=52 was studied [4].The energy of the nuclear levels, and the spin and parity values were adopted from this evaluation, while the total decay energies are from the atomic mass evaluation [5].All relevant published experimental data for 52m Mn and 52 Mn were a e-mail: aluca@nipne.roidentified and copies stored for subsequent use (eight and seventeen references, respectively).The cut-off dates for the references were January and March 2016, respectively.Both the compilation and evaluation of the nuclear decay data sets were then undertaken.Finally, the decay scheme parameters were analyzed and tested.

Results
52m Mn decays 98.295(42)% by electron capture and β+ to excited levels of 52 Cr, and by isomeric transition (IT) to the ground state of 52 Mn (1.705(42)%), Fig. 1. 52 Mn decays 100% by electron capture and β+ to excited levels of 52 Cr.Both radionuclides have important emissions of positrons (allowed transitions) and gamma-rays on a wide energy range.The half-life values adopted represent the weighted averages of three and seven experimental values for 52m Mn and 52 Mn, respectively.

Recommended decay data
The results obtained for the main decay data of 52m Mn and 52 Mn are presented in Table 1: half-life, decay energy, and energies and emission probabilities of the different transitions.Other evaluated data: fluorescence yields: ω K ( 52 Mn) = 0.289 (5).The conversion electrons have very low emission probabilities of the order of 10 −4 (K shell) and less.

Normalization factor for the γ -ray transitions
The Normalization factor (F) is used to calculate the absolute γ -ray emission probabilities from the adopted γ -ray Table 1.Evaluated decay data for 52m Mn and 52 Mn. relative intensities.The Normalization Factor was calculated by imposing the following two conditions.52m Mn: 98.295(42)% of the transitions (all, with the exception of the IT transition) populate the ground state of the 52 Cr daughter: F = 0.98254(42).For 52 Mn: 100% of the transitions (with the exception of the IT decay) populate the ground state of the 52 Cr daughter: F = 0.999866(2).

Testing the consistency of decay schemes
According to the SAISINUC testing tools, the sum of all the energies involved in the 52m Mn decay (EC, γ , etc.), with the exception of the gamma-ray isomeric transition, is 5089.1 (36) keV, which is in very good agreement with the Q EC value: 5088.9 (19) keV.