Measurements of 64Cu and 68Ga half-lives and γ-ray emission intensities

A new determination of the 68Ga half-life and evaluation of literature data

Inconsistencies within the 68Ga half-life dataset have been repeatedly identified in nuclear decay data evaluations performed over the past decade. In this paper, a half-life has been determined using ionisation chambers measurements and HPGe gamma-ray spectrometry (T1/2 = 67.783(27) min). The current literature has been reviewed and possible causes of discrepancy have been identified, such as neglected contaminant effects, robustness of analysis, and underestimation of systematic effects. This could lead to a significant improvement of the half-life in future evaluations.

Status of the decay data for medical radionuclides: existing and potential diagnostic γ emitters, diagnostic β+ emitters and therapeutic radioisotopes

Recommended half-lives and specific well-defined emission energies and absolute emission probabilities are important input parameters that should be well-defined to assist in ensuring the diagnostic and therapeutic efficacy of individual radionuclides when applied in the field of nuclear medicine. Bearing in mind the nature of these requirements, approximately one hundred radionuclides have been considered and re-assessed as to whether their decay data are either adequately quantified, or require further in-depth measurements to improve their existing status and merit full re-evaluations of their decay schemes. The primary aim of such a review is to provide sufficient information on the existing and future requirements for such atomic and nuclear data.

60 years of absolute standardization of radionuclides by coincidence counting methods in the Romanian metrology laboratory

This review paper presents the contribution of the Radionuclide Metrology Laboratory (RML) to the development and practical application of the coincidence counting methods. It is also intended to pay tribute to Dr. Enric Leon Grigorescu, the founder of our school of radionuclide metrology. A synthetic treatment of the method, applied to some classes of radionuclides with their common and particular aspects in standardization, is presented: pioneering calculation of instrumental corrections, specific method corrections applied for various types of decay schemes in the variant of efficiency extrapolation, results obtained in international comparisons.

Disintegration rate and gamma-ray emission probability per decay measurement of Cu-64

The procedure followed by the Nuclear Metrology Laboratory (LMN) at the IPEN for the standardization of activity of ⁶⁴Cu is described. The measurement was carried out in a 4π (PC) β-γ coincidence system. The activity per unit mass of the solution was determined by the extrapolation technique. The events were registered using a Time to Amplitude Converter (TAC) associated with a Multi-channel Analyzer. The gamma-ray emission probability per decay of the 1345.7keV transition of ⁶⁴Cu determined with a calibrated REGe gamma-ray spectrometer was (0.472 ± 0.010) %, in agreement with the literature.

Determination of photon emission probability for the main gamma ray and half-life measurements of 64Cu

The National Institute of Standards and Technology (NIST) performed new standardization measurements for 64Cu. As part of this work the photon emission probability for the main gamma-ray line and the half-life were determined using several high-purity germanium (HPGe) detectors. Half-life determinations were also carried out with a NaI(Tl) well counter and two pressurized ionization chambers.

Assessing the absolute quantitative accuracy of Positron Emission Tomography for Cu-64 using traceable calibrated phantoms

Using uniform cylindrical phantoms containing calibrated solutions of ¹⁸F and ⁶⁴Cu, we evaluated for the first time the accuracy with which the activity concentration of ⁶⁴Cu can be quantified on an absolute basis using Positron Emission Tomography (with X-ray Computed Tomography, PET-CT). The scanner was first calibrated for ¹⁸F using the manufacturer's calibration protocol and a phantom with an activity concentration value traceable to the U.S. National standard. By using a similarly calibrated ¹⁸F solution phantom, we were able to determine a correction factor that can be applied to the ⁶⁴Cu imaging data that gave a result that is consistent with 100% recovery with a combined standard uncertainty of 2%. We also demonstrate how a calibrated, solid phantom containing ⁶⁸Ge as a long-lived ¹⁸F surrogate can be used to monitor and transfer the correction factor to other studies.

Measurement of the half-life of ⁶⁸Ga

The half-life of the positron-emitter (68)Ga has been measured by following the decay rate with two systems based on ionization chamber and Ge detectors. The decay rate was measured for periods of time up to 10 half-lives. The combination of the 6 results obtained with both systems gives a value of T1/2=67.845(18) min, in good agreement with recommended data and with an uncertainty lower than any other previously reported value.