Standardization of 68Ge/68Ga Using Three Liquid Scintillation Counting Based Methods

Abstract

A solution containing 68Ge in equilibrium with its daughter, 68Ga, has been standardized for the first time at the National Institute of Standards and Technology (NIST) using 3 liquid scintillation-based techniques: live-timed 4πβ -γ anticoincidence (LTAC) counting, the Triple-to-Double Coincidence Ratio (TDCR) method, and 3H-standard efficiency tracing with the CIEMAT1/NIST (CNET) method. The LTAC technique is much less dependent on level scheme data and model-dependent parameters and was thus able to provide a reference activity concentration value for the master solution with a combined standard uncertainty of about 0.3 %. The other two methods gave activity concentration values with respective differences from the reference value of +1.2 % and −1.5 %, which were still within the experimental uncertainties. Measurements made on the NIST “4π”γ secondary standard ionization chamber allowed for the determination of calibration factors for that instrument, allowing future calibrations to be made for 68Ge/68Ga without the need for a primary measurement. The ability to produce standardized solutions of 68Ge presents opportunities for the development of a number of NIST-traceable calibration sources with very low (<1 %) relative standard uncertainties that can be used in diagnostic medical imaging.

Impact of Recent Change in the National Institute of Standards and Technology Standard for 18F on the Relative Response of 68Ge-Based Mock Syringe Dose Calibrator Standards

“…The ratio of calculated doses deposited in the ionization chamber gas for the solid mock syringe to the solutionfilled mock syringe was 0.995 (4) and is consistent with the results given in our previous work (3).…”

Development of a Traceable Calibration Methodology for Solid68Ge/68Ga Sources Used as a Calibration Surrogate for18F in Radionuclide Activity Calibrators

“…The solutions, and derivatives thereof, were calibrated for radioactivity content at NIST by either primary or secondary methods, as described in Zimmerman et al (5). All dilutions were performed using a carrier solution containing nominally 45 mg each of nonradioactive GeCl 4 and GaCl 3 per gram of solution in 0.5 M HCl.…”

“…As a potential solution, NIST recently developed a primary standard for the relatively long-lived (half-life, 270.95(16) d) radionuclide 68 Ge in equilibrium with its positron-emitting decay daughter, 68 Ga (5), for the first time. Although the decay properties of 68 Ga are not identical to those of 18 F, there are enough similarities that it has been suggested that 68 Ge/ 68 Ga could be used as a reasonable surrogate, assuming that the necessary correction factors can be determined.…”

Fiducial Volume of the Edelweiss Germanium Bolometers for Dark Matter Search Using Cosmogenic Activation

“…All the latter give X-rays between 4 and 8 keV. [1,2]. 68 Ge has a 288 days half-life and disintegrates by 100% electron capture (E.C.)…”

“…We have studied the 10 InterDigit bolometers [3] in operation in the Underground Laboratory of Modane (LSM) during the last WIMP search of the Edelweiss-II experiment [4]. They are all 400 g germanium crystals, but two different geometries are present : a cylindrical one (corresponding to half the bolometers, denoted ID40X with X ∈ [1,5]) and a geometry with bevelled edges (also corresponding to half the bolometers, denoted IDX with X ∈ [2, 6]). A more complete description of the detectors is given in Ref.…”