The measurement of radiopharmaceuticals used in nuclear medicine services is generally done through calibrated dose calibrators linked to the SI by the LNHB. Short half-life radionuclides, such as ¹¹C (T_1/2 = 20 min) or ¹⁵O (T_1/2 = 2 min), are produced in situ and are difficult to transport for calibration in a primary laboratory. For these reasons, it was necessary to develop a portable primary measuring device that could be used on site.

Achievements:
Design of the portable system.
Optimization for the measurement of short half-life radionuclides:
– use of compact photomultipliers,
– integration in a polymer mechanical system,
– manufacturing by fused deposition modeling (3D printing),
– integration of miniature acquisition electronics, coupled to a laptop PC.

 

Major results:
Validation of a prototype by comparison with the laboratory’s TDCR primary measurement system.
The next developments should make it possible to couple this measuring device with a microfluidic sampling system to limit the irradiation dose to operators and to limit the quantities of solution that are consumed for quality control.

REFERENCES:
– Broda R., Cassette P., Kossert K. Radionuclide metrology using liquid scintillation counting. Metrologia, 44 (4) (2007)
– Marco Capogni, Pierino De Felice, A prototype of a portable TDCR system at ENEA, Applied Radiation and Isotopes, Volume 93, 2014, Pages 45-51
Collaboration with Sofia University

The photon beams delivered by the Varian TrueBeam medical accelerator installed on the DOSEO platform are now the reference beams used for calibration of clinical radiotherapy centres. This required new metrological references in terms of absorbed dose in water.

Achievements:
Water and graphite calorimeters are used at LNHB as primary instruments for photon and electron beam measurements of the absorbed dose in water.
In the case of the Varian TrueBeam accelerator, calorimeters were used to determine the calibration coefficients in absorbed dose to water of 3 reference ionization chambers for the different beam qualities delivered (6, 10, 15 and 20 MV). They are plotted according to a beam quality index called TPR20,10 (Tissue Phantom Ratio 20,10).

 

Major results:
The uncertainty obtained on the calibration coefficients of the ionization chambers is about 0.5%.
The results showed a good agreement with the calibration coefficients previously obtained from graphite calorimeters on the beams of the old LNHB accelerator (Delphes, Saturne 43).
The equipment redundancy (graphite and water calorimeter) at LNHB is unique in Europe. It provides references based on two independent methods and thus consolidates its references by improving the control of uncertainties for the calibration of clinical centres.

The concentration of thoron in France is estimated to be one-tenth that of radon and is therefore a significant public health issue. To meet the need for traceability of measurements of this natural thorium descendant, a new primary standard instrument has been developed and validated at the LNHB to calibrate the instruments for measuring thoron volume activity in air.

Achievements:
– Creation of an adapted thoron measurement system (short half-life: 55.8 s)
– Complete study of the nuclear properties of radon, thoron and their progeny
– Description of charge distribution of thoron progenies nano-particles and their transport in air

Major results:
Analysis of the alpha spectra obtained made it possible to accurately qualify the volumic activity of a thoron atmosphere with an associated 1% relative standard uncertainty. The portable device thus made it possible to calibrate the thoron atmosphere produced in the Baccara facility, the experimental radon chamber of the IRSN Aerosol Physics and Metrology Laboratory (LPMA) dedicated to radon metrology studies.
Comparisons with ENEA (Italy) in the MetroNORM European Metrology Project

REFERENCES:
This work has been supported by the European Metrology Research Programme (EMRP), JRP-Contract IND57 MetroNORM.
– Sabot B., Pierre S., Michielsen N., Bondiguel S., Cassette P., (2015), Development of a primary thoron activity standard for the calibration of thoron measurement instruments, Radiat Prot Dosimetry 167 (1-3), 70-74.
https://doi.org/10.1093/rpd/ncv221
– Sabot B., Pierre S., Michielsen N., Bondiguel S., Cassette P., (2016), A new thoron atmosphere reference measurement system, Appl Radiat Isot. 109, 205-209.
http://dx.doi.org/10.1016/j.apradiso.2015.11.055
– Sabot B., (2015), Calibration of thoron (²²⁰Rn) activity concentration monitors, PhD Thesis,
http://www.theses.fr/2015SACLS122