National Henri Becquerel Research Articles

Calibration of helical tomotherapy machine using EPR/alanine dosimetry

Current codes of practice for clinical reference dosimetry of high-energy photon beams in conventional radiotherapy recommend using a 10 x 10 cm2 square field, with the detector at a reference depth of 10 cm in water and 100 cm source to surface distance (SSD) (AAPM TG-51) or 100 cm source-to-axis distance (SAD) (IAEA TRS-398). However, the maximum field size of a helical tomotherapy (HT) machine is 40 x 5 cm2 defined at 85 cm SAD. These nonstandard conditions prevent a direct implementation of these protocols. The purpose of this study is twofold: To check the absorbed dose in water and dose rate calibration of a tomotherapy unit as well as the accuracy of the tomotherapy treatment planning system (TPS) calculations for a specific test case. Both topics are based on the use of electron paramagnetic resonance (EPR) using alanine as transfer dosimeter between the Laboratoire National Henri Becquerel (LNHB) 60Co-gamma-ray reference beam and the Institut Curie's HT beam. Irradiations performed in the LNHB reference 60Co-gamma-ray beam allowed setting up the calibration method, which was then implemented and tested at the LNHB 6 MV linac x-ray beam, resulting in a deviation of 1.6% (at a 1% standard uncertainty) relative to the reference value determined with the standard IAEA TRS-398 protocol. HT beam dose rate estimation shows a difference of 2% with the value stated by the manufacturer at a 2% standard uncertainty. A 4% deviation between measured dose and the calculation from the tomotherapy TPS was found. The latter was originated by an inadequate representation of the phantom CT-scan values and, consequently, mass densities within the phantom. This difference has been explained by the mass density values given by the CT-scan and used by the TPS which were not the true ones. Once corrected using Monte Carlo N-Particle simulations to validate the accuracy of this process, the difference between corrected TPS calculations and alanine measured dose values was then found to be around 2% (with 2% standard uncertainty on TPS doses and 1.5% standard uncertainty on EPR measurements). Beam dose rate estimation results were found to be in good agreement with the reference value given by the manufacturer at 2% standard uncertainty. Moreover, the dose determination method was set up with a deviation around 2% (at a 2% standard uncertainty).

Activity measurements of the radionuclide 124Sb by the LNE–LNHB, France for the ongoing comparison BIPM.RI(II)-K1.Sb-124

In 2007, the Laboratoire national de métrologie et d'essais–Laboratoire national Henri Becquerel (LNE–LNHB), France submitted a sample of known activity of 124Sb to the International Reference System (SIR) for activity comparison at the Bureau International des Poids et Mesures (BIPM). The activity was about 5.3 MBq. The key comparison reference value (KCRV) has been recalculated to include this new value and the degrees of equivalence between each equivalent activity for the three participants measured in the SIR and the KCRV are presented in a table and graphically.Main text.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCRI Section II, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Sci-Sat AM(2): Brachy - 04: Brachytherapy Air-Kerma Calibrations at Ionizing Radiation Standards, NRC

The majority of Canadian cancer clinics now offer brachytherapy treatments, but source calibrations currently require transfer chambers to be sent out of the country. The logistical difficulties involved in shipping delicate and crucial medical equipment internationally prompted the Canadian user committee to encourage the Ionizing Radiation Standards (IRS) group, Institute for National Measurement Standards, NRC, to develop brachytherapy standards in Canada and to provide brachytherapy calibrations to the Canadian radiation therapy community. The IRS group has undertaken the development of primary standards for brachytherapy. Using a technique similar to that employed by the French primary standards Laboratoire National Henri Becquerel (LNHB), the IRS version of the dosimetric standard realization for 192Ir will use a non-contact, indirect distance measuring method. The HDR calibration facility is under construction and should be operational in 2010. If there are no unexpected set-backs, HDR calibrations should be available in the beginning of 2011. In addition, IRS is actively searching for a Ph.D. candidate to begin development of an IRS LDR facility.

Preface

Primary activity standardisations were performed on solutions of 18F using 4πβ–γ coincidence counting and liquid scintillation counting (LSC) according to the CIEMAT/NIST method. A β+-emission probability of 96.86% was used for both methods. The various standardised 18F solutions were measured in ionisation chambers of the Physikalisch-Technische Bundesanstalt (PTB) and compared by determining radionuclide calibration factors. Already in 2001 an 18F solution had been standardised at the PTB and compared with the results of nine national metrology institutes (NMIs), using the ISOCAL IV secondary radionuclide calibrators of the National Physical Laboratory (NPL) as transfer instruments and a 68Ge check source solution. These results were linked to the International Reference System (SIR) at the Bureau International des Poids et Mesures (BIPM) by aliquots of solutions sent by the Laboratoire National Henri Becquerel (BNM-LNHB) and the NPL. Further on, in 2005, PTB sent an aliquot of an 18F solution to the SIR for ionisation chamber measurements. A value of the equivalent activity was determined and included in the key comparison database (KCDB). The recent PTB value of the equivalent activity of the SIR is in good agreement with the key comparison reference value determined from five NMIs. These results confirm that the standardisation of 18F solutions can be achieved with the accuracy required for use in nuclear medicine and, in particular, for applications in positron emission tomography (PET).

Bilateral comparison of an alanine/ESR dosimetry system at radiotherapy dose levels

To improve the signal to noise ratio and to reduce the uncertainty for Electron Spin Resonance (ESR) readout of alanine dosimeters irradiated in the dose range of 2–10 Gy, new spectrometer settings have been proposed for microwave power, modulation amplitude, conversion time, sweeps of the spectrum and orientations of the alanine pellets ( Garcia et al., 2009 ). To check the reliability of the new spectrometer settings at radiotherapy dose levels, a bilateral dose comparison in terms of absorbed dose to water was performed between the CEA LIST Laboratoire National Henri Becquerel (LNHB) and the Radiometrology Center of the China Institute of Atomic Energy (RC-CIAE). Eighteen alanine dosimeters were irradiated with 2, 5 and 10 Gy. Each dosimeter was readout with the new spectrometer settings developed within the framework of the collaboration. The results of D meas / D nom at both laboratories in the dose range of 2–10 Gy are within the tolerance limits. The maximum deviations observed are within the extended uncertainties ( k = 2).

Activity measurements of the radionuclide 111Infor the LNE–LNHB, France in the ongoing comparison BIPM.RI(II)-K1.In-111

In 2006, the Laboratoire national de métrologie et d'essais–Laboratoire national Henri Becquerel (LNE–LNHB) submitted a sample of known activity of 111In to the International Reference System (SIR). The value of the activity submitted was about 14 MBq. This provides a new result for France in the matrix of degrees of equivalence in the key comparison database that enables them to maintain their degrees of equivalence for this radionuclide. The key comparison reference value has been re-evaluated and the comparison, identifier BIPM.RI(II)-K1.In-111, now contains five valid results.Main text.To reach the main text of this paper, click on Final Report.Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCRI Section II, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Update of the BIPM.RI(II)-K1.Tc-99m comparison of activity measurements for the radionuclide 99mTc to include new results for the LNE–LNHB and the NPL

In 2007 and 2008 respectively, the Laboratoire national de métrologie et d'essais–Laboratoire national Henri Becquerel (LNE–LNHB), France and the National Physical Laboratory (NPL), UK, submitted ampoules with between 10 MBq and 130 MBq activity of 99mTc to the International Reference System (SIR), to update their results in the BIPM.RI(II)-K1.Tc-99m comparison. Together with the four other national metrology institutes (NMI) that are participants, thirteen samples have been submitted since 1983. The key comparison reference value (KCRV) has been recalculated to include the latest primary results of the PTB and the LNE–LNHB as this makes the evaluation more robust. The degrees of equivalence between each equivalent activity measured in the SIR are given in the form of a matrix for all six NMIs. A graphical presentation is also given.Main text.To reach the main text of this paper, click on Final Report.Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCRI Section II, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Activity measurements of the radionuclide 57Co for the NMIJ, Japan and the LNE–LNHB, France in the ongoing comparison BIPM.RI(II)-K1.Co-57

In 2006 and 2007, the National Metrology Institute of Japan (NMIJ) and the Laboratoire national de métrologie et d'essais–Laboratoire national Henri Becquerel (LNE–LNHB) submitted samples of known activity of 57Co to the International Reference System (SIR). The values of the activity submitted were about 1.7 MBq and 3.7 MBq respectively. The new key comparison results have replaced the previous results for Japan and France. These new results have enabled a re-evaluation of the key comparison reference value. The matrix of degrees of equivalence in the key comparison database that now contains twelve results, identifier BIPM.RI(II)-K1.Co-57, has been updated with the new results.Main text.To reach the main text of this paper, click on Final Report.Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCRI Section II, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Comparison of the standards for air kerma of the LNE–LNHB and the BIPM for 137Cs gamma radiation

A direct comparison of the standards for air kerma of the Laboratoire National de Métrologie et d'Essais–Laboratoire National Henri Becquerel (LNE–LNHB), France and of the Bureau International des Poids et Mesures (BIPM) was carried out in the 137Cs radiation beam of the BIPM in November 2008. The result, expressed as a ratio of the LNE–LNHB and the BIPM standards for air kerma, is 0.9984 with a combined standard uncertainty of 2.6 × 10−3. The result of the earlier direct comparison in 137Cs γ rays, made in 1995, was 1.0019(30); taking into account the changes made to the BIPM standard and using the present correction factors for the LNE–LNHB standard, the 1995 result becomes 0.9989(26), which is in agreement with the present comparison result.Main text.To reach the main text of this paper, click on Final Report.Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCRI Section I, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Comparison of air kerma standards of LNE–LNHB and NPL for 192Ir HDR brachytherapy sources: EUROMET project no 814

An indirect comparison has been made in the air kerma standards for high dose rate (HDR) 192Ir brachytherapy sources at the Laboratoire National Henri Becquerel (LNHB) and the National Physical Laboratory (NPL). The measurements were carried out at both laboratories between November and December 2004. The comparison was based on measurements using well-type transfer ionization chambers and two different source types, Nucletron microSelectron HDR Classic and version 2. The results show the reported calibration coefficients to agree within 0.47% to 0.63%, which is within the overall standard uncertainty of 0.65% reported by both laboratories at the time of this comparison. Following this comparison, some of the NPL primary standard correction factors were re-evaluated resulting in a change of +0.17% in the overall correction factor. The new factor was implemented in May 2006. Applying the revised chamber factor to the measurements reported in this comparison report will reduce the difference between the two standards by 0.17%.

Comparative study of two drying techniques used in radioactive source preparation: Freeze-drying and evaporation using hot dry nitrogen jets

Quantitative solid sources are used widely in the field of radionuclide metrology. With the aim to improve the detection efficiency for electrons and x-rays, a comparative study between two source drying techniques has been undertaken at LNE-Laboratoire National Henri Becquerel (LNE-LNHB, France). In this paper, freeze-drying using commercial equipment is compared with a system of drying using hot jets of nitrogen developed at Institute for Reference Materials and Measurements (IRMM, Belgium). In order to characterize the influence of self-absorption, the detection efficiencies for 51Cr sources have been measured by coincidence counting and photon spectrometry.

Activity measurements of the radionuclide 54Mn for the LNE–LNHB, France, NPL, United Kingdom and the MKEH, Hungary, in the ongoing comparison BIPM.RI(II)-K1.Mn-54

In 2006, the Laboratoire national de métrologie et d'essais–Laboratoire national Henri Becquerel (LNE–LNHB), France, the National Physical Laboratory (NPL), UK and the Magyar Kereskedelmi Engedélyezési Hivatal (MKEH), Hungary submitted samples of known activity of 54Mn to the International Reference System (SIR). The range of the activities submitted was from 480 kBq to 1530 kBq. The key comparison results for these three national metrology institutes (NMIs) have replaced their previous results in the matrix of degrees of equivalence in the key comparison database that contains eleven results, identifier BIPM.RI(II)-K1.Mn-54.Main text.To reach the main text of this paper, click on Final Report.Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCRI Section II, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Activity measurements of the radionuclide 201Tl for the LNE–LNHB, France, PTB, Germany and the NPL, UK in the ongoing comparison BIPM.RI(II)-K1.Tl-201

In 2005, the Laboratoire national de métrologie et essais–Laboratoire national Henri Becquerel (LNE–LNHB) and the Physikalisch-Technische Bundesanstalt (PTB) each submitted a sample of known activity of 201Tl to the International Reference System (SIR). In 2006, the National Physical Laboratory (NPL) submitted their first sample. The range of values of the activity submitted was between 2 MBq and 63 MBq. These key comparison results have been included in the re-evaluated key comparison reference value and replaced the previous results for France and Germany in the matrix of degrees of equivalence in the key comparison database that now contains seven results, identifier BIPM.RI(II)-K1.Tl-201.Main text.To reach the main text of this paper, click on Final Report.Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCRI Section II, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

63Ni, its half-life and standardization: Revisited

Recent liquid scintillation (LS) measurements at the National Institute of Standards and Technology (NIST) and at the Laboratoire National Henri Becquerel (LNHB) on a standardized 63Ni solution that has been tracked for nearly 40 years have resulted in several important findings: (i) a 63Ni half-life value of 101.2±1.5 a has been determined with the present decay data. This value is consistent with a previous specific activity determination and with an earlier value from decay measurements; and it appears to be more satisfactory than a recent data evaluator's recommended value of 98.7 a. (ii) All solution standards of 63Ni as disseminated by NIST for the past 38 + years are internally consistent with past and recent standardizations. (iii) Primary LS standardizations of 63Ni by the triple-to-double coincidence ratio (TDCR) method and by CIEMAT/NIST 3H-standard efficiency tracing (CNET) appear to be comparable, although the latter methodology is believed to be inherently inferior. (iv) There is excellent measurement agreement between NIST and LNHB for 63Ni primary standardizations.

Some specific features of ionization chamber calibrations in linac x-ray beams at the LNE-LNHB

The purpose of this note is to give some details about the modus operandi employed today to calibrate ionization chambers in radiotherapy linac photon beams at the Laboratoire National Henri Becquerel (LNE-LNHB). Some specific features are described: first the equipment (including the external monitoring ionization chambers), second the calculations of the profile or radial non-uniformity correction factors (up to 0.5% effect for commonly used ionization chambers) and finally the calculations to get the calibration coefficients for customer beam qualities.

Activity standardisation of 18F and ionisation chamber calibration for nuclear medicine

Primary activity standardisations were performed on solutions of (18)F using 4pibeta-gamma coincidence counting and liquid scintillation counting (LSC) according to the CIEMAT/NIST method. A beta(+)-emission probability of 96.86% was used for both methods. The various standardised (18)F solutions were measured in ionisation chambers of the Physikalisch-Technische Bundesanstalt (PTB) and compared by determining radionuclide calibration factors. Already in 2001 an (18)F solution had been standardised at the PTB and compared with the results of nine national metrology institutes (NMIs), using the ISOCAL IV secondary radionuclide calibrators of the National Physical Laboratory (NPL) as transfer instruments and a (68)Ge check source solution. These results were linked to the International Reference System (SIR) at the Bureau International des Poids et Mesures (BIPM) by aliquots of solutions sent by the Laboratoire National Henri Becquerel (BNM-LNHB) and the NPL. Further on, in 2005, PTB sent an aliquot of an (18)F solution to the SIR for ionisation chamber measurements. A value of the equivalent activity was determined and included in the key comparison database (KCDB). The recent PTB value of the equivalent activity of the SIR is in good agreement with the key comparison reference value determined from five NMIs. These results confirm that the standardisation of (18)F solutions can be achieved with the accuracy required for use in nuclear medicine and, in particular, for applications in positron emission tomography (PET).

Editorial summary of the EXRS 2006 conference

The 12th European X-ray Spectrometry Conference was held between June 19 and 23, 2006, in Paris, France. The organizers were the Laboratoire National Henri Becquerel, CEA, and the Ecole Normale Sup ´ erieure de Lyon, CNRS. The venue of the conference was the Cite Internationale Universitaire, the famous complex of the Universite de Paris built between the two World Wars as an international meeting ground for knowledge and peace. The 35-ha park surrounding the Maison Internationale, which hosted the meeting, is a place for students from over 125 nations to get together, and is spread out among 37 turn-of-the-century residences.

Activity measurements of the radionuclide 124Sbby the LNE–LNHB, France as a pilot study for the ongoing comparison BIPM.RI(II)-K1.Sb-124

In 2005, the Laboratoire national de métrologie et d'essais – Laboratoire national Henri Becquerel (LNE–LNHB) submitted a sample of known activity of 124Sb to the International Reference System (SIR) in the frame of a pilot study. The value of the activity submitted was about 5.9 MBq. The comparison result shows agreement within the standard uncertainty with the published result for France in the key comparison identified as BIPM.RI(II)-K1.Sb-124.Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCRI.

Comparison of dosimetric standards of USA and France for HDR brachytherapy

A bilateral comparison of national dosimetric standards for high dose rate brachytherapy has been conducted between the Laboratoire National Henri Becquerel and the University of Wisconsin Accredited Dosimetry Calibration Laboratory. A complete overview of the methods that are currently in use to establish the two national standards is given. The comparison has been carried out using well-type transfer ionization chambers. Three units have been calibrated in both laboratories, and calibration coefficients have been compared. The discrepancies between the two measurements are within 0.3%.

Comparison of the standards for absorbed dose to waterof the BNM-LNHB and the BIPM for 60Co γ rays

A comparison of the standards for absorbed dose to water of the Bureau National de Métrologie – Laboratoire National Henri Becquerel (BNM-LNHB), Saclay, France and of the Bureau International des Poids et Mesures (BIPM) has been made in 60Co radiation under the auspices of the key comparison BIPM.RI(I)-K4. The comparison result expressed as a ratio of the BNM-LNHB and the BIPM standards for absorbed dose to water is 0.9970 (0.0053). The degrees of equivalence between the BNM-LNHB and the other participants in this comparison have been calculated and the results are given in the form of a matrix for the 12 national metrology institutes (NMIs) that have taken part in the ongoing comparison for absorbed dose to water. A graphical presentation is also given.Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by Section I of the Consultative Committee for Ionizing Radiation (CCRI(I)), according to the provisions of the Mutual Recognition Arrangement (MRA).