Development of a new method to characterize low-to-medium energy X-ray beams (E≤150 keV) used in dosimetry
Description
In the field of dosimetry, the knowledge of the whole photon fluence spectrum is an essential parameter. In the low-to-medium energy range (i.e. E≤150 keV), the LNHB possess 5 X-ray tubes and iodine-125 brachytherapy seeds, both emitting high fluence rates. The performance of calculation (either Monte Carlo codes or deterministic software) is flawed by increasing uncertainties on fundamental parameters at low energies, and modelling issues. Therefore, direct measurement using a high purity germanium is preferred, even though it requires a time-consuming set-up and mathematical methods to infer impinging spectrum from measured ones (such as stripping, model-fitting or Bayesian inference). Concerning brachytherapy, the knowledge of the seed's parameters has been improved. Moreover, various calculated X-ray tube fluence spectra have been compared to measured ones, after unfolding. The results of all these methods have then be assessed, as well as their impact on dosimetric parameters. (author)
Abstract (French)
En dosimetrie, la distribution energetique des photons emis par une source constitue un parametre incontournable. Dans la gamme des basses et moyennes energies (i.e. E≤150 keV ici), le LNHB possede 5 tubes a rayons X ainsi que des grains de curietherapie a l'iode 125, presentant des hauts debits de fluence. La determination du spectre emis par calcul (deterministe ou Monte-Carlo) est limitee, dans la gamme d'energie consideree, par les incertitudes elevees sur les bases de donnees ainsi que par les approximations du modele. La mesure directe avec un detecteur au germanium ultra-pur a donc ete retenue, bien que necessitant de lourds moyens. De plus, le spectre mesure est le produit de convolution du spectre emis recherche par la reponse du systeme. Une fois la reponse du detecteur modelisee, il est possible de 'deconvoluer' la mesure, i.e. de remonter au spectre reellement emis en corrigeant (par stripping, model-fitting, inference bayesienne) les deformations spectrales induites par le processus de detection. Pour la curietherapie, le modele de grain-source a ainsi pu etre ajuste. Pour les tubes a rayons X, les resultats obtenus avec differents codes Monte-Carlo et 4 logiciels deterministes ont ete compares a un spectre dit de reference obtenu par mesure et deconvolue. Ainsi l'impact sur certaines grandeurs dosimetriques de la methode utilisee a pu etre quantifie
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Additional details
Additional titles
- Original title (French)
- Developpement d'une methode de caracterisation spectrale des faisceaux de photons d'energies inferieures a 150 keV utilises en dosimetrie
Identifiers
Publishing Information
- Imprint Pagination
- 213 p.
- Report number
- FRCEA-TH--6824
INIS
- Country of Publication
- France
- Country of Input or Organization
- France
- INIS RN
- 47013535
- Subject category
- S61: RADIATION PROTECTION AND DOSIMETRY;
- Resource subtype / Literary indicator
- Thesis
- Descriptors DEI
- BRACHYTHERAPY; DOSIMETRY; GERMANIUM; MONTE CARLO METHOD; RADIATION PROTECTION; SEEDS; SPECTRA UNFOLDING; X RADIATION; X-RAY TUBES
- Descriptors DEC
- CALCULATION METHODS; DATA PROCESSING; ELECTROMAGNETIC RADIATION; ELECTRON TUBES; ELEMENTS; EQUIPMENT; IONIZING RADIATIONS; MEDICINE; METALS; NUCLEAR MEDICINE; PROCESSING; RADIATIONS; RADIOLOGY; RADIOTHERAPY; THERAPY; X-RAY EQUIPMENT
Optional Information
- Notes
- 156 refs.; Available from the INIS Liaison Officer for France, see the 'INIS contacts' section of the INIS-NKM website for current contact and E-mail addresses: http://www.iaea.org/inis/Contacts/; Also available from Service Commun de la Bibliotheque, 15 Rue Georges Clemenceau, 91400 Orsay (France)