Development of a 3D dosimetric method by gel and optical readout for the implementation of end-to-end quality assurance in stereotactic radiotherapy
Description
Modern external radiotherapy techniques, such as stereotactic radiotherapy which uses small radiation beams, enable to deliver precisely high doses to the tumor, while sparing adjacent healthy tissues. However, this improvement goes with increasing complexity of the treatment plans delivered and it is, therefore, necessary to ensure the safety of these treatments through adapted quality assurance. End-to-end quality assurance is a unique tool to test the whole treatment chain encountered by patients in hospitals. Dosimetric gels, which are still in the research stage, could enable a better implementation of this type of quality assurance as they are currently the only dosimeters able of measuring 3D dose distributions with high spatial resolution. Fricke-Xylenol orange-Gelatin (FXG) gel read by optical computed tomography has already been used in the literature to perform end-to-end quality assurance, however on a dose range restricted to 4 Gy, which is not adapted to stereotactic treatments. In this study, the composition of the FXG gel has been optimized and a dual-wavelength reading method has been developed in order to span an absorbed dose range representative of stereotactic treatments (0.25 - 10 Gy). This method has been characterized and validated in small irradiation fields. Then, end-to-end quality assurance tests have been implemented in a clinical setting for the treatment of intracranial tumors by stereotactic radiotherapy on the Novalis TrueBeam STx (Varian) and the CyberKnife (Accuracy) accelerators. The planned and measured dose distributions have been compared using different analysis tools, such as gamma-index and superposition of isodose curves, dose profiles and dose-volume histograms. Point and planar measurements with other dosimeters have also been performed to extend this comparison. The results obtained have shown that the 3D end-to-end quality assurance method using FXG gel and dual-wavelength optical readout is accurate, appropriated for stereotactic radiotherapy and provides additional information to the quality assurance currently performed in clinical routine with more conventional dosimetric methods. (author)
Abstract (French)
Les techniques modernes de radiotherapie externe, telles que la radiotherapie stereotaxique qui utilise des petits faisceaux d'irradiation, permettent aujourd'hui de delivrer precisement de fortes doses a la tumeur tout en epargnant les tissus sains adjacents. Cette amelioration s'accompagne cependant d'une complexification des plans de traitement delivres. Il est alors necessaire de securiser les traitements par la mise en place de controles qualite adaptes a ces nouvelles techniques. Parmi ceux-ci, les controles qualite end-to-end permettent de tester l'ensemble de la chaîne de traitement rencontree par les patients a l'hopital. Les gels dosimetriques, encore a l'etat de recherche, pourraient permettre une meilleure mise en place de ce type de controles car ils sont actuellement les seuls dosimetres capables de mesurer des distributions de dose en 3D avec une haute resolution spatiale. Le gel Fricke-Xylenol orange-Gelatin (FXG) associe a une lecture par tomographie optique a deja ete utilise dans la litterature pour realiser des controles qualite end-to-end, cependant sa gamme de dose d'utilisation etait limitee a 4 Gy et ne permettait pas son utilisation pour des applications stereotaxiques. Dans cette etude, la composition du gel FXG a ete optimisee et une methode de double lecture optique a ete developpee afin d'envisager l'utilisation de cette methode dosimetrique sur une gamme de dose representative des traitements stereotaxiques ([0,25 ; 10] Gy). Cette methode a ete caracterisee et validee dans des petits champs d'irradiation. Plusieurs controles qualite end-to-end ont ensuite ete mis en place en milieu clinique pour le traitement de tumeurs intracraniennes par stereotaxie sur les accelerateurs Novalis TrueBeam STx (Varian) et CyberKnife (Accuray). Les distributions de dose mesurees par gel et celles planifiees ont ete comparees en utilisant differents outils d'analyse tels que le gamma-index et la superposition de courbes isodoses, de profils de dose et d'histogrammes dose-volume. Des mesures ponctuelles et planaires avec d'autres dosimetres ont aussi ete effectuees pour completer cette comparaison. Les resultats obtenus ont montre que la methode de controle qualite 3D end-to-end par gel FXG et double lecture optique est precise, adaptee a la radiotherapie stereotaxique et apporte des informations supplementaires aux controles qualite actuellement effectues en routine clinique avec des methodes dosimetriques plus conventionnelles
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Additional details
Additional titles
- Original title (French)
- Developpement d'une methode de dosimetrie 3D par gel avec lecture optique pour la mise en place de controles qualite end-to-end en radiotherapie stereotaxique
Publishing Information
- Imprint Pagination
- 164 p.
- Report number
- FRCEA-TH--16206
INIS
- Country of Publication
- France
- Country of Input or Organization
- France
- INIS RN
- 54091822
- Subject category
- S62: RADIOLOGY AND NUCLEAR MEDICINE;
- Resource subtype / Literary indicator
- Thesis
- Descriptors DEI
- COMPUTERIZED TOMOGRAPHY; DOSE RATES; DOSIMETRY; IMAGE SCANNERS; IONIZING RADIATIONS; NEOPLASMS; OPTICAL EQUIPMENT; QUALITY ASSURANCE; RADIOACTIVITY; RADIOTHERAPY
- Descriptors DEC
- DIAGNOSTIC TECHNIQUES; DISEASES; EQUIPMENT; MANAGEMENT; MEDICINE; NUCLEAR MEDICINE; QUALITY MANAGEMENT; RADIATIONS; RADIOLOGY; THERAPY; TOMOGRAPHY
Optional Information
- Notes
- 109 refs.; Available from the INIS Liaison Officer for France, see the INIS website for current contact and E-mail addresses