Personalized pretreatment QA for intracranial stereotactic treatments using gel dosimetry and 3D printing of phantom: A feasibility study - IRSN - Institut de radioprotection et de sûreté nucléaire Accéder directement au contenu
Communication Dans Un Congrès Année : 2019

Personalized pretreatment QA for intracranial stereotactic treatments using gel dosimetry and 3D printing of phantom: A feasibility study

Résumé

Introduction.In stereotactic radiotherapy, pretreatment patient-specific quality controls (PSQA) are performed on generic phantoms to check the agreement between the dose calculated by the treatment planning system (TPS) and the measured dose by a point or 2D detector. For those controls, gel dosimetry seems a promising technique as it presents several advantages compared with conventional dosimeters such as 3D absolute dose determination with high spatial resolution [1]. Thus, we investigated the feasibility of gel dosimetry in combination with a patient-based 3D printed phantom for personalized PSQA. Methods. CT images of a patient treated by intracranial stereotactic radiotherapy were processed to generate a STL file. Phantom was 3D printed at scale 1:1 using an Ultimaker 3 extended 3D printer. The phantom consisted in a 1.2mm thick wall made of PET and the nose was printed separately to be used as a plug. This phantom filled with water includes a cylindrical insert at the target location to place a radiochromic gel jar. It was scanned with the patient’s stereotactic mask and the patient plan was recalculated using the phantom CT on the iPlan TPS (BrainLab). The radiochromic gels were manufactured and calibrated according to a protocol developed at IRSN [2]. One treatment fraction was delivered on the phantom with the gel in place using a Novalis TrueBeam STX accelerator. Gels were optically read following the protocol and data analysis was performed using MatLab. Results. A good agreement is found between the dose distribution measured with the gel and calculated with the TPS. For a coronal slice at the center of the gel dosimeter, the local 2D 3 mm-3% gamma-index was evaluated within the central 85% of the cylinder diameter. The gamma passing rate reaches 86.5%. In the same region, the local 3D 3 mm-3% gamma-index passing rate is 95.2%. Within the central 85% of the cylinder volume, 87.2% and 96.2% of points pass the local 2 mm-2% and the global 1 mm-2% gamma-index 3D respectively. Conclusions. This study presents promising results for personalized PSQA for stereotactic radiotherapy and this work could be extended to end-to-end tests. Other cases are currently investigated in order to benchmark the methods and the reproducibility of the measurement protocol.
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Dates et versions

irsn-04343868 , version 1 (14-12-2023)

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J. Colnot, S. Chiavassa, G. Delpon, Christelle Huet. Personalized pretreatment QA for intracranial stereotactic treatments using gel dosimetry and 3D printing of phantom: A feasibility study. 58èmes Journées Scientifiques de la Société Française de Physique Médicale, Jun 2019, Angers, France. pp.12, ⟨10.1016/j.ejmp.2019.09.100⟩. ⟨irsn-04343868⟩

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