Presenter of 1 Presentation
SPATIALLY FRACTIONATED PROTON THERAPY OF EYE CANCER - FEASIBILITY STUDIES
Abstract
Background and Aims
In hypofractionated proton therapy of eye melanoma (4x15 Gy(RBE)) the eyelid should be shifted from the treatment field to avoid strong skin reactions. It is usually painful for the patient and sometimes even not possible for anatomical reasons. The aim of these studies was to demonstrate the dosimetric feasibility of spatially fractionated proton therapy (SFPT) of eye with the closed eyelid. The proton beam is formed using a mesh collimators. The potential benefit of SFPT is better regeneration of microvascular structures of the irradiated eyelid.
Methods
Within the work the mesh-grid brass collimator and the dedicated range modulator were designed to obtain uniform Spread-Out Bragg Peak (SOBP) within the target volume. The system was verified at the proton eye therapy facility at IFJ PAN. The dose depth distributions was measured using Markus ionization chamber in the water phantom. Lateral profile has been determined in PMMA slab phantom using 2-D (LiF:Mg,Cu,P) thermoluminescent foils and the ProBImS scintillator system with a CCD camera.
Results
Peak-to-Valley-Dose-Ratio (PVDR) at the region of collimator was varying between 3 to 5 but due to the proton scattering the dose distribution at the depth of the tumor (15-29 mm) was practically uniform.
Conclusions
The studies demonstrated that it is possible to form the proton beam to perform the SFTP treatment of eye melanoma through the closed eyelid.
The study was partially supported by the Horizon 2020 project INSPIRE Grant No. 730983.
Author Of 3 Presentations
SPATIALLY FRACTIONATED PROTON THERAPY OF EYE CANCER - FEASIBILITY STUDIES
Abstract
Background and Aims
In hypofractionated proton therapy of eye melanoma (4x15 Gy(RBE)) the eyelid should be shifted from the treatment field to avoid strong skin reactions. It is usually painful for the patient and sometimes even not possible for anatomical reasons. The aim of these studies was to demonstrate the dosimetric feasibility of spatially fractionated proton therapy (SFPT) of eye with the closed eyelid. The proton beam is formed using a mesh collimators. The potential benefit of SFPT is better regeneration of microvascular structures of the irradiated eyelid.
Methods
Within the work the mesh-grid brass collimator and the dedicated range modulator were designed to obtain uniform Spread-Out Bragg Peak (SOBP) within the target volume. The system was verified at the proton eye therapy facility at IFJ PAN. The dose depth distributions was measured using Markus ionization chamber in the water phantom. Lateral profile has been determined in PMMA slab phantom using 2-D (LiF:Mg,Cu,P) thermoluminescent foils and the ProBImS scintillator system with a CCD camera.
Results
Peak-to-Valley-Dose-Ratio (PVDR) at the region of collimator was varying between 3 to 5 but due to the proton scattering the dose distribution at the depth of the tumor (15-29 mm) was practically uniform.
Conclusions
The studies demonstrated that it is possible to form the proton beam to perform the SFTP treatment of eye melanoma through the closed eyelid.
The study was partially supported by the Horizon 2020 project INSPIRE Grant No. 730983.
PRELIMINARY RESULTS OF DOSIMETRY AUDIT OF ACTIVE SCANNING PROTON BEAMS
Abstract
Background and Aims
Seven proton therapy centers collaborating within INSPIRE project participated in the mailed dosimetry audit of proton therapy treatment units utilizing spot scanning beams organized by EURADOS WG9 'Radiation dosimetry in radiotherapy'.
Methods
Prototype assembly for positioning the detectors in the water phantom has been developed and tested during simultaneous irradiation at IFJ PAN in Krakow and PTC in Prague in June 2020. Alanine, radiophotoluminescent and thermoluminescent detectors from five European institutes have been irradiated with 10 x 10 cm2 single layer field and 10 x 10 x 10 cm3 plan.
Results
Very good agreement between the two centers has been obtained for alanine, RPL and TL detectors. Based on the results of the initial experimental campaign, the assembly for detector positioning has been modified. As a next step, one assembly for each participating center has been produced including the corresponding number of water-proof detector holders. In the frame of INSPIRE join research activity, audit manuals, detectors and holder assemblies were distributed to participating centers. Audit irradiations took place in all centers during March-April 2021.
Conclusions
The obtained results provide an indication of dosimetric agreement between centers and bases for definition of standardization procedures in dosimetry of active scanning proton beams. After a successful initial experience, mailed audit of scanning proton beams may become a part of clinical routine helping in standardization of active proton beam dosimetry.
This work was partially supported from the European Union's H2020 Research and Innovation Programme, under Grant Agreement No: 730983 (INSPIRE project).
IN VITRO MEASUREMENTS OF PROTON RBE: A MULTI-CENTRIC COMPARISON OF EXPERIMENTAL PROCEDURES AND RESULTS
Abstract
Background and Aims
We present the current status and outcomes of the joint radiobiological experiment performed at eight European proton therapy centers or research institutes. The study aims to spot the potential differences in the in vitro proton RBE values measured by different groups sharing a similar setup and identify its causes.
Methods
A phantom and a protocol for sample preparation and post-processing are shared among the participants to ensure minimal differences in the biological part of the experimental procedure. In this phantom, V79 cells grow on the polyester slides that can be inserted at different depths, which enables their simultaneous irradiation at multiple positions within the radiation field. The setup is irradiated with proton beams with two SOBP configurations (6 cm, 6 Gy, and 4 cm, 8 Gy), followed by the reference photon irradiation (LINAC or x-ray), and the biological effect is evaluated using a colony-forming assay.
Results
The study is still ongoing, and the spread of data for measured cell survival is yet to be evaluated. However, some non-obvious differences in the experimental procedures and setups are already revealed, e.g. post-processing timing or varying dose distributions in the beam plateau/fall-off regions.
Conclusions
As an outcome of the experiment, we plan to summarize the details of the experimental procedure for biological experiments with proton beams, differing between the centers across Europe. Accounting for these details would help to harmonize future studies in the field.
This work was supported by EU Horizon2020 grant 730983 (INSPIRE).