The tolerance of proton radiotherapy — preliminary results

Introduction. Because the specific proton beam dose distribution (i.e. the so-called ’Bragg curve’), proton radiotherapy ensures that the high-dose region is precisely confined to the target volume while minimizing the dose delivered to healthy tissues/critical organs surrounding the tumour or to those lying in the path of the proton beam. This method has been used for patients in Kraków since November 2016. Aim. To report the early tolerance outcomes to proton radiotherapy in patients completing their treatment just before the end of August 2017. Materials and methods. Study subjects were 47 patients who had completed their treatment before the end of August 2017 with a mean age of 41.6 years (range: 16–76, median: 40). The most frequent diagnoses were skull base tumours (22 pts. — 46.8%) and brain G1 or G2 gliomas (17 pts. — 36.2%), whereas the most frequent histological types were chordomas (17 pts. — 36.2%). Proton radiotherapy was administered by pencil beam scanning and consisted of using the intensity modulated proton therapy (IMPT) technique. The total dose given per cancer type averaged as follows: (i) 70 and 74 Gy(RBE), for respectively chodrosarcomas and chordomas, (ii) 54 Gy(RBE) for brain gliomas and (iii) 70 Gy(RBE) for paranasal sinuses tumours. Early tolerance was prospectively evaluated and measured according to the CTCAE scale, version 4.03. Results. In all, 91 side effects (SE) were recorded in 44 patients. The intensity of SEs were as following: 62 SEs (68.1%) were of grade 1 intensity, 21 SEs (23.1%) were of grade 2 and 8 SEs (8.8%) were of grade 3. The most frequently developed SEs were skin reactions (29 pts. — 61.7%) or oral/pharyngeal mucositis (20 pts. — 42.6%). Because the patient follow-up period was short, presented results only describes the early tolerance to this therapy. Our findings of mild intensities for the most early side effects, at (grades 1 or 2) are consistent with other published studies

The tolerance of proton radiotherapy — preliminary results

Introduction. Because the specific proton beam dose distribution (i.e. the so-called ’Bragg curve’), proton radiotherapy ensures that the high-dose region is precisely confined to the target volume while minimizing the dose delivered to healthy tissues/critical organs surrounding the tumour or to those lying in the path of the proton beam. This method has been used for patients in Kraków since November 2016. Aim. To report the early tolerance outcomes to proton radiotherapy in patients completing their treatment just before the end of August 2017. Materials and methods. Study subjects were 47 patients who had completed their treatment before the end of August 2017 with a mean age of 41.6 years (range: 16–76, median: 40). The most frequent diagnoses were skull base tumours (22 pts. — 46.8%) and brain G1 or G2 gliomas (17 pts. — 36.2%), whereas the most frequent histological types were chordomas (17 pts. — 36.2%). Proton radiotherapy was administered by pencil beam scanning and consisted of using the intensity modulated proton therapy (IMPT) technique. The total dose given per cancer type averaged as follows: (i) 70 and 74 Gy(RBE), for respectively chodrosarcomas and chordomas, (ii) 54 Gy(RBE) for brain gliomas and (iii) 70 Gy(RBE) for paranasal sinuses tumours. Early tolerance was prospectively evaluated and measured according to the CTCAE scale, version 4.03. Results. In all, 91 side effects (SE) were recorded in 44 patients. The intensity of SEs were as following: 62 SEs (68.1%) were of grade 1 intensity, 21 SEs (23.1%) were of grade 2 and 8 SEs (8.8%) were of grade 3. The most frequently developed SEs were skin reactions (29 pts. — 61.7%) or oral/pharyngeal mucositis (20 pts. — 42.6%). Because the patient follow-up period was short, presented results only describes the early tolerance to this therapy. Our findings of mild intensities for the most early side effects, at (grades 1 or 2) are consistent with other published studies.

APPLICATION OF IMAGE ANALYSIS METHODS FOR ISOCENTER QUALITY ASSURANCE IN RADIOTHERAPY

One of the major procedures for testing the geometrical accuracy of devices used in radiotherapy treatments is the test of the geometrical position of the radiation isocenter. The importance of the test reflects the fact that geometrical position of the radiation isocenter generally affects the tumor targeting. At present the geometric accuracy is assessed with the Winston-Lutz test which checks the position of an image of a ball marker with the respect to the center of the radiation field as projected on a detector plane. Obviously, determination of coordinates of a single marker is not sufficient to fully account for a complicated geometry of a therapeutic device. The purpose of the study was to design a new image analysis tool to better determine the isocenter. The proposed automated procedure for determining isocenter position uses projection data acquired for a special cube phantom. The projection images of a phantom are acquired for various angles of rotation of the gantry. A procedure is proposed to extract some geometric characteristics of a therapeutic device from the projection images

APPLICATION OF IMAGE ANALYSIS METHODS FOR ISOCENTER QUALITY ASSURANCE IN RADIOTHERAPY

One of the major procedures for testing the geometrical accuracy of devices used in radiotherapy treatments is the test of the geometrical position of the radiation isocenter. The importance of the test reflects the fact that geometrical position of the radiation isocenter generally affects the tumor targeting. At present the geometric accuracy is assessed with the Winston-Lutz test which checks the position of an image of a ball marker with the respect to the center of the radiation field as projected on a detector plane. Obviously, determination of coordinates of a single marker is not sufficient to fully account for a complicated geometry of a therapeutic device. The purpose of the study was to design a new image analysis tool to better determine the isocenter. The proposed automated procedure for determining isocenter position uses projection data acquired for a special cube phantom. The projection images of a phantom are acquired for various angles of rotation of the gantry. A procedure is proposed to extract some geometric characteristics of a therapeutic device from the projection images

Effect of Fiber Reinforcement on the Compression and Flexural Strength of Fiber-Reinforced Geopolymers

This work aimed to determine the effect of the addition of different types of reinforcing fibers on the strength properties of geopolymers such as flexural and compressive strength. Geopolymers are an attractive alternative to conventional binders and building materials; however, one of the main problems of their widespread use is their low resistance to brittle fracture. To improve the mechanical properties, reinforcement in the form of glass, carbon, and basalt fibers (as grids) was applied to geopolymers in the following work. Additionally, composites with these fibers were produced not only in the matrix of pure geopolymer but also as a hybrid variant with the addition of cement. Furthermore, basalt grids were used as reinforcement for geopolymers not only based on ash but also metakaolin. An additional variable used in the study was the molar concentration of the alkali solution (5 M and 10 M) for the different types of geopolymer samples. The mechanical properties of geopolymer materials and geopolymer–cement hybrids are the highest when reinforcement in the form of carbon fiber is used. Strength values for geopolymers reinforced with basalt mats depend on the number of reinforcement layers and the concentration of the alkaline solution used. All produced composites were tested for compressive strength and bending strength. When using basalt mesh, it was possible to achieve a bending strength of 12 MPa. The highest compressive strength that was achieved was the value of 66 MPa, while for samples not reinforced with fibers, only about 40 MPa was achieved

Clinical simulations of prostate radiotherapy using BOMAB-like phantoms: Results for photons

Workshop on dosimetry for second cancer risk estimation; EURADOS annual meeting 2012; Vienna (Austria); 6-10 Feb 2012International audienceIn this part of work carried out by Working Group 9 (Radiation Protection Dosimetry in Medicine) of the European Radiation Dosimetry Group (EURADOS), water tank experiments described in this issue (Bordy et al., 2013) were extended to a BOMAB-like phantom. This phantom is more clinically realistic than a water tank, sufficiently to allow the simulation of some clinical treatments. In the experiments to be described, four types of prostate treatment were simulated: Volumetric Modulated Arc Therapy (VMAT, 6 MV), Tomotherapy (6 MV), IMRT (6 MV and 18 MV), 5-field conformal radiotherapy (15 MV) and 4-field conformal radiotherapy (6 MV and 18 MV). Irradiations were performed in two centres, University Hospital of Santa Chiara, Pisa, Italy and Centre of Oncology M. Skłodowska-Curie Memorial Institute, Krakow, Poland. Whatever the difficulties and uncertainties in risk estimation, its foundation lies in the knowledge of the absorbed dose to the irradiated organs. Thus the measurement of out-of-field doses is a crucial pre-requisite for risk estimation and is the subject of the EURADOS Working Group 9. For photon out-of-field dose measurements TLD, OSL and RPL dosimeters were used. Comparison of dosimeters under the same irradiation conditions showed that dosimeters generally agreed to within 3% compared with ion chamber reference measurements. Other comparisons were possible with these data. They include a comparison of doses (beam profiles) in different positions in the BOMAB phantom, a comparison of different treatment modalities in the two contributing clinical centres (Pisa and Krakow) and a comparison of dose profiles resulting from the different treatment techniques and the corresponding doses calculated by the treatment planning systems used to generate the treatment plans. Finally, preliminary measurements of surface doses at selected points on the trunk of the BOMAB phantom were made using diode detectors. Comparison of out-of-field doses for different modalities in the two clinical centres shows that differences in out-of-field doses for the same Planning Treatment Volume (PTV) can be even a factor of 4. For sparing adjacent organs-at-risk the best results were obtained for IMRT. On the other hand the lowest out-of-field doses were for MLC conformal therapy