Abstract
We evaluate the impact of an air gap and optimization of this air gap for the MP512 silicon detector array when operated in dosimetry mode for small photon field measurements in solid water. We present output factor measurements for 6MV and 10 MV photon beams with the square field sizes ranging from 0.5 to 10 cm2. The size of the air gap above the MP512 detector was changed from 0.5, 1.0, 1.2, 2.0 and 2.6 mm. We compare the output factors measurements of the MP512 with EBT3 film and the MOSkin dosimeter. For the two photon energies investigated, we find that the output factor measured by the MP512 reduce with increasing air gap and reducing of field size. The reduction in output factor is most pronounced for the 0.5 and 1 cm2 field sizes. The air gap of 0.5 mm and 1.2 mm showed good agreement with the EBT3 film and MOSkin output factor for 6 and 10 MV photon fields, respectively. The negligible effect on dosimetry for the field sizes larger than 4x4 cm2 demonstrates that the electronic disequilibrium caused by small air gap only influences the dosimetry measurements for small fields. The study shows that the output factor reduction is enhanced by increasing of air gap and demonstrates that the optimal air gap for the MP512 at 6 and 10 MV photon fields is 0.5mm.
Highlights
Modern radiation treatment techniques such as Stereotactic Radiosurgery (SRS) and Stereotactic Body Radiation Therapy (SBRT) are increasingly being used in cancer treatment
We evaluate the impact of an air gap and optimization of this air gap for the Magic Plate 512 (MP512) silicon detector array when operated in dosimetry mode for small photon field measurements in solid water
For small field sizes (0.5 and 1 cm2) at 6 MV, the MP512 measured output factor reduces with increasing air gap above the detector
Summary
Modern radiation treatment techniques such as Stereotactic Radiosurgery (SRS) and Stereotactic Body Radiation Therapy (SBRT) are increasingly being used in cancer treatment. Large doses per fraction of SRS/SBRT are delivered in small photon radiation fields leading to steep dose gradients, Quality assurance (QA) is needed to ensure that the delivered dose matches the plan dose distribution [1]. Current commercial dosimetric QA tools for SRS/SBRT include ionization chambers, used for point dose measurements, as well as two-dimensional diode arrays and pixelated ionization chamber arrays. ArcCHECK (Sun Nuclear, Melbourne, FL) contain an array of 1386 diodes distributed in a cylindrical acrylic phantom. The Delta (ScandiDos, Uppsala, Sweden), which consist of 1069 silicon diodes in a crossed array inside a cylindrical polymethylmethacrylate (PMMA) phantom, requires the recalculation of the dose on a CT scan phantom for the verification procedure. In small irradiation field dose delivery via SRS and SBRT, the QA procedure needs
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
