Wiener filter applied with a multi-channel method for EBT2 film dosimetry

2016 ◽  
Vol 33 (6) ◽  
pp. 1742-1752
Author(s):  
Liyun Chang ◽  
Yi-Chun Du
Keyword(s):  
Radiation Therapy ◽  
Spatial Resolution ◽  
High Spatial Resolution ◽  
Wiener Filter ◽  
Content Type ◽  
Depth Dose ◽  
Dosimetry System ◽  
A New Technique ◽  
Ebt2 Film ◽  
Mc Method

Purpose – EBT2 film, a convenient quality assurance (QA) tool with high 2D dosimetry resolution, has been widely used in the dosimetry application of radiation therapy with lots of benefits especially its self-development, water equivalent, energy independent and high spatial resolution. However, the higher inhomogeneity between the pixels of EBT2 image, needed to be averaged out according to the traditional method, but it could sacrifice the spatial resolution. To solve this problem, the purpose of this paper is to introduce a Wiener filter (WF) technique applied with a multi-channel (MC) method. Design/methodology/approach – The EBT2 film was calibrated by using the percentage depth dose method combined with the WF technique and a MC method. Then the calculated film doses were compared with the measurement doses by the edge detector with the water phantom. Findings – With high spatial resolution to be 0.2 mm, the results demonstrate that the EBT2 film calibration through both of the WF technique and MC method has higher accuracy (within 2 percent) and lower uncertainty. Originality/value – A new technique of WF with MC method was presented to calibrate the dosimetry system of EBT2 film. With high spatial resolution (0.2 mm), the studies show that the combination of WF technique with MC method can have high accuracy with low noises to calibrate EBT2 film. This method can also be applied to all the QAs of treatment planning of radiation therapy by using the EBT2 film.

SU-E-T-244: High Spatial Resolution EBT2 Film Dosimetry

2012 ◽  
Vol 39 (6Part13) ◽  
pp. 3759-3759
Author(s):  
D Poppinga ◽  
A Schoenfeld ◽  
B Poppe ◽  
N Chofor
Keyword(s):  
Spatial Resolution ◽  
High Spatial Resolution ◽  
Film Dosimetry ◽  
Ebt2 Film

Synchrotron X-ray microbeam dosimetry with a 20 micrometre resolution scintillator fibre-optic dosimeter

2018 ◽  
Vol 25 (3) ◽  
pp. 826-832 ◽  
Author(s):  
James Archer ◽  
Enbang Li ◽  
Marco Petasecca ◽  
Andrew Stevenson ◽  
Jayde Livingstone ◽  
...  
Keyword(s):  
Radiation Therapy ◽  
Spatial Resolution ◽  
Light Signal ◽  
External Beam Radiation ◽  
Probe Design ◽  
Sensitive Volume ◽  
Fibre Optic ◽  
Beam Radiation ◽  
X Ray ◽  
Depth Dose

Cancer is one of the leading causes of death worldwide. External beam radiation therapy is one of the most important modalities for the treatment of cancers. Synchrotron microbeam radiation therapy (MRT) is a novel pre-clinical therapy that uses highly spatially fractionated X-ray beams to target tumours, allowing doses much higher than conventional radiotherapies to be delivered. A dosimeter with a high spatial resolution is required to provide the appropriate quality assurance for MRT. This work presents a plastic scintillator fibre optic dosimeter with a one-dimensional spatial resolution of 20 µm, an improvement on the dosimeter with a resolution of 50 µm that was demonstrated in previous work. The ability of this probe to resolve microbeams of width 50 µm has been demonstrated. The major limitations of this method were identified, most notably the low-light signal resulting from the small sensitive volume, which made valley dose measurements very challenging. A titanium-based reflective paint was used as a coating on the probe to improve the light collection, but a possible effect of the high-Zmaterial on the probes water-equivalence has been identified. The effect of the reflective paint was a 28.5 ± 4.6% increase in the total light collected; it did not affect the shape of the depth-dose profile, nor did it explain an over-response observed when used to probe at low depths, when compared with an ionization chamber. With improvements to the data acquisition, this probe design has the potential to provide a water-equivalent, inexpensive dosimetry tool for MRT.

Towards high spatial resolution tissue-equivalent dosimetry for microbeam radiation therapy using organic semiconductors

2021 ◽  
Vol 28 (5) ◽  
Author(s):  
Jessie A. Posar ◽  
Matthew Large ◽  
Saree Alnaghy ◽  
Jason R. Paino ◽  
Duncan J. Butler ◽  
...  
Keyword(s):  
Radiation Therapy ◽  
Dose Rate ◽  
Spatial Resolution ◽  
High Spatial Resolution ◽  
Sensitive Volume ◽  
Tissue Quality ◽  
X Ray ◽  
Microbeam Radiation Therapy ◽  
Tissue Equivalent ◽  
Barrier Film

Spatially fractionated ultra-high-dose-rate beams used during microbeam radiation therapy (MRT) have been shown to increase the differential response between normal and tumour tissue. Quality assurance of MRT requires a dosimeter that possesses tissue equivalence, high radiation tolerance and spatial resolution. This is currently an unsolved challenge. This work explored the use of a 500 nm thick organic semiconductor for MRT dosimetry on the Imaging and Medical Beamline at the Australian Synchrotron. Three beam filters were used to irradiate the device with peak energies of 48, 76 and 88 keV with respective dose rates of 3668, 500 and 209 Gy s−1. The response of the device stabilized to 30% efficiency after an irradiation dose of 30 kGy, with a 0.5% variation at doses of 35 kGy and higher. The calibration factor after pre-irradiation was determined to be 1.02 ± 0.005 µGy per count across all three X-ray energy spectra, demonstrating the unique advantage of using tissue-equivalent materials for dosimetry. The percentage depth dose curve was within ±5% of the PTW microDiamond detector. The broad beam was fractionated into 50 microbeams (50 µm FHWM and 400 µm centre-to-centre distance). For each beam filter, the FWHMs of all 50 microbeams were measured to be 51 ± 1.4, 53 ± 1.4 and 69 ± 1.9 µm, for the highest to lowest dose rate, respectively. The variation in response suggested the photodetector possessed dose-rate dependence. However, its ability to reconstruct the microbeam profile was affected by the presence of additional dose peaks adjacent to the one generated by the X-ray microbeam. Geant4 simulations proved that the additional peaks were due to optical photons generated in the barrier film coupled to the sensitive volume. The simulations also confirmed that the amplitude of the additional peak in comparison with the microbeam decreased for spectra with lower peak energies, as observed in the experimental data. The material packaging can be optimized during fabrication by solution processing onto a flexible substrate with a non-fluorescent barrier film. With these improvements, organic photodetectors show promising prospects as a cost-effective high spatial resolution tissue-equivalent flexible dosimeter for synchrotron radiation fields.

High spatial resolution AEM observations of yttrium segregation in chromia scales grown on Co-45%Cr

1986 ◽  
Vol 44 ◽  
pp. 518-519
Author(s):  
K. Przybylski ◽  
A. J. Garratt-Reed ◽  
G. J. Yurek
Keyword(s):  
Spatial Resolution ◽  
Outer Surface ◽  
Maximum Concentration ◽  
High Spatial Resolution ◽  
Reactive Elements ◽  
Chromia Scales

The addition of so-called “reactive” elements such as yttrium to alloys is known to enhance the protective nature of Cr2O3 or Al2O3 scales. However, the mechanism by which this enhancement is achieved remains unclear. An A.E.M. study has been performed of scales grown at 1000°C for 25 hr. in pure O2 on Co-45%Cr implanted at 70 keV with 2x1016 atoms/cm2 of yttrium. In the unoxidized alloys it was calculated that the maximum concentration of Y was 13.9 wt% at a depth of about 17 nm. SIMS results showed that in the scale the yttrium remained near the outer surface.

Integration of Core-Edge Spectroscopy Methods for the Study of Polymers

1996 ◽  
Vol 54 ◽  
pp. 154-155
Author(s):  
E. G. Rightor
Keyword(s):  
Excited State ◽  
Polymer Blends ◽  
Gas Phase ◽  
Spatial Resolution ◽  
High Spatial Resolution ◽  
Electronic States ◽  
Core Electron ◽  
Bulk Solids ◽  
Development Application

Core edge spectroscopy methods are versatile tools for investigating a wide variety of materials. They can be used to probe the electronic states of materials in bulk solids, on surfaces, or in the gas phase. This family of methods involves promoting an inner shell (core) electron to an excited state and recording either the primary excitation or secondary decay of the excited state. The techniques are complimentary and have different strengths and limitations for studying challenging aspects of materials. The need to identify components in polymers or polymer blends at high spatial resolution has driven development, application, and integration of results from several of these methods.

Sign in / Sign up

Export Citation Format

Share Document