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One of the critical challenges facing imaging studies of the 21-cm signal at the Epoch of Reionization (EoR) is the separation of astrophysical foreground contamination. These foregrounds are known to lie in a wedge-shaped region of $(k_{\perp},k_{\parallel})$ Fourier space. Removing these Fourier modes excises the foregrounds at grave expense to image fidelity, since the cosmological information at these modes is also removed by the wedge filter. However, the 21-cm EoR signal is non-Gaussian, meaning that the lost wedge modes are correlated to the surviving modes by some covariance matrix. We have developed a machine learning-based method which exploits this information to identify ionized regions within a wedge-filtered image. Our method reliably identifies the largest ionized regions and can reconstruct their shape, size, and location within an image. We further demonstrate that our method remains viable when instrumental effects are accounted for, using the Hydrogen Epoch of Reionization Array and the Square Kilometre Array as fiducial instruments. The ability to recover spatial information from wedge-filtered images unlocks the potential for imaging studies using current- and next-generation instruments without relying on detailed models of the astrophysical foregrounds themselves., Comment: 15 pages, 15 figures, 2 tables. Replaced to match accepted MNRAS version. Modified title and some extra clarifying text added, but results unchanged from v1

This work presents an analytic design procedure for 2D filters with wedge-shaped frequency response. The design starts from a wide-band, maximally-flat zero-phase low-pass prototype filter, to which a frequency mapping is applied, which leads to the 2D filter with the desired shape. The overall frequency response of the wedge filter is determined in a factored form, and the filter matrices result directly decomposed as a convolution of smaller matrices, a major advantage in implementation. The resulted filter is parametric, being adjustable depending on specifications, namely orientation and aperture angles. Several wedge filter design examples are provided, for various specifications.

Analytical-convoluted and numerical Gaussian models have been used in recent decades for radiotherapy treatment planning software/calculations, to perform accurately radiation dose delivery –numerical, analytical, or numerical-analytical. The objective of this evoluted-contribution was to obtain an exact dose delivery, 3D analytical-integral-equation solution, for the triple Gaussian model of wedge filters, since previous/initial 2D approximations of other authors, although correct, were not completely exact. Additionally, to set conceptual and mathematical-geometrical differences between the beam modification created by Multi-Leaf Collimator and Wedge Filters, either standard or Conformal. Ever the precision, from mathematical theory algorithms to real laboratory measurements, a series of simulations are presented. The generic triple Gaussian model of Ulmer and Harder sets an Attenuation Exponential Factor, AEF, well approximated in 2 variables, namely, u and z. This evoluted contribution of the research contribution was specially focused on numerical methods and approximation analysis of the integral equation resolution –with extent details about numerical data, Appendix 3. In this paper we set a detailed spatial-spherical geometry discussion/proof towards the determination of a 3D integral form of the delivery dose in water. In other words, with an AEF for magnitude-values of variables u,v, and z. Simulations, based on these new determinations were shown with sharp presentation of the numerical-computational software and functional programming series development. Computing encode techniques are explained with some practical examples for numerical radiotherapy calculus.

In this paper, we proposed an efficient quality assurance method which can measure direct tissue maximum ratio (TMRDir), total scatter factor (Scp, Dir), wedge factor (WFDir), tissue phantom ratio 20/10 (TPR20/10Dir) by using a calibration water phantom and a Farmer chamber. The TMRDir was compared with the calculated TMR (TMRCal) that was calculated from the percentage depth dose at the time of the linear accelerator installation. Scp, Dir, WFDir and TPR20/10Dir calculated from TMRDir were compared with Scp, BD, WFBD, and TPR20/10BD measured at the time of the linear accelerator installation. The difference between TMRDir and TMRCal was approximately within 1% except for using 60° wedge filter. The difference between Scp, Dir and Scp, BD was within 1%, between WFDir and WFBD was within 2%, between TPR20/10Dir and TPR20/10BD was within 1%, these differences were acceptable levels of AAPM TG-142 report. Also, coefficient of variation (CV) of TMRDir, ScpDir, WFDir and TPR20/10Dir when changing days and measuring multiple times were approximately within 1%, these CVs were reference levels of AAPM TG-106 report. We validated that was an efficient quality assurance method by measuring direct tissue maximum ratio, but the propose method has limited in measurable field size.

This work proposes an efficient analytic method for designing a class of 2D filters useful in image processing, namely wedge-shaped filters, which can be considered components of a directional filter bank. The design starts from a 1D digital filter prototype transfer function. Using accurate approximations and specific frequency mappings, first an unilateral, half-plane filter with a given orientation is obtained. Using two such unilateral 2D filters with imposed orientation angles, a desired directional wedge filter is derived, with specified orientation and aperture angles. Its transfer function results directly in a factored form, which is an advantage in implementation. The resulted wedge filter is parametric and tunable, since the specified parameters occur in the final matrix form of the filter transfer function.

One of the most important issues in the field of radiotherapy is the correct distribution of the dose around the volume of interest or planning target volume (PTV). For making this possible the exact isodose in a treatment plan has to cover the PTV, so it is used the wedge which is a part of the linear accelerator head. Wedge plays the role of a filter and usually it is called wedge filter. The wedge filter is in use almost in all treatment plans, for all the parts of the body. In this paper it is consider the use of the wedge filter for treatment of rectum tumors. The process starts with the scanning of the patient and the deliantion of the interest’s volums in the Monaco system. In the following the imagins have been sent in the treatment planning system for making the nesessary plans for treatment of the rectum. Two plans were done, one with the use of the wedge and the other without using it. The dose volume histogram helps for compering the results of the plans. The best conformity of the isodoses it was for the plan with the use of wedge through volume of interest, which is planning target volume (PTV).

FLUKA-based Monte Carlo calculations of microdosimetric distributions in water phantom involving a walled spherical Tissue-Equivalent Proportional Counter filled with tissue-equivalent propane gas have been studied for an indigenously developed telecobalt machine. The simulated site size considered in the study was 2 μm. In the Monte Carlo calculations, field size was varied from 10 cm × 10 cm to 35 cm × 35 cm and the depth was varied as 5-20 cm. The study also includes calculation of microdosimetric distributions with a 30° wedge filter. The efficiency of the calculations was improved up to a factor of 26 by choosing appropriate cut off values for production and transport of electrons. The calculated microdosimetric distributions of telecobalt machine is distinctly different from that of a bare 60Co source which is attributed to the influence of scattered photons from the machine head and the water phantom.

International audience; Objective: To assess the interactive Skin Dose Map® tool (SDMTool) integrated to the radiation dose management system (RDMS) DoseWatch® with Gafchromic® films for implementation in routine practice.Methods: A retrospective dose estimation software SDMTool was used to calculate Peak Skin Dose (PSD) and display the patient skin dose distribution. PSD was calculated with a triangle mesh of 0.055 cm2 resolution on ICRP 110 male anthropomorphic phantom and with a square ROI of 1 cm2 on flat phantom. The tool uses Radiation Dose Structured Reports (RDSR) data to model exposure events and calculate the PSD per event. The PSD and the skin dose distribution estimated with SDMTool were evaluated in comparison with Gafchromic® films positioned under the PMMA phantom (20 cm) for 13 configurations. Measurements were performed on a Philips system. Statistical analysis were carried out to compare PSDFilm and PSDSDM.Results: Average differences between PSDFilm and PSDSDM were 6% ± 6% (range from -3% to 22%) for flat phantom and 5% ± 7% (range from -3% to 25%) for ICRP phantom. Concordance was good between the measured PSDFilm and the estimated PSDSDM with Lin's coefficient estimation and 95% Confidence Interval of 0.979 [0.875; 0.984] for flat phantom and 0.977 [0.877; 0.985] for ICRP phantom. Dose map representations are concordant for 11 of the 13 tests on PMMA phantom. Disparities arose from the limitations of the RSDR format: table displacement during fluoroscopy events and the use of wedge filter.Conclusion: The results found in this experimental evaluation show that the SDMTool is a suitable alternative to Gafchromic® film to calculate PSD.

This work proposes an analytic technique for designing 2D wedge-shaped filters which can be regarded as components of an uniform directional filter bank. The design starts from a zero-phase low-pass prototype filter, to which a specific frequency transformation is applied to obtain wedge filters. A correction low-pass filter may be used to remove some marginal distortions in the filter frequency response. Finally, the 2D wedge filter transfer function results directly in factored form, which is an advantage in implementation. Moreover, the 2D wedge filter function is parametric and can be tuned according to the imposed specifications, like orientation and aperture angle.

In modern multi-slice CT systems, bowtie shape wedge filter is widely used for optimizing patient received radiation dose distribution. Since wedge filter is usually fixed in the path of X-ray, the induced scatter radiation could give impact on image quality under certain cases. In order to compensate this extra scatter radiation and improve the image quality, we introduced a wedge scatter correction algorithm integrated in the raw data pre-processing workflow. After the algorithm is implemented on our latest CT systems, the improvement can be seen from both water phantom images and clinical patient images.

This work evaluates the dosimetric properties of newly developed optically stimulated luminescence (OSL) films, fabricated with either Al2O3:C or Al2O3:C,Mg, using a prototype laser scanning reader, a developed image reconstruction algorithm, and a 6 MV therapeutic photon beam. Packages containing OSL films (Al2O3:C and Al2O3:C,Mg) and a radiochromic film (Gafchromic EBT3) were irradiated using a 6 MV photon beam using different doses, field sizes, with and without wedge filter. Dependence on film orientation of the OSL system was also tested. Diode-array (MapCHECK) and ionization chamber measurements were performed for comparison. The OSLD film doses agreed with the MapCHECK and ionization chamber data within the experimental uncertainties (

Aim of the study: Accurate skin dose assessment is necessary during breast radiotherapy to assure that the skin dose is below the tolerance level and is sufficient to prevent tumour recurrence. The aim of the current study is to measure the skin dose and to evaluate the geometrical/anatomical parameters that affect it. Material and methods : Forty patients were simulated by TIGRT treatment planning system and treated with two tangential fields of 6 MV photon beam. Wedge filters were used to homogenise dose distribution for 11 patients. Skin dose was measured by thermoluminescent dosimeters (TLD-100) and the effects of beam incident angle, thickness of irradiated region, and beam entry separation on the skin dose were analysed. Results : Average skin dose in treatment course of 50 Gy to the clinical target volume (CTV) was 36.65 Gy. The corresponding dose values for patients who were treated with and without wedge filter were 35.65 and 37.20 Gy, respectively. It was determined that the beam angle affected the average skin dose while the thickness of the irradiated region and the beam entry separation did not affect dose. Since the skin dose measured in this study was lower than the amount required to prevent tumour recurrence, application of bolus material in part of the treatment course is suggested for post-mastectomy advanced breast radiotherapy. It is more important when wedge filters are applied to homogenize dose distribution.

Aim: The aim of this study was to report commissioning and performance evaluation of Bhabhatron-II TAW (an Indian made machine). Materials and Methods: Commissioning comprises of following quality assurance (QA) (a) electrical QA, (b) mechanical QA, (c) radiation QA and (d) survey of installation. Electrical QA were done for various components of the unit for its functionality. Mechanical QA were done and the measured data were verified as per guidelines of Atomic Energy Regulatory Board (AERB), India and vendor's specified values. Cylindrical ionization chamber, electrometer, ready pack films, water phantom, thermometer and barometer were used during radiation QA and survey of installation procedures. Moreover, the data so generated were fed to treatment planning system (TPS) for dose calculation and also kept in proper tabular manner for clinical use. Results: Couch and collimator parameters were found to comply the tolerance criteria. Source strength of 172.2 roentgen per minute at 1 meter (RMM) was measured with an absolute dose rate of 225.76 cGy/min at dmax for 10cm x 10cm field size at normal treatment distance (NTD). Shutter timer error of 0.004 min was measured and incorporated in the clinical data. A maximum of 3.66 % variation was noted for 300 (15W × 20) physical wedge transmission factor between measured and vendor specified value. Radiation leakage through beam limiting device (BLD) and outside BLD were found to be within the limits prescribed by AERB. Conclusion: Commissioning is a prerequisite process after installation of a radiation therapy machine for medical purpose. Bhabhatron-II machine has several advantages over other telecobalt machine. Features like high source storage capacity of machine head, one pair of asymmetric jaw, closure of jaws to 0 cm x 0 cm during radiation emergency and presence of one motorized wedge filter makes it unique and yet cost effective telecobalt machine..

Knowledge of the effective energy of 320-multidetector computed tomography (CT) is important for quality assurance and quality control. Evaluation in two dimensions is necessary because the effective energy varies depending on the shape of the wedge filter located in the CT device. The purpose of this study was to measure the two-dimensional effective energy distribution of the CT using GAFCHROMIC EBT3 (EBT3), which has a weak energy dependence. The exposure parameters of the 320-multidetector CT were 120 kV, 500 mA, and 5.0 s, and the X-ray tube was stopped at the 0 o’clock position. To avoid scattered radiation, the distance between the EBT3 and other scatterers was set to 200 mm or more. The Al filter thickness was increased from 2 to 20 mm. The irradiated area was divided into 54 compartments, and the density attenuation ratio was measured. The half-value layers (HVLs) were determined using the density attenuation ratios. The effective energies were obtained from the HVLs, and the two-dimensional effective energy distribution was evaluated. Because the thickness of the wedge filter in the longitudinal direction (parallel to the bed) remained unchanged, the variation in the effective energy was negligible in this direction. On the other hand, in the lateral direction (perpendicular to the bed), because the wedge filter gradually thickened from the center to the side, the effective energy from the center to the side increased. The two-dimensional effective energy distribution of the CT could thus be measured using EBT3.

This study is aimed at assessing whether dynamic wedge filters are appropriate to be used instead of physical wedge filters. The X-ray energy generated from linear accelerator is commercialize 6 MV and 10 MV. 15°, 30°, 45°, and 60° of physical wedge filter was irradiated by dose rate 100, 200, 300, 400, 500, and 600 MU/min for each angle and for comparison with a dynamic wedge filter, irradiate 96 times under the same conditions. The measurement conditions are as 100 ㎝ source-film distance and 10 × 10 ㎝ irradiated surface. A developed film was scanned and analyzed after a calibration through a dose analysis program and the dose rate was compared after calculating the standard deviation. Dynamic wedge filters make dose, scattered rays and treatment time reduced and very useful due to less irradiated doses to patients. The errors at each dose rate under the same conditions were irrelevant. Thus, treatment based on a high dose rate depending on the patient is expected to be feasible. Keyword : radiation therapy, linear accelerator, wedge filter, dynamic wedge filter, physical wedge filter

Tunable multichannel filtering properties of a one-dimensional photonic crystal wedge constructed from two one-dimensional photonic crystals are demonstrated theoretically. Using the transfer matrix method, it is shown that the filtering properties, including the frequency and number of channels, can be tuned by adjusting the lateral position of the incident beam, the incident angle and the apex angle of the wedge. The angular response of the PC wedge filter is also analyzed.

Techniques, using physical wedge filter and using dynamic wedge filter and FIF(Field in Field) and ISCT(Irregular Surface Compensating Technique), have been developed according to progress of radiation therapy of breast cancer. Measurement of dose was done to judge the usefulness of technique using three cases, non tissue loss after breast conserving operating and tissue loss after breast conserving operating and mastectomy. Dose indexes of breast tissue, CI (Conformity Index), HI (Homogeneity Index) and QOC (Quality of Coverage), dose index of skin, or dose indexes of lung, volume of 50 percent dose and 20 percent dose were estimated and compared. Using dynamic wedge filter is useful plan at non tissue loss allowing for high dose of lung. FIF and ISCT are useful plan at tissue loss. ISCT is useful plan at mastectomy. Henceforth, we need to apply to valid plan and body type and thorax size.

The development of the planetary exploration for landers makes it more and more necessary to have at our disposal small and light instruments. This is why we are developing in our laboratory a light imaging spectrometer with a wedge filter making the spectral splitting. This design already developed in other laboratories has the great advantage to need a limited number of optical components. However its drawback is that at a given instant the different spectral pixels don’t see the same spot in the field. We propose a new design to remedy this drawback by the adjunction of a dispersive system in the fore-optics.

Purpose: To evaluate impact on surface dose, Depth of dose maximum (dmax) and depth dose distribution due to physical wedge filters for different wedge angle were studied for 6MV flattened (6MV FB) and 7MV unflattened (7MV UFB) photon beams. Methods: The flattening filter and primary collimator are the major sources of producing the scattered radiation and these parameters affect the surface dose, dmax and dose distribution. In this study, open fields surface dose, dmax and depth dose distribution values were compared with physical wedge filter for 6MV FB and 7MV UFB .The measurement carried out in Siemens ‐ ARTISTE linear accelerator with diode detector along the central axis of the beam at 100 cm source to surface distance using IBA blue water phantom for 6MV FB and 7MV UFB x‐ray beams. Results: The surface dose increased as the field size increased for open and physical wedge fields for 6MV FB and 7MV UFB beams. For open fields, Surface doses relative to the dose at dmax ranged from 0.443 to 0.569 and 0.463 to 0.668 for field sizes of 5 × 5 to 20×20 cm2 for the 7MV UFB and 6MV FB beam respectively. The measured surface dose for 150, 300,450 and 600 wedge field values are 0.396 to 0.504, 0.366 to 0.484, 0.342 to 0.464 and 0.347 to 0.47 respectively for 7MV UFB and 0.424 to 0.566, 0.398 to 0.555, 0.3860 to 0.5430 and 0.389 to 0.55 respectively for 6MV FB. Conclusions: We found that dmax of wedged beams were higher than those open beams for field size up to 10 × 10 cm2, Surface doses of wedged beams were lower than those of open beams for 7MV UFB and 6MV FB. Surface dose of the 7MV UFB were lower than the 6MV FB for open and wedged beams.

As a tunable optical filter, angle-tuned thin film narrowband filter is widely used in dense wavelength division multiplexing (DWDM) system. In oblique incidence, the transmitting facular broadens obviously, which will cause a decrease in transmissivity and rectangular degree of the filter. The transmitting spectrum characteristics and the transmitting facular broadening are also influenced by the non-parallel incident and emergent interfaces' wedge angle of the wedge filter. In the present paper, the transmitting intensity distribution in different incident angle of the wedge filter has been calculated, and the influences of the wedge angle to the transmissivity and the half bandwidth are also analyzed. The proper wedge angle and incident orientation will improve the characteristics of the transmitting spectrum. A 100 GHz DWDM angle-tuned wedge filter was fabricated which has a wedge angle of 0.8°. Compared with the parallel angle-tuned filter, the wedge filter can enhance the transmissivity and the rectangular degree in oblique incidence and its tunable wavelength range will increase 10 nm.

Wedge filters are commonly used to achieve dose uniformity in the target volume in radiotherapy and can be categorized as physical wedges (PWs) and enhanced dynamic wedges (EDWs). The EDW generates PW-like dose profiles while moving the upper jaw in the Y directions with a varying dose rate in the treatment beams. Task Group 53 of the AAPM (American Association of Physicists in Medicine) recommended that the dynamic wedge be verified before implementation in the radiation treatment planning (RTP) system. The aim of this study was to use the I’mRT MatriXX to verify the dose profiles of the EDWs manufactured by Varian. We used Pencil Beam Convolution algorithms (eclipse 8.6) for the calculation and I’mRT MatriXX with Plastic Water® phantom MULTICube for dose measurements. The gamma indices of the calculations and the measurements for the EDWs were 84.84% and 86.54% in 2%/2 mm tolerance, and 99.47% and 99.64% in 3%/3 mm tolerance for wedge angles of 15°, 30°, 45° and 60°, respectively. The dose distributions differed between the calculations using the system and the measurements in the penumbra and the outer beam regions of the wedge fields. We confirmed that the dosimetric verifications of the EDW were acceptable when using the criterion for external beam dose calculations of Task Group 53.

This study investigated differences between the physical wedge and the dynamic wedge distributions of radiation by using an intensity-modulated radiotherapy (ImRT) MatriXX. The linear accelerator used X-rays with energy levels of 6 MV and 10 MV to adjust the collimator by motoring the independent jaws (X1, X2, Y1, Y2) for setting wedge angles of 15, 30, 45, and 60 degrees. The collimator field size was set as 10 × 10 cm2 or 20 × 20 cm2 at the maximum dose point. The dose distribution for each wedge had ±5% and ±11% errors for field sizes of 10 × 10 cm2 and 20 × 20 cm2, respectively. The error was greatest at a wedge angle of 45 degrees and was pronounced at the end of the dynamic wedge where Y1 and Y2 met. Consequently, concluded that the dose distributions were similar for both wedges for the field size of a small beam profile. The beam dose was greatly increased at the end of the dynamic wedge. A more precise estimate of the therapeutic dose of radiation for a dynamic wedge that nearly matches that of the physical wedge can be achieved by correcting of the increasing part of the beam dose. The findings imply that a heavy wedge filter should not be used when calculating the isodose distribution and the therapeutic dose.

The CR-39 [diethylene glycol bis-(allylcarbonate)] neuron detection method was used to measure the dose of neutrons generated in X-ray (photon) therapy conducted in a linear accelerator, and to use high-energy photons as part of the clinical applications to examine the problems associated with the dose for patients caused by the generation of neutrons from high-energy photons used for cancer therapy. According to the experimental results, 0.35 mSv, 0.65 mSv 1.82 mSv of fast neutrons on average were generated from 1 Gy, 2 Gy and 5 Gy of photon irradiation, respectively, whereas 0.26 mSv, 0.56 mSv and 1.23 mSv of thermal neutrons were generated. Both fast neutrons and thermal neutrons produced an increase in the dose of neutrons generated with increasing irradiation dose. With in regard to the dose generated within and around the irradiation area of the photon rays, it was confirmed that more neutrons were generated within the irradiation area. A wedge filer was used to measure the generation of neutrons. According to the measurement results, the generation of neutrons increased when a wedge filter was used. When the SRS cone that required a high dose was used, more neutrons were detected than those in the previous experiment. When fast neutrons were used, 2.85 mSv neutrons on average were generated from 5 Gy of photon irradiation. When thermal neutrons were used, 1.37 mSv neutrons on average were generated from 5 Gy of photon irradiation. Overall, approximately 1.6 times and 1.12 times more fast and thermal neutrons, respectively, were generated than in the case of a general treatment with 5 Gy of photon irradiation.

BACKGROUND AND OBJECTIVE: Breast cancer is the most common cancer in women worldwide and radiotherapy is the best treatment choice after mastectomy. One of the main aims of radiotherapy is applying the uniform dose distribution in all treatment volume. The objective of this study was to evaluate the chest wall angle by reference axis (vertical and horizontal) and use optimum wedge filter in post-mastectomy radiotherapy.METHODS: One hundred and forty cases of breast cancer after mastectomy surgery were included in this study. Patients were planned by ALFARD treatment planning system (TPS) or three-dimensional (3D) CorePLAN Treatment Planning System (TPS). Dose Volume Histograms (DVHs) with different wedge angles and without wedge were obtained for every case. DVHs were analyzed and compared for finding optimum wedge angle. Chest wall angle with reference axis was determined by GetData software. The wedge angel and chest wall angel were compared to reach the equation between them.FINDINGS: The optimum wedge angle was the function of chest wall angles. In all cases the compensating wedge filter causes better homogeneity index and results of chest wall angle determination were in good agreement with the results of DVHs as gold standard for determining homogeneity index.CONCLUSION: Finding of this study showed that an improved chest wall angle in mastectomy patients is a new method for choosing optimum wedge angle. Also time cost of this method is better than DVH technique.

A universal wedge filter of 15W � 20 cm 2 and 60 � nominal wedge angle is designed and placed between the collimating jaws and penumbra trimmers inside the treatment head. A pneumatically driven actuating mechanism toggles the wedge between the wedge IN position and wedge OUT position. The effective wedge angles were determined using an analytical formula. An accumulated wedge profile at a depth of 10 cm which was measured using a 2D profiler and dose values at depths of 10 cm and 20 cm for the same experimental setup were used as input parameters in the formula used for determining effective wedge angles. The relationship between the wedge beam weight and effective wedge angle was established. The planned wedge angles were compared with the measured wedge angles and the differ- ences are found to be less than 2 � throughout the range of field sizes. Planned doses for various field sizes and wedge angles were measured for verification and the differences were found to be less than 1.8%. This study established that the relationship between the beam weights and effective wedge angles implemented for the motorized wedge filter of medical linacs is not directly applicable for the motorized wedge filter of Telecobalt.

Photoneutrons produced during radiation therapy with high energy photons is the main source of unwanted out-of-field received doses of patients. To analyze the neutron dose equivalent (NDE) for wedged beams and its variation with field size, Monte Carlo (MC) modeling of an 18 MV photon beam was performed using MCNPX MC code. The results revealed that the NDE is on average 6.5 times higher for wedged beams. For open beams, the NDE decreased with increasing field size especially for field sizes >20×20 cm 2 . While, for wedged beams, the NDE increased with field size. It was suggested that the increase of NDE for wedged beams should be taken into account in radiation-induced secondary cancer risk estimations and radiation protection calculations.

A simplified approach to creating narrow visible and near IR transmission bands with thin films is outlined utilising just five layers on glass, three of which are thin silver. These films have very high reflection at most wavelengths except for a narrow anti-reflection band where reflectance can be very close to zero and transmittance is close to 70%. In addition these properties are combined with IR reflectance approaching 99% for a very small thermal signature. Spatial variation of narrow band colour is easily achieved and is demonstrated with production of a simple wedge filter covering the full visible spectrum. Measured CIE colour contours in transmittance and reflectance are presented and spectral data on experimental films is compared with ideal models. Potential sources of small departures from ideal models are examined to assess the scope for future improvements.

Radiotherapy represents the most widely spread technique to control and treat cancer. To increase the treatment efficiency, high energy linacs are used. However, applying high energy photon beams leads to a non-negligible dose of neutrons contaminating therapeutic beams. In addition, using conventional linacs necessitates applying wedge filters in some clinical conditions. However, there is not enough information on the effect of these filters on the photoneutrons produced. The aim of this study was to investigate the change of photoneutron dose equivalent due to the use of linac wedge filters. A high energy (18 MV) linear accelerator (Elekta SL 75/25) was studied. Polycarbonate films were used to measure the dose equivalent of photoneutrons. After electrochemical etching of the films, the neutron dose equivalent was calculated using Hp(10) factor, and its variation on the patient plane at 0, 5, 10, 50 and 100 cm from the center of the X-ray beam was determined. By increasing the distance from the center of the X-ray beam towards the periphery, the photoneutron dose equivalent decreased rapidly for the open and wedged fields. Increasing of the field size increased the photoneutron dose equivalent. The use of wedge filter increased the proportion of the neutron dose equivalent. The increase can be accounted for by the selective absorption of the high energy photons by the wedge filter.

Conformal/Standard radiotherapy wedges [refs 3–7,Casesnoves 2005] present several bioengineering-industrial design difficulties to obtain an optimal beam/beamlets-IMRT upper-surface radiation distribution, avoiding that them could emerge undesirably from lateral walls instead the lower wedge plane. We calculated the improved exact beamlet limit-angle mathematical method for a standard/conformal wedge filter design. It was developed with basic mathematical algorithms, geometrical design, and Numerical Simulations linked to this mathematical formulation. All that was done using the AAA algorithm integral attenuation exponential factor [AEF], which modulates the convolution kernel of the integral dose delivery. Results comprise the geometrical design of the conformal wedge, showed in several sketches, and simulations with appropriate software. In addition, a series of geometrical formulas/tables for the beamlets limits, trigonometric AEF background, and mathematical formulation with the simulations of the AEF for a 2-steps conformal wedge are obtained.

India’s first lunar mission, Chandrayaan-1, will have a Hyper-Spectral Imager in the visible and near-infrared spectral bands along with other instruments. The instrument will enable mineralogical mapping of the Moon’s crust in a large number of spectral channels. The planned Hyper-Spectral Imager will be the first instrument to map the lunar surface with the capability of resolving the spectral region, 0.4 to 0.92 Μm, in 64 continuous bands with a resolution of better than 15 nm and a spatial resolution of 80 m. Spectral separation will be done using a wedge filter and the image will be mapped onto an area detector. The detector output will be processed in the front-end processor to generate the 64-band data with 12-bit quantization. This paper gives a description of the Hyper-Spectral Imager instrument.

Kodak EDR2 film has been calibrated across the range of exposure conditions encountered in our cardiac catheterization laboratory. Its dose-response function has been successfully modelled, up to the saturation point of 1 Gy. The most important factor affecting film sensitivity is the use of beam filtration. Spectral filtration and kVp together account for a variation in dose per optical density of -10% to +25%, at 160 mGy. The use of a dynamic wedge filter may cause doses to be underestimated by up to 6%. The film is relatively insensitive to variations in batch, field size, exposure rate, time to processing and day-to-day fluctuations in processor performance. Overall uncertainty in the calibration is estimated to be -20% to +40%, at 160 mGy. However, the uncertainty increases at higher doses, as the curve saturates. Artefacts were seen on a number of films, due to faults in the light-proofing of the film packets.

Installation of a modern high-energy Siemens Primus linear accelerator at the Northern Centre for Cancer Treatment (NCCT) provided the opportunity to investigate the optimal clinical implementation of the Siemens virtual wedge filter. Previously published work has concentrated on the production of virtual wedge angles at 15 degrees, 30 degrees, 45 degrees, and 60 degrees as replacements for the Siemens hard wedges of the same nominal angles. However, treatment plan optimization of the dose distribution can be achieved with the Primus, as its control software permits the selection of any virtual wedge angle from 15 degrees to 60 degrees in increments of 1 degrees. The same result can also be produced from a combination of open and 60 degrees wedged fields. Helax-TMS models both of these modes of virtual wedge delivery by the wedge angle and the wedge fraction methods respectively. This paper describes results of timing studies in the planning of optimized patient dose distributions by both methods and in the subsequent treatment delivery procedures. Employment of the wedge fraction method results in the delivery of small numbers of monitor units to the beam's central axis; therefore, wedge profile stability and delivered dose with low numbers of monitor units were also investigated. The wedge fraction was proven to be the most efficient method when the time taken for both planning and treatment delivery were taken into consideration, and is now used exclusively for virtual wedge treatment delivery in Newcastle. It has also been shown that there are no unfavorable dosimetric consequences from its practical implementation.

We characterized a recently proposed implantable GaN-based dosimeter in clinical conditions, for its application in external radiotherapy according to ESTRO (European Society for Radiotherapy & Oncology) practical guidelines. Our studies were carried out using a 6 MV photon beam with the dosimeter under test in a water tank or a PMMA phantom. They were focused on evaluating short term and long term reproducibility of measurements, and assessing the effects of parameters such as field size, source-skin distance, use of wedge filter, beam incidence, dose rate, accumulated dose, GaN-induced dose perturbation, air cavities and temperature. The estimated repeatability and reproducibility are better than 0.5% and 2% at 1 σ respectively. There are no significant effects of the parameters under our studies, apart from field size and temperature. The field-size dependence is due to over-compensation of the GaN response method of the dosimeter, the resulting errors remain lower than 5% for field sizes up to 10 × 10 cm 2 . The temperature dependence mainly results from the GaN luminescence properties, and causes the GaN response to decrease steadily when increasing temperature, with a sensitivity of −1.4%/°C. The observed quasi-linear temperature dependence may facilitate the correction to improve the accuracy of measurements.

Yüksek Lisans Tezi Radyoterapide, ışın alanının geometrik sınırları dışındaki çevredeki normal yapıları etkileyen doz miktarı klinik açıdan önemlidir. Primer ışın alanı dışında kritik organlara ait radyasyon dozları, tedaviden önce değerlendirilmeli ve gerektiğinde düşürülmelidir. Bu çalışmadaki amacımız kliniğimizde kullanılan çok yapraklı kolimatör esaslı iki lineer akseleratör cihazında (Elekta Synergy ve Varian 2100 C/D) açık ve kama filtreli alanlarda periferik dozları ölçerek, tedavi planlama sisteminden hesaplanan değerlerle karşılaştırmaktır. Periferik doz ölçümleri 6, 15 ve 18 MV foton enerjilerinde, su eşdeğeri katı fantomlar üzerinde 0.6 cc iyon odası ve Gafkromik film kullanılarak gerçekleştirildi. Ölçümler 5x5, 10x10 ve 15x15 cm alanlarda, kaynak yüzey mesafesi 100 cm olacak şekilde, farklı derinliklerde (dmax derinliğinde ve yüzeyden 5 cm ve 10 cm derinliklerde) ve alan kenarından lateralde maksimum 30 cm uzaklığa kadar her 5 cm’de (0, 5, 10, 15, 20, 25 ve 30 cm) yapıldı. Periferik doz ölçümleri açık alanlar yanında 15o, 30o, 45o ve 60o kama filtreli alanlarda dinamik, motorize veya hard kama filtre kullanılarak yapıldı. Bütün ışınlamalar cihazın gantry ve kolimatör açıları 0o’de ve cihazın ışın aksı katı fantoma dik olacak şekilde yapıldı. Elde edilen ölçümler her bir cihaz için ilgili tedavi planlama sisteminde hesaplanan değerler ile karşılaştırıldı.53 Çalışmamızda yaptığımız doz ölçümlerine göre periferik doz alan kenarından uzaklaştıkça eksponansiyel olarak azalmakta, alan boyutu artışı ile artmaktadır. Açık alanlarda foton enerjisi artıkça periferik doz artarken, kama filtreli alanlarda enerji artıkça azalmaktadır. Ayrıca aynı enerjide ve aynı alanda kama filtre açısı arttıkça, periferik doz da artmaktadır. Çalışmamızda periferik dozun alan boyutunun, ölçüm yapılan derinliğin, foton enerjisinin ve kullanılan kama filtresi türü ile açısının bir fonksiyonu olduğu sonucuna varıldı. Abstract The amount of the radiation dose affecting the surrounding normal structures outside the geometric field boundary is a clinical important factor in radiotherapy. Radiation doses to critical organs outside the primary radiation field should be evaluated prior to treatment and reduced when it is found to be necessary. Our aim in this study is to measure the peripheral doses of open and wedge filtered fields with two linear accelerators (Elekta Synergy and Varian 2100 C/D) in use at our clinic, and to compare these measurements with the values calculated at treatment planning systems. The measurements of peripheral doses are carried out for 6, 15 and 18 MV photons using a 0.6 cc ionization chamber and Gafchromic films in a water equivalent solid phantom. Measurements are performed for 5x5, 10x10 and 15x15 cm sized fields at a source to surface distance of 100 cm at different depths (dmax, 5 cm and 10 cm) and up to a maximum lateral distance of 30 cm beyond the field edges at every 5 cm (0, 5, 10, 15, 20, 25 and 30 cm). The peripheral doses are first measured at open fields and then with 15o, 30o, 45o and 60o wedge filters, using dynamic, motorized or hard wedge systems. All measurements are registred along the longitudinal axis of the beam, perpendicular to solid phantom with gantry and collimator angles of the machine both set at 0o. The resultant measurements are compared with the values calculated at the correspondent points at treatment planning system of each linac.As a result of our measurements, it is found that peripheral dose decreases exponentially as the distance from field edge increases, it increases as the field size increases. It also increases when photon energy increases for open fields, whereas it decreases for wedge filtered respective fields when phantom energy increases Furthermore it increases as the wedge angle increases within the same field size and same phantom energy. It is concluded that peripheral dose values are a function of the field size, depth of the measurement point, energy of the photon and wedge filter used and its angle.

Yüksek Lisans Tezi Radyoterapide, ışın alanının geometrik sınırları dışındaki çevredeki normal yapıları etkileyen doz miktarı klinik açıdan önemlidir. Primer ışın alanı dışında kritik organlara ait radyasyon dozları, tedaviden önce değerlendirilmeli ve gerektiğinde düşürülmelidir. Bu çalışmadaki amacımız kliniğimizde kullanılan çok yapraklı kolimatör esaslı iki lineer akseleratör cihazında (Elekta Synergy ve Varian 2100 C/D) açık ve kama filtreli alanlarda periferik dozları ölçerek, tedavi planlama sisteminden hesaplanan değerlerle karşılaştırmaktır. Periferik doz ölçümleri 6, 15 ve 18 MV foton enerjilerinde, su eşdeğeri katı fantomlar üzerinde 0.6 cc iyon odası ve Gafkromik film kullanılarak gerçekleştirildi. Ölçümler 5x5, 10x10 ve 15x15 cm alanlarda, kaynak yüzey mesafesi 100 cm olacak şekilde, farklı derinliklerde (dmax derinliğinde ve yüzeyden 5 cm ve 10 cm derinliklerde) ve alan kenarından lateralde maksimum 30 cm uzaklığa kadar her 5 cm’de (0, 5, 10, 15, 20, 25 ve 30 cm) yapıldı. Periferik doz ölçümleri açık alanlar yanında 15o, 30o, 45o ve 60o kama filtreli alanlarda dinamik, motorize veya hard kama filtre kullanılarak yapıldı. Bütün ışınlamalar cihazın gantry ve kolimatör açıları 0o’de ve cihazın ışın aksı katı fantoma dik olacak şekilde yapıldı. Elde edilen ölçümler her bir cihaz için ilgili tedavi planlama sisteminde hesaplanan değerler ile karşılaştırıldı.53 Çalışmamızda yaptığımız doz ölçümlerine göre periferik doz alan kenarından uzaklaştıkça eksponansiyel olarak azalmakta, alan boyutu artışı ile artmaktadır. Açık alanlarda foton enerjisi artıkça periferik doz artarken, kama filtreli alanlarda enerji artıkça azalmaktadır. Ayrıca aynı enerjide ve aynı alanda kama filtre açısı arttıkça, periferik doz da artmaktadır. Çalışmamızda periferik dozun alan boyutunun, ölçüm yapılan derinliğin, foton enerjisinin ve kullanılan kama filtresi türü ile açısının bir fonksiyonu olduğu sonucuna varıldı. Abstract The amount of the radiation dose affecting the surrounding normal structures outside the geometric field boundary is a clinical important factor in radiotherapy. Radiation doses to critical organs outside the primary radiation field should be evaluated prior to treatment and reduced when it is found to be necessary. Our aim in this study is to measure the peripheral doses of open and wedge filtered fields with two linear accelerators (Elekta Synergy and Varian 2100 C/D) in use at our clinic, and to compare these measurements with the values calculated at treatment planning systems. The measurements of peripheral doses are carried out for 6, 15 and 18 MV photons using a 0.6 cc ionization chamber and Gafchromic films in a water equivalent solid phantom. Measurements are performed for 5x5, 10x10 and 15x15 cm sized fields at a source to surface distance of 100 cm at different depths (dmax, 5 cm and 10 cm) and up to a maximum lateral distance of 30 cm beyond the field edges at every 5 cm (0, 5, 10, 15, 20, 25 and 30 cm). The peripheral doses are first measured at open fields and then with 15o, 30o, 45o and 60o wedge filters, using dynamic, motorized or hard wedge systems. All measurements are registred along the longitudinal axis of the beam, perpendicular to solid phantom with gantry and collimator angles of the machine both set at 0o. The resultant measurements are compared with the values calculated at the correspondent points at treatment planning system of each linac.As a result of our measurements, it is found that peripheral dose decreases exponentially as the distance from field edge increases, it increases as the field size increases. It also increases when photon energy increases for open fields, whereas it decreases for wedge filtered respective fields when phantom energy increases Furthermore it increases as the wedge angle increases within the same field size and same phantom energy. It is concluded that peripheral dose values are a function of the field size, depth of the measurement point, energy of the photon and wedge filter used and its angle.

This study introduces a new concept, the super-omni wedge, and proposes an algorithm for optimizing beam weights, wedge angles, and wedge orientations on the basis of this new concept. The super-omni wedge is a generalization of the omni wedge. Instead of combining one open beam and two orthogonal wedged beams, it uses two orthogonal pairs of nominal wedged beams to generate a wedged dose distribution with an arbitrary wedge angle and an arbitrary wedge orientation. The orientations of a pair of nominal wedges are opposite each other. In this way, the effective wedge orientation can vary from 0 degrees to 360 degrees rather than being restricted to one quadrant. When the concept of the super-omni wedge is used, the optimization of beam weights, wedge angles, and wedge orientations for J beams is transformed into the optimization of beam weights for 4J beams. A quadratic dose-based objective function is defined, and the method of sequential quadratic programming is used to find the 4J beam weights that minimize it. After the weights of the nominal wedged beams have been determined, the beams can be delivered in one of four methods: Directly, by using the omni wedge technique, by using the universal wedge technique, and by using the virtual wedge technique. When tested with two clinical cases, the algorithm achieved homogeneous dose distributions in target volumes while meeting the constraints to the organs at risk. A prominent feature of the algorithm is that there is no need to manually preselect the orientations of nominal wedges.

Kodak EDR 2 film was calibrated across the range of beam qualities and exposure rates typically used in our cardiac catheterisation laboratory. Its dose-response curve was successfully modelled up to its saturation point of 1 Gy. The consistency of the film's response with film batch, time between exposure and processing processor and day-to-day variations in performance, was investigated. The effects of field size, exposure rate, beam quality and use of the dynamic wedge filter were quantified. The overall uncertainty in dose was estimated to be between -20% and +40%, at 160 mGy. This uncertainty increases as the film approaches its saturation point. In addition, some unusual artefacts were observed.

Wedge filters frequently do not provide optimal distribution in the chest wall, lung, and areolarnipple complex because they extend through the entire width of tangential radiation fields for breast cancer. In addition, medial wedge filters increase dose to the contralateral breast. In order to overcome these shortcomings, a new method of acrylic compensation was investigated. A universal acrylic breast compensator (ABC) was designed, with patient data, to extend anteriorly from the central axis. To accurately display build-up data, the ABC was entered into the treatment planning system as a wedge filter. Dose homogeneity within the compensated breast, chest wall, and lung volumes was assessed using 3-D planning and dose volume histograms. Dose to the contralateral breast was evaluated using thermoluminescent dosimetry in a polystyrene phantom. Opened, wedged, and compensated conditions were irradiated using the above described techniques. Due to lack of extension of the ABC posteriorly to the central axis (allowing lung inhomogeneity to correct for increased patient thickness), ABCs reduced the high dose regions in the chest wall and lung as compared to wedge filters. ABCs reduced hot spot in the areolar-nipple complex more efficiently as compared to wedge filters. ABCs also reduced dose to the contralateral breast by more than 20% relative to wedge filters. Wedge filters can be inefficient because of lung transmission and contour topography. Excessive dose to the chest wall, lung, and areolar-nipple complex, and contralateral breast can be alleviated with the use of a universal acrylic breast compensator. Its convenience and dosimetric advantages both in treatment planning and daily application offer a useful tool in the management of breast cancer.

Introduction An increasing number of pacemaker patients are receiving radiotherapy in various sites in our department. The need hence arises to accurately determine the radiation burden of pacemaker devices for radiotherapy patients, given the limited tolerance of such devices reported by manufacturers and select the best treatment parameters during the design of their treatment plan. Purpose This study aims to investigate the dependence of pacemaker dose on the type of wedge filter implemented in the radiotherapy machine, comparing the effect of dynamic wedges of various angles to the effect of the universal motorized wedge. Materials and methods In this study two different linear accelerators were used. All measurements were performed with 6 MV photon beams, at a range of distances from the field centre, for wedged and open beams. Dose was measured for dynamic wedges 15°, 30°, 45° and 60° and corresponding motorized wedge angles, for various wedge orientations. Moreover, the above estimated doses were compared with the data from two different treatment planning systems. Results The effect of the wedge filter can elevate the pacemaker dose significantly compared to that of an open field. Comparing the wedge designs measured in this study, the use of a dynamic wedge decreases the pacemaker burden. The pacemaker estimated dose from treatment planning systems diverged from the measured values. Conclusion This study provides data about the pacemaker exposure for different wedge systems. Furthermore, the treatment planning system’s dose estimation errors can not be neglected.

To evaluate the influence of mid treatment hemoglobin level with the other prognostic factors on the outcome in patients with Tis-T1N0 glottic carcinoma treated with radiotherapy (RT). Between October 1995 and December 2008, a total of 84 patients diagnosed with Tis-T1N0 glottic carcinoma were treated with definitive RT. The influence of tumor, treatment, and patient-related factors on local control (LC) and overall survival (OS) were analyzed. The median follow up time was 30 months (ranges, 4-180 months). Local and/or locoregional relapse was observed in 11 patients (13%) (3 locoregional and 8 local). The estimated 5- and 10-year LC and OS rates were 87%, 85%, and 87%, 70% for the entire study group, respectively. Multivariate analyses revealed that older age (>= 50 years) and the use of wedge-filter were found to be favorably influencing the LC (p= 0.025 and p= 0.030, respectively). Mid treatment hemoglobin level more than 13 g/dl was determined statistically significant for improving both LC and OS (p= 0.011 and p= 0.021). Older age and use of wedge filter were found to be independent prognostic factors for LC. Mid treatment hemoglobin level of more than 13 g/dl was correlated to superior LC and OS rates. Monitoring the changes of hemoglobin levels during therapy has to be considered to improve the outcome.

Wedge filters constitute a useful type of Beam Modification Devices (BME) in Radiation Therapy. Its use is routinary in both Forward and Inverse Treatment Planning Optimization (ITPO). In previous contributions we presented the exact/approximated path of a Pencil Photon-Beam (AAA Model, Anisothropic Analytic Algorithm), through standard manufacturing alloy wedges. It was found a so-defined Limit-Angle (LA), beyond of which the outpoint of the beam is located improperly at the lateral side of the wedge. LA exists because of the photon-beam physical divergence phenomenon. In this paper we carry out the Geometrical and Analytical determination of the LA in function of the beam divergence angle, collimator output distance, and the size parameters of the wedge filter. Two methods are used, Geometrical and Analytical. A series of Mathematical Formulations for LAs, is shown with basic approximations according to the industrial manufacturing wedge standards. Formulation is verified with Optimization Mathematical Methods.Copyright © 2012 by ASME