Silicon semiconductor detectors used in radiation dosimetry have different properties, just as e.g. ionisation chambers, affecting the interaction of with matter vicinity sensitive volume detector, wall materials, and also collection charges liberated detector by radiation. The charge depends on impurities, lattice imperfections other properties crystal. In this paper relevant parameters a silicon intended for are reviewed. influence doping material, level, various effects damage, mechanical...

A p-type silicon radiation detector has been constructed and the effect of damage on sensitivity dose rate dependence studied. The showed, in contrast to an n-type detector, a linear response for clinically relevant qualities, rates preirradiation doses.

A quality control system especially designed for dosimetry in scanning proton beams has been and tested. The consists of a scintillating screen mounted at the beam-exit side phantom, observed by low noise CCD camera with long integration time. purpose instrument is to make fast accurate two-dimensional image dose distribution position phantom. linearity signal dose, signal, influence ionization density on field size have investigated. spatial resolution 1.3 mm (1 s.d.), which sufficiently...

Currently, most clinical range-modulated proton beams are assumed to have a fixed overall relative biological effectiveness (RBE) of 1.1. However, it is well known that the RBE increases with depth in spread-out Bragg peak (SOBP) and becomes about 10% higher than mid-SOBP at 2 mm from distal edge (Paganetti 2003 Technol. Cancer Res. Treat. 413-26) can reach values 1.3-1.4 vitro (Robertson et al 1975 35 1664-77, Courdi 1994 Br. J. Radiol. 67 800-4). We present fast method for applying...

Three-dimensional dosimetry with good spatial resolution can be performed using polymer gel dosimetry, which has been investigated for of different types particles. However, there are only sparse data concerning the influence linear energy transfer (LET) properties radiation on absorbed dose response. The purpose this study was to investigate possible LET dependence a dosimeter proton beam measurements. Polymer containing antioxidant tetrakis(hydroxymethyl)phosphonium (THP) irradiated 133...

Sputtering a gold contact on n‐silicon or sputter‐etching the silicon surface prior to deposition of results in Schottky barrier which shows height depends sputtering voltage and time, is lower than corresponding obtained by evaporation contact. On p‐silicon sputtered also influenced conditions. The modifications are caused thin positively charged layer formed semiconductor near metal‐semiconductor junction. During sputter etching subject bombardment Ar ions with energies about voltage. If...

A theoretical investigation concerning sensitivity variations in semiconductor detectors used the short-circuit mode at different temperatures and pre-irradiation dose levels has been compared with experimental results. Initially, a drop of more than 15% kGy-1 increase temperature less 1% per 10 degrees C was found for p-type silicon detectors. After 5 kGy 20 MeV electrons these values were changed to about 6.5% 3% C, respectively. As rise obtained detector when applied patient, change be...

Abstract Objective . Ionization chambers, mostly used for beam calibration and reference dosimetry, can show high recombination effects in pulsed dose rate proton beams. The aims of this paper are: first, to characterize the linearity response newly designed asymmetrical monitor chambers (ABMC) a 100–226 MeV per pulse scanned beam; secondly, calibrate ABMC with PPC05 (IBA Dosimetry) plane parallel ionization chamber compare home-made Faraday cup (FC). Approach was evaluated both FC PTW 60019...

The implementation of two algorithms for calculating dose distributions radiation therapy treatment planning intermediate energy proton beams is described. A pencil kernel algorithm and a depth penetration have been incorporated into commercial three-dimensional system (Helax-TMS, Helax AB, Sweden) to allow conformal techniques using irregularly shaped fields, range modulation, modification calculation non-coplanar beams. developed from the Fermi-Eyges formalism Molière multiple-scattering...

Describes a dual-scattering-foil technique for flattening of radiotherapeutic charged particle beams. A theory optimization shapes and thicknesses the scattering foils is presented. The result universal optimal secondary-scatterer profile, which can be adapted to any beam by simple scaling procedure. calculation mean square angle after passing through done using generalized Fermi-Eyges model transport. It shown that fluence profile in plane interest made flat better than 1% inside predefined...

Semiconductor detectors based on p-type silicon and designed for in vivo measurement of entrance dose at the reference point from photon radiation fields, are described. To estimate absorbed measurements with a thin detector, field-size dependent correction factors must be applied to reading, as shape buildup curve varies field size. decrease or avoid factors, detector can covered cap. The presence such will cause perturbation field. Therefore, design irrespective its type, intended patient...

Depth dose measurements in continuous cobalt radiation and pulsed roentgen rays were performed with nonirradiated preirradiated detectors made of n-type silicon. A change the relative signal at 15 cm depth 5 to 10 per cent was found ray fields when detector damaged. Further experiments showed that had a superlinear response characteristic high rates. theoretic model worked out non-linearity is explained by properties recombination centers created during preirradiation. The are also...

Objectives – To evaluate the therapeutic efficiency and adverse effects of stereotactic proton beam treatment cerebral arteriovenous malformations (AVM). Material methods Twenty-six patients treated in Uppsala during 1991–97 were included (men = 14, women 12; mean age 39, range 23–64). The nidus volumes ranged from 0.3 to 102 ml (mean 24, median 13). follow-up clinical evaluation, magnetic resonance imaging (and/or computed tomography) every 6–12 months for 3 years final angiography. Results...

Semiconductor detectors based on p-type silicon but with different doping levels have been investigated. The linearity response dose rate (dose per pulse in a pulsed beam), the sensitivity drop and variation temperature investigated after preirradiation, radiation damage, qualities. It was shown that detector low level, high resistivity, showed nonlinear if damaged energy photon beam which contains neutrons. By increasing level it resistivity of 0.2 Omega cm stayed linear preirradiation...

Three-dimensional dose planning systems employing accurate proton transport algorithms are essential for calculating absorbed distributions in therapy. In this paper, a pencil beam algorithm the of protons materials interest radiation therapy is developed. The Fermi-Eyges multiple-scattering theory used to derive equations fluence and distributions. Moliere predict mean square scattering angles develop an expression root (RMS) radial spread beam, as function depth, arbitrary material. A...

Abstractp-silicon semiconductor detectors were partially shielded with lead filters of various geometries the purpose to minimize quality dependence in assessments depth dose distributions large fields cobalt radiation. It is shown that a shielding detector, front side excluded, reduced signal error from about 3 less than one per cent maximum as compared an ionization chamber. Shielding was also done by encapsulating detector mixture wolfram powder and epoxy resin, similar results. The...

The properties of silicon diode detectors, used for dosimetry in clinical proton beams, were investigated with special regard to the measurement relative dose distributions water. Different types detector studied, and resulting signal versus depth water phantom compared corresponding obtained a plane-parallel NACP ionization chamber. measurements performed beam an initial energy 173 MeV. It is shown that Hi-p gives which proportional density crystal all parts Bragg curve, levels accumulated...

Absorbed doses determined with a sealed water calorimeter operated at 4 degrees C are compared the results obtained using ionization chambers and IAEA TRS-398 code of practice in 10 MV photon beam (TPR(20,10) = 0.734) 175 MeV proton (at depth corresponding to residual range, R(res) 14.7 cm). Three NE 2571 two FC65-G were calibrated terms absorbed-dose-to-water (60)Co Swedish secondary standard dosimetry laboratory, directly traceable BIPM. In quality, calorimetry was found agree ionometry...

Radiation treatment is commonly employed in the of meningiomas. The aim this study was to evaluate effectiveness and safety hypofractionated high-energy proton therapy as adjuvant or primary for WHO grade I A total 170 patients who received irradiation with protons meningiomas between 1994 2007 were included study. majority tumours located at skull base (n = 155). Eighty-four treated post subtotal resection, 42 tumour relapse 44 upfront radiotherapy after diagnosis based on typical...

Ferrous sulphate gel dosimetry has the potential for measurement of absorbed dose distributions in proton therapy. The chemical properties are altered according to radiation and these changes can be evaluated three dimensions using MRI. purpose this work was investigate a ferrous used with clinical beams.

A beam source model, i.e. a model for the initial phase space of beam, scanned proton beams has been developed. The is based on parameterized particle sources with characteristics found by fitting towards measured data per individual line. specific aim this to make it applicable majority various systems currently available or under development, overall purpose drive dose calculations in treatment planning. characterized an energy spectrum, radial and angular distributions deflections...