scholarly journals Evaluation of a micro ionization chamber for dosimetric measurements in image-guided preclinical irradiation platforms

2021 ◽  
Author(s):  
Ileana Silvestre Patallo ◽  
Rebecca Carter ◽  
David Maughan ◽  
Andrew Nisbet ◽  
Giuseppe Schettino ◽  
...  
Keyword(s):  
Ionization Chamber ◽  
Small Volume ◽  
Small Animal ◽  
X Rays ◽  
Medium Energy ◽  
X Ray ◽  
Small Fields ◽  
Ion Recombination ◽  
Primary Standards ◽  
Volume Ionization

Abstract Image-guided small animal irradiation platforms deliver small radiation fields in the medium energy x-ray range. Commissioning of such platforms, followed by dosimetric verification of treatment planning, are mostly performed with radiochromic film. There is a need for independent measurement methods, traceable to primary standards, with the added advantage of immediacy in obtaining results. This investigation characterizes a small volume ionization chamber in medium energy x-rays for reference dosimetry in preclinical irradiation research platforms. The detector was exposed to a set of reference x-ray beams (0.5 to 4 mm Cu HVL). Leakage, reproducibility, linearity, response to detector’s orientation, dose rate, and energy dependence were determined for a 3D PinPoint ionization chamber (PTW 31022). Polarity and ion recombination were also studied. Absorbed doses at 2 cm depth were compared, derived either by applying the experimentally determined cross-calibration coefficient at a typical small animal radiation platform “user’s” quality (0.84 mm Cu HVL) or by interpolation from air kerma calibration coefficients in a set of reference beam qualities. In the range of reference x-ray beams, correction for ion recombination was less than 0.1%. The largest polarity correction was 1.4% (for 4 mm Cu HVL). Calibration and correction factors were experimentally determined. Measurements of absorbed dose with the PTW 31022, in conditions different from reference were successfully compared to measurements with a secondary standard ionization chamber. The implementation of an End-to-End test for delivery of image-targeted small field plans resulted in differences smaller than 3% between measured and treatment planning calculated doses. The investigation of the properties and response of a PTW 31022 small volume ionization chamber in medium energy x-rays and small fields can contribute to improve measurement uncertainties evaluation for reference and relative dosimetry of small fields delivered by preclinical irradiators while maintaining the traceability chain to primary standards.

Search of a small volume ionization chamber for the establishment of LNHB primary standards in a 2x2 cm2

2011 ◽  
Vol 27 ◽  
pp. S21-S22
Author(s):  
M. Le Roy ◽  
L. de Carlan ◽  
F. Delaunay ◽  
M. Donois ◽  
P. Fournier ◽  
...  
Keyword(s):  
Ionization Chamber ◽  
Small Volume ◽  
Primary Standards ◽  
Volume Ionization

scholarly journals The use of fricke dosimetry for low energy x-rays

2006 ◽  
Vol 49 (spe) ◽  
pp. 17-23 ◽  
Author(s):  
Carlos de Austerlitz ◽  
Viviane Souza ◽  
Heldio Pereira Villar ◽  
Aloisio Cordilha
Keyword(s):  
Ionization Chamber ◽  
Parallel Plate ◽  
Low Energy ◽  
Calibration Factor ◽  
X Rays ◽  
Measuring Systems ◽  
X Ray ◽  
Dose Measurements

The performance of four X-ray qualities generated in a Pantak X-ray machine operating at 30-100 kV was determined with a parallel-plate ionization chamber and a Fricke dosimeter. X-ray qualities used were those recommended by Deutsch Internationale Normung DIN 6809 and dose measurements were carried out with Plexiglas® simulators. Results have shown that the Fricke dosimeter can be used not only for soft X-ray dosimetry, but also for the maintenance of low-energy measuring systems' calibration factor.

Exosat Observations of H2252−035: Pulse Phase and Orbital Phase Dependent Low Energy Absorption and Iron Line Emission

1987 ◽  
Vol 93 ◽  
pp. 281-292
Author(s):  
W. Pietsch ◽  
W. Voges ◽  
E. Kendziorra ◽  
M. Pakull
Keyword(s):  
Energy Absorption ◽  
Line Emission ◽  
Low Energy ◽  
Gas Absorption ◽  
X Rays ◽  
Medium Energy ◽  
Iron Line ◽  
X Ray ◽  
Low Energies ◽  
Optical Light Curve

AbstractThe 805 sec pulsing X-ray source H2252−035 has been observed for 7 h on September 14/15 and on September 17, 1983 in X-rays with the low energy telescope and the medium energy detectors of EXOSAT. While below 2 keV the semiamplitude of the 805 s pulses is ~ 100% in the 2.3–7.9 keV band it is only ~ 40%. X-ray dips that are more pronounced in low energies occur simultaneously with the orbital minimum of the optical light curve. The medium energy spectra during dips with respect to the non dip spectrum can be explained by just enhanced cold gas absorption of an additional absorbing column of 2 1022 cm−2. Model spectra for the 805 s minimum have to include a strong iron emission line at 6.55 keV with an equivalent width of 3 keV in addition to a reduced continuum intensity (radiating area) and enhanced low energy absorption.

Estimation of the X-rays RBE Uncerainty Related to Determination of Absorbed Dose in Radiobiological Experiments

2018 ◽  
Vol 63 (2) ◽  
pp. 62-64 ◽  
Author(s):  
А. Белоусов ◽  
A. Belousov ◽  
Г. Крусанов ◽  
G. Krusanov ◽  
А. Черняев ◽  
...  
Keyword(s):  
Biological Tissue ◽  
Ionization Chamber ◽  
Culture Medium ◽  
Relative Biological Effectiveness ◽  
Spectral Composition ◽  
Absorbed Dose ◽  
X Rays ◽  
X Ray ◽  
Biological Effectiveness

Purpose: Determining the absorbed dose produced by photons, it is often assumed that it is equal to the radiation kerma. This assumption is valid only in the presence of an electronic equilibrium, which in turn is never ensured in practice. It leads to some uncertainty in determining the absorbed dose in the irradiated sample during radiobiological experiments. Therefore, it is necessary to estimate the uncertainty in determining the relative biological effectiveness of X-rays associated with uncertainty in the determination of the absorbed dose. Material and methods: The monochromatic X-ray photon emission is simulated through a standard 25 cm2 plastic flask containing 5 ml of the model culture medium (biological tissue with elemental composition C5H40O18N). The calculation of the absorbed dose in a culture medium is carried out in two ways: 1) the standard method, according to which the ratio of the absorbed dose in the medium and the ionization chamber is equal to the ratio of kerma in the medium and air; 2) determination of the absorbed dose in the medium and in the sensitive volume of the ionization chamber by computer simulation and calculating the ratio of these doses. For each primary photon energies, 108 histories are modeled, which makes it possible to achieve a statistical uncertainty not worse than 0.1 %. The energy step was 1 keV. The spectral distribution of X-ray energy is modeled separately for each set of anode materials, thickness and materials of the primary and secondary filters. The specification of the X-ray beams modeled in this work corresponds to the standards ISO 4037 and IEC 61267. Within the linear-quadratic model, the uncertainty of determining the RBEmax values is directly proportional to the uncertainty in the determination of the dose absorbed by the sample under study. Results: At energy of more than 60 keV, the ratios for water and biological tissue practically do not differ. At lower energies, up to about 20 keV, the ratio of the coefficients of air and water is slightly less than that of air and biological tissue. The maximum difference is ~ 1 % than usual and the equality of absorbed doses in the ionization chamber and sample is justified. At photon energy of 60 keV for the geometry in question, the uncertainty in determining the dose is about 50 %. For non-monochromatic radiation, the magnitude of the uncertainty is determined by the spectral composition of the radiation, since the curves vary greatly in the energy range 10–100 keV. It is shown that, depending on the spectral composition of X-ray radiation, uncertainty in the determination of the absorbed dose can reach 40–60 %. Such large uncertainty is due to the lack of electronic equilibrium in the radiation geometry used in practice. The spread of RBE values determined from the data of radiobiological experiments carried out by different authors can be determined both by differences in the experimental conditions and by uncertainty in the determination of the absorbed dose. Using Fricke dosimeters instead of ionization chambers in the same geometry allows you to reduce the uncertainty approximately 2 times, up to 10–30 %. Conclusion: The computer simulation of radiobiological experiments to determine the relative biological effectiveness of X-ray radiation is performed. The geometry of the experiments corresponds to the conditions for the use of standard bottles placed in the side holders. It is shown that the ratio of absorbed doses and kerma in the layers of biological tissue and air differ among themselves with an uncertainty up to 60 %. Depending on the quality of the beam, the true absorbed dose may differ from the one calculated on the assumption of kerma and dose equivalence by 50 %. Uncertainty in determining the RBE in these experiments is of the same order. The results are presented for X-ray beams with negligible fraction of photons with energies less than 10 keV. For beams of a different quality, the uncertainty in determination can significantly increase. For the correct evaluation of RBE, it is necessary to develop a uniform standard for carrying out radiobiological experiments. This standard should regulate both the geometry of the experiments and the conduct of dosimetric measurements.

Free-air ionization chamber, FAC-IR-300, designed for medium energy X-ray dosimetry

2017 ◽  
Vol 12 (01) ◽  
pp. T01008-T01008 ◽  
Author(s):  
S.M. Mohammadi ◽  
H. Tavakoli-Anbaran ◽  
H.Z. Zeinali
Keyword(s):  
Ionization Chamber ◽  
Medium Energy ◽  
X Ray ◽  
Free Air ◽  
Air Ionization

SECONDARY RADIATION FROM X-RAY FILTERS: I. SINGLE-METAL FILTERS

1942 ◽  
Vol 20a (11) ◽  
pp. 185-194
Author(s):  
G. A. Wrenshall ◽  
H. J. Nichols
Keyword(s):  
Intensity Distribution ◽  
Ionization Chamber ◽  
Operating Conditions ◽  
Secondary Radiation ◽  
X Rays ◽  
X Ray ◽  
Chamber Method ◽  
Aluminium Copper ◽  
Standard Operating

Using an ionization chamber method, the intensity distribution and quality of forward transmitted secondary X-rays from filters of aluminium, copper, tin, and lead have been measured under standard operating conditions. Geometrical arrangements of X-ray tube, defining apertures, filter, and receiver commonly used in medical and industrial radiology are employed. Suggestions for minimizing the intensity of the secondary radiation reaching the receiver from single-metal filters are submitted.

Rotating crystal X-Ray photographs

1927 ◽  
Vol 21 (117) ◽  
pp. 258-271 ◽  
Author(s):  
Gilbert Greenwood
Keyword(s):  
Flat Plate ◽  
Ionization Chamber ◽  
The Other ◽  
X Rays ◽  
X Ray ◽  
Chamber Method ◽  
Powder Method ◽  
Small Crystal ◽  
Royal Institution

Since the original experiments of M. von Laue on the diffraction of X-rays by crystals, other and more suitable methods of research have been devised. The Bragg ionization-chamber method and the Debye-Scherrer powder method are now quite well known. The newest technique is that of the so-called 'rotating crystal', which is based essentially on some experiments of M. de Broglie. This method was first employed and developed in the Kaiser Wilhehm Institut für Faserstoffchemie in Berlin. It has recently been extended by the work of J. D. Bernal in the Royal Institution in London.There are two methods of making this type of photograph. In both a small crystal is rotated in a beam of X-rays and the reflected beams recorded photographically, in one case on a flat plate, and in the other on a cylindrical film the axis of which coincides with the axis about which the crystal is rotated.

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