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At least 19 recordsLinked to original sources
PubMed2004

[Interaction between a ceiling pendent-type lead acrylic protective board for use in IVR and scattered radiation].

Scattered radiation was measured following the application of a ceiling pendent-type lead acrylic protective board (protective board) for use in IVR, and the dose-reduction rate was obtained. As a result of the interaction between the protective board and the scattered radiation, the dose reduction rate in the space between the protective board and floor surface became negative, resulting in an increase in scattered radiation. It was demonstrated that the increase in scattered radiation could be prevented by installing an added filter. This report presents a method to evaluate the effect of a protective board on scattered radiation by converting its property to that of a material with a similar effective density, and explains the experimental results. This report also shows that a conventional method, which calculates scattered radiation on the basis of lead equivalent, carries the risk of underestimating the effect on scattered radiation. The necessity of training operators based on the above findings is also emphasized.

Acrylates↗
PubMed1987

[A procedure for taking into account scattered radiation and scattered light in the densitometric determination of intravascular iodine content].

Scattered light and scattered radiation are two significant sources of error during video densitometry and lead to local under-estimation of iodine concentration. A procedure is described using digital subtraction angiography which largely eliminates both factors. The measured intravascular iodine concentration is close to the true value throughout the entire intensifier field and quantitative evaluation is independent of local factors. The reduction of the artifacts improves diagnostic certainty during visual evaluation also.

Absorptiometry, Photon↗
PubMedDate not supplied

A technique for the correction of scattered radiation in a PET system using time-of-flight information.

The time-of-flight information has been used in the development of a correction technique for the effects of radiation scattering in a positron emission tomography system. A two-dimensional function describing the scattered radiation distribution is added to the response of the system. A deconvolution filter that depends on parameters that were experimentally determined from measurements of a linear source located in a scattering medium is derived. The method was tested on cold spot cylindrical phantoms. The relative intensity of events from scattered radiation is significantly reduced and the contrast is thus improved. This technique does not require any additional computing time and can be included in standard reconstruction procedure.

Electrons↗
PubMedDate not supplied

Method for estimating the intensity of scattered radiation using a scatter generation model.

An analytical formula for estimating the intensity of scattered radiation in an x-ray image under various exposure conditions has been developed. The formula was derived using measured data of scatter and primary intensity for various exposure conditions. To simplify the formula, a scatter generation model was constructed mathematically which assumes that the scattered fluence in a material depends on three processes: (1) scattering of the primary photons; (2) scattering of previously scattered photons; and (3) attenuation of the scattered photons. Using this model, the dependence of scatter-to-primary ratio on phantom thickness and the tube voltage was expressed by a simple equation. Parameters included in the model were determined from the analysis of measured data. Based on empirical data, it was assumed that the dependence of scatter-to-primary ratio on air gap and field size is not affected by variations of phantom thickness and tube voltage. The final formula, which does not include the term of phantom thickness, gives an estimate of the intensity of the scattered radiation from exposure conditions. The scatter intensity estimated using the formula was compared with measured data for various phantom thicknesses, tube voltages, air gaps, and field sizes; the results show that the intensity of scattered radiation can be estimated within about +/- 10% using predetermined parameters.

Mathematics↗
PubMed2004

Dose due to scattered radiation in external radiotherapy: a prostate cancer case history.

One of the authors was subjected to external radiotherapy with 6 MeV photons to treat a prostate cancer. The dose due the radiation scattered by the target was measured by means of pen dosemeters distributed along the body. Subsequently, both the equivalent dose delivered to some organs and the effective dose delivered to the body, due to scattering only, were evaluated.

Algorithms↗
PubMed1992

Measurements of computed tomography radiation scatter.

This paper describes the measurement of scattered radiation from a computed tomography (CT) scanner in a clinical situation and compares the results with those obtained from a CT performance phantom and with data obtained from CT manufacturers. The results are presented as iso-dose contours. There are significant differences between the data obtained and that supplied by manufacturers, both in the shape of the iso-dose contours and in the nominal values. The observed scatter in a clinical situation (for an abdominal scan) varied between 3% and 430% of the manufacturers' stated values, with a marked reduction in scatter noted at the head and feet of the patient. These differences appear to be due to the fact that manufacturers use CT phantoms to obtain scatter data and these phantoms do not provide the same scatter absorption geometry as patients. CT scatter was observed to increase as scan field size and slice thickness increased, whilst there was little change in scatter with changes in gantry tilt and table slew. Using the iso-dose contours, the orientation of the CT scanner can be optimised with regard to the location and shielding requirements of doors and windows. Additionally, the positioning of staff who must remain in the room during scanning can be optimised to minimise their exposure. The data presented here allows for realistic radiation protection assessments to be made.

Models, Structural↗
PubMedDate not supplied

Measurement of the average path length of gamma-rays in samples using scattered radiation.

A method for measuring the average path length traversed by gamma-rays in a sample is presented. In this method the amount of radiation scattered within the sample at small angles and registered in the spectrum is measured. It is shown that the increase in counts in an energy interval close to the energy of the emitted gamma-rays, relative to the value attained in the absence of the interaction between the gamma-rays and the sample, is proportional to the average path length in the sample. Measurements of the average path length in samples of cylindrical geometry with various dimensions and at several energies are presented and compared with the predicted values. The differences between the measured and predicted values are discussed.

Journal Article↗
PubMed2005

Two-particle model to study fluctuations of scattered radiation: multiple-scattering effects.

The intensity fluctuations of light scattered from a simple particle aggregate system consisting of two dipole-like particles separated by a fixed distance and floating freely in space are calculated numerically and analyzed statistically. The behavior of two statistical parameters, the second-order factorial moment of the intensity fluctuations and the probability of obtaining zero cross-polarized intensity, are studied as a function of both the particle polarizability and the interparticle distance. Effects of multiple-scattering processes on these statistical parameters are accounted for in particular.

Journal Article↗
PubMed1999

[Determination of monitor radiation scattering contribution in photon radiation of clinical electron linear accelerators].

BACKGROUND: Modern linear accelerators permit the use of irregular fields due to their flexible collimator systems with separately movable jaws or multileaf collimators. When using such irregular fields in the clinical practice output factors have to be corrected for enhanced backscatter to the dose monitor as compared with the conventional block shieldings. METHODS: A method is presented to detect the monitor backscatter contributions to the output factor for irregular field settings. RESULTS: The monitor backscatter factors have been measured using a telescopic device for 2 different treatment head geometries (Varian Clinac 2100C/D, General Electric Saturne 15) and for 3 photon radiation qualities (nominal energies X6, X18, X12). A method is introduced to calculate the monitor backscatter for arbitrary irregular treatment fields from the experimental data for square or rectangular fields. CONCLUSIONS: Besides the corrections for changes in phantom scatter and changes in the aperture, corrections for monitor backscatter have to be taken into account in many clinical cases. They can contribute up to more than 10% compared with the monitor values for free regular fields.

Humans↗
PubMed2004

Use of a sterile, disposable, radiation-absorbing shield reduces occupational exposure to scatter radiation during pectoral device implantation.

The aim of this study was to demonstrate the effectiveness of a radiation-absorbing shield in reducing physicians' occupational radiation exposure during pectoral device implantation. A sterile, disposable, lead-free radiation-absorbing surgical drape containing x-ray attenuation material was evaluated. Twenty procedures used the radiation absorbing drape, and 20 were performed without the shielding. Radiation exposure was measured using thermoluminescent dosimetry collar badges. Use of the protective shield was associated with a time adjusted 80% reduction in radiation dose (0.009 mrem/s with shielding vs 0.047 mrem/s without shielding, P < 0.05) to the physician performing the procedures. The radiation-absorbing surgical drape did not interfere with technical performance nor add procedural time, and all procedures were successfully completed. This study demonstrates that a sterile, disposable, radiation-absorbing drape provides a convenient means of augmenting conventional radiation shielding. Use of this protective shielding greatly reduces operators' occupational exposure to scatter radiation during pectoral device implantation without compromising sterility or procedural technique.

Bismuth↗
PubMed1987

[Radiation burden in heart catheter studies--significance of measures for reducing scatter radiation].

During diagnostic and, more particularly, therapeutic intervention, such as transluminal coronary angioplasty, the operator may be exposed to a considerable degree of scatter radiation. In our study, we measured the level of radiation exposure of the head, unprotected knees and lower legs. A flexible lead screen, attached to the catheterization table (0.5 mm Pb) reduced scatter radiation of the lower legs by 95%. In addition, scatter radiation exposure of the head decreased by 54% by covering the patient with a rubber leaden blanket (0.25 mm Pb). Finally, the use of these supplementary yet simple measures did not hinder or interfere with the examination procedure in any way.

Cardiac Catheterization↗
PubMed1986

Scattered radiation grids in cephalometric radiography.

Scattered radiation grids are routinely used in medical radiological examinations of the skull, but less commonly in cephalometric radiography. Because the grids involve an increased radiation dose, it is necessary to determine whether the diagnostic quality of cephalometric radiographs is improved by a grid to an extent that justifies this increased dose. This investigation has failed to demonstrate any improvement in the identification of five landmarks. It is thus concluded that there is no justification for the use of scattered radiation grids in cephalometric radiography.

Adult↗
PubMed2001

A method for calculating the dose to a multi-storey building due to radiation scattered from the roof of an adjacent radiotherapy facility.

With modern urbanization trends, situations occur where a general-purpose multi-storey building would have to be constructed adjacent to a radiotherapy facility. In cases where the building would not be in the primary x-ray beam, "skyshine" radiation is normally accounted for. The radiation scattered from the roof side-wise towards the building can also be a major contributing factor. However, neither the NCRP reports nor recently published literature considered this. The current paper presents a simple formula to calculate the dose contribution from scattered radiation in such circumstances. This equation includes workload, roof thickness, field size, distance to the reference point and a normalized angular photon distribution function f(theta), where theta is the angle between central axis of the primary beam and photon direction. The latter was calculated by the Monte Carlo method (EGS4 code) for each treatment machine in our department. For angles theta exceeding approximately 20 degrees (i.e., outside the primary beam and its penumbra) the angular distribution function f(theta) was found to have little dependence on the shielding barrier thickness and the beam energy. An analytical approximation of this function has been obtained. Measurements have been performed to verify this calculation technique. An agreement within 40% was found between calculated and measured dose rates. The latter combined the scattered radiation and the dose from "skyshine" radiation. Some overestimation of the dose resulted from uncertainties in the radiotherapy building drawings and in evaluation of the "skyshine" contribution.

Biophysical Phenomena↗
PubMed2002

Scattered radiation level during videofluoroscopy for swallowing study.

AIM: To evaluate the scattered radiation exposure to the surroundings during videofluoroscopy for swallowing study (VFSS). MATERIALS AND METHODS: Scattered radiation exposure was measured using an ion chamber survey meter for 17 adult patients undergoing videofluoroscopy for swallowing study. The cumulative dose area product of each case was also recorded. Data were presented as mean +/- standard deviation. RESULTS: The scattered radiation exposure at a distance of 150 cm from the patient and the dose area product recorded were 149 +/- 78 microR (range 42-308 microR) and 842 +/- 544 cGy.cm(2) (range 258-2151 cGy.cm(2)), respectively, for a single study of 18 +/- 6 minutes. A formula was then derived for estimating the scattered radiation dose to muscle tissue at an arbitrary distance based on the accumulated dose area product. With this formula, the mean scattered radiation dose to naked muscle tissue of the surrounding people at a distance of 30-100 cm from the patient were estimated to be 33.68-3.03 microSv respectively. CONCLUSION: The scattered radiation detriment associated with videofluoroscopy for swallowing study was well within acceptable levels.

Adult↗
PubMed2003

Scattered radiation from applicators in clinical electron beams.

In radiotherapy with high-energy (4-25 MeV) electron beams, scattered radiation from the electron applicator influences the dose distribution in the patient. In most currently available treatment planning systems for radiotherapy this component is not explicitly included and handled only by a slight change of the intensity of the primary beam. The scattered radiation from an applicator changes with the field size and distance from the applicator. The amount of scattered radiation is dependent on the applicator design and on the formation of the electron beam in the treatment head. Electron applicators currently applied in most treatment machines are essentially a set of diaphragms, but still do produce scattered radiation. This paper investigates the present level of scattered dose from electron applicators, and as such provides an extensive set of measured data. The data provided could for instance serve as example input data or benchmark data for advanced treatment planning algorithms which employ a parametrized initial phase space to characterize the clinical electron beam. Central axis depth dose curves of the electron beams have been measured with and without applicators in place, for various applicator sizes and energies, for a Siemens Primus, a Varian 2300 C/D and an Elekta SLi accelerator. Scattered radiation generated by the applicator has been found by subtraction of the central axis depth dose curves, obtained with and without applicator. Scattered radiation from Siemens, Varian and Elekta electron applicators is still significant and cannot be neglected in advanced treatment planning. Scattered radiation at the surface of a water phantom can be as high as 12%. Scattered radiation decreases almost linearly with depth. Scattered radiation from Varian applicators shows clear dependence on beam energy. The Elekta applicators produce less scattered radiation than those of Varian and Siemens, but feature a higher effective angular variance. The scattered radiation decreases somewhat with increasing field size and is spread uniformly over the aperture. Experimental results comply with the results of simulations of the treatment head and electron applicator, using the BEAM Monte Carlo code, and Siemens, but feature a higher effective angular variance. The scattered radiation decreases somewhat with increasing field size and is spread uniformly over the aperture. Experimental results comply with the results of simulations of the treatment head and electron applicator, using the BEAM Monte Carlo code.

Algorithms↗
PubMed1992

The dependence of the scattered radiation dose to personnel on technique factors in diagnostic radiology.

The measurement and prediction of scattered radiation dose to staff in diagnostic radiology is particularly important, owing to the increased use and complexity of interventional radiology. The air kerma-area product and scattered radiation dose in the vicinity of the patient couch, for both overcouch and undercouch X-ray tube geometries, were simultaneously monitored. The scattered radiation distribution at the couchside was deduced at a range of tube potentials for both overcouch and undercouch X-ray tube geometries. The variation of scattered radiation with field size on both geometries was investigated, as well as the variation with focus-table distance on an overcouch tube geometry. It was discovered that the scattered radiation dose at a point correlated with the air kerma-area product and the result may be used for radiation protection purposes. A method of predicting the scattered radiation dose at a given position is described.

Humans↗