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PubMed1999

[Principle and application of scattering power function method in X-ray fluorescence analysis. III. Continuous scattering radiation].

The study in this paper shows that the relationship between mass attenuation coefficient and continuous scattering radiation at wavelength 0.081 nm is not an inverse proportion supposed as the scattering internal standard method but a power function in a wide range of matix composition. Experimental results are in good agreement with that of theoretical prediction. A new method is recommended for matrix absorption correction using the 1.22 power function of continuous scattering radiation at wavelength 0.081 nm and used for microelement Sr determination in geological samples as an application example. The accuracy of the results by this method is nearly 4 times better than that from the traditional scattering internal method in a wide range of matrix composition.

English Abstract↗
PubMed1992

Photon absorption measurements of bone density in the presence of scattered radiation.

Bone density measurements are frequently carried out using photon absorptiometry techniques. The analysis of data collected in this way depends upon scatter-free detector signals. In practice the detector and source collimation lead to high levels of scattered radiation being detected. An analysis of the problem using photon transport computer models has shown that the current systems are reasonably insensitive to the scatter contribution except where patient changes occur over a long series of measurements or where new results taken with DEXA are compared with those taken on older systems such as DPA. This is frequently the case since the major body of data related to serial bone density measurements has been achieved with DPA. Inclusion of scattered radiation in the bone density calculations can lead to a 0.5-3.5% reduction between system types. Patient size changes could lead to a reduction in bone density of 0.5% (femoral neck measurement) to 1% (lumbar spine measurement).

Absorptiometry, Photon↗
PubMedDate not supplied

Dynamic radiography. An evaluation of cardiac motion by the analysis of scattered radiation during fluoroscopy.

A non-invasive technique, utilizing scattered radiation, has been developed to monitor and measure the motion of the epicardial surface during fluoroscopy. A number of dogs were studied using a monitoring device which consists of an X-Ray beam collimator, collimated sodium iodide dectetors and their associated electronics. The detector signals are computer processed to obtain frequency fingerprints of epicardial motion that may, in the future, indicate the condition of the myocardium.

Computers↗
PubMed1980

Scatter radiation to the hands from insertion of transvenous pacemakers.

Using ring film-badge dosimeters, scatter radiation to the hands of the operating surgeon was measured during the transvenous insertion of nine permanent pacemakers and one inferior vena cava umbrella. Average fluoroscopy time was 12 minutes. The average dose of radiation was 25.5 mrems. The calculated yearly exposure of a surgeon inserting pacemakers at this rate is approximately 3 R. This falls well within the "maximum permissible dose" to the hands, which is currently 75 R per year.

Fluoroscopy↗
PubMed2006

Impact of a lead glass screen on scatter radiation to eyes and hands in interventional cardiologists.

The objective of this study was to assess the impact of a transparent lead glass screen (TLGS) on scatter radiation to the eyes and the hands in interventional cardiologists and to compare the results to the recommended annual threshold values of 150 and 500 mSv, respectively. Local radiation doses to the left eye and the ring finger of the left hand of three operators (A, B, C) were assessed by thermoluminiscence dosimeters during 813 coronary angiographies (CAs), including 190 ad hoc percutaneous coronary interventions (PCIs) either with a TLGS placed between patient and operator [615 CAs including 138 ad hoc PCIs; dose-area product (DAP) = 84.9 +/- 71.3 Gy x cm(2)], or without (198 CAs including 52 PCIs; DAP = 85.7 +/- 61.5 Gy x cm(2)). To determine the efficacy of the TLGS, average DAP-normalized local doses were calculated. Using a TLGS, operator A, B, and C performed 259 (in 9 months), 211 (in 8 months), and 145 CAs (in 8 months) with TLGS and acquired cumulative eye lens doses of 5.5, 1.5, and 1.0 mSv corresponding to extrapolated annual doses of 7.3, 2.3, and 1.5 mSv. The cumulative finger doses were 9.6, 10.3, and 6.4 mSv, resulting in extrapolated annual doses of 12.8, 15.5, and 9.6 mSv. Compared to 139 (in 5 months), 36 (in 2 months), and 23 CAs (in 2 months) without TLGS, the use of a TLGS reduced the DAP-normalized eye dose by a factor of 19 (with TLGS 0.153 vs. without TLGS 2.924 microSv/Gy x cm(2)), whereas only a weak effect on the dose to the hands was observed (with TLGS 0.504 vs. without TLGS 0.578 microSv/Gy x cm(2)). The consequent use of a TLGS efficiently reduces scatter radiation to the operator's eyes in daily practice, but has only minimal effects on the dose to the hands.

Aged↗
PubMed1990

[The effect of scattered radiation and tube focal size on the background density of x-ray pictures using an x-ray exposure system].

By experimental variation of scattered radiation (various field sizes with and without grid) it is shown, that even under defined experimental conditions there is little or negligible influence of scattered radiation on the photographic density of films. The variation is less than 5% for tube voltages between 55 and 120 kV (Exposure control system Robotron type 20041). Variations of film density connected with changes of focal spot size are explained by changes of kVp (insufficient tube load compensation) and by differences of energy sensitivity of ionization chambers and screen-film combinations as well as differences in exposure time for different focal sizes. Short exposure times below 200 ms and constant tube voltages result in equal film exposure, if different focal sizes are used.

Quality Control↗
PubMedDate not supplied

Physical characteristics of scattered radiation in diagnostic radiology: Monte Carlo simulation studies.

We applied Monte Carlo methods for the simulation of x-ray scattering in water phantoms. The phantom thickness was varied from 5 to 20 cm, and the monoenergetic incident x rays were varied from 15 to 100 keV. Eight screen pairs and a total absorption system were used as x-ray receptors. We determined the angular, spectral, and spatial distributions of the scattered radiation and the scatter fractions recorded in the image plane. The dependence of these properties on the incident x-ray energy, the phantom thickness, and the energy response of the recording system was examined. The results of this study provide useful information for the development of antiscatter techniques and for the evaluation of radiographic procedures.

Models, Theoretical↗
PubMedDate not supplied

Scattered radiation in chest radiography.

Luminance scatter fractions were measured for patients and phantoms in various regions of the chest film. Scatter fractions were found to be highly variable, being quite high in the regions of the chest with a large equivalent tissue thickness (e.g. mediastinum, chest wall, and subdiaphragmatic areas). For example, approximately 90% of the radiation reaching the mediastinum region of the chest film was found to be scattered radiation when a grid was not used. Even with a 12:1 grid, less than 50% of the available primary beam contrast was being displayed in the mediastinum. In regions of the chest film with high scatter fractions, film latitude was also a problem, further reducing image contrast in these regions. Image contrast and scatter fractions in chest radiography were investigated for different scatter rejection techniques including air gaps, antiscatter grids, and slit radiography.

Humans↗
PubMedDate not supplied

Dosimetric measurement of scattered radiation from dental implants in simulated head and neck radiotherapy.

The purpose of this study was to examine the dose enhancement at bone-implant interfaces from scattered radiation during simulated head and neck radiotherapy. Three cylindric implant systems with different compositions (pure titanium, titanium-aluminum-vanadium alloy, titanium coated with hydroxyapatite) and a high gold content transmandibular implant system (gold-copper-silver alloy) were studied. Extruded lithium fluoride single crystal chips were used as thermoluminescent material to measure radiation dose enhancement at 0, 1, and 2 mm from the bone-implant interface. The relative doses in buccal, lingual, mesial, and distal directions were also recorded and compared. The results indicated that the highest dose enhancement occurred at a distance of 0 mm from the bone-implant interface for all the implant systems studied. The transmandibular implants had higher scattered radiation than other groups at 0 mm and at 1 mm from the bone-implant interface. There was no significant difference of dose enhancement between buccal, lingual, mesial, and distal directions. Titanium implants coated with hydroxyapatite demonstrated the best results under the simulated irradiation.

Alloys↗
PubMed1977

Sensitivity of radiographic screens to scattered radiation and its relationship to image contrast.

For incident X-ray beams of greater than 60 kVp, intensifying screens of rare earth phosphors produced higher radiographic image contrast in the presence of scattered radiation than did screens of calcium tungstate. This was attributed to fundamental energy absorption interaction differences. X-ray absorption is a function of the position of the k-absorption edge of the screen phosphor relative to the X-ray energy spectra of the primary and scattered X-rays. Spectral measurements of X-ray absorption showed that the ratio of primary absorption to scattered absorption is higher for the rare earth screens, causing lower relative sensitivity to the non-information-containing scattered radiation from the radiographic object.

Gadolinium↗
PubMed1977

Radiation scattering and the determination of regional cerebral blood flow by radioisotope clearance.

The sources of error involved in the measurement of regional cerebral blood flow (rCBF) with radioactive tracers in man have been studied. This report shows that one of the main sources is the weakness of the energy emitted by the tracers used. Clearance curves obtained with scalp detectors are subject to interference: the radiation measured originates not only in the region studied but also, by scattering, from the rest of the brain. Because of the weak energy levels involved, the scattered radiation contributes significantly to the total measured radiation, and for the same reason it is impossible to distinguish clearly the scattered radiation from that arriving directly. These systematic errors in rCBF measurements were studied quantitatively by in vitro tests and computer simulation, and limits were established for resulting alterations of all varialbes determined (grey and white matter flow, mean flow, compartment weight). It was concluded that the biologic origin of a modification of rCBF can be affirmed only in the case of changes of at least 10%.

Cerebrovascular Circulation↗
PubMedDate not supplied

Experimental and theoretical energy and angular dependencies of scattered radiation in the mammography energy range.

Predicted scatter characteristics from a Monte Carlo code have been compared to an experiment for a 4.0-cm-thick acrylic resin (Plexiglas) phantom and 27.3-keV radiation. The results show generally good agreement, except that in the scattered spectra the predictions appear to underestimate the proportion of photons in the low-energy tail of the scattered radiation. The angular dependency of the energy-integrated scattered radiation fluence is in excellent agreement with the predictions.

Mammography↗
PubMed1975

Exposure of the radiologist to scattered radiation during angiography.

At least 90% of the exposure of a radiologist's crystalline lens and right hand to scattered radiation during angiography, investigated by thermoluminescent dosimetry, proves to be due to radiography during and immediately after manual injection of the contrast medium. Therefore, manual injection should be replaced by remotely controled injection by means of an injector. The exposure of a radiologist's gonads (measured behind a lead apron) proves negligible. At the low exposure rates to be expected, integrating measurements should be made.

Angiography↗
PubMed1987

[Measures for reducing exposure to scattered radiation in urologic roentgen diagnosis].

A simple device to reduce the urologic examiner's exposure to radiation is presented. The doses the examiner and his assistant staff are exposed to performing various methods of urologic radiodiagnosis were measured and the following exposure to radiation determined with and without radioprotective device. The measurements demonstrate, that already by simple measures considerable reduction of the exposure to radiation can be obtained for examiner and assistant personnel. The frequently neglected importance of scattered radiation resulting from urologic radiography is discussed.

Humans↗
PubMed1995

Scattered radiation in a neonatal surgical unit.

We studied the doses of "scattered" received by neonates in a Neonatal Surgical Unit by placing thermoluminescent dosemeters in various positions expect the direct beam. Doses of "scattered" radiation received by neonates as a results of exposure of their neighbours to X-ray examinations were found to be negligible. Sick neonates need not be moved from their neighbours undergoing exposure to X-rays.

Humans↗
PubMed1988

The influence of the single-event energy-deposition distribution on the signal-to-noise ratio in x-ray images in the presence of scattered radiation.

The single-event energy-deposition distribution has been included in the signal-to-noise ratio for the detection of low-contrast detail in x-ray projection imaging. Calculations for an ideal detector show that this results in a higher signal-to-noise ratio for energy proportional detection than for the counting technique when scattered radiation is present, in contradiction to what has previously been assumed. The difference is less than 20% for photon spectra typical of medical radiography. If scattered radiation is reduced, the difference between energy proportional detection and counting diminishes. For very efficient scatter reduction, counting is slightly better than energy proportional detection.

Models, Theoretical↗