Estimating the Absorbed Dose to Critical Organs During Dual X-ray Absorptiometry

Considered the issues of X-ray dose control during diagnostic and therapeutic procedures using imaging tools. The dose of X-ray radiation from the visualization devices absorbed by the biological tissue of a person was determined when monitoring the position of the patient on the therapeutic table of the electron accelerator before the radiation therapy session. The processes of transmission of photons and electrons through the medium were simulated, and the X-ray spectra were measured. The emission spectrum of the Varian G-242 Rotating Anode X-ray Tube was obtained using an XR-100-CdTe spectrometer. The absorbed dose is calculated by the Monte Carlo method. The absorbed dose in the water phantom at tube voltage up to 80 kV was 0,9–1,5 mGy.

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Structural study of the X-ray-induced enzymatic reaction of octahaem cytochromecnitrite reductase

Acta Crystallographica Section D Biological Crystallography ◽

10.1107/s1399004715003053 ◽

2015 ◽

Vol 71 (5) ◽

pp. 1087-1094 ◽

Cited By ~ 6

Author(s):

A. A. Trofimov ◽

K. M. Polyakov ◽

V. A. Lazarenko ◽

A. N. Popov ◽

T. V. Tikhonova ◽

...

Keyword(s):

Nitrite Reductase ◽

Catalytic Reaction ◽

Active Sites ◽

Enzymatic Reaction ◽

Absorbed Dose ◽

Free Form ◽

Data Sets ◽

X Rays ◽

X Ray ◽

Site Water

Octahaem cytochromecnitrite reductase from the bacteriumThioalkalivibrio nitratireducenscatalyzes the reduction of nitrite to ammonium and of sulfite to sulfide. The reducing properties of X-ray radiation and the high quality of the enzyme crystals allow study of the catalytic reaction of cytochromecnitrite reductase directly in a crystal of the enzyme, with the reaction being induced by X-rays. Series of diffraction data sets with increasing absorbed dose were collected from crystals of the free form of the enzyme and its complexes with nitrite and sulfite. The corresponding structures revealed gradual changes associated with the reduction of the catalytic haems by X-rays. In the case of the nitrite complex the conversion of the nitrite ions bound in the active sites to NO species was observed, which is the beginning of the catalytic reaction. For the free form, an increase in the distance between the oxygen ligand bound to the catalytic haem and the iron ion of the haem took place. In the case of the sulfite complex no enzymatic reaction was detected, but there were changes in the arrangement of the active-site water molecules that were presumably associated with a change in the protonation state of the sulfite ions.

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Patient Absorbed Dose in Coronary Angiography Determined by the Flat Panel Digital Detector X-ray System

Japanese Journal of Radiological Technology ◽

10.6009/jjrt.kj00000921772 ◽

2003 ◽

Vol 59 (3) ◽

pp. 423-426 ◽

Cited By ~ 6

Author(s):

TAKAAKI KITAI ◽

TAKESI OGAWA ◽

SADAHIKO SANO

Keyword(s):

Coronary Angiography ◽

Absorbed Dose ◽

Flat Panel ◽

X Ray ◽

Digital Detector

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Analysis of Sensitometry in Radiographic Films using Optical Density Measurement

European Journal of Medical and Health Sciences ◽

10.24018/ejmed.2020.2.4.430 ◽

2020 ◽

Vol 2 (4) ◽

Author(s):

Oladotun A. Ojo ◽

Peter A. Oluwafisoye ◽

Charles O. Chime

Keyword(s):

Quality Control ◽

Optical Density ◽

Density Measurement ◽

Absorbed Dose ◽

Good Prediction ◽

Radiographic Film ◽

X Ray ◽

Dose Curve ◽

Optical Density Measurement ◽

Before And After

The sensitivity of radiographic films is an important factor to the clarity and accuracy of X-ray exposure to patients during treatment or diagnostic periods. It is therefore important to do a thorough analysis of the sensitivity of the radiographic film before and after exposure to enhance the Quality Assurance (QA) and the Quality Control (QC), of the exposure procedures. The optical densities (OD) of each film was measured, with a densitometer model MA 5336, made by GAMMEX. These values were then converted to the absorbed dose (X mGy), which is the amount of dose absorbed by each patient. The optical density versus the dose curve, followed the expected pattern, showing a good prediction from the General model, that the films employed in the exposures were of good quality and standard. Hence the optical density versus dose sensitometric curves depicts the outcome of the various films sensitivity after an exposure to the X-ray radiation through the patients.

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To scavenge or not to scavenge, that is STILL the question

Journal of Synchrotron Radiation ◽

10.1107/s0909049512046237 ◽

2012 ◽

Vol 20 (1) ◽

pp. 23-36 ◽

Cited By ~ 25

Author(s):

Elizabeth G. Allan ◽

Melissa C. Kander ◽

Ian Carmichael ◽

Elspeth F. Garman

Keyword(s):

Crystal Size ◽

Chemical Species ◽

Absorbed Dose ◽

Dose Dependence ◽

Radiation Chemistry ◽

X Ray ◽

On Line ◽

Crystallization Conditions ◽

Effects Of Radiation ◽

Dose Tolerance

An extensive radiation chemistry literature would suggest that the addition of certain radical scavengers might mitigate the effects of radiation damage during protein crystallography diffraction data collection. However, attempts to demonstrate and quantify such an amelioration and its dose dependence have not yielded consistent results, either at room temperature (RT) or 100 K. Here the information thus far available is summarized and reasons for this lack of quantitative success are identified. Firstly, several different metrics have been used to monitor and quantify the rate of damage, and, as shown here, these can give results which are in conflict regarding scavenger efficacy. In addition, significant variation in results from data collected from crystals treated in nominally the same way has been observed. Secondly, typical crystallization conditions contain substantial concentrations of chemical species which already interact strongly with some of the X-ray-induced radicals that the added scavengers are intended to intercept. These interactions are probed here by the complementary technique of on-line microspectrophotometry carried out on solutions and crystals held both at 100 K and RT, the latter enabled by the use of a beamline-mounted humidifying device. With the help of computational chemistry, attempts are made to assign some of the characteristic spectral features observed experimentally. A further source of uncertainty undoubtedly lies in the challenge of reliably measuring the parameters necessary for the accurate calculation of the absorbed dose (e.g.crystal size and shape, beam profile) and its distribution within the volume of the crystal (an issue addressed in detail in another article in this issue). While microspectrophotometry reveals that the production of various species can be quenched by the addition of scavengers, it is less clear that this observation can be translated into a significant gain in crystal dose tolerance for macromolecular crystallographers.

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