X-ray Tube Housing Research Articles

Doses and spectra, of leaking-out and scattered photons from X-ray tubes used in dentistry

Diagnosis by X-ray image are procedures widely used to improve the diagnosis or to follow the evolution of a medical procedure, also are used to support the cancer treatment with linear accelerators. The procedure involves the X-ray unit and the detection system, while the X-ray beam is projected onto the patient; along this procedure X-rays are scattered out from the patient body and X-rays leak-out from the X-ray unit. Both, the scattered and the leaking out radiation, are important during the evaluation or the design of the shielding barriers. X-ray tube features like voltage, electric current, target and filter are related to the dose due to the scattered and leakage radiation. Also, the dose due to the scattered radiation depends upon the scattering angle; while the dose due to the leaking out radiation, depend upon the X-ray tube housing. The objective of this work was to estimate, using Monte Carlo methods, the X-ray spectra and doses (air Kerma and Ambient dose equivalent) produced by scattered and leaking out radiation of 70, 80 and 90 kV X-ray units.

CRT-500.11 The Contribution of X-Ray Tube Housing Leak to Radiation Exposure in the Cath Lab

It has been assumed that the vast majority of the x-ray exposure to the cardiac cath lab heart team originates from scatter radiation (SR) from the patient and that x-ray leakage from the x-ray tube housing (XRT) is negligible. We investigated radiation leakage directly from the XRT and its

Investigation of conventional diagnostic X-ray tube housing leakage radiation using ion chamber survey meter in Mizoram, India

Leakage radiation that transmitted the protected X-ray tube housing was measured and compared with national and international safety standard. To the best of the authors’ knowledge, no tube housing leakage measurement has been done so far in the present study area. The authors considered all the conventional diagnostic X-ray units in Mizoram, India. Ion chamber survey meter was used to measure leakage radiation and it was placed at 5 different positions (left, right, front, back, top) of the X-ray tube. Measurements were done at 1 m focus-to-detector distance by projecting X-ray tube vertically downward with collimator diaphragms closed completely. SPSS statistics for windows, version 17.0 (SPSS, Inc., Chicago, IL, USA) was used to derived mean, standard error of the mean etc. The tube housing leakage exposure rates ranged between 0.03 mRh-1 and 500 mR h-1; among the 5 positions, rate measured in the front direction has the highest mean at 41.61±8.63 mR h-1; whereas the top has the lowest 4.57±1.16 mRh-1. Tube housing radiation level ranged from 0.01 to 58 mR in one hour. Leakage radiation was minimum at the top position of the tube and maximum in the front direction. All the equipment were in compliance with national and international standard norms, the highest leakage radiation level was 50.43% of the safety limit.

Physical and mechanical properties of polyamide 6/polystyrene (PA6/PS) reinforced by PbO2 composites for X-ray shielding

Thermal, electrical, as well as mechanical behavior of blends of polyamide 6/polystyrene (PA6/PS) (50/50 wt/wt%) loaded with different concentrations of lead dioxide (PbO2) were investigated for X-ray shielding. Thermal stability and hardness (shore D) of these composites are studied. Addition of PbO2 decreases the thermal stability of the prepared composites. Stability of thermal properties confirmed by determining the activation energy for the thermal decomposition of unfilled PA6/PS and filled composites according to the Horowitz and Metzger method. Dielectric properties of bulk PbO2 have been investigated as a function of frequency and temperature in the frequency range from 40 Hz to 5 × 106 Hz and in the temperature range from 293 K to 423 K. The characterization of the prepared composites is done using scanning electron microscope. With PbO2-loaded PA6/PS blends composites, the dielectric properties were significantly influenced by γ-irradiation effects that ε′ and [Formula: see text] values increase with radiation dose up to 100 kGy for samples loaded with PbO2. Linear attenuation coefficient μ and half-value layer (HVL) of all composites strongly depend on the concentration of the filler used and the applied voltage of X-ray machine. HVL of the obtained composites that loaded with 100 wt/wt% of PbO2 nearly 3 mm can be used as X-ray tube housing, equipment housings and castings, electronic devices protection, and so on.

CT brain artefact due to air bubbles in the oil cooling system: characteristic band-like configuration on sagittal reformatted image.

To retrospectively review the imaging characteristics of CT artefacts due to air bubbles within the oil cooling system of the X-ray tube housing. Air bubbles were introduced into the oil cooling system of the X-ray tube housing during tube replacement in one of the CT scanners in the authors' institution. All 126 CT brain studies performed in this period were retrospectively reviewed. One hundred and four studies were negative for artefacts. Artefacts were confirmed in 5 and considered probable in 17 studies, respectively. The imaging characteristics of artefacts in these 22 cases were analysed. All artefacts manifested as ill-defined hypoattenuations in the periventricular/subcortical white matter of bilateral cerebral hemispheres with/without involvement of the internal capsule and basal ganglia. The posterior fossa was also involved in two (40%) confirmed and four (24%) probable studies. A band-like configuration of hypoattenuations on sagittal images was observed in five (100%) confirmed and eight (47%) probable studies. Air bubble artefacts manifested as hypoattenuations in the periventricular/subcortical white matter of the supratentorial brain. A characteristic band-like configuration was observed in the sagittal reformatted image, which is useful for differentiating it from periventricular small vessel disease.

Shielding of medical imaging X-ray facilities: a simple and practical method.

The most widely accepted method for shielding design of X-ray facilities is that contained in the National Council on Radiation Protection and Measurements Report 147 whereby the computation of the barrier thickness for primary, secondary and leakage radiations is based on the knowledge of the distances from the radiation sources, the assumptions of the clinical workload, and usage and occupancy of adjacent areas. The shielding methodology used in this report is complex. With this methodology, the shielding designers need to make assumptions regarding the use of the X-ray room and the adjoining areas. Different shielding designers may make different assumptions resulting in different shielding requirements for a particular X-ray room. A more simple and practical method is to base the shielding design on the shielding principle used to shield X-ray tube housing to limit the leakage radiation from the X-ray tube. In this case, the shielding requirements of the X-ray room would depend only on the maximum radiation output of the X-ray equipment regardless of workload, usage or occupancy of the adjacent areas of the room. This shielding methodology, which has been used in South Australia since 1985, has proven to be practical and, to my knowledge, has not led to excess shielding of X-ray installations.

Dental Staff Doses with Handheld Dental Intraoral X-Ray Units

A handheld portable dental intraoral x-ray system is available in the United States and elsewhere. The system is designed to minimize the user's radiation dose. It includes specially designed shielding of the x-ray tube housing and an integral radiation shield to minimize backscatter. Personnel radiation dose records were obtained from 18 dental facilities using both the handheld system and a wall mounted dental x-ray system, providing 661 individual dose measurements. Dental staff doses were also compared for the handheld and conventional systems using both film and digital imaging for the same facilities and staff members. The results indicate that the doses for the handheld systems are significantly less than for wall-mounted systems. The average monthly dose for the handheld systems was 0.28 μSv vs. 7.86 μSv (deep dose equivalent) for the wall-mounted systems, a difference that is statistically significant at the p = 0.01 level. Consequently, there should be no concern about the use of this handheld dental intraoral x-ray system. Additional shielding efforts, (e.g., wearing a lead apron) will not provide significant benefit nor reduce staff radiation dose.

Effect of patient support pads on image quality and dose in fluoroscopy

An investigation was performed of the changes in image quality and patient dose as a result of increasing filtration for fluoroscopy performed under automatic brightness control. Filtration was added either at the x-ray tube housing (i.e., scatter-free geometry) or adjacent to a tissue equivalent phantom simulating the patient (i.e., with-scatter geometry). Patient doses were expressed in terms of the total energy imparted to patients simulated by either a 10 cm (i.e., pediatric) or 20 cm (i.e., adult) acrylic phantoms. Changes in image quality were determined by measuring the relative visibility of circular disks in a Leeds Test Object 10 contrast-detail phantom. In the scatter-free geometry, the addition of 4 mm Al filtration reduced the energy imparted by 27% (10 cm phantom) and 20% (20 cm phantom). In the with-scatter geometry, the corresponding reductions in energy imparted were 17% and 9% for the 10 and 20 cm phantoms, respectively. The visibility of low contrast disks generally decreased as the thickness of the added aluminum increased but the location of the added Al (i.e., with-scatter or scatter-free geometry) had no significant effect on the resultant image quality. These results demonstrate that the use of patient support pads with a thickness of approximately 4 mm Al will generally have an adverse impact on fluoroscopic image quality and result in modest reductions (approximately 10%) of adult patient doses.

放射線診断システムにおける人間工学的検討 : 一般撮影における被検者の動作空間を考慮した STD

Current practices for patiant safety control in radiological diagnosis involve may problems. For solving of these problems, we have to bear in mind that the mental and physical capacity of patients tend to be limted during radiological testing. When radiography is performed using a general X-ray device at a source table distance (STD) of 100cm, the patient's head can touch the X-ray tube housing during position adjustment on the stand (up and down adjustment) or the patient is made to take an unnatural posture during body positioning. With this in mind, we carried out a questionnaire survey about SID. This survery disclosed that more than 92% of the institutions have adaped 100cm STD. We then conducted a three-dimensional analysis of a patient's posture and motion by video taping patients during positioning on an roentgenographic table. This analysis revealed that the adoption of the 120cm STD resulted in less contact between the patient's head and X-ray tube housing, less of a unnatural body position and less time required for positioning adjustment when compared to those at 100cm STD. These results indicate that the current STD (100cm) is not suitable for safe and smooth adjustment of the positioning of a patient's body of an roentgenographic table. We examined the optimum STD, taking into consideration the dimensions of patient's movement and posture during an X-ray examination.

Determination of x‐ray spectra and of the scattered component up to 300 kV

Several x-ray spectra, including those of the ISO reference radiations, were measured by 2-hp Ge detectors. Measurements were carried out in different experimental conditions with regard to detector size, beam collimation, and SDD. A stripping procedure to improve the spectrum analysis was developed on the basis of a detailed evaluation (by means of a Monte Carlo method) of the detector's spurious effects. These effects include K-photon escape, Compton photon escape, electron escape, and collimation effect. The stripping procedure also allows us to determine directly the spectra of possible scattered radiation reaching the detector in addition to the primary beam. When the primary beam is heavily filtered, the leakage radiation from the x-ray tube housing scattered onto the detector may not be negligible even when the x-ray tube is provided with appreciable shielding. Possible practical consequence of these effects are discussed. The results obtained on the ISO x-ray spectra are in agreement with previous determinations. The advantage of the present procedure is its more immediate applicability to Ge detectors of any size and with different beam collimation conditions.

3.立体拡大撮影における焦点サイズおよび焦点間隔距離(II.立体拡大撮影技術について)

Serial stereoscopic magnification radiography was easily performed due to the development of a device which has a microfocus rotating within the same X-ray tube housing. Comparied with contact stereoscopic radiography, there are some advantages in this technique, such as an increase in detail recognition, higher quality images anda decrease in the exposure of patients to radiation. In this study, we evaluated the followings using the X-ray tube for serial stereoscopic magnification radiography. 1. Modulation for the microfocal spot size.While the focusing voltage or the tube current was appropriately changed, the focal spot became smaller almost being reduced to the nominal spot size. 2. Comparison of the discrimination between in the stereoscopic magnification technique and the contact stereoscopic technique. The former's focal spot separation was 25mm or 50mm, and the latter was 100mm. 3. Stereoscopic image using our originaal charts and scales.

The protective housing for a diagnostic x-ray tube.

Like all the other components making up the radiographic system, the x-ray tube housing has for many years received the attention of those people and organizations interested in x-ray protection. Occasionally one reads or hears the comment that only in the last few years has any attention been given to the matter of patient protection. While it may be true that patient protection has been emphasized in recent years, that it was ignored earlier is not true. Like all other factors involved in exposure control, the diagnostic tube housing has been subject to changing recommendations which reflected then current technology and philosophy. A review of the history of these recommendations should be of interest to all who are involved in the use of x-rays in medicine or dentistry. In 1901 William Rollins conducted a series of experiments on whole-body exposures of guinea pigs to x rays. He exposed an animal two hours daily to “the x-light,” and on the eleventh day it died. Another animal similarly exposed died o...

A new apparatus for the complete spherical checking of radiation leakage from diagnostic x-ray tubes.

A leakage survey on an X-ray tube housing by conventional methods takes a considerable time if carried out in a reasonably complete fashion and there is still the possibility that narrow beams of leakage radiation will be missed. An apparatus has been developed which will make a complete survey, automatically, in 12 minutes, and incorporates 50 Geiger-Muller tubes of special design. Directions in which the leakage exceeds a pre-set level are indicated by lamps and it is a simple matter to take measurements in these directions. Routine leakage testing of X-ray tubes is, therefore, possible. Use of this method is also valuable in design work, permitting reduction in the leakage to levels well below the international maximum without the large weight increase that would result from increasing the thickness of protective materials in an indiscriminate manner.

Further Problems in X-Ray Protection

In view of the necessity for protection against stray radiation in photofluorographic units (1, 2), the Tuberculosis Control Division of the U. S. Public Health Service has developed a program of personnel protection which is herein described. In addition to the provision of adequate protective equipment, measures had to be taken to see that such equipment was properly used and that needless exposure was avoided. In doing this it was necessary to take into account the human factor of heedlessness and to see that operators had to take precautions whether or not they wished to do so. These steps having been taken, it was considered essential to determine by physical means whether the protection provided was adequate. Further, in view of the shortcomings of the accepted permissible dose, it was considered advisable to check workers for evidence of injury. It is believed that this program will provide not only the best possible protection but will yield much needed information concerning the problems of exposure and injury. Procedures Location of Equipment: Since the photofluorographic equipment in use is of portable type, operators are directed first of all to give attention to its location and arrangement. Airy, spacious rooms, 18 × 20 feet or larger, are desirable. The equipment should be so arranged that the x-ray beam is directed toward an outside wall, preferably toward a window. The x-ray machine should be at least 8 to 10 feet from side walls in order to reduce reflected radiation and provide adequate freedom of movement of patients and operators. Alignment: Operators are instructed to check alignment with 14 × 17-inch films as described in the first paper of this series (p. 565). In order to keep stray radiation at a minimum, the primary x-ray beam should be limited strictly to the field of the fluoroscopic screen. Such beams can be obtained by properly adjusting the position and angle of the extension cone. Unnecessary Primary Radiation: Some primary radiation escapes through the x-ray tube housing but, as shown in the first paper, this is not the most serious source of stray radiation. Occasionally “leaks” occur in the tube housing due to faulty construction, failure to keep all parts in place, etc. Operators are asked to check for leaks with films and to explore the field around the tube in order to know where the intensity is greatest. Holes in the tube housing should be covered with lead (or other adequate absorbing materials) and the beam of primary radiation confined strictly to the area of the fluorographic screen. The fact that a so-called “ray-proof” tube is being used should not lead to a false sense of security, as the lead housing of such tubes is intended to do no more than cut the escaping radiation to a reasonably safe level. Some idea of the quantity and quality of radiation that will escape from ray-proof tubes operated under a variety of conditions has been given recently in a paper by White, Cowie, and de Lorimier (3).