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Ambient dose during intraoral radiography with current techniques: Part 1 conversion factor for scattered radiation using a rectangular collimator
摘要： The aim of this study was to establish a conversion factor for assessing the scattered radiation produced during intraoral radiography with a rectangular collimator in areas where the remnant beam is not present. The dose level in the remnant beam will be addressed in another study. A radiological phantom (Rando) in the upright position was exposed to radiation delivered by a Planmeca Intra X-ray unit over 9 exposure geometries (right side of a full mouth series). For each geometry, the scattered radiation dose was measured at 5 locations in the horizontal plane and 4 locations in the vertical plane in front of the patient. The measurements were corrected for background and leakage radiation. An inventory of the distributions of the different geometries with respect to their share of the total workload was created in order to assign the correct weightings of the total ambient scattered radiation for the different geometries. The weightings were used to construct a scattered radiation pattern for a representative mix of exposures. The maximum value found in this pattern was used to arrive at a safe conversion factor. The scattered ambient radiation dose was evenly distributed over the horizontal plane. The scattered ambient radiation dose ranged from 20 to 65% lower in the vertical plane. The conversion factor established for scattered ambient radiation was 0.05 μSv per mAs at 1 meter. This factor is 3-fold lower than the conversion factors reported previously.
关键词： radiation protection,dental radiography,radiation monitoring,Dental Equipment
更新于2025-09-23 15:23:52
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Ambient dose during intra-oral radiography with current techniques: Part 2 quantifying the remnant beam - an <i>in vivo</i> study
摘要： Objectives: (1) To find a safe reference transmission factor for the remnant beam to be used when assessing the remnant beam during intra-oral radiography. (2) To identify factors such as exposure type, side (left or right), gender and age that might significantly affect transmission. Methods: Measurements were performed in the remnant beam during 323 intra-oral exposures of 43 patients. The exposure parameters were 60 kV and 7 mA. These measurements were compared with values in the same setting, but without a patient present to arrive at a transmission value. Differences between types of exposure [bitewing (BW), incisor and canine (IC) periapical, premolar and molar (PM) periapical], exposure side (left or right), gender and age were statistically analysed. The reference value was based on the exposure yielding the highest transmission value, to which a safety margin of two standard deviations (SDs) was added, and then rounding up. Results: The respective mean transmission values (SD) for BW, IC and PM exposures were as follows: 1.78% (1.15%), 0.639% (0.63%) and 2.60% (0.98%). The differences between PM and IC and between BW and IC were significant (p > 0.01). The differences between exposure side, gender and age were not significant. The reference transmission value, which was calculated from the highest mean transmission percentage for PM (2.60%) plus twice the SD (0.98%) and rounding up, was 5%. Conclusions: A transmission factor of 5% could be used to assess the remnant beam during intra-oral radiography. Anterior exposures led to significantly lower transmission values than posterior exposures.
关键词： radiation protection,dental radiography,dental equipment,radiation monitoring
更新于2025-09-23 15:23:52
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The development of new image receptor-holding instruments with appropriate horizontal X-ray beam angulation for periapical radiographs
摘要： Objectives: This study aimed to develop new image receptor-holding instruments with appropriate horizontal X-ray beam angulation, based on the anatomical data of posterior region interproximal surfaces derived from archived CT images. Methods: CT images of 92 patients with sound upper and lower dental arches were collected from our CT database and analyzed to determine the angles between the tangential interproximal contact line and the central groove line of posterior teeth. The average angle for each site was calculated and used to modify instruments using a three-dimensional printer. The utilities of the conventional and the modified instruments for viewing proximal surfaces were compared using two dry skulls. Results: The right and left sides of each site, except for the lower second premolar and first molar sites, did not differ significantly. The difference between the sites was 2.0°; hence, we calculated mean values for the two sides at each site. In the maxilla, the angles of the first and second premolar, second premolar and first molar, and first and second molar to the groove line were 83.9° (±5.4°), 84.4° (±3.9°), 81.6° (±5.1°), while those in the mandible were 85.0° (±9.2°), 85.0° (±4.0°), and 90.6° (±4.9°), respectively. The holding instruments modified to 80° demonstrated better proximal viewing ability in the upper molar region than conventional instruments. conclusions: The mean angles of the interproximal surfaces were determined from CT data. The image receptor holding-instruments were modified according to these angles to allow appropriate X-ray angulation, which facilitated improved observation of the proximal surfaces of teeth in the posterior region in this pilot in vitro study.
关键词： dental radiography,X-ray beam,holding instruments,periapical radiograph
更新于2025-09-23 15:22:29