The Effect of KVP on the Dose Equivalent Received From Scattered Radiation by Radiography Personnel

Abstract

Radiographs were made of a canine pelvis using 60, 90, and 117 kVp. Thermoluminescent dosimeters were used to measure absorbed dose within the primary beam and from scattered radiation in adjacent regions. Lithium fluroide (LiF) dosimeters were selected because of the similarity of their radiation absorption to that of soft tissue. The absorted dose to the dog per radiograph was reduced as kVp increased. A similar trend was observed in dose equivalent from scattered radiation to adjacent regions. In all cases the dose equivalent per radiograph from scattered radiation was less than three orders of magnitude below the recommended maximum permissible dose for radiation workers.

Decreased dose of radiation to dogs during acquisition of elbow radiographs using draped shielding

“…The findings that higher mAs resulted in more radiation in the primary beam and that higher kVp resulted in a higher dose of scatter and tube leakage radiation were expected. However the finding that higher mAs resulted in less scatter and tube leakage radiation was surprising and in conflict with results from a prior study demonstrating that dose should vary linearly with mAs when source to detector distance and kVp are constant (Wrigley and Borak 1983). In the present study, exposure settings were selected to produce clinically diagnostic elbow radiographs of growing giant breed dogs (5.5–28 kg bodyweight), thus there was little variation in the mAs values used (0.64–1 mAs, with 82 per cent at 0.8 mAs) and kVp was not held constant.…”

“…While these zero values precluded analysis of any dose of radiation less than 0.01 mSv, more zero values under protective shielding supports conclusion of the present study that shielding is protective to dogs receiving elbow radiographs. The reasons the authors selected lithium fluoride thermoluminescent dosimetry badges instead of ionisation chambers were that dosimetry badges made it feasible to measure seven different locations simultaneously, they have energy response nearly equivalent to that of soft tissue, good sensitivity (0.01 mSv), relatively high precision, low cost and they have been used to detect scatter radiation in prior studies in veterinary medicine (Wrigley and Borak 1983). These attributes combined with the fact that this method was sufficiently sensitive to detect a significant decrease in radiation with the use of protective shielding make it likely that the findings of this study are valid and a similar protective effect of shielding would have been found if an even more sensitive detector of radiation had been used, such as using seven ionisation chambers simultaneously.…”

“…The use of protective lead shielding consisting of lead gown and gloves significantly reduces the dose of scatter and tube leakage radiation received by veterinary personnel performing radiographs (Wrigley and Borak 1983, Tyson and others 2011). Potential sources of radiation to veterinary personnel and patients include radiation from the primary beam, scatter radiation and tube leakage radiation (Fig 1).…”