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Reduction of eye lens radiation dose by orbital bismuth shielding in pediatric patients undergoing CT of the head: A Monte Carlo study
Author(s) -
Perisinakis Kostas,
Raissaki Maria,
Tzedakis Antonis,
Theocharopoulos Nicholas,
Damilakis John,
Gourtsoyiannis Nicholas
Publication year - 2005
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.1881852
Subject(s) - imaging phantom , electromagnetic shielding , dosimetry , monte carlo method , nuclear medicine , thermoluminescent dosimeter , eye lens , reduction (mathematics) , lens (geology) , medicine , optics , brachytherapy , materials science , biomedical engineering , dosimeter , physics , radiology , radiation therapy , mathematics , statistics , geometry , composite material
Our aim in the study was to assess the eye lens dose reduction resulting from the use of radioprotective bismuth garments to shield the eyes of pediatric patients undergoing head CT. The Monte Carlo N ‐particle transport code and mathematical humanoid phantoms representing the average individual at different ages were used to determine eye lens dose reduction accomplished with bismuth shielding of the eye in the following simulated CT scans: (a) scanning of the orbits, (b) scanning of the whole head, and (c) 20° angled scanning of the brain excluding the orbits. The effect of bismuth shielding on the eye lens dose was also investigated using an anthropomorphic phantom and thermoluminescence dosimetry (TLD). Eye lens dose reduction achieved by bismuth shielding was measured in 16 patients undergoing multiphase CT scanning of the head. The patient's scans were divided in the following: CT examinations where the eye globes were entirely included ( n = 5 ) , partly included ( n = 6 ) and excluded ( n = 5 ) from the scanned region. The eye lens dose reduction depended mainly on the scan boundaries set by an operator. The average eye lens dose reduction determined by Monte Carlo simulation was 38.2%, 33.0% and < 1 % for CT scans of the orbits, whole head, and brain with an angled gantry, respectively. The difference between the Monte Carlo derived eye lens dose reduction factor values and corresponding values determined directly by using the anthropomorphic phantom head was found less than 5%. The mean eye lens dose reduction achieved by bismuth shielding in pediatric patients were 34%, 20% and < 2 % when eye globes were entirely included, partly included and excluded from the scanned region, respectively. A significant reduction in eye lens dose may be achieved by using superficial orbital bismuth shielding during pediatric head CT scans. However, bismuth garments should not be used in children when the eyes are excluded from the primarily exposed region.