| Reference dosimetry during diagnostic CT examination using XR-QA radiochromic film model. | |
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MedLine Citation:
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PMID: 21978057 Owner: NLM Status: Publisher |
Abstract/OtherAbstract:
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Purpose: The authors applied 2D reference dosimetry protocol for dose measurements using XR-QA radiochromic film model during diagnostic computed tomography (CT) examinations carried out on patients and humanoid Rando phantom.Methods: Response of XR-QA model GAFCHROMIC™ film reference dosimetry system was calibrated in terms of Air-Kerma in air. Four most commonly used CT protocols were selected on their CT scanner (GE Lightspeed VCT 64), covering three anatomical sites (head, chest, and abdomen). For each protocol, 25 patients ongoing planned diagnostic CT examination were recruited. Surface dose was measured using four or eight film strips taped on patients' skin and on Rando phantom. Film pieces were scanned prior to and after irradiation using Epson Expression™ 10000XL document scanner. Optical reflectance of the unexposed film piece was subtracted from exposed one to obtain final net reflectance change, which is subsequently converted to dose using previously established calibration curves.Results: The authors' measurements show that body skin dose variation has a sinusoidal pattern along the scanning axis due to the helical movement of the x-ray tube, and a comb pattern for head dose measurements due to its axial movement. Results show that the mean skin dose at anterior position for patients is (51 ± 6) mGy, (29 ± 11) mGy, (45 ± 13) mGy and (38 ± 20) mGy for head, abdomen, angio Abdomen, and chest and abdomen protocol (UP position), respectively. The obtained experimental dose length products (DLP) show higher values than CT based DLP taken from the scanner console for body protocols, but lower values for the head protocol. Internal dose measurements inside the phantom's head indicate nonuniformity of dose distribution within scanned volume.Conclusions: In this work, the authors applied an Air-Kerma in air based radiochromic film reference dosimetry protocol for in vivo skin dose measurements. In this work, they employed green channel extracted from the scanned RGB image for dose measurements in the range from 0 to 200 mGy. Measured skin doses and corresponding DLPs were higher than DLPs provided by the CT scanner manufacturer as they were measured on patients' skin. |
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Authors:
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Jonathan Boivin; Nada Tomic; Bassam Fadlallah; François Deblois; Slobodan Devic |
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Publication Detail:
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Type: JOURNAL ARTICLE |
Journal Detail:
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Title: Medical physics Volume: 38 ISSN: 0094-2405 ISO Abbreviation: - Publication Date: 2011 Sep |
Date Detail:
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Created Date: 2011-10-7 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 0425746 Medline TA: Med Phys Country: - |
Other Details:
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Languages: ENG Pagination: 5119 Citation Subset: - |
Affiliation:
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Institut de Génie Biomédical, Université de Montréal, Montréal, Québec H3C 3J7, Canada. |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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