| In-patient to isocenter KERMA ratios in CT. | |
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MedLine Citation:
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PMID: 21992356 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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PURPOSE: To estimate in-patient KERMA for specific organs in computed tomography (CT) scanning using ratios to isocenter free-in-air KERMA obtained using a Rando phantom. METHOD: A CT scan of an anthropomorphic phantom results in an air KERMA K at a selected phantom location and air kerma K(CT) at the CT scanner isocenter when the scan is repeated in the absence of the phantom. The authors define the KERMA ratio (R(K)) as K∕ K(CT), which were experimentally determined in a Male Rando Phantom using lithium fluoride chips (TLD-100). R(K) values were obtained for a total of 400 individual point locations, as well as for 25 individual organs of interest in CT dosimetry. CT examinations of Rando were performed on a GE LightSpeed Ultra scanner operated at 80 kV, 120 kV, and 140 kV, as well as a Siemens Sensation 16 operated at 120 kV. RESULTS: At 120 kV, median R(K) values for the GE and Siemens scanners were 0.60 and 0.64, respectively. The 10th percentile R(K) values ranged from 0.34 at 80 kV to 0.54 at 140 kV, and the 90th percentile R(K) values ranged from 0.64 at 80 kV to 0.78 at 140 kV. The average R(K) for the 25 Rando organs at 120 kV was 0.61 ± 0.08. Average R(K) values in the head, chest, and abdomen showed little variation. Relative to R(K) values in the head, chest, and abdomen obtained at 120 kV, R(K) values were about 12% lower in the pelvis and about 58% higher in the cervical spine region. Average R(K) values were about 6% higher on the Siemens Sensation 16 scanner than the GE LightSpeed Ultra. Reducing the x-ray tube voltage from 120 kV to 80 kV resulted in an average reduction in R(K) value of 34%, whereas increasing the x-ray tube voltage to 140 kV increased the average R(K) value by 9%. CONCLUSIONS: In-patient to isocenter relative KERMA values in Rando phantom can be used to estimate organ doses in similar sized adults undergoing CT examinations from easily measured air KERMA values at the isocenter (free in air). Conversion from in-patient air KERMA values to tissue dose would require the use of energy-appropriate conversion factors. |
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Authors:
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Walter Huda; Kent M Ogden; Robert L Lavallee; Marsha L Roskopf; Ernest M Scalzetti |
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Publication Detail:
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Type: Journal Article; Research Support, N.I.H., Extramural |
Journal Detail:
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Title: Medical physics Volume: 38 ISSN: 0094-2405 ISO Abbreviation: Med Phys Publication Date: 2011 Oct |
Date Detail:
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Created Date: 2011-10-13 Completed Date: 2011-12-13 Revised Date: 2012-03-13 |
Medline Journal Info:
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Nlm Unique ID: 0425746 Medline TA: Med Phys Country: United States |
Other Details:
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Languages: eng Pagination: 5362-9 Citation Subset: IM |
Affiliation:
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Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston, SC 29425-3230, USA. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Adult Air Algorithms Body Size Humans Male Monte Carlo Method Phantoms, Imaging Radiometry Thermoluminescent Dosimetry / methods* Tissue Distribution Tomography Scanners, X-Ray Computed Tomography, X-Ray Computed / methods* Water / chemistry Whole Body Imaging / methods X-Rays |
| Grant Support | |
ID/Acronym/Agency:
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R01 EB000460/EB/NIBIB NIH HHS |
| Chemical | |
Reg. No./Substance:
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7732-18-5/Water |
| Comments/Corrections | |
Comment In:
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Med Phys. 2012 Jan;39(1):562
[PMID:
22225326
]
Med Phys. 2011 Dec;38(12):6787-8 [PMID: 22149860 ] |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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