| Dosimetric considerations of symmetric and asymmetric 60Co teletherapy split fields. | |
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MedLine Citation:
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PMID: 904593 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Split fields are commonly used for a variety of treatments for which local shielding is desired; a single field is split into two fields by means of lead blocks placed in the beam. The condition for assuming independence of the two fields is investigated by using the area over perimeter calculational method and comparing this to experimental depth-dose data measured in a water phantom using a Shonka ionization chamber. Two principal variations affecting dose distributions are examined: block width and position of the block expressed as the fractional perpendicular distance between the central ray of the overall field and the center of the block. An intercomparison between calculation and experimental data shows that the right and left sides of the split field behave as independent fields giving TAR values in agreement with experimental data to within +/-1%. If the fields are asymmetric and if the larger field is less than 70% of the total area including the blocked part, then the dosimetry should be based on average TARs, off-center ratios, and backscatter factors for the two fields. If the larger area is greater than 70% of the total area, then the treatment time can be calculated from the larger field only. |
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Authors:
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D E Wrede; S B Givens |
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Publication Detail:
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Type: Journal Article |
Journal Detail:
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Title: Medical physics Volume: 4 ISSN: 0094-2405 ISO Abbreviation: Med Phys Publication Date: 1977 Sep-Oct |
Date Detail:
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Created Date: 1977-11-25 Completed Date: 1977-11-25 Revised Date: 2000-12-18 |
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: 437-40 Citation Subset: IM |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Cobalt Radioisotopes
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therapeutic use* Radioisotope Teletherapy* Radiotherapy Dosage* |
| Chemical | |
Reg. No./Substance:
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0/Cobalt Radioisotopes |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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