| In vivo estimation of midline dose maps by transit dosimetry in head and neck radiotherapy. | |
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MedLine Citation:
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PMID: 12515706 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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The aim of the present study is to compare the calculated midline dose map with the in vivo measured midline dose map, using portal detectors in conjunction with a pair of diodes. Measurements were performed in 10 patients treated for head/neck cancer and irradiated with lateral opposed 6 MV X-ray beams. The relative exit dose map, derived from transmission dose data of a portal film combined with the absolute entrance/exit dose measured by the diodes, can be used to derive the corresponding midline dose map by applying appropriate algorithms. Midplane dose values were estimated in eight relevant anatomic positions and compared with the corresponding calculated values with our three-dimensional (3D) treatment planning system using two-dimensional (2D) (Batho) and 3D (ETAR) inhomogeneity correction algorithms. In vivo estimated midplane doses agree within +/-3.5% relative to treatment planning calculations in 89 of 116 measurements points, with only 4 of 116 points outside +/-5%. A variation between measured and calculated dose can be found according to anatomical location. For air inhomogeneity, mean deviations were +2.2% (1 standard deviation (SD) approximately 1.7%) for both Batho and ETAR algorithms; for bone structures, mean deviations were approximately -0.6% (1 SD approximately 2.7%) for both algorithms. The worst agreement was found in the anterior neck where the mean deviation between measured and calculated midline dose was +3.1% (1 SD=1.4%) and +3.4% (1 SD= 2%) using Batho and ETAR, respectively. Sufficiently accurate 2D midplane dose maps may be simply obtained in vivo in the irradiation of head/neck cancer by using a portal detector in combination with a pair of diodes, in order to verify the dose actually delivered during treatment. |
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Authors:
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S Broggi; C Fiorino; R Calandrino |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: The British journal of radiology Volume: 75 ISSN: 0007-1285 ISO Abbreviation: Br J Radiol Publication Date: 2002 Dec |
Date Detail:
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Created Date: 2003-01-07 Completed Date: 2003-02-11 Revised Date: 2006-11-15 |
Medline Journal Info:
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Nlm Unique ID: 0373125 Medline TA: Br J Radiol Country: England |
Other Details:
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Languages: eng Pagination: 974-81 Citation Subset: AIM; IM |
Affiliation:
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Università degli Studi di Milano, Scuola di Specializzazione in Fisica Sanitaria, Milano, Italy. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Algorithms Head and Neck Neoplasms / radiotherapy* Humans Radiometry / methods* Radiotherapy Dosage Radiotherapy Planning, Computer-Assisted Radiotherapy, Conformal / methods Radiotherapy, High-Energy / methods |
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