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Göteborgs universitets publikationer

Jaw position uncertainty and adjacent fields in breast cancer radiotherapy.

Författare och institution:
Emma Hedin (Institutionen för kliniska vetenskaper, sektionen för onkologi, radiofysik, radiologi och urologi, Avdelningen för radiofysik); Anna Bäck (Institutionen för kliniska vetenskaper, sektionen för onkologi, radiofysik, radiologi och urologi, Avdelningen för radiofysik); Roumiana Chakarova (Institutionen för kliniska vetenskaper, sektionen för onkologi, radiofysik, radiologi och urologi, Avdelningen för radiofysik)
Publicerad i:
Journal of applied clinical medical physics / American College of Medical Physics, 16 ( 6 ) s. 5673
ISSN:
1526-9914
Publikationstyp:
Artikel, refereegranskad vetenskaplig
Publiceringsår:
2015
Språk:
engelska
Fulltextlänk:
Sammanfattning (abstract):
Locoregional treatment of breast cancer involves adjacent, half blocked fields matched at isocenter. The objective of this work is to study the dosimetric effects of the uncertainties in jaw positioning for such a case, and how a treatment planning protocol including adjacent field overlap of 1 mm affects the dose distribution. A representative treatment plan, involving 6 and 15 photon beams, for a patient treated at our hospital is chosen. Monte Carlo method (EGSnrc/BEAMnrc) is used to simulate the treatment. Uncertainties in jaw positioning of ± 1 mm are addressed, which implies extremes in reality of 2 mm field gap/overlap when planning adjacent fields without overlap and 1 mm gap or 3 mm overlap for a planning protocol with 1 mm overlap. Dosimetric parameters for PTV, lung and body are analyzed. Treatment planning protocol with 1 mm overlap of the adjacent fields does not considerably counteract possible underdosage of the target in the case studied. PTV-V95% is for example reduced from 95% for perfectly aligned fields to 90% and 91% for 2 mm and 1 mm gap, respectively. However, the risk of overdosage in PTV and in healthy soft tissue is increased when following the protocol with 1 mm overlap. A 3 mm overlap compared to 2 mm overlap results in an increase in maximum dose to PTV, PTV-D2%, from 113% to 121%. V120% for 'Body-PTV' is also increased from 5 cm3 to 14 cm3. A treatment planning protocol with 1 mm overlap does not considerably improve the coverage of PTV in the case of erroneous jaw positions causing gap between fields, but increases the overdosage in PTV and doses to healthy tissue, in the case of overlapping fields, for the case investigated.
Ämne (baseras på Högskoleverkets indelning av forskningsämnen):
MEDICIN OCH HÄLSOVETENSKAP ->
Klinisk medicin ->
Cancer och onkologi
MEDICIN OCH HÄLSOVETENSKAP ->
Klinisk medicin ->
Radiologi och bildbehandling ->
Radiofysik
Postens nummer:
234489
Posten skapad:
2016-04-11 11:06
Posten ändrad:
2016-06-23 14:08

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