Patient positioning in head and neck cancer : Setup variations and safety margins in helical tomotherapy.
Strahlenther Onkol
; 194(5): 386-391, 2018 05.
Article
em En
| MEDLINE
| ID: mdl-29372290
ABSTRACT
OBJECTIVE:
To evaluate the interfractional variations of patient positioning during intensity-modulated radiotherapy (IMRT) with helical tomotherapy in head and neck cancer and to calculate the required safety margins (sm) for bony landmarks resulting from the necessary table adjustments. MATERIALS ANDMETHODS:
In all, 15 patients with head and neck cancer were irradiated using the Hi-Art II tomotherapy system between April and September 2016. Before therapy sessions, patient position was frequently checked by megavolt computed tomography (MV-CT). Necessary table adjustments (ta) in the right-left (rl), superior-inferior (si) and anterior-posterior (ap) directions were recorded for four anatomical points second, fourth and sixth cervical vertebral body (CVB), anterior nasal spine (ANS). Based upon these data sm were calculated for non-image-guided radiotherapy, image-guided radiotherapy (IGRT) and image guidance limited to a shortened area (CVB 2).RESULTS:
Based upon planning CT the actual treatment required ta from -0.05 ± 1.31 mm for CVB 2 (ap) up to 2.63 ± 2.39 mm for ANS (rl). Considering the performed ta resulting from image control (MV-CT) we detected remaining ta from -0.10⯱ 1.09 mm for CVB 4 (rl) up to 1.97⯱ 1.64 mm for ANS (si). After theoretical adjustment of patients position to CVB 2 the resulting ta ranged from -0.11⯱ 2.44â¯mm for CVB6 (ap) to 2.37⯱ 2.17 mm for ANS (si). These data imply safety margins uncorrected patient position 3.63-9.95â¯mm, corrected positioning based upon the whole target volume (IGRT) 1.85-6.63 mm, corrected positioning based upon CVB 2 (IGRT) 3.13-6.66 mm.CONCLUSIONS:
The calculated safety margins differ between anatomic regions. Repetitive and frequent image control of patient positioning is necessary that, however, possibly may be focussed on a limited region.Palavras-chave
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Planejamento da Radioterapia Assistida por Computador
/
Neoplasias Otorrinolaringológicas
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Carcinoma de Células Escamosas
/
Adenocarcinoma
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Radioterapia de Intensidade Modulada
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Posicionamento do Paciente
Tipo de estudo:
Guideline
/
Observational_studies
Limite:
Adult
/
Aged
/
Aged80
/
Female
/
Humans
/
Male
/
Middle aged
Idioma:
En
Revista:
Strahlenther Onkol
Assunto da revista:
NEOPLASIAS
/
RADIOTERAPIA
Ano de publicação:
2018
Tipo de documento:
Article
País de afiliação:
Alemanha