Immobilisation precision in VMAT for oral cancer patients

M. N. Norfadilah, Rozilawati Ahmad, S. P. Heng, K. S. Lam, A. B.Ahmad Radzi, L. S.H. John

Research output: Contribution to journalArticle

Abstract

A study was conducted to evaluate and quantify a precision of the interfraction setup with different immobilisation devices throughout the treatment time. Local setup accuracy was analysed for 8 oral cancer patients receiving radiotherapy; 4 with HeadFIX® mouthpiece moulded with wax (HFW) and 4 with 10 ml/cc syringe barrel (SYR). Each patients underwent Image Guided Radiotherapy (IGRT) with total of 209 cone-beam computed tomography (CBCT) data sets for position set up errors measurement. The setup variations in the mediolateral (ML), craniocaudal (CC), and anteroposterior (AP) dimensions were measured. Overall mean displacement (M), the population systematic (Σ) and random (σ) errors and the 3D vector length were calculated. Clinical target volume to planning target volume (CTV-PTV) margins were calculated according to the van Herk formula (2.5Σ+0.7σ). The M values for both group were < 1 mm and < 1° in all translational and rotational directions. This indicate there is no significant imprecision in the equipment (lasers) and during procedure. The interfraction translational 3 dimension vector for HFW and SYR were 1.93±0.66mm and 3.84±1.34mm, respectively. The interfraction average rotational error were 0.00±0.65° and 0.34±0.59°, respectively. CTV-PTV margins along the 3 translational axis (Right-Left, Superior-Inferior, Anterior-Posterior) calculated were 3.08, 2.22 and 0.81 mm for HFW and 3.76, 6.24 and 5.06 mm for SYR. The results of this study have demonstrated that HFW more precise in reproducing patient position compared to conventionally used SYR (p<0.001). All margin calculated did not exceed hospital protocol (5mm) except S-I and A-P axes using syringe. For this reason, a daily IGRT is highly recommended to improve the immobilisation precision.

Original languageEnglish
Article number012025
JournalJournal of Physics: Conference Series
Volume851
Issue number1
DOIs
Publication statusPublished - 31 May 2017

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syringes
immobilization
cancer
radiation therapy
margins
planning
waxes
random errors
trucks
systematic errors
cones
tomography
lasers

ASJC Scopus subject areas

  • Physics and Astronomy(all)

Cite this

Norfadilah, M. N., Ahmad, R., Heng, S. P., Lam, K. S., Radzi, A. B. A., & John, L. S. H. (2017). Immobilisation precision in VMAT for oral cancer patients. Journal of Physics: Conference Series, 851(1), [012025]. https://doi.org/10.1088/1742-6596/851/1/012025

Immobilisation precision in VMAT for oral cancer patients. / Norfadilah, M. N.; Ahmad, Rozilawati; Heng, S. P.; Lam, K. S.; Radzi, A. B.Ahmad; John, L. S.H.

In: Journal of Physics: Conference Series, Vol. 851, No. 1, 012025, 31.05.2017.

Research output: Contribution to journalArticle

Norfadilah, M. N. ; Ahmad, Rozilawati ; Heng, S. P. ; Lam, K. S. ; Radzi, A. B.Ahmad ; John, L. S.H. / Immobilisation precision in VMAT for oral cancer patients. In: Journal of Physics: Conference Series. 2017 ; Vol. 851, No. 1.
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