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:: Volume 4, Issue 1 (Summer 2006) ::
Int J Radiat Res 2006, 4(1): 1-6 Back to browse issues page
Measurement of the immobilisation efficacy of a head fixation system
M.A. Mosleh-Shirazi , H. Taylor, A.P. Warrington, F.H. Saran
, mosleh_amin@hotmail.com
Abstract:   (13003 Views)
Background: In order to assign appropriate planning target volume (PTV) margins, each centre should measure the patient positioning deviations for their set-up techniques. At the Royal Marsden Hospital, UK, a conformal shell (cast) system is used when a stereotactic frame is not suitable. In this paper, we report on a series of measurements with the aim of obtaining the systematic and random components of positioning error when using the above-mentioned shell system. Materials and Methods: The verification protocol was based on orthogonal pairs of anterior-posterior and lateral electronic portal images (EPIs) used to check the isocentre position. The isocentre verification results of paediatric patients were analysed. A practical ‘off-line’ patient set-up correction strategy had been used with the aim of reducing systematic errors. The verification protocol involved EPI acquisition on the first three fractions and then on a weekly basis. Additional images were taken if an isocentre movement was applied based on a 3 mm tolerance for a consistent 1D discrepancy. Results: Four patients required isocentre corrections ranging between 2 mm and 4 mm. Following the off-line corrections, the residual systematic errors in each direction were within 0.5 mm while the 1D random variation was about 1.0 mm. Conclusions: The head fixation system in conjunction with the correction strategy successfully kept the random and systematic positioning errors within an acceptable level well within the 3 mm tolerance. The measured components of positioning error can be used to define appropriate PTV margins.
Keywords: Treatment verification, Patient immobilisation, Head fixation devices, Electronic portal imaging, Patient positioning correction, Brain radiotherapy
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Type of Study: Original Research | Subject: Radiation Biology
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Mosleh-Shirazi M, Taylor H, Warrington A, Saran F. Measurement of the immobilisation efficacy of a head fixation system. Int J Radiat Res. 2006; 4 (1) :1-6
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Volume 4, Issue 1 (Summer 2006) Back to browse issues page
International Journal of Radiation Research
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