Evaluation of dose difference in the delivered dose due to lung tumor motion in conventional, conformal and IMRT treatment techniques using in-house developed dynamic phantom

Respiration-induced tumor motion during radiation delivery introduces dose difference between the planned dose and the target-received dose. This study investigated the magnitude of the dose difference due to tumor motion on two-dimensional (2D) conventional radiation therapy, three-dimensional conformai radiation therapy (3DCRT) and intensity modulated radiation therapy (IMRT) dose delivery. In this work, a typical 2D plan with opposing fields, 3DCRT and IMRT plans (five fields) were delivered to a dynamic phantom that was capable of moving in any user-defined pattern. The phantom was kept in static mode and the delivered dose was measured using GaF chromic film that was sandwiched at the centre of the cylindrical target parallel to the horizontal plane. The same procedure was repeated with the target set in linear sinusoidal motion with amplitude of ± 1.2 cm and a frequency of 16 cycles/min (0.27 Hz). The films exposed at both static and dynamic modes were compared and analyzed using Verisoft software. Detailed gamma analyses were carried out between the dose delivered at phantom kept under static mode and the dose delivered at phantom under dynamic mode for various combinations of distance-to-agreement (DTA) criteria of 1 mm, 2 mm, 3 mm, 5 mm and dose criteria of 2%, 3%, 4%, and 5%. The obtained values demonstrated that 3DCRT and IMRT delivery had larger dose difference due to tumor motion than conventional 2D treatment delivery.