Abstract：Changes in the tumour position due to inter and intra-fractional motion introduce uncertainty in IMRT delivery. In this work, we experimentally evaluated the effect of inter and intra-fractional motion uncertainties in the IMRT delivery. A lung patient was planned with rive field dynamic IMRT for a total dose of 60 Gy in 30 fractions using 6 MV photon beam at a dose rate of 400 MU/min. The plan was delivered on varian CL2100CD linear accelerator with millennium 120 MLC for a single fraction and measured using IMRT MatriXX placed on Quasar motion platform, aligned with respect to isocentre for planar as well as point dose measurements. This measurement was summated for 30 fractions and taken as a reference. 30 measurements were performed for each inter-fractional, intra-fractional and combined effect. The setup errors (Mean+SD) used to simulate the inter-fractional displacements were RL: -0.10+0.27 mm, SI: 0.17+0.45 mm, AP: -0.04+0.38 mm and Rot: 0.02+0.86 degree. The intra-fractional motion was simulated using the motion platform parallel to the MLC leaf motion, for an amplitude of 1 cm and a period of 4 s. The planner fluence of inter, intra-fractional motion and combination of both was analyzed against the reference using gamma criteria of 3%/3 mm. Similarly, the point dose measurements were also compared. The maximum deviation in point dose during a single fraction was -3.8%, 3.1% and -5.9% for inter-fractional, intra-fractional and combined respectively. The same resulted in deviation of -0.4%, -0.3% and 0.1% respectively when summated for 30 fractions. The percentage of pixels failing the gamma criteria during a single fraction was 28.0%, 16.4% and 28.5% for inter-fractional, intra-fractional and combined respectively. The same revealed 11.4%, 12.4% and 19.2% respectively when summated. Though the point dose deviations were nullified over 30 fractions, the planner fluence variation was observed to be considerable.
. [J]. 中国生物医学工程学报(英文版）, 2017, 26(1): 1-4.
Maria Das KJ, Arpita Agarwal, Yoganathan SA, Gowtharu Raj D, Shaleen Kumar. Investigation of lnter and Intra-fractional Uncertainties in Lung IMRT Delivery. Chinese Journal of Biomedical Engineering, 2017, 26(1): 1-4.
[1] Martel MK, Haken RKT, Hazuka MB, et al. Estimation of tumor control probability model parameters from 3-D dose distributions of non-samll cell lung cancer patients[J]. Lung Cancer,1999, 24(1):31-37. [2] Bortfeld T, Jokivarsi K, Goitein M, et al. Effects of intra-fraction motion on IMRT dose delivery: Statistical analysis and simulation[J]. Physics in Medicine and Biology, 2002, 47:2203-2220. [3] Jiang SB, Pope C, Al Jarrah KM, et al. An experimental investigation on intrafractional organ motion effects in lung IMRT treatments[J]. Physics in Medicine and Biology, 2003, 48: 1773-1784. [4] Pemler P, Besserer J, Lombriser N, et al. Influence of respiration-induced organ motion on dose distributions in treatments using enhanced dynamic wedges[J]. Medical Physics， 2001， 28： 223440. [5] Mechalakos J, Yorke E, Mageras GS, et al. Dosimetric effect of respiratory motion in external beam radiotherapy of the lung[J]. Radiotherapy and Oncology, 2004, 71: 191-200.
