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Treatment planning considerations of reshapeable automatic intensity modulator for intensity modulated radiation therapy
Author(s) -
Xu Tong,
AlGhazi Muthana S.,
Molloi Sabee
Publication year - 2004
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.1774112
Subject(s) - intensity modulation , collimator , isocenter , computer science , radiation treatment planning , intensity (physics) , medical physics , artificial intelligence , optics , radiation therapy , medicine , physics , radiology , phase modulation , phase noise
As compared with multi‐leaf collimator based intensity modulated radiation therapy (IMRT) techniques, physical modulators have the major advantage of temporally invariant intensity map delivery which makes it more flexible with monitor unit rate, simpler resolution of interrupted treatment and easier implementation and use with respiratory gating. However, traditional physical modulator techniques require long fabrication time and operator intervention during treatments. It has been previously proposed [Xu et al., Med. Phys. 29 , 2222–2229 (2002)] that a reshapeable automatic intensity modulator (RAIM) can automatically produce physical modulators by molding a deformable high x‐ray attenuation material using a matrix of computer‐controlled pistons. RAIM can potentially eliminate the limitations of traditional physical modulators. The present study addresses the treatment planning considerations of RAIM for IMRT. In this study, a 3D treatment‐planning system (PLUNC) was modified to include the capability of providing treatment planning using RAIM. Two clinically representative cases were studied: nasopharyngeal and prostate tumors. First, the RAIM system with two different spatial resolutions at isocenter, 1 × 1 cm 2and 0.5 × 0.5 cm 2 , were evaluated. The treatment planning results of RAIM were then compared with other IMRT techniques such as smooth modulator with ideal (100%–2%) and limited (100%–13%) intensity modulation ranges, segmental multi‐leaf collimator (SMLC) with ten intensity levels, 1 cm leaf width and 0.5 cm step size and serial tomotherapy using the Peacock ® system. Bringing the spatial resolution of RAIM down to 0.5 × 0.5 cm 2did not show improvement due to the effect of penumbra. The RAIM system with 1 × 1 cm 2proved slightly inferior as compared to the ideal smooth physical modulator but better than the SMLC technique and the smooth modulator with limited modulation range. When compared to serial tomotherapy, RAIM is only inferior in brain stem sparing for the nasopharynx case. Furthermore, the RAIM system with 1 × 1 cm 2resolution required significantly lower monitor units as compared to the other IMRT techniques for the two cases studied.