Physics in Medicine & Biology
Jan 28, 2013
4D VMAT, gated VMAT, and 3D VMAT for stereotactic body radiation therapy in lung
E Chin, S K Loewen, A Nichol and K Otto 2013 Phys. Med. Biol. 58 749
Greater biologically effective dose with hypofractionated stereotactic body radiation therapy (SBRT) over conventionally fractionated radiotherapy has improved local control and overall survival in inoperable, early stage non-small cell lung cancer (NSCLC), but further dose escalation is limited by normal tissue toxicity. In SBRT planning with three dimensional volumetric modulated arc therapy (3D VMAT), normal tissue dose limits can be breached because a larger treatment volume is required to account for tumour motion during respiration. Four dimensional (4D) VMAT is a novel technique that synchronizes intensity modulation over patient respiratory cycles to exploit relative tumour and normal tissue motion. This planning study on three patients with NSCLC confirmed enhanced normal tissue sparing by 4D VMAT over 3D VMAT and similar tissue sparing by 4D VMAT compared to gated VMAT (duty cycle: 40–60%). For lung cancer SBRT, 4D VMAT can achieve similar dose escalation to gated VMAT while delivering treatment 35–50% faster.
About the author
E Chin, S K Loewen, A Nichol (University of British Columbia, Vancouver, Canada, and BC Cancer Agency—Vancouver Centre, Canada) and K Otto (University of British Columbia, Vancouver, Canada)