TITLE:
Partial and Full Arc Volumetric Modulated Arc Therapy in Lung Cancer Stereotactic Body Radiotherapy with Different Definitions of Internal Target Volume Based on 4D CT
AUTHORS:
Wu Wang, Didi Chen, Ce Han, Xiaomin Zheng, Yongqiang Zhou, Changfei Gong, Congying Xie, Xiance Jin
KEYWORDS:
Lung Cancer, Stereotactic Body Radiotherapy, Four Dimensional Computed Tomography, Internal Target Volume, Volumetric Modulated Arc Therapy
JOURNAL NAME:
International Journal of Medical Physics, Clinical Engineering and Radiation Oncology,
Vol.7 No.4,
November
9,
2018
ABSTRACT: Purpose: To
investigate the feasibility of partial arc volumetric modulated arc therapy
(VMAT) in lung cancer stereotactic body radiotherapy (SBRT), as well the
volumetric and dosimetric effects of different internal target volume (ITV)
definitions with 4D CT. Methods: Fourteen patients with primary and metastatic
lung cancer underwent SBRT were enrolled. Full and partial arc VMAT plans were
generated with four different ITVs: ITVall, ITVMIP, ITVAIP and
ITV2phases,
representing ITVs generated from all 10 respiratory phases, maximum intensity
projection (MIP), average intensity projection (AIP), and 2 extreme respiratory
phases. Volumetric and dosimetric differences, as well as MU and delivery time
were investigated. Results: Partial arc VMAT irradiated more dose at 2
cm away from planning target volume (PTV) (P = 0.002),
however, it achieved better protection on mean lung dose , lung V5, spinal
cord, heart and esophagus compared with full arc VMAT. The average MU and delivery
time of partial arc VMAT were 240 and 1.6 min less than those of full arc VMAT.
There were no significant differences on target coverage and organ at risks
(OARs) sparing among four ITVs. The average percent volume differences of ITVMIP, ITVAIP and
ITV2phases to ITVall were
8.6%, 13.4%, and 25.2%, respectively. Conclusions: Although partial arc
VMAT delivered more dose 2 cm out of PTV, it decreases the dose to lung, spinal
cord, and esophagus, as well decreased the total MU and delivery time compared
with full arc VMAT without sacrificing target coverage. Partial arc VMAT was
feasible and more efficient for lung SBRT.