Effects of breathing variation on gating window internal target volume in respiratory gated radiation therapy.

Published

Journal Article

PURPOSE: To investigate the effects of breathing variation on gating window internal target volume (ITVGW) in respiratory gated radiation therapy. METHOD AND MATERIALS: Two-dimensional dynamic MRI (dMRI) of lung motion was acquired in ten volunteers and eight lung cancer patients. Resorted dMRI using 4DCT acquisition method (RedCAM) was generated for selected subjects by simulating the image rebinning process. A dynamic software generated phantom (dSGP) was created by moving a solid circle (to mimic the "tumor") with dMRI-determined motion trajectories. The gating window internal target area (ITAGw, 2D counterpart of ITVGW) was determined from both RedCAM and dSGP/dMRI. Its area (A), major axis (L1), minor axis (L2), and similarity (S) were calculated and compared. RESULTS: In the phantom study of 3 cm tumor, measurements of the ITAGW from dSGP (A =10.0 +/- 1.3 cm2, L1=3.8 +/- 0.4 cm, and L2=3.3 +/- 0.1 cm) are significantly (p <0.001) greater than those from RedCAM (A=8.5 +/- 0.7 cm(2), L1 =3.5 +/- 0.2 cm, and L2=3.1 +/- 0.1 cm). Similarly, the differences are significantly greater (p <0.001) for the 1 cm tumor (A=1.9 +/- 0.5 cm(2), L1 =1.9 +/- 0.4 cm, and L2=1.3 +/- 0.1 cm in dSGP; A=l1.3 +/- 0.1 cm(2), L1=1.5 +/- 0.2 cm, and L2 = 1.1 +/- 0.1 cm in RedCAM). In patient studies, measurements of the ITAGW from dMRI (A =15.5 +/- 8.2 cm(2), Ll=5.0 +/- 1.1 cm, and L2=3.8 +/- 1.2 cm) are also significantly greater (p <0.05) than those from RedCAM (A=13.2 +/- 8.5 cm(2), L1=4.3 +/- 1.4 cm, and L2=3.7 +/- 1.2 cm). Similarities were 0.9 +/- 0.1, 0.8 +/- 0.1, and 0.8 +/- 0.1 in the 3 cm tumor phantom, 1 cm tumor phantom, and patient studies, respectively. CONCLUSION: ITVGW can be underestimated by 4DCT due to breathing variations. An additional margin may be needed to account for this potential error in generating a PTVGW. Cautions need to be taken when generating ITVGW from 4DCT in respiratory gated radiation therapy, especially for small tumors (<3 cm) with a large motion range (>1 cm).

Full Text

Duke Authors

Cited Authors

  • Cai, J; McLawhorn, R; Read, PW; Larner, JM; Yin, F-F; Benedict, SH; Sheng, K

Published Date

  • August 2010

Published In

Volume / Issue

  • 37 / 8

Start / End Page

  • 3927 - 3934

PubMed ID

  • 20879555

Pubmed Central ID

  • 20879555

International Standard Serial Number (ISSN)

  • 0094-2405

Digital Object Identifier (DOI)

  • 10.1118/1.3457329

Language

  • eng

Conference Location

  • United States