4D-CT-based target volume definition in stereotactic radiotherapy of lung tumours: Comparison with a conventional technique using individual margins

Hof, Holger; Rhein, Bernhard; Haering, Peter; Kopp-Schneider, Annette; Debus, Jürgen; Herfarth, Klaus

doi:10.1016/j.radonc.2009.08.040

« Previous Next »Radiotherapy & Oncology
Volume 93, Issue 3 , Pages 419-423, December 2009

4D-CT-based target volume definition in stereotactic radiotherapy of lung tumours: Comparison with a conventional technique using individual margins

Holger Hof
- University of Heidelberg, Department of Radiation Oncology, Heidelberg, Germany
- Corresponding author. Address: Universitaetsklinikum Heidelberg, Abt. Radioonkologie und Strahlentherapie, INF 400, D-69120 Heidelberg, Germany.
Bernhard Rhein
- German Cancer Research Center (DKFZ), Department of Medical Physics, Heidelberg, Germany
Peter Haering
- German Cancer Research Center (DKFZ), Department of Medical Physics, Heidelberg, Germany
Annette Kopp-Schneider
- German Cancer Research Center (DKFZ), Division of Biostatistics, Heidelberg, Germany
Jürgen Debus
- University of Heidelberg, Department of Radiation Oncology, Heidelberg, Germany
Klaus Herfarth
- University of Heidelberg, Department of Radiation Oncology, Heidelberg, Germany

Received 27 March 2009; received in revised form 24 August 2009; accepted 25 August 2009. published online 27 September 2009.

Abstract

Purpose

To investigate the dosimetric benefit of integration of 4D-CT in the planning target volume (PTV) definition process compared to conventional PTV definition using individual margins in stereotactic body radiotherapy (SBRT) of lung tumours.

Material and methods

Two different PTVs were defined: PTV_conv consisting of the helical-CT-based clinical target volume (CTV) enlarged isotropically for each spatial direction by the individually measured amount of motion in the 4D-CT, and PTV_4D encompassing the CTVs defined in the 4D-CT phases displaying the extremes of the tumour position. Tumour motion as well as volumetric and dosimetric differences and relations of both PTVs were evaluated.

Results

Volumetric examinations revealed a significant reduction of the mean PTV by 4D-CT from 57.7 to 40.7cm³ (31%) (p<0.001). A significant inverse correlation was found for the motion vector and the amount of inclusion of PTV_4D in PTV_conv (r=−0.69, 90% confidence limits: −0.87 and −0.34, p=0.007). Mean lung dose (MLD) was decreased significantly by 17% (p<0.001).

Conclusions

In SBRT of lung tumours the mere use of individual margins for target volume definition cannot compensate for the additional effects that the implementation of 4D-CT phases can offer.

Keywords: 4D-CT, Target volume definition, Stereotactic radiotherapy, Lung tumours, Tumour motion