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A study for the dosimetric evaluation of rotational setup error forlung stereotactic body radiation therapy*

Published online by Cambridge University Press:  01 August 2018

Sina Mossahebi
Affiliation:
Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD, USA
Ulrich Langner
Affiliation:
Department of Radiation Oncology, Boston University School of Medicine, Boston, MA, USA
Karl Prado
Affiliation:
Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD, USA
Minsik Lee
Affiliation:
Department of Radiation Oncology, Asan Medical Center, University of Ulsan College School of Medicine, Seoul, Korea
ByongYong Yi*
Affiliation:
Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD, USA
*
Author for correspondence: ByongYong Yi, Departmentof Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD,USA. Email: byi@umm.edu

Abstract

Purpose

To investigate the necessity of rotational shifts by considering dosimetricimpact of rotational errors on stereotactic body radiation therapy(SBRT).

Materials and methods

20 lung patients with the lesion size <5 cm treated with SBRT havebeen selected for dosimetric analysis. Three-dimensional dose has beenrotationally shifted (±1°, ±3°,±5° for pitch, roll and yaw) and overlaid to the originalcomputed tomography images. The dose–volume histograms of18-rotational plans of each patient were compared to those of the originalplan.

Results

No significant dosimetric differences were observed in target coverage. Forall of the cases up to 5° in any couch angle dose differences ofD99 and D95 were<3%. Variations of conformity index were observed to be lessthan 0·05. None of the organ at risk doses exceeded the dose limit.The V20 differences of the ipsilateral and thetotal lungs were less than 0·4%.

Conclusion

It has been found to be unnecessary to perform rotational shifts up to5° for lung SBRT treatments; the translational shift is sufficientfor the cases used in this study. This method may be applied and testedafter planning and before treatment initiation to rule out exceptionallyextreme cases.

Information

Type
Original Article
Copyright
© Cambridge University Press 2018 

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