Influence of intra- and interfraction motion on planning target volume margin in liver stereotactic body radiation therapy using breath hold

Patricia A K Oliver; Mammo Yewondwossen; Clare Summers; Conor Shaw; Slawa Cwajna; Alasdair Syme

doi:10.1016/j.adro.2020.10.023

Influence of intra- and interfraction motion on planning target volume margin in liver stereotactic body radiation therapy using breath hold

Adv Radiat Oncol. 2020 Nov 19;6(1):100610. doi: 10.1016/j.adro.2020.10.023. eCollection 2021 Jan-Feb.

Authors

Patricia A K Oliver¹, Mammo Yewondwossen^{1

2

3}, Clare Summers², Conor Shaw¹, Slawa Cwajna², Alasdair Syme^{1

2

3}

Affiliations

¹ Department of Medical Physics, Nova Scotia Health Authority, Halifax, Canada.
² Department of Radiation Oncology, Dalhousie University, Halifax, Canada.
³ Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Canada.

Abstract

Purpose: This study aimed to investigate intra- and interfraction motion during liver stereotactic body radiation therapy for the purpose of planning target volume (PTV) margin estimation, comparing deep inspiration breath hold (DIBH) and deep expiration breath hold (DEBH).

Methods and materials: Pre- and posttreatment kV cone beam computed tomography (CT) images were acquired for patients with liver cancer who were treated using stereotactic body radiation therapy with DIBH or DEBH. A total of 188 images were analyzed from 18 patients. Positioning errors were determined based on a comparison with planning CT images and matching to the liver. Treatment did not proceed until errors were ≤3 mm. Standard deviations of random and systematic errors resulting from this image matching process were used to calculate PTV margin estimates.

Results: DIBH errors are generally larger than DEBH errors, especially in the anterior-posterior and superior-inferior directions. Posttreatment errors tend to be larger than pretreatment errors, especially for DIBH. Standard deviations of random errors are larger than those of systematic errors. Considering both pre- and posttreatment cone beam CT images, PTV margins for DIBH and DEBH are estimated as anterior-posterior, superior-inferior, right-left = (5.7, 6.3, 3.0) mm and (3.1, 3.4, 2.8) mm, respectively.

Conclusions: This study suggests that DEBH results in more reproducible target positioning, which could in turn justify the use of smaller PTV margins.