The frequency of re-planning and its variability dependent on the modification of the re-planning criteria and IGRT correction strategy in head and neck IMRT

Radiation Oncology

Eva Maria Stoiber³  Rolf Bendl²  Jürgen Debus³  Kristina Giske¹  Markus Stoll¹ 

[1] Department of Medical Physics in Radiation Oncology, DKFZ, INF 280, 69120 Heidelberg, Germany;Faculty of Medical Informatics, Heilbronn University, Heilbronn, Germany;Department of Radiation Oncology, University Hospital, Heidelberg, Germany

关键词: Re-planning frequency;    Re-planning criteria;    Dose variations;    Deformable image registration;    Head and neck cancer;    Image-guided radiation therapy;   

Others  :  1151979
DOI  :  10.1186/1748-717X-9-175

 received in 2014-01-10, accepted in 2014-07-31,  发布年份 2014

【 摘 要 】

Background

To analyse the frequency of re-planning and its variability dependent on the IGRT correction strategy and on the modification of the dosimetric criteria for re-planning for the spinal cord in head and neck IG-IMRT.

Methods

Daily kV-control-CTs of six head and neck patients (=175 CTs) were analysed. All volumes of interest were re-contoured using deformable image registration. Three IGRT correction strategies were simulated and the resulting dose distributions were computed for all fractions. Different sets of criteria with varying dose thresholds for re-planning were investigated. All sets of criteria ensure equivalent target coverage of both CTVs, but vary in the tolerance threshold of the spinal cord.

Results

The variations of the D95 and D2 in respect to the planned values ranged from -7% to +3% for both CTVs, and -2% to +6% for the spinal cord. Despite different correction vectors of the three IGRT strategies, the dosimetric differences were small. The number of fractions not requiring re-planning varied between 0% and 11% dependent on the applied IGRT correction strategy. In contrast, this number ranged between 32% and 70% dependent on the dosimetric thresholds, even though these thresholds were only gently modified.

Conclusions

The more precise the planned dose needs to be maintained over the treatment course, the more frequently re-planning is required. The influence of different IGRT correction strategies, even though geometrically notable, was found to be of only limited relevance for the re-planning frequency. In contrast, the definition and modification of thresholds for re-planning have a major impact on the re-planning frequency.

【 授权许可】

   
2014 Stoll et al.; licensee BioMed Central Ltd.

【 图 表 】

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