Comparison of lung tumor motion measured using a model-based 4DCT technique and a commercial protocol

Publication date: Available online 11 November 2017
Source:Practical Radiation Oncology
Author(s): D. O'Connell, N. Shaverdian, A.U. Kishan, D.H. Thomas, T.H. Dou, J.H. Lewis, J.M. Lamb, M. Cao, S. Tenn, P. Lee, D.A. Low
PurposeTo compare lung tumor motion measured with a model-based technique to commercial 4DCT and describe a workflow for using model-based 4DCT as a clinical simulation protocol.Methods20 patients were imaged using a model-based technique and commercial 4DCT. Tumor motion was measured on each commercial 4DCT dataset, and was calculated on model-based datasets for three breathing amplitude percentile intervals: 5th–85th, 5th–95th and 0th–100th. Internal target volumes (ITV) were defined on the 4DCT and 5th to 85th interval datasets and compared using Dice similarity. Images were evaluated for noise and rated by two radiation oncologists for artifacts.ResultsMean differences in tumor motion magnitude between commercial and model-based images were 0.47±3.0mm, 1.63±3.17mm, and 5.16±4.90mm for the 5th–85th, 5th–95th, and 0th–100th amplitude intervals, respectively. Dice coefficients between ITVs defined on commercial and 5th–85th model-based images had a mean value of 0.77±.09. Single standard deviation image noise was 11.6±9.6 HU in the liver and 6.8±4.7 HU in the aorta for the model-based images compared to 57.7±30 and 33.7±15.4 for commercial 4DCT. Mean model error within the ITV regions was 1.71±0.81mm. Model-based images exhibited reduced presence of artifacts at the tumor compared to commercial.ConclusionTumor motion measured with the model-based technique using the 5th to 85th percentile breathing amplitude interval corresponded more closely to commercial 4DCT than the 5th–95th or 0th–100th intervals, which showed greater motion on average. The model-based technique tended to display increased tumor motion when breathing amplitude intervals wider than 5th–85th were used due to the influence of unusually deep inhalations. These results suggest that care must be taken in selecting the appropriate interval during image generation when using model-based 4DCT methods.



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