Realistic CT data augmentation for accurate deep-learning based segmentation of head and neck tumors in kV images acquired during radiation therapy
- Publisher:
- Wiley
- Publication Type:
- Journal Article
- Citation:
- Medical Physics, 2023, 50, (7), pp. 4206-4219
- Issue Date:
- 2023-07-01
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Background Using radiation therapy RT to treat head and neck H N cancers requires precise targeting of the tumor to avoid damaging the surrounding healthy organs Immobilisation masks and planning target volume margins are used to attempt to mitigate patient motion during treatment however patient motion can still occur Patient motion during RT can lead to decreased treatment effectiveness and a higher chance of treatment related side effects Tracking tumor motion would enable motion compensation during RT leading to more accurate dose delivery Purpose The purpose of this paper is to develop a method to detect and segment the tumor in kV images acquired during RT Unlike previous tumor segmentation methods for kV images in this paper a process for generating realistic and synthetic CT deformations was developed to augment the training data and make the segmentation method robust to patient motion Detecting the tumor in 2D kV images is a necessary step toward 3D tracking of the tumor position during treatment Method In this paper a conditional generative adversarial network cGAN is presented that can detect and segment the gross tumor volume GTV in kV images acquired during H N RT Retrospective data from 15 H N cancer patients obtained from the Cancer Imaging Archive were used to train and test patient specific cGANs The training data consisted of digitally reconstructed radiographs DRRs generated from each patient s planning CT and contoured GTV Training data was augmented by using synthetically deformed CTs to generate additional DRRs in total 39 600 DRRs per patient or 25 200 DRRs for nasopharyngeal patients containing realistic patient motion The method for deforming the CTs was a novel deformation method based on simulating head rotation and internal tumor motion The testing dataset consisted of 1080 DRRs for each patient obtained by deforming the planning CT and GTV at different magnitudes to the training data The accuracy of the generated segmentations was evaluated by measuring the segmentation centroid error Dice similarity coefficient DSC and mean surface distance MSD This paper evaluated the hypothesis that when patient motion occurs using a cGAN to segment the GTV would create a more accurate segmentation than no tracking segmentations from the original contoured GTV the current standard of care This hypothesis was tested using the 1 tailed Mann Whitney U test Results The magnitude of our cGAN segmentation centroid error was mean standard deviation 1 1 0 8 mm and the DSC and MSD values were 0 90 0 03 and 1 6 0 5 mm respectively Our cGAN segmentation method reduced the segmentation centroid error p 0 001 and MSD p 0 031 when compared to the no tracking segmentation but did not significantly increase the DSC p 0 294 Conclusions The accuracy of our cGAN segmentation method demonstrates the feasibility of this method for H N cancer patients during RT Accurate tumor segmentation of H N tumors would allow for intrafraction monitoring methods to compensate for tumor motion during treatment ensuring more accurate dose delivery and enabling better H N cancer patient outcomes 2023 The Authors Medical Physics published by Wiley Periodicals LLC on behalf of American Association of Physicists in Medicine
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