Assessment of tumor motion reproducibility with audio‐visual coaching through successive 4D CT sessions

Abstract

This study aimed to compare combined audio‐visual coaching with audio coaching alone and assess their respective impact on the reproducibility of external breathing motion and, one step further, on the internal lung tumor motion itself, through successive sessions. Thirteen patients with NSCLC were enrolled in this study. The tumor motion was assessed by three to four successive 4D CT sessions, while the breathing signal was measured from magnetic sensors positioned on the epigastric region. For all sessions, the breathing was regularized with either audio coaching alone (AC, normaln=5) or combined with a real‐time visual feedback (A/VC, normaln=8) when tolerated by the patients. Peak‐to‐peak amplitude, period and signal shape of both breathing and tumor motions were first measured. Then, the correlation between the respiratory signal and internal tumor motion over time was evaluated, as well as the residual tumor motion for a gated strategy. Although breathing and tumor motions were comparable between AC and AV/C groups, A/VC approach achieved better reproducibility through sessions than AC alone (mean tumor motion of 7.2 mm±1 vs. 8.6 mm±1.8 mm, and mean breathing motion of 14.9 mm±1.2 mm vs. 13.3 mm±3.7 mm, respectively). High internal/external correlation reproducibility was achieved in the superior‐inferior tumor motion direction for all patients. For the anterior‐posterior tumor motion direction, better correlation reproducibility has been observed when visual feedback has been used. For a displacement‐based gating approach, A/VC might also be recommended, since it led to smaller residual tumor motion within clinically relevant duty cycles. This study suggests that combining real‐time visual feedback with audio coaching might improve the reproducibility of key characteristics of the breathing pattern, and might thus be considered in the implementation of lung tumor radiotherapy.PACS number: 87

Impact of motion induced artifacts on automatic registration of lung tumors in Tomotherapy

“…Interestingly, previous research in our institution [26] showed that audio coaching based on breathing sounds involving uninterrupted inspiration/expiration directives played an important role in reducing intra-but also inter-fraction variations Table 1 3D tumor-based registration errors (mean ± standard deviation) for different registration techniques, using as a metric either the sum of squared voxel intensity differences (SSD), a normalized correlation (NC) or a registration of the centers of mass estimated from either voxel intensity weighted center of mass (WCM) or masks delineated with a threshold-based method on MV-CT and the internal target volume on average kV-CT (MCM). Registration errors were assessed with a ROI size of 10 mm, excluding thus the thoracic wall.…”

Motion management strategies and technical issues associated with stereotactic body radiotherapy of thoracic and upper abdominal tumors: A review from NRG oncology

“…Several factors must be considered when choosing the breathing phase and depth at which to have patients hold their breath. The end expiration phase is the most reproducible phase . Nakamura et al found a 5‐mm internal margin was necessary to account for variations in GTV (pancreas) position with repeated, video‐coached breath holds at end expiration .…”

“…Using external surrogates to monitor breathing avoids the risks inherent to implanting fiducials. Coaching while monitoring the abdominal wall, chest wall, or lung tidal volume has been demonstrated to improve the reproducibility of respiration …”

Image-guided radiotherapy and motion management in lung cancer

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