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Comparison Between Pulmonary Ventilation-Based Dose-Function Metrics and Perfusion-Based Dose-Function Metrics in Radiotherapy for Lung Cancer
Y Nakajima1,2*, N Kadoya2 , T Kimura3 , K Hioki4 , T Yamamoto5 , (1) Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital, Tokyo, Tokyo, (2) Tohoku University Graduate School of Medicine, Sendai, ,(3) Hiroshima University Graduate School of Biomedical Sciences, Hiroshima, Hiroshima, (4) Hiroshima University Hospital, Hiroshima, Hiroshima, (5) UC Davis School of Medicine, Sacramento, CA
Presentations
TH-AB-FS4-5 (Thursday, August 3, 2017) 7:30 AM - 9:30 AM Room: Four Seasons 4
Purpose: Several active clinical trials of lung functional avoidance radiotherapy with different imaging modalities for ventilation or perfusion are currently underway. Lung cancer patients often show ventilation-perfusion mismatch, while its significance in radiotherapy planning is not well known. The purpose of this study was to compare ventilation-based dose-function metrics with perfusion-based dose-function metrics.
Methods: Pretreatment 4D-CT and 99mTc-MAA SPECT perfusion images of 60 lung cancer patients (47 patients with non-small cell lung cancer, and 13 patients with small cell lung cancer) treated with radiotherapy (median dose: 70 Gy) were used for the study. Ventilation images were created by deformable image registration of 4D-CT image sets and image analysis for regional volume change as a surrogate for ventilation. Ventilation and perfusion images were both converted into percentile distribution images. We assessed the Pearson’s correlation coefficients as well as the agreements between the ventilation-based and perfusion-based dose-function metrics, i.e., the functional mean lung dose (fMLD) and functional V (fV) 5, 20, and 40 Gy (percent lung function receiving a given dose).
Results: Correlations between the ventilation-based and perfusion-based dose-function metrics were strong (range, 0.95-0.98). Overall the ventilation-based metrics were greater than the perfusion-based metrics, e.g., ventilation-based fMLD 14.3±1.3 Gy vs. perfusion-based fMLD 13.1±1.3 Gy. The 95% limits of agreement were less than 4%, while the agreements varied widely between individual patients with absolute (relative) differences as large as 4.0 Gy (48%) for the fMLD and 9.2% (55.1%) for the fV20.
Conclusion: This study has demonstrated strong correlations and small limits of agreement between the ventilation-based and perfusion-based dose-function metrics, suggesting that ventilation-based radiotherapy plan evaluation may be comparable to perfusion-based evaluation. However, the agreements between the ventilation-based and perfusion-based metrics varied widely between individual patients. Future work will focus on correlating the dose-function metrics with clinical pulmonary toxicity data.
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