Use of 4-Dimensional Computed Tomography-Based Ventilation Imaging to Correlate Lung Dose and Function With Clinical Outcomes

Abstract

Purpose Four-dimensional computed tomography (4DCT)-based ventilation is an emerging imaging modality that can be used in the thoracic treatment planning process. The clinical benefit of using ventilation images in radiation treatment plans remains to be tested. The purpose of the current work was to test the potential benefit of using ventilation in treatment planning by evaluating whether dose to highly ventilated regions of the lung resulted in increased incidence of clinical toxicity. Methods and Materials Pretreatment 4DCT data were used to compute pretreatment ventilation images for 96 lung cancer patients. Ventilation images were calculated using 4DCT data, deformable image registration, and a density-change based algorithm. Dose—volume and ventilation-based dose function metrics were computed for each patient. The ability of the dose—volume and ventilation-based dose—function metrics to predict for severe (grade 3+) radiation pneumonitis was assessed using logistic regression analysis, area under the curve (AUC) metrics, and bootstrap methods. Results A specific patient example is presented that demonstrates how incorporating ventilation-based functional information can help separate patients with and without toxicity. The logistic regression significance values were all lower for the dose—function metrics (range P=.093-.250) than for their dose—volume equivalents (range, P=.331-.580). The AUC values were all greater for the dose—function metrics (range, 0.569-0.620) than for their dose—volume equivalents (range, 0.500-0.544). Bootstrap results revealed an improvement in model fit using dose—function metrics compared to dose—volume metrics that approached significance (range, P=.118-.155). Conclusions To our knowledge, this is the first study that attempts to correlate lung dose and 4DCT ventilation-based function to thoracic toxicity after radiation therapy. Although the results were not significant at the .05 level, our data suggests that incorporating ventilation-based functional imaging can improve prediction for radiation pneumonitis. We present an important first step toward validating the use of 4DCT-based ventilation imaging in thoracic treatment planning.

CT ventilation functional image-based IMRT treatment plans are comparable to SPECT ventilation functional image-based plans

“…For the lungs, the following dose-volume metrics were investigated: the mean lung dose (MLD), V 20 , and effective dose (D eff ) [28]. We also calculated the dose-function histogram (DFH) [29] and the following dose-function metrics: fV 20 , functional MLD (fMLD) [30], and functional effective dose (fD eff ) [7]. Vinogradskiy et al demonstrated a higher predictive power of these dose-function metrics for pneumonitis compared to dose-volume metrics [7].…”

“…The CT ventilation images were smoothed using a 3D Gaussian filter kernel (7 Â 7 Â 3 or 9 Â 9 Â 3 depending on the CT voxel dimension) to match the expected spatial resolution of the SPECT ventilation images. Then, the smoothed CT ventilation images and original (unsmoothed) SPECT ventilation images were converted into percentile distribution images by replacing the ventilation value of each voxel with the corresponding cumulative distribution function (CDF k ) scaled to the range [0,1] (mean 0.5) in a manner similar to Vinogradskiy et al [7]. Abbreviations: SCLC = small-cell lung cancer, NSCLC = non-small-cell lung cancer, RUL = right upper lobe.…”

“…Lung dose-function metrics were found to improve predictive power for pulmonary toxicity compared to dose-volume metrics [6,7]. The mean functional V 20 (fV 20 ) (percent lung function receiving P20 Gy) for patients who developed Grade P3 pneumonitis was 4.3% greater (p = 0.09) than those who did not, and it was closer to statistical significance than the V 20 (percent lung volume receiving P20 Gy) (p = 0.33) [7].Several modalities exist for pulmonary ventilation imaging [8][9][10][11]. Ventilation images can also be acquired by a method based on four-dimensional (4D) computed tomography (CT) and image processing/analysis [12,13], henceforth referred to as CT ventilation imaging.…”

“…This hypothesis is supported by several reports in the literature. Lung dose-function metrics were found to improve predictive power for pulmonary toxicity compared to dose-volume metrics [6,7]. The mean functional V 20 (fV 20 ) (percent lung function receiving P20 Gy) for patients who developed Grade P3 pneumonitis was 4.3% greater (p = 0.09) than those who did not, and it was closer to statistical significance than the V 20 (percent lung volume receiving P20 Gy) (p = 0.33) [7].…”

Using 4DCT‐ventilation to characterize lung function changes for pediatric patients getting thoracic radiotherapy

“…4DCT‐ventilation has been gaining momentum in radiation oncology because 4DCT simulations are frequently acquired as part of the standard treatment planning process; which enables the calculation of 4DCT‐ventilation‐based lung function without burdening the patient with an extra imaging procedure. There have been two clinical applications of 4DCT‐ventilation in radiation oncology: functional radiotherapy (designing radiation treatment plans that minimize dose to functional lung) and thoracic treatment assessment 4, 5, 6, 7…”