(Sunday, 7/29/2018) 3:00 PM - 6:00 PM
Room: Exhibit Hall
Purpose: A new abdominal compression belt was introduced recently in our clinic. This work presents an analysis of its effectiveness to reduce respiratory motion of lung tumors.
Methods: 8-phase 4D simulation CTs were acquired for 13 lung cancer patients with and without the ZiFix compression belt (QFix, Avondale, PA). Tumor motion was calculated via deformable registration of CT phases using the software OpenREGGUI (https://openreggui.org/). First, the physician-contoured iGTV was propagated from the 8-phase-average of the compression-belt scan to that of the no-compression-belt scan. Next, the full-inhale and full-exhale phases for both scans were registered, and 80th-percentile motion (3D and magnitude) was calculated over all voxels in the respective iGTVs. To investigate morphological dependencies, iGTV volume and the iGTV-centroid-to-ipsilateral-diaphragm distance were also recorded.
Results: Tumor motion magnitudes ranged from 1.4-16.1mm without compression (0.2-2.6mm L-R, 0.1-4.0mm A-P, 0.3-16.0mm S-I) and 1.0-11.2mm with compression (0.2-2.7mm L-R, 0.3-5.5mm A-P, 0.6-11.2mm S-I). Compression reduced motion magnitude in six patients, by an average of 1.9mm. These reductions were almost entirely in the S-I direction (average reductions 0.1mm L-R, 0.0mm A-P, 1.9mm S-I). The largest reduction in magnitude was 5.9mm. There was a correlation between diaphragm distance and change in motion magnitude (Spearman’s rho=0.69, p<0.01), meaning that the compression belt was more effective for tumors closer to the diaphragm. No correlation was found between tumor volume and motion reduction.
Conclusion: The ZiFix abdominal compression belt can reduce lung tumor motion, but for a subset of patients it does not. This may be due to patients adapting their breathing pattern while wearing the belt (i.e. chest breathing instead of abdominal breathing). The belt is more effective at reducing motion for tumors closer to the diaphragm. Continuing work on this topic will evaluate the reproducibility of the belt and the dosimetric impacts of its influence on lung tumor motion.
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