Improved OAR Sparing In Lung Lattice Sfrt Using Breath-Hold Respiratory Motion Management
Abstract
Purpose
Spatially fractionated radiation therapy (SFRT) requires accurate placement of high-dose vertices to preserve peak-to-valley dose ratios (PVDR) and limit dose to surrounding organs at risk (OARs). This study evaluates the impact of breath-hold–based motion management using the SDX system on lung SFRT planning.
Methods
Six lung cancer CT datasets with respiratory motion exceeding 5 mm were retrospectively analyzed. For each case, SFRT plans were generated on a Varian TrueBeam linac. CT scans were acquired using 4DCT (mean CT) and the SDX Respiratory Gating System (DYN’R Medical Systems). Two motion-management strategies were compared: (1) SFRT GTV derived from the internal target volume (ITV) on the mean CT, and (2) SFRT GTV contoured directly on the SDX breath-hold CT. To assess the dosimetric impact of motion, SFRT GTVs and vertex geometries defined on the mean CT were propagated onto the SDX CT, and OAR doses were recalculated
Results
Results indicate that using SDX-based motion management reduced the average V7 Gy for the lung and liver from 28.6 cc to 7.4 cc and from 8.4 cc to 6.8 cc, respectively. The average D1 cc for the rib decreased from 10.1 Gy to 7.3 Gy. Using mean CT–derived vertices on SDX CT without recontouring led to less reliable sparing, highlighting geometric mismatches between free-breathing and breath-hold anatomies and an increased likelihood of high-dose SFRT vertices extending beyond the true GTV into adjacent OARs.
Conclusion
Breath-hold motion management systems, such as SDX, improve target definition and OAR sparing, supporting their routine use for SFRT of mobile lung targets.