Key result
4pi-optimized VT SBRT trajectories reduce at-risk organ doses vs conventional methods without compromising target coverage.
Why the study?
The study was conducted to investigate the possible advantages of using 4pi-optimized arc trajectories in stereotactic body radiation therapy of ventricular tachycardia to minimize healthy tissue exposure.
Does a 4pi-optimized arc trajectory plan improve dose sparing to organs at risk compared to a conventional trajectory plan in VT-SBRT?
Does a 4pi-optimized arc trajectory plan improve dose sparing to organs at risk compared to a conventional trajectory plan in VT-SBRT?
Using 4pi-optimized trajectories in VT-SBRT significantly reduces radiation exposure to noncardiac organs at risk compared to conventional coplanar arcs, making it a suitable delivery technique.
PURPOSE: To investigate the possible advantages of using 4pi-optimized arc trajectories in stereotactic body radiation therapy of ventricular tachycardia (VT-SBRT) to minimize exposure of healthy tissues. METHODS AND MATERIALS: Thorax computed tomography (CT) data for 15 patients were used for contouring organs at risk (OARs) and defining realistic planning target volumes (PTVs). A conventional trajectory plan, defined as two full coplanar arcs was compared to an optimized-trajectory plan provided by a 4pi algorithm that penalizes geometric overlap of PTV and OARs in the beam's-eye-view. A single fraction of 25 Gy was prescribed to the PTV in both plans and a comparison of dose sparing to OARs was performed based on comparisons of maximum, mean, and median dose. RESULTS: A significant average reduction in maximum dose was observed for esophagus (18%), spinal cord (26%), and trachea (22%) when using 4pi-optimized trajectories. Mean doses were also found to decrease for esophagus (19%), spinal cord (33%), skin (18%), liver (59%), lungs (19%), trachea (43%), aorta (11%), inferior vena cava (25%), superior vena cava (33%), and pulmonary trunk (26%). A median dose reduction was observed for esophagus (40%), spinal cord (48%), skin (36%), liver (72%), lungs (41%), stomach (45%), trachea (53%), aorta (45%), superior vena cava (38%), pulmonary veins (32%), and pulmonary trunk (39%). No significant difference was observed for maximum dose (p = 0.650) and homogeneity index (p = 0.156) for the PTV. Average values of conformity number were 0.86 ± 0.05 and 0.77 ± 0.09 for the conventional and 4pi optimized plans respectively. CONCLUSIONS: 4pi optimized trajectories provided significant reduction to mean and median doses to cardiac structures close to the target but did not decrease maximum dose. Significant improvement in maximum, mean and median doses for noncardiac OARs makes 4pi optimized trajectories a suitable delivery technique for treating VT.
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Reis et al. (2021) studied Ventricular tachycardia (n=15). 4pi-optimized arc trajectories vs. Conventional trajectory plan (two full coplanar arcs) was evaluated on PTV maximum dose (Dmax) (p=0.650). 4pi-optimized trajectories for ventricular tachycardia SBRT significantly reduced mean and median doses to cardiac and noncardiac organs at risk compared to conventional trajectories without compromising target coverage.
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