Room: Exhibit Hall
Purpose: To create a knowledge-based planning (KBP) model and determine if implementation would decrease dose to normal heart tissue for cardiac stereotactic body radiation therapy (SBRT) for the treatment of refractory ventricular tachycardia.
Methods: KBP software was used to create a cardiac model from the original clinical treatment plans (CP) of 23 patients that had received cardiac SBRT (25Gy/1 fraction to the arrythmogenic focus) for the ablation of ventricular tachycardia on a prospective Phase I trial. We then compared the internal target volume (ITV) and planning target volume (PTV) coverage by treatment plan type. Heart â€“ PTV mean dose, Heart-PTV V25 Gy, V20 Gy, V15Gy, V10Gy, V5Gy, and the ratio of the 50% isodose volume to the PTV (R50%) were also compared for each group. Paired t-tests were used to compare continuous values, and values are reported as means Â± standard error of the mean (SEM) for each group.
Results: In comparing the delivered CP to the KBP, no difference was seen in target coverage to the ITV (CP 99.5 Â± 0.21 versus 99.7 Â± 0.15, p=0.2) or PTV (CP 99.4 Â± 0.3 versus KBP 99.6 Â± 0.2, p=0.07). The difference in global maximum heart dose by treatment plan type approached, but did not reach significance (CP 43.3 Â± 0.5 versus KPB 42.3 Â± 0.4, p=0.07). KBP did deliver significantly lower mean heart dose, Heart-PTV mean dose, Heart-PTV V25 Gy, V20 Gy, V15Gy, V10Gy, and V5Gy (Table 1). Additionally, the R50% was significantly lower for the KBP compared to the CP (2.8 Â± 0.08 versus 4.8 Â± 0.26, p<0.001).
Conclusion: For the treatment of ventricular tachycardia using single fraction cardiac SBRT, a KBP model significantly improved several Heart-PTV parameters. KBP also improved the conformality of the treatment plan without decreasing coverage to the ITV/PTV to the arrythmogenic focus.
Not Applicable / None Entered.