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Clinical Assessment of Potential Difference in Motion-Tracking Irradiation for Liver Tumors Using Radixact Synchrony®

Year: 2025

Type: article

Abstract: This study aimed to advance the precision of motion-managed radiotherapy and provide robust information for clinical practice in terms of necessary margins using Radixact Synchrony® (Accuray, Sunnyvale, USA). A retrospective analysis was conducted on 88 irradiation sessions in nine cases of motion-tracking irradiation for liver tumors. Two gold markers were placed near the tumor, and a planning target volume (PTV) margin of 5 mm was set. The interruption threshold for potential difference (PD) (the statistical prediction value of the three-dimensional (3D) distance error from the predictive model) was set at 3.0 mm during treatment. PD values obtained before and during treatment, as well as the number of interruptions, were analyzed. A multiple regression analysis was performed to evaluate the influence of various planning parameters, which were obtained during four-dimensional (4D) treatment planning, on the 95th percentile value of PD (PD95). The mean PD95 was 2.9 ± 0.6 mm. In the four cases where interruptions occurred, the average ± SD number of interruptions per fraction was 7.5 ± 4.6, 3.6 ± 2.5, 2.5 ± 1.5, and 1.0 ± 1.1, respectively. The coefficient of determination (adjusted R2) between PD95 and planning parameters was 0.802 (p < 0.01), showing a positive correlation with respiratory motion amplitude (p = 0.017) and a negative correlation with inter-marker distance (p = 0.049). No treatment interruptions were experienced in 83.0% of a total of 88 fractions. To conclude, setting a PD interruption threshold of 3.0 mm for motion-tracking irradiation using Radixact Synchrony® under metallic marker guidance for liver tumors was appropriate for minimizing treatment interruptions with sufficient dosimetric precision. In addition, inter-marker distance and respiratory motion amplitude were associated with PD95.

Source: Cureus

DOI: 10.7759/cureus.81598