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

Area of Science:

• Radiation Oncology
• Medical Physics
• Image-Guided Therapy

Background:

• Motion-managed radiotherapy requires precise tumor targeting to minimize radiation dose to healthy tissues.
• Liver tumors present unique challenges due to respiratory motion, necessitating advanced tracking techniques.
• Radixact Synchrony offers real-time motion tracking for improved treatment accuracy.

Purpose of the Study:

• To evaluate the efficacy of a 3.0 mm potential difference (PD) interruption threshold for motion-tracking radiotherapy of liver tumors.
• To determine necessary margins and provide clinical guidance for motion-managed radiotherapy using Radixact Synchrony.
• To analyze the relationship between planning parameters and treatment accuracy in liver SBRT.

Main Methods:

• Retrospective analysis of 88 irradiation sessions across nine liver tumor cases using Radixact Synchrony.
• Placement of two gold markers near the tumor with a 5 mm planning target volume (PTV) margin.
• Analysis of potential difference (PD) values and treatment interruptions, with multiple regression analysis of planning parameters on PD95.

Main Results:

• The mean 95th percentile PD (PD95) was 2.9 ± 0.6 mm.
• 83.0% of fractions experienced no treatment interruptions with the 3.0 mm PD threshold.
• PD95 showed a significant positive correlation with respiratory motion amplitude and a negative correlation with inter-marker distance (adjusted R²=0.802).

Conclusions:

• A 3.0 mm PD interruption threshold is appropriate for motion-tracking liver radiotherapy using Radixact Synchrony with metallic markers.
• This threshold effectively minimizes treatment interruptions while maintaining dosimetric precision.
• Respiratory motion amplitude and inter-marker distance are key factors influencing treatment accuracy (PD95).