Synchronized Contrast-Enhanced 4DCT Simulation for Target Volume Delineation in Abdominal SBRT

Area of Science:

• Medical Imaging
• Radiation Oncology

Background:

• Abdominal SBRT planning faces challenges with tumor visibility and respiratory motion.
• Current methods using triple-phase CT and unenhanced 4DCT can lead to target delineation variability.

Purpose of the Study:

• To evaluate the technical feasibility and benefits of contrast-enhanced 4DCT (ce4DCT) simulation for abdominal SBRT.
• To compare ce4DCT with standard imaging protocols for target delineation accuracy.

Main Methods:

• Twenty-two patients underwent baseline and contrast-enhanced 4DCT scans with personalized contrast timing.
• Tumor visibility was assessed by experts; target volumes were delineated and compared using Dice, Jaccard indices, and centroid shift.
• Standard triple-phase CT with unenhanced 4DCT was simulated for comparison.

Main Results:

• ce4DCT significantly improved tumor visibility throughout the breathing cycle in 20 patients.
• ce4DCT-derived target volumes were larger and showed less overlap with standard methods (Dice 69%, Jaccard 53%).
• Significant differences in target delineation were observed between liver and pancreatic tumors.

Conclusions:

• ce4DCT simulation is feasible and optimizes tumor enhancement for SBRT planning.
• This technique mitigates uncertainties related to poor visibility and respiratory motion.
• Standard imaging protocols result in high target delineation variability, rendering isotropic margins less effective.