Assessment of Lung Tumor Motion from PET/CT for Personalized Abdominal Compression Decisions In SBRT
Abstract
Purpose
Abdominal compression in lung SBRT aims to reduce respiratory motion, but its benefit varies among patients and may cause discomfort or limited motion reduction. PET/CT, routinely acquired for lung cancer staging, provides high-resolution anatomical (CT) and metabolically averaged functional (PET) information. Respiratory motion–induced blurring and displacement on PET images can be leveraged to estimate tumor motion. This study evaluates whether PET/CT-derived motion metrics can guide patient-specific decisions on abdominal compression in lung SBRT.
Methods
A total of 110 lung SBRT patients with both PET/CT and 4DCT scans were included. Tumor motion magnitudes from PET/CT and 4DCT were compared in left–right (LR), anterior–posterior (AP), superior–inferior (SI), and combined directions.
Results
4DCT and CT/PET motion differences were centered near zero across all directions, indicating good agreement. LR differences were tightly clustered within ±0.2 cm; AP differences showed a slightly wider spread but largely remained within ±0.3 cm. SI differences were more variable, with some exceeding 0.5 cm, reflecting dominant respiratory motion. Overall combined differences were small (<0.3–0.4 cm) for most cases. Agreement was highest in LR (97.3% within 3 mm, 100% within 4 mm) and AP (90% within 3 mm, 99.1% within 5 mm). SI agreement was lower (83.6% within 3 mm, 92.7% within 5 mm), consistent with greater motion along this axis. When all directions were combined, 73.6% of cases agreed within 3 mm, 82.7% within 4 mm, and 90.9% within 5 mm.
Conclusion
PET/CT-derived tumor motion shows strong agreement with 4DCT and may provide a practical, patient-specific tool to determine the necessity of abdominal compression in lung SBRT using imaging already acquired in routine care.