Assessment of Lung Tumor Motion from PET/CT for Personalized Abdominal Compression Decisions In SBRT
Poster
AAPM-Lung_Motion.pdf Hosted by AAPM · 0.6 MBAbstract
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.