Room: Exhibit Hall | Forum 2
Purpose: In radiotherapy for pancreatic cancer, there is a growing interest in MR-guided radiotherapy using direct tumor tracking. We aimed to quantify the magnitude of respiratory-induced pancreatic motion of each pancreatic region during abdominal compression (AC) using cine-MRI and its relationship with body mass index (BMI).
Methods: The 2D cine-MRI images were obtained during free-breathing and AC in 10 healthy volunteers. To characterize respiratory motion of each pancreatic region (head, body and tail), the respiratory motion in anterior-posterior (AP) and superior-inferior (SI) directions were calculated using in-house developed software. For each pancreatic region, we evaluated the magnitude of the pancreatic motion with or without AC. Furthermore, the relationship between these results and BMI were evaluated. By using receiver operating characteristic (ROC) curve analysis, BMI with largest sensitivity and specificity of the pancreatic motion in SI direction was defined as the optimal cut-off level.
Results: The cut-off level of BMI was determined as 21 kg/mÂ² (low-BMI, <21 kg/mÂ²; high-BMI, â‰¥21 kg/mÂ²) using ROC curve analysis. The magnitude of pancreatic motion in SI direction was greater than those in AP direction. A magnitude of respiratory motion in SI at head, body and tail regions with free-breathing were 17.0, 16.1, 24.6 mm in low-BMI group and 18.4, 15.2, 20.1 mm in high-BMI group, respectively. Those with AC were 11.5, 11.3, 15.7 mm in low-BMI group and 10.5, 8.9, 14.6 mm in high-BMI group, respectively. In low-BMI group, there was a large difference in magnitude of pancreatic motion depending on the region of the pancreas with or without AC.
Conclusion: In the treatment planning for the pancreatic tumor, it is necessary to consider that the magnitude of respiratory-induced pancreatic motion varies depending on the region of the pancreas with or without AC and are more affected in low-BMI group.