Room: ePoster Forums
Purpose: To quantify the margins and internal organs at risk volume (IRVs) of interatrial septum (IAS) and interventricular septum (IVS) based on ECG-gated 4DCT.
Methods: Twenty patients who received ECG-gated 4DCT scan in breath-hold were enrolled. The 4DCT images were sorted into 20 phases (0%, 5%â€¦â€¦90%, 95%) at 5% interval according to cardiac cycle. Then, the IAS and IVS were contoured slice by slice. We calculated the margins of IAS and IVS caused by heartbeat. And the fusion of IAS and IVS both in 20 phases were defined as the absolute IRV (IAS20 and IVS20). The margins of IAS and IVS were applied to each phase, and we modified margins according to the coverage rate on IAS20 and IVS20. And then calculated the coverage rate of modified margins to IAS and IVS.
Results: (1) The margins of IAS and IVS in left-right (LR), cranio-caudal (CC) and anterior-posterior (AP) coordinates were 3mm, 3mm, 3mm; 3mm, 3mm, 2mm. (2) The volume of IAS20 was (11.80Â±3.72) cm3, which was 2.9 times greater than maximum volume of IAS. The volume of IVS20 was (60.45Â±12.92) cm3, which was 1.6 times greater than maximum volume of IVS. (3) The modified margins of IAS and IVS in LR, CC and AP coordinates were 7mm, 10mm, 7mm; 5mm, 3mm, 4mm.The average coverage rate of IAS and IVS were (95.88Â±3.29) % and (95.24Â±2.54) %, respectively.
Conclusion: The margins of IAS and IVS in LR, CC and AP coordinates were 7mm, 10mm, 7mm; 5mm, 3mm, 4mm defined as IRVs. The definition of IRVs would contribute to the protection both of IAS and IVS.