The margin of internal risk volume on atrial septal and ventricular septal based on electrocardiograph gating 4DCT

Abstract

Background: The aim of this study was to quantify the margin of internal risk volume (IRV) on the atrial septum (AS) and ventricular septum (VS) based on electrocardiograph gating (ECG-gating) 4DCT.Methods: Twenty patients were enrolled and received an ECG-gating 4DCT scan performed in breathhold, and CT images were reconstructed at 5% intervals of the cardiac cycle for a total of 20 phases (0-95%).The contouring of the AS and VS were delineated in each phase, and the displacements and margin of the AS and VS were calculated. We fused the total of the AS and VS (0-95% phase), which were recorded as AS 20 and VS 20 . The margins were applied to the AS and VS in every phase and revised according to the cover rate of AS 20 and VS 20 .Results: (I) The margins of the AS and VS according to displacements in the left-right, cranio-caudal, and antero-posterior direction were 3 mm, 3 mm, and 3 mm; and 3 mm, 3 mm, and 2 mm, respectively. (II) The volume of AS 20 was (11.80±3.72) cm 3 , which was 2.9 times larger than the maximum volume of the AS. The volume of VS 20 was (60.45±12.92) cm 3 , which was 1.6 times larger than the maximum volume of the VS. (III)The emendatory margins of the AS and VS in the left-right, cranio-caudal, and antero-posterior direction were 7 mm, 10 mm, and 7 mm; and 5 mm, 3 mm, and 4 mm, respectively. The emendatory margins were added to the AS and VS, and the coverage rates were (95.88±3.29)% and (95.24±2.54)%, respectively. Conclusions:The margin of IRV on the AS and VS could cover the movement of AS and VS induced by heartbeat in the left-right, cranio-caudal, and antero-posterior direction respectively during thoracic radiotherapy.

Quantitative analysis of the impact of respiratory state on the heartbeat-induced movements of the heart and its substructures

“…The study found that the left anterior descending and left circumflex coronary arteries exhibited significant motion in the head-foot direction relative to the LR and front-back directions, which is comparable with the results of the present study. Li et al [ 17 ] identified larger motion amplitudes in the AP and head-foot directions of the AS than those of the VS in their AS study. This finding aligns with the observed motion patterns of the VS and AS in response to heartbeats during the three breathing states evaluated in this research.…”