Abstract
Background: Cardiac movement can affect the accuracy of the evaluation of the location of heart and its substructures by planning computed tomography (CT). We aimed to measure the margin displacement and calculate compensatory margins through breath-hold electrocardiograph (ECG)-gated 4-dimensional magnetic resonance imaging (4D-MRI) for oesophageal radiotherapy.Methods: The study enrolled 10 patients with oesophageal radiotherapy plans and pretreatment 4D-MRI data. The displacement of the heart and its substructures was measured between the end of the systolic and diastolic phases in one cardiac cycle. The compensatory margins were calculated by extending the planning CT to cover the internal target volume (ITV) of all structures. Differences between groups were tested with the Kruskal-Wallis H test.Results: The extent of movement of the heart and its substructures during one cardiac cycle were approximately 4.0-26.1 mm in the anterior-posterior (AP),left-right (LR), and cranial-caudal (CC) axes, and the compensatory margins should be applied to the planning CT by extending the margins by 1.7, 3.6, 1.8, 3.0, 2.1, and 2.9 mm for the pericardium, 1.2, 2.5, 1.0, 2.8, 1.8, and 3.3 mm for the heart, 3.8, 3.4, 3.1, 2.8, 0.9, and 2.0 mm for the interatrial septum, 3.3, 4.9, 2.0, 4.1, 1.1, and 2.9 mm for the interventricular septum, 2.2, 3.0, 1.1, 5.3, 1.8, and 2.4 mm for the left ventricular muscle (LVM), 5.9, 3.4, 2.1, 6.1, 5.4, and 3.6 mm for the antero-lateral papillary muscle (ALPM), and 6.6, 2.9, 2.6, 6.6, 3.9, and 4.8 mm for the postero-medial papillary muscle (PMPM) in the anterior, posterior, left, right, cranial, and caudal directions.Conclusions: The locations of the heart and its substructures determined by planning CT were not able to represent the true positions due to cardiac movement, and compensatory margins can be applied to decrease the influence of movement.
Accuracy of Magnetic Resonance Imaging of the Knee in the Community Setting
