Читать книгу Interventional Cardiology - Группа авторов - Страница 260

In MSCT scanners, X‐rays are generated by a tube mounted on a rotating gantry with the patient centered within the bore of the gantry. There are two principal modes of scanning – sequential/axial scanning and spiral/helical scanning. In sequential scanning (prospective ECG triggering), X rays are generated while the table is stationary in a predetermined imaging window during diastole (since cardiac motion is minimized during diastole). In spiral scanning, the table moves continuously at a fixed speed relative to the gantry rotation. After data acquisition, an optimal reconstruction window is chosen within the cardiac cycle to minimize motion artifact (retrospective ECG gating).

Sequential scanning helps reduce the dose of radiation, whereas helical scanning has the advantage of allowing for cine evaluation of ventricular function and having a greater ability to correct for artifact during arrhythmias [1]. Both have similar temporal and spatial resolution [2]. DSCT, consisting of two X ray sources mounted at an angle of 90 degrees, has led to a significant improvement in temporal resolution [3]. The introduction of DSCT has omitted the need to lower patients’ heart rates.