CT functional assessment: Why and how?

Cardiac computed tomography (CT) is used primarily to assess coronary anatomy, but it can also provide clinically relevant information on ventricular and atrial size and function. The optimal approach depends on the clinical question, scanner capability, heart rhythm, radiation dose, and whether full-cycle cine assessment or a limited-phase surrogate is sufficient. This review summarizes practical strategies for CT functional assessment, including retrospective electrocardiogram (ECG)-gated cine CT, low-dose functional cine protocols, recirculation-phase cine CT, and prospectively ECG-triggered coronary CT angiography. Prospective diastolic acquisitions can provide mid-diastolic volume and mass indices, whereas systolic acquisitions can yield left ventricular ejection fraction over 100 ms of systole (LVEF_100ms), a surrogate marker of left ventricular systolic function. These approaches may extend the value of cardiac CT without additional radiation or contrast in selected settings, including atrial fibrillation. Functional assessment should be planned before scanning; the acquisition method should be clearly specified; and full-cycle cine ejection fraction remains the reference CT-derived measure, whereas limited-phase and low-dose approaches are informative but not interchangeable.