End-systolic volume (ESV) is the volume of blood in a ventricle at the end of contraction, or systole, and the beginning of filling, or diastole. ESV is the lowest volume of blood in the ventricle at any point in the cardiac cycle. The end-systolic volume is determined by the sum of the computed left/right ventricular cross-sectional areas determined by the endocardial contours at the end of the systolic ejection phase chosen as the images with the smallest blood volume accounting for slice thickness and gap. ESV can be used clinically as a measurement of the adequacy of cardiac emptying, related to systolic function. Along with end-diastolic volume, ESV determines the stroke volume, or output of blood by the heart during a single phase of the cardiac cycle. The stroke volume is the difference between the end-diastolic volume and the end-systolic volume. The end-systolic volume index (ESVI) is the end-systolic volume corrected for the body surface area (BSA). The normal range of stroke volume is 50 to 100 ml. ESV can be measured using two-dimensional echocardiography, MRI (magnetic resonance tomography) or cardiac CT (computed tomography) or SPECT (single photon emission computed tomography).