A Survey of Three-Dimensional Modeling Techniques for Quantitative Functional Analysis of Cardiac Images - Advance Image Processing in Magnetic Resonance Imaging - page 280

Stroke volume (SV) . This is defined as the volume ejected between the end
of diastole and the end of systole.

SV = end-diastolic volume(EDV)-end-systolic volume(ESV) (9.3)

Alternatively, SV can be computed from velocity-encoded MR images of
the aortic arch by integrating the flow over a complete cardiac cycle
[63]. Similarly to LVM and LVV, SV can be normalized to total body
surface. This corrected SV is known as stroke volume index (SVI).
Healthy subjects have a normal SVI of 45

8 ml/m 2 [48].
Ejection fraction (EF): This is a global index of left-ventricular fiber short-
ening and is generally considered as one of the most meaningful mea-
sures of the left-ventricular pump function. It is defined as the ratio of
SV to the EDV.

±

SV
EDV

EDV ESV
EDV

−

EF = × 100 % = × 100 % (9.4)

Lorenz et al. measured normal values of EF with MRI [48]. They found
values of 67 7% (47-76%) for the

RV. Similar values were obtained with ultrafast CT, echocardiography,
and x-ray angiocardiography [48,14].
Cardiac output (CO): The role of the heart is to deliver an adequate quantity
of oxygenated blood to the body. This blood flow is known as the CO and
is expressed in liters per minute. Because the magnitude of the CO is
proportional to body surface, one person may be compared to another by
means of the cardiac index (CI), that is, the CO adjusted for body surface
area. Lorenz et al. [48] reported normal CI values of 2.9

± 5% (57-78%) for the LV and 61 ±

± 0.6 l/min/m 2

and a range of 1.74-4.03 l/min/m 2 .
The CO was originally assessed using Fick's method or the indicator dilu-
tion technique [64]. It is also possible to estimate this parameter as the
product of the volume of blood ejected with each heartbeat (the SV) and
the heart rate (HR).

CO =× SV HR (9.5)

In patients with mitral or aortic regurgitation, a portion of the blood ejected
from the LV regurgitates into the left atrium or ventricle and does not enter the
systemic circulation. In these patients, the CO computed with angiocardiography
exceeds the forward output. In patients with extensive wall motion abnormalities
or misshapen ventricles, the determination of SV from angiocardiographic views
can be erroneous. Three-dimensional imaging techniques provide a potential
solution to this problem because they allow accurate estimation of the irregular
left-ventricular shape.