Biomedical Engineering Reference
In-Depth Information
are relatively rare and cardiac MRI has yet to become a commonly used
tool in clinical medicine.
Computerized Tomography (CT)
: Multidetector technology has made car-
diac CT possible enabling angiography, perfusion and function studies. The
main limitation of this screening modality remains the acquisition time
with multirow detectors, which may be solved with upcoming spiral CT,
electron beam CT and ultrafast CT technologies.
Single Photon Emission Computed Tomography (SPECT)
: Commonly
referred to as myocardial perfusion imaging, this technique is used to vi-
sualize myocardial blood flow distribution using intravenous injection of
a radionuclide detected by single crystal gamma camera rotating around
the patient's body. This modality can be used to assess ejection fraction
and regional wall motion but cannot provide detailed views of anatomical
structures.
Positive Emission Tomography (PET)
: Similar to SPECT, this technique
visualizes myocardial blood flow using intravenous injection of positron-
emitting tracers detected by multiple rings of stationary detectors encir-
cling the patient's body to produce a series of multiple tomographic im-
ages encompassing the heart. Specific tracers have been developed for
the evaluation and quantification of numerous physiological processes,
including regional myocardial blood flow, metabolic processes, oxygen
consumption, receptor activity, and membrane function. When compared
to SPECT, PET images have been shown to be more accurate in clinical
studies but PET scanners remain costly and therefore less widely available
than standard SPECT systems.
Two-Dimensional Echocardiography (2DE)
: Two-dimensional echocar-
diography is the fastest, least expensive, and least invasive screening
modality for imaging the heart. Because of the three-dimensional struc-
ture and deformation of the heart muscle during the cardiac cycle, anal-
ysis of irregularly shaped cardiac chambers or description of valve mor-
phology using 2D images is inherently limited. A second existing prob-
lem with 2DE, constrained to planar views, is that highly trained clini-
cians are required to perform the studies. But, despite its limited image
quality and its limitation to planar acquisition, 2DE is one of the most
