Biomedical Engineering Reference
In-Depth Information
The identification of targets specific for a scientific or clinical question is
the first and crucial step in the development of a tracer. These targets can be
located \behind" barriers and therefore might not be easily accessible upon
injection of a tracer into the blood. In this context, such barriers are the
cellular membrane, which does not allow for a general entrance of drugs, and
the blood-brain barrier being highly selective to protect the brain. Beside this
barrier aspect the accessibility of a molecular target for a given tracer in vivo
is dependent on the structure of the compound (antagonist, agonist, enzyme
inhibitor, etc.), which should provide high anity and specificity while having
low metabolism. Reviews are suggested for further reading [2, 7, 27, 17].
2.4 Applications
2.4.1 Preclinical applications
With the development of tailored and dedicated imaging devices for study-
ing animals such as small animal PET and SPECT or fluorescence reflectance
and tomography, the field of applying emission tomography in preclinical stud-
ies has broadened substantially over the past years. Recent developments have
achieved high resolution small animal imaging and now do allow human-like
imaging even in mice with respect to sensitivity, and temporal and spatial
resolution. This is of great interest for translational studies using PET and
SPECT, which have been established for years in clinical algorithms, whereas
optical imaging is limited in this respect. Since in small animal scanners the
imaging technology is pushed to its theoretical limit and the size of the ob-
ject to be imaged is small, artifacts conflicting with accurate and quantitative
imaging can occur from various angles (partial volume, attenuation, move-
ment, etc.) and demand the application of dedicated correction methods.
Small animal imaging can be and frequently is used in different aspects of
basic and translational biomedical research such as:
•
Phenotyping . Imaging to characterize mouse models mimicking human
diseases. Phenotyping of new and existing animal models is substan-
tially supported by functional and molecular small animal imaging, es-
pecially since small animal imaging characteristically can be performed
non-invasively and serially in an individual animal. Furthermore, whole-
body imaging is of particular value to discover pathologies developing
in organs \outside" the focus of the study.
•Monitoring. Imaging to monitor morphological, functional and molecu-
lar changes in the spontaneous time course or induced by interventional
studies (pharmaceutical treatment, surgical intervention, gene therapy,
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