Animal Models for Preclinical Imaging - Nanotechnology for Biomedical Imaging and Diagnostics - page 468

Arterial injuries in mice and rats can be implemented as models of angioplasty
injury and healing. This type of injury requires moderate technical skill for isolation
and cannulation of the carotid or femoral artery. For carotid artery injury, the bifurca-
tion of the common carotid artery into the internal and external branches is isolated.
A small wire or bulbous probe is inserted through the external carotid artery and into
the common carotid and to denude the endothelial layer by repeated abrasion. The
external carotid is then ligated. Care must be taken to prevent debris from entering
the internal carotid artery and causing stroke. Care must also be taken in imaging with
this model as damage is done to surrounding tissues, which may result in nonspecific
accumulation of imaging agents, obscuring intravascular signal.
Ischemic injuries, such as myocardial infarction, have been investigated using the
murine hindlimb ischemia model. In this model, the femoral artery is removed, sig-
nificantly reducing the blood delivery in the lower limb. Blood delivery is regenerated
over time through expansion of collateral circulation by arteriogenesis and angiogen-
esis. Angiogenesis is a desired method for tissue healing, and drugs to improve
angiogenesis are needed.

16.4.3.2 Thrombosis/Clot Models Thrombosis occurs when blood vessels are
occluded by blood clots or intravascular debris and can result in injury and pain in
peripheral tissues or stroke when intracranial blood vessels are occluded. Diagnosis
of thrombotic disease is relatively straightforward clinically, but treatment can be
a challenge when the chronology is unknown. Animal models of thrombosis are
needed for development of therapies to ameliorate the disease and to better under-
stand sequelae.

16.4.3.3 Aneurysm Aneurysm is a silent killer that develops over time. A pocket
forms in the wall of an artery after a tiny rupture in the smooth muscle lining. The
pocket enlarges and may rupture at any time resulting in immediate death when
affecting the aorta or large artery in the brain. Early detection of aortic aneurysm is
inhibited by lack of clinical signs or indications of predisposition. A diagnostic
method for the detection of an aneurysm prior to rupture would save many lives.
Animal models of aortic aneurysm require surgical isolation of the vessel fol-
lowed by local injection of elastase or other agents to damage the vessel wall. Mouse
models have been used for many years and are well characterized. The difficulty in
imaging is the relatively small size of the abdominal aorta in mice and the difficulty
in reducing motion influence on data collection. Gating of image acquisition can
significantly improve the resolution of these studies.

16.4.4 infectious disease models for imaging

16.4.4.1 Bacterial Infection Advancements in imaging of bacterial infections
will help to improve therapies and treatments and aid in the prevention of progres-
sion of the disease within the host. Currently, the most common method for imaging
bacterial infection is by using bacteria transfected with fluorescent proteins and/or
bioluminescent constructs (luciferase).