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the low sensitivity of radiopaque contrast agents and the potential cytotox-
icity associated with them. However, for reasons stated in this chapter, it
would be highly desirable to have a robust method that allows monitoring
of radiopaque cells using X-ray. This chapter covers what has been accom-
plished so far in this field.
17.2 How Can Cell Therapy Benefit from
Image-Guided Delivery?
For over three decades, physicians have used image guidance for delivery
of various therapeutic agents. Initially described in the 1970s for catheter-
directed delivery of vasoactive drugs to control emergent gastrointestinal
bleeding, locoregional delivery of therapeutic agents has now exponentially
grown and is utilized for a variety of conditions, including treatment of uter-
ine fibroids, unresectable liver tumors, intracranial/extracranial neoplasm,
treatment of vascular malformations, and catheter-directed thrombolysis.
With the expansion in these clinical applications, the imaging technology
has also grown in parallel and now provides unique capabilities for future
targeted therapies. Finally, with this rapid growth in targeted delivery, vast
resources of experience have been gained that can be parlayed for emerging
applications, such as cellular therapies.
The main goal of local delivery is to increase the concentration of a spe-
cific therapeutic agent in a target tissue with minimal nontarget distribution.
Compared to systemic therapy, local delivery provides a high level of thera-
peutic efficacy with minimal systemic effects. However, the success of any
local therapy depends on the precision and accuracy of delivery to the region
of interest. Currently, the majority of clinical delivery procedures, (such as
transcatheter arterial chemoembolization [TACE] and arteriovenous malfor-
mation [AVM] embolizations) are performed predominantly with a trans-
vascular approach. A transvascular approach for delivery not only provides
the highest possible precision but also has several other advantages: (a) the
local administration results in increased local tissue concentration, (b) the
hemodynamics of the vascular bed can be altered through the administra-
tion of vasoactive compounds (i.e., vasodilation or embolization), and (c) the
prolonged dwell time and slow uptake of the therapeutic agent results in
greater efficacy (Llovet et al . 2002).
In an analogous manner, cellular therapies can take advantage of these
techniques to enhance the delivery process. Although some cellular thera-
pies are adequately managed with systemic delivery, certain organs and con-
ditions require a targeted approach for maximum effect. In fact, due to the
anatomical constraints of the vascularity of specific organs, systemic therapy
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