Chemistry Reference
In-Depth Information
decades of advancements in the development of anticancer compounds, studies still
show that age-related death rates for people with cancer have not improved
[
2
]. Next-generation drugs are able to overcome resistances to first-line chemother-
apeutics and in many cases improve safety profiles. However, if there is ultimately
no improvement in survival rates, then the only effect these new drugs are having
on the public is maintaining high health-care costs. Current advancements in
medical imaging techniques are aimed at offering the opportunity to make a
significant change in cancer treatment, which could produce cancer cures or long-
term survival with good quality of life (GQL). While conventional imaging instru-
mentation is very effective, advancements in machinery and improved understand-
ing of computer models and the physics behind a lot of these technologies have
ushered in an era of exponential growth in cancer imaging. It is now the belief of
many that while chemotherapeutics hold an undeniable importance in the treatment
of cancer, it is through improved imaging systems where the real improvements can
be made to lead to the overall reduction in cancer deaths.
Among these conventional imaging modalities, magnetic resonance imaging
(MRI) bears the greatest clinical utility due to its versatility [
3
]. Not only does
MRI provide superb spatial resolution and unparalleled soft tissue contrast in living
subjects, but it can also detect certain tissue functions and molecular species via the
use of specialized MRI techniques, some of which do not rely on the use of target-
specific contrast-enhancing agents [
4
]. Therefore, MRI permits concurrent collec-
tion of anatomical and physiological information of the disease state. In addition,
MRI has two advantages that make it stand out among other imaging modalities
[
5
]. Unlike positron emission tomography (PET), single-photon emission computed
tomography (SPECT), or computed tomography (CT), MRI does not use dangerous
ionizing radiation which leads to the second advantage which is that there is no
upper limit to the scanning frequency of a patient in a specific time span. However,
MRI has very poor sensitivity when compared with other imaging modalities, and
this has many manifestations [
6
]. First, MRI acquisition can take a long time and a
large dose of imaging agents to produce adequate signal. As a result, a particular
subset of patients is predisposed to potential health complications when using
contrast-enhancing agents (insert renal toxicity data). Another result of the poor
sensitivity, and therefore high requirement of MRI contrast agents, is that it creates
a difficult-to-solve challenge for researchers to design target-specific probes when
cellular and molecular targets exist in low concentrations in living subjects [
7
]. The
high amounts of image contrast agents are one of the major reasons why MRI is
such an expensive imaging modality. When considering cost, one must also con-
sider not only the high cost of purchasing MRI machines but also the high cost of
their maintenance. MRI magnets can only effectively function when they are
cooled below their critical temperature. In order to achieve this, liquid helium is
used as a coolant; however, with the current global supply of helium shrinking, the
cost to operate MRI machines has increased. Overall, MR imaging is extremely
potent, although it is not the most sensitive and cost-effective modality. Not only
has MRI revolutionized clinical cancer diagnostics, it also adds a powerful tool to
