Page 40 - Bio Engineering Approaches to Cancer Diagnosis and Treatment

2.5 Radiopharmaceutical imaging 37

99m
albumin labelled with Tc. The first lymph node draining a cancer is sentinal lymph
node [38]. The absence of cancer cells in sentinal lymph node represent the absence
of metastatic cancer cells in all the other nodes. Lymphoscintigraphy can prevent
unnecessarily surgery if the sentinal lymph node is found to be free of cancer cells.
One of the important parameters for well-characterized lymphatic drainage is the
size of radiocolloids which is inversely proportional to the draining [34]. As already
mentioned, immunoscintigraphy applies antibody to target specific antigens. One of
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the well-studied cancer with immunoscintigraphy is prostate. In was labeled with
capromab pendetide which is binding to the prostate membrane specific antigen.
Radiopharmacutics use not only for imaging but also for therapy. RIT and PRRT
can specifically irradiate cancer cells. These systems involve low-dose irradiation
from radionuclides targeted tumor. The therapeutic effects lead to the absorption of
energy from radionuclide’s emissions. Over expression of peptides involved in pro-
liferation and angiogenesis is used for labeling radionecleotides for investigation of
receptor-positive tumors. Radiolabeled bombasin, somatostatin and neuropeptide Y
are used in scintigraphy to examine receptor-positive cancer cells. One of the most
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studied radiolabeled nucleotide in this field of interest is In-DTPA-octeotride used
for somatostatin targeting scintigraphy imaging. Also, this radionucleotide has been
labeled for α and β radionuclides therapy for PRRT. Another examples are the use
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of Y-DOTATOC and b-particle for radionuclides therapy [34]. Another application
of radionucleotides is for scintimammography. There is a need to develop a gamma
camera with the ability of reducing the scattering from external sources specially
when the image is taken near the chest wall. Also, designing a camera with improv-
ing image resolution at the edge of detector will improve the quality of images
taken from breast tissue near to the chest wall [34]. Based on the special character-
istic features of breast tissue, breast specific gamma camera imaging is developed
[39, 40]. This new type of camera possess small field of view which increases the
image resolution, improves flexibility of movement and applies compression to the
breast to examine small lesion. Another application of radiopharmaceuticals is in
angiogenesis imaging. Integrin is one of the cell adhesion molecules which plays
an important role in angiogenesis and metastasis. 99m Tc RGD radiopharmaceutical
probe has been introduced for early detection of angiogenesis and metastasis and
has a potential application for antiangiogenic therapy [41, 42]. There is a special
interest in the application of scintigraphy for following drug delivery using nanopar-
ticles [43]. Application of nanocarriers such as carbon nanotubes, graphene oxides,
liposomes, lipoplexs, polymers, and so on to deliver bioactive nucleic acids, not
only increase the biocompatibility and solubility, exhibit no immunogenic response
as well.
Another application of scintigraphy is to evaluate multidrug resistance. In the
absence of p-glycoprotein, radiopharmaceutical agents such as 99m Tc MIBI able to
translocate across the cell membrane and concentrate inside the cells due to its posi-
tive charge while the presence of p-glycoprotein makes 99m Tc MIBI to pump out of
the cells. So, radionucleotides can find out if the designed drug can effectively treat
multidrug resistance or not.