Page 39 - Bio Engineering Approaches to Cancer Diagnosis and Treatment

36 CHAPTER 2 Diagnostic imaging in cancer

agents used for imaging, radiotherapy or both (theranostic purpose). These molecules
inject intravenously and consider as relatively noninvasive methods.
Nuclear medicine mainly uses γ radiation for cancer imaging while α and β radia-
tion mainly applied for radioimmunotherapy (RIT). Typical radionuclides used in
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cancer imaging include I, I, Ga, 99m Tc, In, and Tl [34]. The uptake and in
vivo distribution of these agents are mainly depend on their pharmokinetic proper-
ties. It should be noted that simple chemistry of these molecules provides feasible
opportunity for ligand conjugation on their surface leading to increase the chance of
accumulation in desired region. Although the amounts of radioactive molecules are
very small, around picogram range, which cannot affect the pharmaco distribution,
the irradiated radioactive energy is sufficient for imaging and therapeutic purpose.
Radiopharmaceutical agents mainly are conjugated to relatively high amount of bio-
logically active ingredient being nonradioactive molecules.
After administration of radionucleotide, the patient is then scanned using single
photon emission CT and planar gamma cameras. In this system valuable informa-
tion regarding to the anatomical details, physiological and functional response can
be obtained. Also, the radiopharmaceutical component in targeted tissue are used
as a diagnostic biomarker. The diagnostic biomarker is designed with the special
interest to the biomolecular targets in special tissue or physiological process. Find-
ing biomolecules with specific interest to one particular biological molecule are of
interest. However, radiolabeled antibodies or radiolabeled small molecules have been
designed with very high affinity to few biomolecules.
Among all the other types of scanner (e.g., CT, MRI, and ultrasound), nuclear
imaging scanners are time-consuming process. The total period of time is needed
for nuclear imaging study depends on technical and biological varieties. After intra-
venously injection of radiopharmaceutical agent, the imaging process is started with
necessarily delay to let the radiopharmaceutical to spread in the whole body. Then,
for data acquisition, patient must spend sufficient time in front of camera to collect
all the necessarily radioactive signals. The amount of time needed for collecting data
is mainly related to the intrinsic properties and concentration of administrated radio-
isotope in the region of interest, the accuracy of camera system as well as the way of
image reconstruction [36].

2.5.1 Application of radiopharmaceutical imaging
There are large verity of applications for radiopharmaceutical imaging including
bone scanning, lymphoscintigraphy, immunoscintigraphy, RIT, peptide receptor
radionuclide therapy (PRRT), scintimammography, angiogenesis imaging, and mul-
tidrug resistance imaging.
One of the main applications of nuclear medicine has been focused on the bone
scanning due to the good sensitivity and low cost. Technetium-based radiopharma-
ceuticals and fluorodeoxyglucose-based positron emission tomography (FDG-PET)
have been used to detect metastases [37]. Another application of nuclear medicine
is lymphoscintigraphy. Lymph node drainage has been studied by human serum