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2.5 Radiopharmaceutical imaging      35




                  while water absorption is far from NIR wavelength. This technic provides valuable
                  information regarding hemoglobin concentration, water percentage, lipid concentra-
                  tion, oxygen saturation, vascularity, and scattering related properties of the targeted
                  tissue [34, 35]. NIR optical tomography can also be used for cancer detection in
                  endoscopy [34].
                     Although NIR optical tomography enjoys high contrast imaging properties, it is
                  restricted to tissue with the ability of transluminated externally. One of the excellent
                  subjects for NIR optical tomography is breast tissues due to the direct contact with
                  NIR detector [35]. Also, the high vasculature of internal tumors such as colon, rec-
                  tum, and prostate provide high contrast for NIR optical tomography.


                  2.4.2  Advantages and disadvantages
                  The advantages of using nonionizing electromagnetic imaging system is described
                  as follow:

                  •  Cancer and other chronic disease treatment by combining chemotherapy with
                     nonmagnetic pulse irradiation
                  •  Diathermy by low-level radiation
                  •  Not known genetic damage
                  •  Cost-effectiveness
                  •  Can scan in multiple plan
                  •  Can scan in 1 mm to several centimeter
                  The disadvantages of using nonionizing electromagnetic imaging are summarized
                  as fallow:

                  •  Photo-aging of the skin
                  •  Corneal injury
                  •  Creating erythema
                  •  Photosensitization
                  •  Thermal retinal injury
                  •  Corneal burn
                  •  Changing the permeability of blood-brain barriers
                  •  Changing hormone level



                  2.5  Radiopharmaceutical imaging
                  Radiopharmaceutical agents are a radioactive component containing radionuclides
                  or radioisotopes. A radioisotope is an unstable atom achieving a more stable level by
                  radiating energy in the form of a positron particle, beta particle, or gamma-ray. The
                  releasing or radiating energy is achieved under three specific mechanisms include
                  physical decay, disintegration, or transition. Releasing energy may either change the
                  isotope of the atom but not the element, or completely change the element by trans-
                  mutation [36]. Radiopharmaceuticals consist of a wide variety of different radioactive
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