**8. Oxidation state of technetium for labeling**

Technetium is found in variable oxidation states ranging from �1 to +7, but it frequently forms complexes in +5 oxidation state. A number of technetium complexes with other oxidation states also exist in increasing order [10]. Complex of technetium in +6, +2 and zero oxidation state are not synthesized because they are not fruitful for medical purpose. Different complexes of technetium that they from in different oxidation states are as follows:


which is used to reduce the pertechnetate 99mTcO4 from +7 oxidation state to lower oxidation state +4 (TcO2.xH2O) is zinc with HCl. However, 20% of technetium reduces to technetium metal by this method. In technetium-99mhydroxyethylidene diphosphonate (HEDP) complex, it is observed that the oxidation state of technetium is changeable which is highly dependent upon the pH of the method which is used to synthesize the complex. In acidic medium, the oxidation state of technetium is +3; in alkaline medium, it is +5; and in neutral medium, it is +4 [11]. This means that a slight change in pH can change the oxidation state of technetium pointing to the fact that they may exist as a mixture of all oxidation states like +3, +5 and +4 in technetium-99mhydroxyethylidene diphosphonate (HEDP) complex.

• Complex of technetium in +3 oxidation state (Tc+3). A number of technetium-99m complexes exist with +3 oxidation state in acidic medium. These complexes include DTPA (diethylenetriamine pentaacetic acid, ethylenediamine tetraacetic acid (EDTA), DMSA (dimercaptosuccinic acid) and hepatobiliary iminodiacetic acid. However, the oxidation state of technetium in the complex EDTA and DTPA become +4 in alkaline as well as in neutral medium. A variety of technetium complexes in which technetium exists in +3 oxidation state are used for myocardial scanning. These include complexes of technetium-99m with phosphine, arsine and BATOs (boronic acid adduct of technetium dioxime comples).

[12]. γ-radiation emitted by indium-111 have an energy of 247 keV and 172 keV and the percentage of γ-radiation emitted by indium-111 is 90.6% with minimal β-radia-

Artificial isotope 39 in number but Indium-111 and Indium-113 are important

These γ-emitting radionuclide labeled compounds can be utilized to identify the exact position and location of the infection in different parts and organs such as brain, arteries, joints, bones and tissues. In **Table 6**, a number of compounds bound

558, 1820, 2704, respectively

**Pathology Sensitivity/**

Reticuloendothelialsystem visualization

osteomyelitis

Soft tissue and bone infection

**accuracy**

High sensitivity low specificity

Spinal infection 93% [2]

Marrow imaging [4]

Prosthetic joint infections 91% [5]

90% [1]

90% [1]

**Refs.**

[2]

[2]

[2]

95% [3]

tion emission that make the indium �111 a good imaging radiotracer.

**SPECT imaging model**

model

model

model

model

model

model

model

model

model

model

111In Human

99mTc Human

99mTc Human

111In Human

99mTc Human

99mTc Human

*General radiopharmaceuticals developed based on SPECT imaging.*

**Labeled radioisotope**

Sulfur colloid 99mTc Human

6. Biotin 111In Human

7. UBI 99mTc Human

8. MDP 99mTc Human

**Properties of indium Values**

*Single-Photon Emission Computed Tomography (SPECT) Radiopharmaceuticals*

Electron affinity (kJ/mol) 29 Heat of vaporization kJ/mol 23.2 Group IIIA (13)

Period 5th Color Silvery white Natural isotopes (two) Indium-113 and Indium-115

Metal category Poor metal (posttransitional)

First, second and third ionization

*DOI: http://dx.doi.org/10.5772/intechopen.93449*

*Physical and chemical properties of indium.*

**Labeled compound**

1. Oxyquinolonelabeled leukocytes

2. Exametazimelabeled leukocytes

3. Methylene diphosphonate

4. Labeled leukocytes

5. HMPAO labeled leukocytes

9. HMPAO-labeled leukocyte

**Table 6.**

**11**

energy (kJ/mol)

**Table 5.**

**Sr no.**

• Complex of technetium in +1 oxidation state (Tc+1). This oxidation state is stabilized with the help of coordinate covalent bond with different types of ligands in aqueous medium. In this oxidation state, compounds are usually stable in water and air.
