**1.1 Radiopharmaceuticals**

These are radioactive medicines that can be given by oral, intravenous or interstitial route to treat or diagnose malignancy. Administration of these drugs is done in the presence of specialist called radio pharmacist. These radioactive medicines have the ability to destroy cancerous cell by emitting radiation when it reaches its target cell. Radiopharmaceuticals for treatment and diagnosis of cancers associated with thyroid, brain, bones or lymphoma already been discovered.

In addition to treatment radiopharmaceuticals are also used for the purpose of diagnosis. The drugs used for diagnosis are called as tracers. The radiation of diagnostic radiopharmaceuticals is smaller as compared to radiation emitted by radiopharmaceuticals used for treatment. Radiopharmaceuticals are either single isotopes or sometimes the isotopes are combined with a kit [1]. The kit is prepackaging of ingredients which are sterile and are meant for preparation of radiopharmaceuticals. They are combination of substances such as antioxidant, buffer, reductant and ligands that are when combined with the radioisotopes produces the resultant product. Kits are very beneficial as they are not in contact with the outer environment so there is no chance of any contamination [2].

#### **1.2 Technetium 99m**

The isotope that is used for the purpose of labeling of kits used for diagnosis is technetium 99m abbreviated as 99mTc (**Figure 1**). It radiates only gamma radiation that is compatible with gamma camera. 99mTc also has the property of binding with the tracers. Advantage of technetium is that it has smaller biological half-life and better renal clearance for the unabsorbed radiopharmaceuticals that helps in getting a better quality of image from the absorbed ones. The dose of technetium depends on the kit, the organ on which it has to be used for imaging and on the test to be performed [3]. Determination of dose for children is very crucial as the cells

**73**

*Theranostics: New Era in Nuclear Medicine and Radiopharmaceuticals*

are in dividing states so sensitivity towards radiation can be higher, organ size body ratio also varies to greater extent in comparison with adult. So in case of children a

Different kit labeled with 99mTc used for imaging of different organs is men-

For detection of the areas that are metabolizing the bones kits with bisphosphonates are used. Scan of bone is done by injecting radiopharmaceuticals into the peripheral vein of patient and then after 3 h imaging is done so that within the three

hours the bisphosphonates will get incorporated into the osteoblast cells.

i.Radiolabelled mercaptoacetyltriglycine (Mag-3; mertiatide)

iii.Radiolabelled dimercaptosuccinic acid (DMSA; succimer

used a tool for studying morphology of renal cortex and ectopic kidney.

injection for it to reach brain and up to 7% reaches the brain.

drugs such as nitrates or calcium channel blockers.

Kit used for the check the blood flow within the brain after conditions like epilepsy, migraine or Alzheimer's disease or stroke of brain contains 99mTc-labeled exametazime. This is product of lipophilic origin without any charge on it and it penetrates better through blood brain barrier. It takes around one minute after

For cardiac imaging, two 99mTc-labeled are tetrofosmin and sestamibi which are employed to ascertain the degree to which myocardial infarction is severe and also help to point out the regions of cardiac ischemia. Images are collected at the state of rest and after stressed activity of cardiac cells. This injection are administered when patient must have consumed any kind of fatty meal. This helps in hepatobiliary clearance of administered radiopharmaceuticals thus aid in getting better image. But it should not be administered when patients has consumed some

In case of lungs scan it is used for the purpose of diagnosis of any kind of embolism in pulmonary tract. Lung scan be of two types perfusion scan or

For the imaging of kidney, there are three radiopharmaceuticals, namely

ii.Radiolabelled diethylenetriaminepentaacetic acid (DTPA; pentetate)

Mag-3; mertiatide is used for the purpose of determining the blood flow to the kidney and for graphically presenting the renal function. Mag-3 has a clearance of 94% after 3 h that helps in getting better quality of image and the exposure of patient to the radiation is also lower. DTPA; pentetate is used to determining rate of glomerular filtration during chemotherapy of kidney. Lastly DMSA; succimer is

*DOI: http://dx.doi.org/10.5772/intechopen.91868*

tioned below.

*1.2.1 Bone*

*1.2.2 Kidney*

*1.2.3 Brain*

*1.2.4 Heart*

*1.2.5 Lungs*

balanced level of administration is required [4].

**Figure 1.** *Chemical structure of technetium 99m.*

#### *Theranostics: New Era in Nuclear Medicine and Radiopharmaceuticals DOI: http://dx.doi.org/10.5772/intechopen.91868*

are in dividing states so sensitivity towards radiation can be higher, organ size body ratio also varies to greater extent in comparison with adult. So in case of children a balanced level of administration is required [4].

Different kit labeled with 99mTc used for imaging of different organs is mentioned below.

### *1.2.1 Bone*

*Medical Isotopes*

**1.1 Radiopharmaceuticals**

**1.2 Technetium 99m**

around 3800 radioisotopes out of which 200 radioisotopes are being used. Among the isotopes that are used most of them are of artificial origin. Artificial radioisotopes are primarily made by two methods as mentioned above i.e. through nuclear reactor and by cyclotron. By nuclear reactor neutrons are introduced into the nucleus of atom whereas in case of cyclotron proton are introduced. To become stable radioisotopes emits alpha or beta particle along with electromagnetic radiation of gamma rays. This phenomenon is called as radioactive decay. These radioisotopes have variety of uses, when they are used in the field of pharmaceuticals they are termed as radiopharmaceuticals.

These are radioactive medicines that can be given by oral, intravenous or interstitial route to treat or diagnose malignancy. Administration of these drugs is done in the presence of specialist called radio pharmacist. These radioactive medicines have the ability to destroy cancerous cell by emitting radiation when it reaches its target cell. Radiopharmaceuticals for treatment and diagnosis of cancers associated

In addition to treatment radiopharmaceuticals are also used for the purpose of diagnosis. The drugs used for diagnosis are called as tracers. The radiation of diagnostic radiopharmaceuticals is smaller as compared to radiation emitted by radiopharmaceuticals used for treatment. Radiopharmaceuticals are either single isotopes or sometimes the isotopes are combined with a kit [1]. The kit is prepackaging of ingredients which are sterile and are meant for preparation of radiopharmaceuticals. They are combination of substances such as antioxidant, buffer, reductant and ligands that are when combined with the radioisotopes produces the resultant product. Kits are very beneficial as they are not in contact with the outer environ-

The isotope that is used for the purpose of labeling of kits used for diagnosis is technetium 99m abbreviated as 99mTc (**Figure 1**). It radiates only gamma radiation that is compatible with gamma camera. 99mTc also has the property of binding with the tracers. Advantage of technetium is that it has smaller biological half-life and better renal clearance for the unabsorbed radiopharmaceuticals that helps in getting a better quality of image from the absorbed ones. The dose of technetium depends on the kit, the organ on which it has to be used for imaging and on the test to be performed [3]. Determination of dose for children is very crucial as the cells

with thyroid, brain, bones or lymphoma already been discovered.

ment so there is no chance of any contamination [2].

**72**

**Figure 1.**

*Chemical structure of technetium 99m.*

For detection of the areas that are metabolizing the bones kits with bisphosphonates are used. Scan of bone is done by injecting radiopharmaceuticals into the peripheral vein of patient and then after 3 h imaging is done so that within the three hours the bisphosphonates will get incorporated into the osteoblast cells.

### *1.2.2 Kidney*

For the imaging of kidney, there are three radiopharmaceuticals, namely

i.Radiolabelled mercaptoacetyltriglycine (Mag-3; mertiatide)

ii.Radiolabelled diethylenetriaminepentaacetic acid (DTPA; pentetate)

iii.Radiolabelled dimercaptosuccinic acid (DMSA; succimer

Mag-3; mertiatide is used for the purpose of determining the blood flow to the kidney and for graphically presenting the renal function. Mag-3 has a clearance of 94% after 3 h that helps in getting better quality of image and the exposure of patient to the radiation is also lower. DTPA; pentetate is used to determining rate of glomerular filtration during chemotherapy of kidney. Lastly DMSA; succimer is used a tool for studying morphology of renal cortex and ectopic kidney.

#### *1.2.3 Brain*

Kit used for the check the blood flow within the brain after conditions like epilepsy, migraine or Alzheimer's disease or stroke of brain contains 99mTc-labeled exametazime. This is product of lipophilic origin without any charge on it and it penetrates better through blood brain barrier. It takes around one minute after injection for it to reach brain and up to 7% reaches the brain.

#### *1.2.4 Heart*

For cardiac imaging, two 99mTc-labeled are tetrofosmin and sestamibi which are employed to ascertain the degree to which myocardial infarction is severe and also help to point out the regions of cardiac ischemia. Images are collected at the state of rest and after stressed activity of cardiac cells. This injection are administered when patient must have consumed any kind of fatty meal. This helps in hepatobiliary clearance of administered radiopharmaceuticals thus aid in getting better image. But it should not be administered when patients has consumed some drugs such as nitrates or calcium channel blockers.

#### *1.2.5 Lungs*

In case of lungs scan it is used for the purpose of diagnosis of any kind of embolism in pulmonary tract. Lung scan be of two types perfusion scan or

#### *Medical Isotopes*

ventilation scan. First, one 99mTc-labeled macroaggregated albumin is injected in the peripheral vein, which is then carried to the pulmonary artery system. It does not get absorbed rather it gets distributed evenly in the capillary bed and helps in diagnosis. Where blood flow is good there will be larger number of particles giving out radiation, whereas where there will less perfusion then less particles will be seen.

In case of ventilation scan, patient is made to inhale radioactive substance such as krypton or 99mTc-labeled DTPA aerosol. Image is obtained where air is seen circulating in lungs [5].
