**1. Introduction**

46 12 Chapters on Nuclear Medicine

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Nuclear Medicine.

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61-68.

In this chapter we intend to illustrate the reader about the use of Cyclotrons to produce easy handle radioisotopes, to be used for medical diagnostics or therapies in Nuclear Medicine. Firstofall, we will describe different activation processes to generate artificial radioisotopes, characteristics needed to be safely used in medicine, such as the relationship between fathers and daughters that can compromise patient or environment health. It also will be describe radioisotopes desire behavior inside human body in order to clarify which isotopes can be activated or not in a cyclotron facility to be used in human medical applications. Nuclear Medicine radioisotopes must fulfill four main characteristics in order to be easy handle by operators and be easily and quickly disposed by patients and not to represent environmental radioactive contamination harm, so they have to have:


In Nuclear Medicine, equipment also has to have a high sensitivity to small amounts of radiation and to different types of radioisotopes. The ideal radioisotopes must be easily eliminated by the patient just after the study has been done in a short period of time which is a function of the physical half life of the isotope and the patient excretion system. The total time elapse for patient elimination of any trace of radioisotope used for study is known as Effective Half Life Time T��� ��� and is related to the time isotope population is reduced to its half due to the radioactive decay of father to daughter (Physical Half Life) T��� ��� and the time patient systems needs to eliminated of isotope from it system (Biological Half Life) ���� ��� in this way:

$$\frac{1}{T\_{1/2}^{eff}} = \frac{1}{T\_{1/2}^{phy}} + \frac{1}{T\_{1/2}^{bio}}$$

So it is not easy to find natural occurrence radioisotopes to fulfill this equation in order to make T��� ��� shorter than biological times of cellular repair. Fortunately in mid 20Th century, there was a huge development of activation processes when man learn how to manipulate atom and its nuclei, so now we have a big amount of radioisotopes for an equally big amount of pacific applications. There are two kinds of manmade machinery capable of modify stable nuclide: Nuclear reactors and particle accelerators. Accelerator can also be

Radiactive Atoms Discharge

Fig. 1. Decay mode of radioactive atoms to reach stability.The action of atoms to split means mass and energy transfer to media. For example, in a 226Ra atom energy excess push it to

Heavy ions α β γ

atom of 222Rn, so where there was one atom now there are three different species born out it

There are several methods for atoms to transfer energy to the media. Remember Einstein´s principle of ܧ ൌ ݉ܿଶ, which means energy is matter and matter is energy. So in their attempt to become stable emits energy/matter to discharge it excess in several ways as in

And scientist began to use this atom fraction to hit different nucleus of known atoms and to

Back in 1929, Ernest Lawrence device a Cyclotron to fulfill his own need to generate high speed ions without needing high voltages he has not access to in Berkeley University. This history began 10 years before when Lord Rutherford used alpha particles coming from Madame Curie´s 226Ra as projectiles to impact a Nitrogen nucleus to transform it into Oxygen.

observe which was the results of the reverse experiment.

Fig. 2. Lawrence´s illustration about Rutherford Experiment.

<sup>2</sup>*He* nucleus (an alpha particle) and 1.4 MeV package of pure energy and another

split out a <sup>4</sup>

figure 1.

mass and energy

divided into two big groups: Linear accelerators and spiral path accelerators or Cyclotrons. The radioisotopes used in Medicine can be from natural ocurrences like 137Cs (used in the last century in Teletherapy machines and in low dose rate brachytherapy) or 192Ir (used nowadays in high dose rate brachytherapy), or can be produced in Reactors or Cyclotrons. Most common reactor products used in Medicine are:

For diagnostic purposes: 51Cr, 125I, 131I, 59Fe, 42K, 177Lu, 99Mo (fission product), 75Se, 24Na, 99mTc, 133Xe (fission product), 159Yt.

For therapeutic purposes: 213Bi, 60Co, 165Dy, 169Er, 125I, 131I, 192Ir, 212Pb, 177Lu, 103Pd, 32P, 188Re, 186Re, 153Sm, 89Sr (fission product), 90Y (fission product).

For diagnostic and therapeutic or other purposes: 60Co, 166Ho, 125I, 99Mo (fission product), 177Yt. Most common radioisotopes produced in Cyclotrons used in Medicine are:

For diagnostic purposes: 11C, 13N, 15O, 18F, (PET studies), 64Cu, 67Ga, 68Ga, 111In, 123I, 124I, 81mKr, 99Mo (activation product), 82Rb, 201Th.

For therapeutic purposes: 67Cu.

For diagnostic, therapeutic or other purposes: 57Co, 82Sr, 68Ge. All of them have to fulfill the four conditions mentioned above.

Knowing all this restrictions radioisotope has to accomplish, to be safely used in human, now we can talk about the characteristics of a cyclotron to produce such an isotope. Later in this chapter we will describe such an installation regarding shielding, environmental safety, radiopharmacy lab, etc.

In Venezuela, we start to install the first baby cyclotron for medical purposes on 2001, so our last section of this chapter is to illustrate how this installation works and how its programs has been accomplish to the present date.
