Radioactivity Practical (Group 4)

Introduction:
Radioactivity or radioactive decay can be identified by the emission of particles from unstable atomic nuclei. Unstable atomic nuclei are ones that do not possess enough binding energy to hold the nucleus together due to an excess of either protons or neutrons.

Radioactive decay can be worked out using quantum physics, but it is still inherently probabilistic, making it impossible work out when an atom will decay. However, predictions can be made based on the statistical behaviour of many atoms. This predictive measure of radioactive probability is called the half-life of an atom. It is defined as the time after which, on average, half of the original material will have decayed.

There are 3 types of radiation that are currently known – alpha (a), beta (b)  and gamma (γ). Alpha radiation can be described as type of radiation in which an alpha particle (which can be written as He2+) is emitted from an atomic nucleus. Beta radiation is a form of radioactive decay in which a beta particle (an electron – e-) is emitted. Gamma radiation consist of photons in the highest observed range of photon energy and has the ability to ionise other atoms, inducing atomic decay.

Importance in clinical medicine:
The most common use of radiation in medicine is x-ray imaging which is mainly used to assess whether bones are broken or not. This falls under radiology in medicine, however x-rays may also be used to take radiographs of the heart and the chest cavity therefore falling under cardiology and pulmonology, for the purpose of diagnosis.

Gamma radiation is used in medicine as well, to sterilize medical equipment and prevent bacterial infection in patients. In oncology, radiation is important for diagnosis, prevention and treatment. CT (computerised tomography) and PET (positron emission tomography) scans are used to locate tumours and diagnose cancer and regular screening can help prevent cancer.

As vital as radiation is to diagnosis, frequent use can cause cancer (due to alteration of DNA sequence in cells) which is why its recommended for physicians to only use radiation when necessary and to refer the patient to the risks of the radiation whether x-rays or gamma radiation before exposing them to it. X-ray or gamma radiation is also used for the treatment of cancer by killing cancerous cells and is commonly known as radiotherapy (RT).

Nuclear energy
Using nuclear fission, electricity can be generated in nuclear reactors.
 * Greenhouse gas emissions are reduced, as the amount of fossil fuels burnt will be less.
 * Compared to the solar panels or wind turbines, a nuclear reactor can be functioning 24/7
 * An uncontrolled version of the nuclear fission chain reaction can be used in a nuclear bomb which can cause mass destruction of life.
 * Nuclear waste that remains after the chain reaction is complete, is high in radioactive isotopes with long half-lives.

Nuclear medicine

 * Advanced and early treatment procedures for serious illnesses such as cancer via the use of radiotherapy
 * The high precision of the instruments used, allows for a simpler and less invasive methods of treating the patient
 * The price of the machinery and facilities required to provide benefits to the patients is high
 * There is always a risk that the patient`s healthy cells may be affected by the radiation used during diagnostic imaging. This can lead to the formation of tumours and eventually cancer.


 * Due to the scattering of the ionising radiation and its unpredictability, the adiologists are under a certain risk of absorbing some of the emitted radiation and are required to wear protective clothing.

How does radioactivity work?
Some nuclei are unstable, this instability leads to a rearrangement of protons and neutrons which results in the emission of radiation (radioactivity).

There are three problems that are associated with an unstable nucleus:

1.   Too many protons repelling each other:  The easiest way is to get rid of some of them is by the process of radioactivity (alpha decay) which results in emission of an alpha particle (2 protons and 2 neutrons).

2.   An improper protons-neutron ratio: In this case, there are too many protons one of them changes into neutrons and gives out a positive beta particle, and if there are too many neutrons, one of them changes to a proton and gives out a negative beta particle. This happens by process of radioactivity (beta decay).

3.   Excess energy (excited state): Here the number of protons and neutrons are balanced but some of them are in the wrong energy level in the nucleus, in this case as the guilty nucleon returns to its proper energy level, only energy is emitted and this happens also by the process of radioactivity (gamma decay).

Ethical problems:

 * Exposure to high doses of radiation over short periods of time can cause radiation poisoning and in some cases death
 * Exposure to legal limits of radiation over a long period of time can cause people to develop cancer (For example, radioactive exposure for the diagnosis of illness)
 * Other ethical problems include infertility in women, birth deformities, etc.

Equipment:
1.    Radiation indicator
 * Excel spreadsheet
 * GamaBeta kit:

2.    Beta and Gamma radiation source

3.    Absorbing plates: 4.    Arresting pin
 * Aluminium
 * Iron
 * Copper

5.    Tripod holder

6.    Digital pulse counter



Methodology:
1.    Set up the GamaBeta kit by placing the Beta/Gamma radiation indicator on the tripod holder

2.    Connect the plug into connector from the Digital pulse counter into the pulse counter socket on the indicator and turn on the sliding switch

3.    In order to assess the background radiation of the environment that you will be working in, make sure that there are no radiation materials nearby as this will interfere with the measurement thus placing the source in another room.

4.    Once this has been done, begin measuring by pressing the ‘start’ button on the Digital pulse counter and allow it to count for 100 seconds (nbg100)

5.    Repeat procedure 10 times and calculate an (nbg100) average

6.    For protection of the radiation by distance, place the radiation source 4cm from the radiation indicator which is the first gap closest to the instrument. To sense the beta particles, make sure that the opening mouth of the radiation output is facing the side where it has ‘B’ marked at the head of the source. Correspondingly, to recognise the gamma particles, make sure the opening is on the side where it has ‘G’ marked on the head

7.    Insert the arresting pin into the gap

8.    Take a measurement of 10 seconds and take an average using a total of 5 values

9.    Repeat the procedure by increasing the distance of the radiation source and the arresting pin to 8 cm (the second gap away from the radiation indicator) and 16cm (the fourth gap away from the Radiation indicator)

10.  Once an average has been calculated for all distances. Determine the ‘corrected’ radioactivity by subtracting this figure from the average of the radioactive background (nbg100) taken from earlier measurement in step 5

11.  To evaluate the protection by shielding, place the radiation source 4cm away from the counter making sure that the absorption layer is placed between the two components on the mortise of the tripod holder

12.  Take five measurements and determine an average for both Beta and Gamma particles

13.  Repeat step 11 for both Iron and Copper making sure that the radiation source is still 4cm away

14.  Likewise, with evaluating the protection by distance in step 10, Use your average for each material and subtract each value from the average background (nbg100)

15.  Enter the data collected into an Excel spreadsheet (shown below) which will help you to make comparisons of each of the radiations and the correlations with increasing distances and different factors of shielding



Conclusion:
Although radiation can have many negative effects on the body, there is still much research into the harnessing of radioactive energy for clinical practise. Nuclear medicine, a branch of medicine that uses radiation to provide information about the functioning of an individual’s specific or in order to treat disease.

The current use of diagnostic techniques in nuclear medicine are widespread. Examples can be seen in PET, RT and the use of radioisotopes in Biochemical analysis (world-nuclear.org, 2016).

Non-invasive predictions in Sentinel Lymph Node Biopsy to assess lymph node metastasis are also in currently being research through increased understanding of radioactive half-life (Thangarajah, F., et al., 2016).

In conclusion, the potential for the clinical application of radioactivity is great, and as our understanding of radioactive mechanisms and our ability to manipulate radioactive paraments progresses, advancements in the clinical application of radioactive decay will continue to further establish itself in modern medicine.

References:
http://www.health.harvard.edu/newsletter_article/Radiation-in-medicine-a-double-edged-sword

http://www.macmillan.org.uk/information-and-support/treating/radiotherapy/radiotherapy-explained/what-is-radiotherapy.html

https://en.wikipedia.org/wiki/Nuclear_power

https://en.wikipedia.org/wiki/Nuclear_medicine

http://healthresearchfunding.org/pros-cons-nuclear-medicine/

World Nuclear Association.(2016). Radioisotopes in Medicine. Available: http://www.world-nuclear.org/information-library/non-power-nuclear-applications/radioisotopes-research/radioisotopes-in-medicine.aspx

Thangarajah, F., et al. (2016). Predictors of sentinel lymph node metastases in breast cancer-radioactivity and Ki-67. The Breast. 30 (1), p87–91.