Updated: May 14
The modern Medical Sciences have evolved from a traditional medicine and surgery format to a rather more robust system with provisions of early diagnosis, checkup, accurate and precise surgery along with collection of patients' case for statistical analysis. Whenever we suffer from a disease or injury, we consult a doctor or therapist to get the best possible cure at the earliest.
It might happen that we get a grave injury in an accident and we need to determine the magnitude of the injury and the victim organ/tissues of such mishap. For this, we have a whole range of diagnostic methods which are also infamous for turning away many patients themselves, thus depriving the hospitals or laboratories of a hefty earning. Nowadays, we have many advanced methods like X-Ray, CT scan, MRI scan and PET scan for detecting many internal injuries and abnormal functioning of body that use electromagnetic radiations as their core working principle. It is a common case that many patients get afraid of getting irradiated and thus, constantly remain in a fear of dying due to radiation. And it becomes an important responsibility of the doctors and technicians to assure the patients about safety.
A natural question arises that how do these machines work and what is radioactivity. Before knowing about the
working principle, it is essential to understand radiation and radiocativity.
Since the 19th Century, it became clear that matter is composed of tiny undivisible entities called atoms. Further experiments revealed that atoms themselves are composed of three types of fundamental particles called electrons (negatively charged), protons (positively charged) and neutrons (neutral). Out of these, the protons and neutrons are placed centrally in a dense structure called nucleus with electrons of different energies revolving around the nucleus in an electron cloud. Experiments show that in every elements number of electrons and protons (atomic number) are unique and same for all elements. Some atoms of an element vary in masses among each other. These arise due to varying number of neutrons present in the nucleus of atoms of same elements and are called isotopes of an element.
It is also known that like charges repel like charges and it was expected that nucleus is not supposed to exist in such case. For this case, the protons and neutrons are bound together by a force called strong nuclear force in the nucleus. Interestingly, the range of this force is of the order of nuclear radius which is typically about 10^(-15) m beyond which this force does not produce any significant effect. To hold the protons together, neutrons are required in the process however, if there are excess of neutrons relative to the protons then the nucleus of the atom of the element becomes highly unstable and readily emits energy in the form of radiation (low energy alpha and beta particles; high energy gamma ray photons) and converts to a more stable nucleus of another element. This spontaneous emission of radiation by a substance on its own is called radioactivity and the substances exhibiting radioactivity are called radioactive substances.
Radiation means emission in common usage and refers to any energy coming out of a source and travelling in the sorroundings. The most common example of radiation is light, which helps us to see our sorroundings. However, there are several types of radiations like gamma rays, X-rays, ultraviolet rays, visible light, infrared rays, microwaves and radio waves in decreasing order of energy. These radiations are composed of massless particles called photons, which are tiny packets of energy (quantum) transfering radiation in space. Of these, the X rays, radio waves and UV rays find most application in medical science and are used in different diagnostic methods.
Working of CT, X-Ray, PET scans and Radiation Therapy
The X-rays are used in X-ray scans, Computed Tomography (CT) scans. The word "tomography" is derived from the Greek words tomos, "slice/section" and grapho, "write". In these techniques a low intensity and frequency X radiation is used to obtain pictures of internal organs and check for any abnormalities present in the body. While X ray resembles taking photography, the difference lies in the fact that here X ray is used in place of light. These X rays are powerful enough to penetrate the soft tissues of our body and only get blocked by bones and are thus used to detect fractures in bones. On the other hand, CT scan employs 3-D X ray scanning by spiralling around the body and produces a 3D cross section image of body in the form of thin slices. The radiations are emitted from an emitter and the unblocked rays emerging from body is collected in the detector plate and the data is processed to create an image.
Similarly, in PET scan– an efficient method to detect cancer, a radioprobe 18-Fluoro-Deoxy -Glucose (18 FDG) is injected in the body and is allowed to be absorbed in the body. The glucose containing radioactive fluorine-18 is absorbed by the tumour cells in high concentrations and the fluorine atom undergoes radioactive decay to emit a positron (positively charged variant of electron). These positrons collide with normal electron in the body and release energy in the form of radiation as both are antiparticles of each other which destroy each other upon coming in contact. This process creates photons, which are sensed by detectors and processed in computers to create an image of the scan. The radioactive Fluorine-18 is made by bombarding normal glucose molecules with neutrons obtained from water molecule having an atom of heavy isotope of oxygen O-18; by converting an oxygen atom of glucose to Fluorine-18 using a cyclotron (a particle accelerator) . These scans are seen by doctors to check for any underlying abnormalities, thus proving to be effective diagnostic tools.
Safety and possible side-effects
The machines at a first glance, look very scary with a stretcher going in and out of a big detecting machine with no one staying in the vicinity of the test subject. The infamous atomic bombings in Japan and Chernobyl reactor disaster in Soviet Union are more than enough to frighten any individual to the marrow. The main highlight here is that the radiations used here are controlled, of low intensity, frequency and of small durations, about 5 minutes to 30 minutes. It can be henceforth inferred from basic intuition that it is of very low energy. Some people who are claustrophobic i.e., extreme fear of small, confined places are reluctant to get the tests and may suffer sickness due to small place. People having any metallic implants are also made to put them off if possible. Some people are found to get nausea like symptoms if they have radiation allergy. The greatest problem arises in PET where many people are skeptical of ingesting radioactive substances and have radiations emitting from one's body and cause genetic mutations and cause harm. However, these ideas are completely baseless as the amount of radioprobe given is extremely less in concentration and only a handful of atoms are radioactive. The greatest misconception is that in medical diagnosis, high enegy gamma rays are also involved, which is not true because if such harmful radiations were meant to be used in the first place, then Medical Science's purpose of making sick healthy would contradict with its practices, which cannot be an acceptable case at all.
As the medical science is progressing at par with latest scientific developments, it is no longer merely an application of human physiology and biochemistry, but an interdisciplinary field encompassing physics, engineering, mathematics, biology, chemistry, statistics, computer science and many more. With each day, the treatment procedures are getting more and more biocompatible with human body and case studies made with ample statistical data. In the near future, the medical science aims for increased longevity of humans and better prevention techniques for diseases at a global scale.