Isotopes are two forms of the same element which differ in the number of neutrons present in the nucleus of a single atom of the element. There are 90 naturally occurring elements with roughly 250 stable isotopes and over 3200 unstable or radioactive isotopes. Different isotopes of the same element often have completely different properties, making some of them invaluable to mankind.
Isotopes have widespread application in the realm of chemistry, biology, archaeology, physics and other sciences. Some of them are as mentioned:-
- Carbon dating
- Surface and groundwater investigation
- Diagnosis of diseases
- Treatment of disease
- Pest control
- Climatology and geology
- Smoke alarms
- Biological tracing
Here, we will check the application of the radio-isotope Technetium-99m (Tc-99m) which is used in a wide range of medical applications.
Tc-99m is a long lived isomer of Tc-99, widely used in nuclear medicine, especially in diagnosis. ‘Isomer’ refers to those nuclei that are able to survive in excited states for abnormally long periods of time. Tc-99m has a half life of approximately 6 hours, and it decays to Tc-99, which has a half life of 215000 years. In order to leave the excited state, TC-99m nuclei emit pure gamma radiation without any accompanying beta rays. Hence it is also called a pure gamma emitter which is a highly desirable property in imaging.
Major applications of Tc-99m include imaging of the skeleton and the heart muscle in particular, but also brain, thyroid, lungs, liver, spleen, kidney, gall bladder, bone marrow, salivary and lacrimal glands, heart blood pool, infections and numerous specialized medical studies. This diagnostic imaging uses Tc-99m as a radioactive tracer which can be detected in the body by medical equipment, such as gamma cameras.
When using technetium-99m, the radioisotope is given to the patient and the escaping gamma rays are shown upon a moving gamma camera which computes and processes the image. To acquire images, the gamma camera is rotated around the patient. Projections are collected at defined points during the rotation, normally every three to six degrees. In most cases, a full 360° rotation is used to collect an optimal reconstruction. The time taken to collect each projection is also variable, but 15–20 seconds are usual. This gives a total scan time of around 15–20 minutes.
The technetium-99m radioisotope is used predominantly in bone and brain scans. For bone scans, it is used directly, as they attempt to heal a skeletal injury, or in some cases as a reaction of these cells to a tumor in the bone. In brain scanning, it is useful for the detection of strokes and dementing illnesses.
The radioactive properties of Tc-99m can be used to identify the predominant lymph nodes draining a cancer, such as breast cancer or melanoma. This is usually performed at the time of the medical checkup. Immunoscintigraphy (finding cancer cells) includes it into an immune system protein capable of binding to cancer cells. A few hours after injection, medical equipment is used to detect the gamma rays emitted by the Technetium-99m; higher concentrations show where the tumor is. This technique is particularly useful for detecting hard-to-find cancers.
There are many advantages of using Tc-99m. First of all, Tc-99m is a metastable isotope that is a gamma decay product of Molybdenum-99 which is an abundant fissile product. Hence, it is technically easy to obtain. Secondly, Tc-99m, while decaying into Tc-99 emits a gamma radiation that is easily detected (140.5 KeV) and, hence provides high resolution. The amount of radiation is low enough such that it is not detrimental to the patient. A common injection for a diagnostic test gives a radiation dose of 0.05 Sv, far below the demarcation for radiation poisoning or harm. Thirdly, Tc-99m has a half life of 6 hours which gives plenty of time for any test. So, the doctors can take their time to record the observations which would reduce observational errors. Tc-99m also activates DNA repair mechanisms in the body that can fix existing mutations. Also it can be paired by conjugating with appropriate antibodies to identifying cancer and other medical conditions.
Everything has its advantages and disadvantages. Moreover Tc-99m is a radioactive isotope. It is expensive to produce the isotope because a nuclear reactor is required for its production. Obviously, radioactive waste is generated in the production of the isotope. During some treatments using Tc-99m, high radiation exposure is required, hence a possibility of tissue damage arises which can lead to sickness and even death. There is danger of Leukemia or lung cancer upto 20 years after treatment. Similarly, genetic damages and mutations in the DNA can cause deformities in the offspring. The radiation source is inside the patient’s body for a few days, exposing others to second hand radiation.
So, what we can conclude from our research on Tc-99m is that, it is a highly useful radioactive isotope used in a whopping 85% of medical diagnosis procedures due to its abundance, highly desirable properties, and versatile functioning. It can also be used in the treatment of cancer and other serious diseases. Ironically enough, its usage is limited by human understanding of diseases. But even though it’s really useful, it has its own risks which are very limited in number. Hence, we see that the advantages greatly overshadow the disadvantages and so, isotopes are very important in the scientific field.