Which of the following isotopes is used in the treatment of cancer?
Isotopes and Their Medical Uses
Isotopes are atoms of the same element that have the same number of protons but a different number of neutrons. Some isotopes are radioactive, meaning they decay over time and emit radiation such as alpha particles, beta particles, or gamma rays. Radioactive isotopes, also known as radioisotopes, have various applications in medicine, both for diagnosis and treatment.
Radioactive Isotopes in Cancer Treatment
Radiation therapy is a common method used to treat cancer. It works by damaging the DNA of cancer cells, which stops them from growing and dividing. This radiation can come from external machines (external beam radiotherapy) or from radioactive sources placed inside the body (brachytherapy). Specific radioactive isotopes are chosen based on the type and energy of the radiation they emit and their half-life.
Let's look at the isotopes listed in the options and their typical uses:
| Isotope | Symbol | Common Use | Relevant to Cancer Treatment? |
|---|---|---|---|
| Mercury-197 | $^{197}_{80}\text{Hg}$ | Diagnostic imaging (e.g., kidney scans) | No (Diagnostic only) |
| Cobalt-60 | $^{60}_{27}\text{Co}$ | External beam radiotherapy for cancer (Cobalt therapy), sterilization | Yes (Therapeutic) |
| Carbon-11 | $^{11}_{6}\text{C}$ | Positron Emission Tomography (PET) imaging (diagnostic) | No (Diagnostic only) |
| Uranium-235 | $^{235}_{92}\text{U}$ | Nuclear fuel, nuclear weapons | No |
As shown in the table, Cobalt-60 ($^{60}_{27}\text{Co}$) is a widely used radioisotope in the treatment of cancer, particularly in older external beam radiotherapy units known as Cobalt therapy machines. It decays by emitting high-energy gamma rays, which are effective at killing cancer cells.
Other isotopes listed, like Mercury-197 and Carbon-11, are primarily used for diagnostic imaging purposes, not for directly treating cancer. Uranium-235 is used in nuclear energy and weapons, not medical treatment.
Therefore, among the given options, Cobalt-60 is the isotope specifically used in the therapeutic treatment of cancer.
Important Questions from Radioactivity
- The energies of the 3 lowest states of an atom are E 0 = −14 eV, E 1 = −9 eV and E 2 = −7 eV. The Einstein coefficients are A 10 = 3 × 10 8 s −1 , A 20 = 1.2 × 10 8 s −1 and A 21 = 8 × 10 7 s −1 . If a large number of atoms are in the energy level E 2 , the mean radiative lifetime of this excited state is
The nuclei of 137 Cs decay by the emission of β - particles with a half life of 30.08 years. The activity (in units of disintegrations per second or Bq) of a 1 mg source of 137 Cs, prepared on January 1, 1980, as measured on January 1, 2021 is closest to
The Q - value of the α - decay of 232 Th to the ground state of 228 Ra is 4082 keV. The maximum possible kinetic energy of the α - particle is closest to
Radioactivity is the characteristic of which of the following?
Particles which can be added to the nucleus of an atom without changing its chemical properties are
