Radioactive tracers like carbon-14 can be used to tag molecules like amino acids that are then incorporated by cells. This allows researchers to track where these molecules go after leaving the cell. Emission tomography uses radioactive tracers and gamma detectors to create 2D or 3D images showing the distribution of tracers inside the body. Positron emission tomography involves injecting a radioactive tracer molecule that emits positrons, colliding with electrons to produce gamma rays detected by a scanner to image biochemical processes. Various isotopes including bismuth-213, chromium-51, and iodine-125 are used as tracers in medical applications like identifying deep vein thrombosis or measuring kidney function.

1. BY- NAKSHATRA PAL SINGH CHAUHAN
ENROLLMENT NO.:- A14587822001
TRACER TECHNIQUE

2. TRACER TECHNIQUE
In medicine, chemistry, and biology, radioactive isotopes like carbon-14 can be utilised as tracers (or labels).
For instance, radioactive atoms can be used to create specific molecules (such amino acids) artificially. The
biological cell can easily accept this molecule, which is now referred to as the tracer or label molecule, and
utilise the amino acid for protein production. The unstable atoms that make up an amino acid can emit
radiation, which a specialised equipment can easily detect. By doing this, we can investigate things like where
an amino acid goes after it leaves the cell and where proteins are made.

3. EMISSION TOMOGRAPHY
Emission tomography is the process of using radioactive tracers in medicine to
produce images that depict the radiation that the tracers emit inside the human body.
SINGLE-PHOTON EMISSION TOMOGRAPHY (SPECT)
A gamma detector can be used to evaluate the strength of the gamma radiation after
injecting a patient's blood with a radioactive isotope that emits gamma rays. As a
result, a 2D representation of the radioactive isotope is created.

4. POSITRON EMISSION TOMOGRAPHY (PET)
• In this method, a patient receives an injection of a synthetic tracer molecule. Then, these
tracer molecules proceed to the area of interest.
• Positron emission occurs in the radioactive atoms of the tracer molecule, and the resulting
β-particle collides with electrons in neighbouring atoms to produce gamma rays.
• Due to momentum conservation, the two gamma rays depart in different paths.
• Then, a gamma detector picks up these radiation.

5. ISOTOPES USED IN MEDICINE
REACTOR RADIOISOTOPES (Half-life Indicated)
• Bismuth-213 (46 min): Used for targeted alpha therapy (TAT), especially
cancers, as it has a high energy (8.4 MeV).
• Chromium-51 (28 Days): Used to label RBC and quantify gastrointestinal protein
loss.
• Iodine-125 (60 Days): used as a diagnostic tool to determine the kidney’s
capacity to filter waste products as well as to identify deep vein thrombosis in
the leg. Additionally, it is frequently employed in radioimmunoassay to
demonstrate the presence of hormones in minute amounts.
• Potassium-42 (12 Hours): Used for the determination of exchangeable
potassium in coronary blood flow.

6. CONCLUSION
SPECT and PET produce images that describe the biochemistry of the
region of interest, unlike X-Ray techniques like CT scans. They paint a better
picture of what is taking place in the region in terms its functionality.
Thank You !