Measurement of radioactivity & Dosimetry Techniques

Radiopharmaceuticals are a category of medicinal formulations containing radioactive isotopes (radionuclides) that are used in the field of nuclear medicine, primarily for diagnostic and therapeutic purposes.
The accurate measurement of radioactivity in these compounds is crucial for several reasons, including ensuring the safety and effectiveness of the dose administered to patients, compliance with regulatory standards, and for the proper execution of diagnostic tests or treatments.

Radioactivity is the process by which unstable atomic nuclei release energy in the form of radiation.
The fundamental units of radioactivity measurement include the becquerel (Bq), which represents one disintegration per second, and the curie (Ci), an older unit that corresponds to approximately 3.7×10103.7×1010 disintegrations per second.

A radiation detection and measurement device that uses the ionization effect produced by radiation upon a gas-filled chamber. It is suitable for detecting relatively low levels of radioactivity.

A sensitive method for measuring radioactivity, where a scintillator (a material that fluoresces in response to ionizing radiation) is used. When radioactive decay particles strike the scintillator, light is produced. A photomultiplier tube detects this light and converts it into an electrical signal, which is then counted. This method is particularly useful for low-energy beta emitters and gamma emitters.

Similar to scintillation counting, but the sample is dissolved or suspended in a liquid scintillant. This technique is highly efficient for beta emitters, as it allows for near-complete absorption of the radiation energy by the scintillant.

Designed specifically for detecting gamma radiation, these devices use sodium iodide (NaI) or germanium detectors to measure the gamma photons emitted by radionuclides. Gamma counters are essential in the quantification of gamma-emitting radionuclides in radiopharmaceuticals.

Specialized instruments used in nuclear medicine to accurately measure the activity of radiopharmaceuticals before administration to patients. They are calibrated to measure the radioactivity of various radionuclides based on their specific gamma emission energies and are crucial for ensuring that patients receive the correct dose.

Semiconductor Detectors:

These detectors, such as silicon or germanium detectors, use a semiconductor material to directly convert ionizing radiation into an electrical signal.
When radiation interacts with the semiconductor, it creates charge carriers (electrons and holes), which are then collected and measured.
Semiconductor detectors offer high energy resolution and are commonly used in gamma spectroscopy.

These devices consist of a gas-filled chamber with two electrodes that measure the ionization caused by radiation.
As ionizing radiation passes through the chamber, it ionizes the gas, creating charged particles (ions).
The ions are collected at the electrodes, generating a small electrical current proportional to the amount of radiation.
Ionization chambers are used for measuring dose rates in various settings, such as medical procedures and environmental monitoring.

TLDs are small devices that contain a chemiluminescent material, which stores energy when exposed to ionizing radiation.
The stored energy is released as light when the material is heated. By measuring the amount of emitted light, the radiation dose can be determined.
TLDs are commonly used for personal radiation monitoring and to measure environmental radiation levels.

These devices use photographic film to measure radiation exposure.
As ionizing radiation interacts with the film, it creates a latent image, which becomes visible when the film is developed.
The degree of blackening or fogging on the film is proportional to the radiation dose.
Film badges have largely been replaced by more modern techniques like TLDs but are still used in some settings.