Gel filtration

Gel dosimetry is a technique used in the field of radiation therapy to measure the dose distribution of radiation. This method is particularly useful in complex radiation fields where 3D dose distribution is required.

History

The concept of gel dosimetry was first introduced in the 1980s. The initial systems were based on Fricke's solution, which changes its chemical properties under the influence of radiation. The development of polymer gel systems in the 1990s expanded the possibilities of gel dosimetry, allowing for more accurate and detailed measurements.

Principles

Gel dosimetry is based on the principle that radiation-induced changes in a gel matrix can be measured and related to the dose of radiation received. The gel matrix, often a polymer, is sensitive to radiation and undergoes changes in its properties when exposed. These changes can be measured using various techniques, such as magnetic resonance imaging (MRI), optical computed tomography (OCT), or X-ray computed tomography (X-ray CT).

Types of Gel Dosimeters

There are several types of gel dosimeters, including Fricke gel dosimeters, polymer gel dosimeters, and normoxic gel dosimeters. Each type has its own advantages and limitations, and the choice of dosimeter depends on the specific requirements of the radiation therapy procedure.

Fricke Gel Dosimeters

Fricke gel dosimeters are based on the Fricke dosimetry system, which uses a solution of ferrous ions in an acidic environment. Radiation causes the ferrous ions to oxidize to ferric ions, and the concentration of ferric ions can be measured to determine the dose of radiation.

Polymer Gel Dosimeters

Polymer gel dosimeters contain monomers that polymerize upon exposure to radiation. The degree of polymerization can be measured using MRI, and is directly related to the dose of radiation received.

Normoxic Gel Dosimeters

Normoxic gel dosimeters are a type of polymer gel dosimeter that contain oxygen scavengers to prevent oxygen from inhibiting the polymerization process. This allows for a more uniform dose response and makes the dosimeter more stable and reliable.

Applications

Gel dosimetry is used in various applications in radiation therapy, including treatment planning, quality assurance, and research. It is particularly useful in situations where a 3D dose distribution is required, such as in intensity-modulated radiation therapy (IMRT) and stereotactic radiosurgery (SRS).

See Also

• Radiation therapy
• Dosimetry
• Fricke's solution
• Magnetic resonance imaging