Technical comparison of the substitutive products

The radiation detection for dosimetric purposes in the medical field of diagnostic radiology, radiotherapy and nuclear medicine is mainly based on the principles of measurement, realized by different detector types, described below. (Main sources: A. Ismail, J.-Y. Giraud, G.N. Lu, R. Sihanath, P. Pittet, J.M. Galvan, J. Balosso, 2009. “Radiotherapy quality insurance by individualized in vivo dosimetry: State of the art” Cancer/Radiothérapie, Volume 13, Issue 3, Pages 182-189; IAEA Training Material on Radiation Protection in Radiotherapy, Lecture 2).  

Ionization chamber. It is a gas-filled cavity containing positive and negative electrodes that measures the amount of radiation passing through the cavity according to the quantity of electric charges obtained by the ionization caused by the radiation.

Thermoluminescent dosimeters (TLD). Thermoluminescence is a phenomenon of phosphorescence activated by heat. The luminescence signal is proportional to the dose received by the TLD material.

Diod. A silicon diode dosimeter is a p-n junction semiconductor.

Metal oxide semiconductor field effect transistor (MOSFET). The Metal oxide semiconductor field effect transistor is a miniature silicon transistor which has an excellent spatial resolution, and offers very little attenuation of the beam due to its small size. Irradiation generates electron-hole pairs within the gate oxide (SiO2) of the MOSFET.

Radiographic films. Ionization of AgBr grains, as a result of radiation interaction, forms a latent image in the film. This image only becomes visible (film blackening) and permanent subsequently to processing.

Radiochromic films. Radiochromic film contains a special dye that is polymerized upon exposure to radiation. The polymer absorbs light, and the transmission of light through the film can be measured with a suitable densitometer.

Dose Area Product (DAP) meters. DAP are large-area, transmission ionization chambers and associated electronics.