IAEA TECDOC 1274 AND ROOM SCATTER CORRECTION

Sothing vashumIAEA TECDOC - 1274 AND ROOM SCATTER CORRECTION

IAEA TECDOC 1274IAEA TECDOC-1274 is an update of IAEA-TECDOC-1079 ( Calibration of Brachytherapy Sources. Guidelines on Standardized Procedures for the Calibration of Brachytherapy Sources at Secondary Standard Dosimetry Laboratories (SSDLs) and Hospitals)report discusses standardization of calibration calibration techniques of the most commonly used gamma and beta ray brachytherapy sources.Report includes a description of suitable detector systems that can be used for the calibration.report gives a description of the systems used at the PSDLs and recommends suitable detectors for calibration for SSDLs and hospitals.

described methods for calibrating brachytherapy sources with photon energies at or above those of 192Ir,2

CHARACTERIZATION OF BRACHYTHERAPY SOURCES

SOURCE DATA

PRIMARY STANDARD

CALIBRATION AT THE SSDL AND HOSPITAL LEVEL.

CALIBRATION USING FREE IN-AIR MEASUREMENT TECHNIQUE

CALIBRATION USING WELL TYPE IONIZATION CHAMBER

CALIBRATION OF BRACHYTHERAPY SOURCES BY USING OTHER DETECTOR

QUALITY CONTROL

Characterisation of brachytherapy sourcesGives the recommended quantities for brachytherapy source specification.GAMMA RAY SOURCES - reference air kermaBETA RAY SOURCES - reference absorbed dose rate in water at a reference distance from the sourceFor planar and concave sources -1 mm from the centre of the source,

for seeds and line sources - 2 mm in the transverse direction from the sources longitudinal axis. For balloon, shell and stent sources - 0.5 mm measured from the surface of the source.

It must be recognized that measurements at these short distances are a difficult task. The distances are chosen from the point of view of the low penetration of the beta rays and the relevance to clinical applications4

Other important quantitiesBeta ray plague sources - depth dose: relative central axis depth dose curve in water for each type of source. - source uniformity: quantified by a parameter, equal to the percentage difference of the maximum and minimum values of relative absorbed dose rate. (