Introduction
The light output from each exposed TLD is measured and recorded. The percent difference is light output from the mean for each TLD is calculated and is known as the element correction coefficient (ECC) (McGinley, 2012).The light output obtained from the individual TLDs is then multiplied by the ECC to determine the corrected light output of the TLD (Shapiro,2007). This makes the “response of each dosimeter comparable to the average response of a population of Dosimeters. This corrected response is what is used to determine the dose to the object on which the TLD is placed.
Graphical Presentation
Because all TLD-1OO’s are not exactly the same, even within the batch in which they were produced, a correction factor must be introduced for every TLD element. A TLD can have some variation in materials composition and in size, compared to other TLDs. The response from the TLD will also be characteristic of that TLD and will be different from the response of other TLDs (Shapiro,2007). Because of these differences, we must ensure the proper correction factor for each TLD element can be used for future exposure of that specific TLD
Discussion
When the ECC is applied to the response of each Individual TL element of any of the Field or the Calibration Dosimeters, its TL efficiency is virtually identical to the mean value of the Calibration Dosimeters group (McGinley, 2012). The Element Correction Coefficient, ECC for element in calibration card ij given by: ECC ij=i/Qij .when
.is the average TL response for element is of the calibration card population and Q is the response of TL element in card j similar to the one described above (Shapiro,2007). The TLD card used here can be subjected to hundred so for use without any noticeable change in their TL efficiency.
Conclusion
The curve of TLD against ECC can have different anomalies in exposure to light and differing temperatures. This means that a small variation in any of the factors influencing the readout of the TLD curve will be reflected in the graph (Shapiro, 2007). The factors that may affect the normal curve of a TLD are incomplete TLD readout, presence of a contaminant on the TLD, light induced peaks, and electrical spikes (McGinley, 2012). Throughout this process, the inherent sensitivity of the Calibration Cards must remain constant (Shapiro, 2007).TLDs is placed in the slot with a start and a stop timer to ensure that all the irradiations were recorded and that they received the same exposure of light (McGinley, 2012). Irradiation location for the TLD has physical significance on the dose thus affecting the ECC; it should be located in a place where it cannot alter the process of determining the ECC values for the entire procedure.
References
Shapiro J., (2007). Radiation Protection: A Guide for Scientists and Physicians, Harvard University Press, Cambridge, MA
McGinley,P., (2012). Shielding Techniques for Radiation Oncology Facilities, 2ndedition: Medical Physics Publishing, Madison, WI
