Comparison of the energy-response factor of LiF and Al2O3 in radiotherapy beams.
A Monte Carlo study of the energy-response factor of aluminium oxide (Al2O3) and lithium fluoride (LiF) TLDs in kilovoltage and megavoltage photon beams relative to 60Co gamma rays has been performed using EGSnrc Monte Carlo simulations. The sensitive volume of the detector was simulated as a disc of diameter 2.85 mm and thickness 1 mm. The phantom material was water and the irradiation depth was 2.0 cm in kilovoltage photon beams and 5.0 cm for megavoltage photon beams. The results show that the energy-response of the Al2O3 and LiF-TLDs is constant within 3% for photon beam energies in the energy range of 60Co gamma rays to 25 MV X rays. However, both detectors show an enhanced response for kilovoltage photon beams, which in the case of 50 kV X rays is 3.2 times higher than that for 60Co gamma rays. The energy-response factor was 1.46 for LiF irradiated in 50 kV X rays. The Al2O3 detector has an energy-response that is 2.2 times higher than that of LiF in 50 kV X rays decreasing to 1.19 for 250 kV X rays. The results show that the addition of 0.1 or 1% of carbon by weight (as dopant) into the Al2O3 does not change the Monte Carlo determined energy-response factor by more than 1%.
Mobit
Paul
P
Medical Physics Department and Oncology Tom Baker Cancer Centre, 1331-29 Street N W, Calgary, Alberta, Canada T2N 4N2. pmobit@dmc.org
Agyingi
Ephraim
E
Sandison
George
G
D000465:Algorithms; D000537:Aluminum Oxide / Q000737:chemistry / Q000528:radiation effects*; D003198:Computer Simulation; D005459:Fluorides / Q000737:chemistry / Q000528:radiation effects*; D018499:Linear Energy Transfer; D018020:Lithium Compounds / Q000737:chemistry / Q000528:radiation effects*; D008422:Materials Testing; D008956:Models, Chemical; D015233:Models, Statistical; D009010:Monte Carlo Method; D011829:Radiation Dosage; D020266:Radiotherapy, Conformal / Q000295:instrumentation* / Q000379:methods; D012062:Relative Biological Effectiveness; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013819:Thermoluminescent Dosimetry / Q000379:methods*
D018020:Lithium Compounds; C027651:lithium fluoride; D000537:Aluminum Oxide; D005459:Fluorides