Improvement on the performance N-(3-methoxypropyl)acrylamide polymer-gel dosimeter by the addition of inorganic salt for application in radiotherapy dosimetry

The effect of lithium chloride (LiCl) on the dose–response performance of the N-(3-methoxypropyl)acrylamide polymer-gel dosimeter (NMPAGAT) was studied for 3-D dose measurements. The NMPAGAT-LiCl dosimeters were irradiated for various doses using a 6 MV medical linear accelerator. A 0.5 Tesla nuclear magnetic resonance (NMR) instrument was used to scan the signal development of the irradiated dosimeters in terms of the spin–spin relaxation rate (R2 = 1/T2) of hydrogen protons within the water molecule. The results show that the R2 dose–response of NMPAGAT-LiCl gels improved with increasing the concentration of LiCl. The R2 sensitivity of dosimeter with a concentration of 1000 mM LiCl was 4 times higher than the same gel without LiCl in the range dose–response of 0–4 Gy. In addition, no significant effects were introduced to the LiCl gel formulation by varying the dose rate and photon energy. R2 of the gel dosimeter was not affected by changing irradiation temperature in the range of 15–25 °C. The dose–response decreased with increasing scanning temperature and was stable for up to 4 days after irradiation.