Prevention of gamma-radiation-induced DNA damage in human lymphocytes using a serine-magnesium sulfate mixture

Objectives: Ionising radiation has deleterious effects on human cells. N-acetylcysteine [NAC] and cysteine, the active metabolite of NAC, are well-known radioprotective agents. Recently, a serine-magnesium sulfate combination was proposed as an antidote for organophosphate toxicity. This study aimed to investigate the use of a serine-magnesium sulfate mixture in the prevention of gamma-radiation-induced DNA damage in human lymphocytes as compared to NAC and cysteine

Methods: This study was carried out at the Iran University of Medical Sciences, Tehran, Iran, between April and September 2016. Citrated blood samples of 7 mL each were taken from 22 healthy subjects. Each sample was divided into 1 mL aliquots, with the first aliquot acting as the control while the second was exposed to 2 Gy of gamma-radiation at a dose rate of 102.7 cGy/minute. The remaining aliquots were separately incubated with 600 micro M concentrations each of serine, magnesium sulfate, serine-magnesium sulfate, NAC and cysteine before being exposed to 2 Gy of gamma-radiation. Lymphocytes were isolated using a separation medium and methyl-thiazole-tetrazolium and comet assays were used to evaluate cell viability and DNA damage, respectively

Results: The serine-magnesium sulfate mixture significantly increased lymphocyte viability and reduced DNA damage in comparison to serine, magnesium sulfate, NAC or cysteine alone [P <0.01 each]

Conclusion: The findings of the present study support the use of a serine-magnesium sulfate mixture as a new, non-toxic, potent and efficient radioprotective agent

[Verification of the accuracy of the delivered dose in pelvic and breast cancer radiotherapy by in-vivo semi-conductor dosimetry]

Delivering maximum dose to tumor and minimum dose to normal tissues is the most important goal in radiotherapy. According to ICRU, the maximum acceptable uncertainty in the delivered dose compared to the prescribed dose should be lower than 5% and this is because of the relationship between absorbed dose, tumor control and normal tissue damage. Absorbed dose accuracy is investigated by an in vivo dosimetry method. In this paper, we compared absorbed dose in the tumors of the breast and pelvic region against the calculated dose. The amount of deviations and the factors that cause this deviation in dose delivery to patients and some methods for decreasing them were evaluated. The entrance and exit doses of 36 pelvi-region cancer patients and 38 breast cancer patients who were treated by cobalt-60 teletherapy were measured using p-type diodes. It should be noted that the transmission method was used to assess the dose at isocenter. Two ionization chambers [0.6cc and 0.3cc] were used for calibration and determination of the correction coefficients in water and slab phantoms. Deviations between calculated and measured doses of entrance, exit and midline point were calculated and the results were shown using histograms. The average and standard deviation for entrance, exit and midline points for pelvis cancer were assessed to be about 0.10%, -1.86% and -1.35% for mean deviation an d5.03%, 7.32% and 5.86% for standard deviation, respectively. The corresponding data for breast cancer were 0.78%, 5.29% and 3.59% for mean deviation and 5.97%, 10.23% and 9.86%, respectively. There was not significant difference between the calculated and measured doses [p>0.1], except exit dose in breast cancer [p<0.05]. The temperature and angle of incidence correction factors were neglected due to their less than 1% deviations. Some error sources are patient setup error, patient motion and dose calculation algorithm error [due to ignoring in homogeneity and patient curvature]. As no significant deviations were found in midline dose, the method used has an acceptable accuracy. In vivo dosminetry can perform a basic role in the quality control of radiotherapy departments

[ dosimetric evaluation of organs at risk in prostate radiation therapy using a MAGIC gel dosimeter]

Multiple fields and presence of hetrerogeneities create complex dose distributions that need three dimentisonal dosimetry. In this work, we investigated MR-based MAGIC gel dosimetry as a three-dimentional dosimetry technique to measure the delivered dose to bladder and rectum in prostate radiation therapy. A heterogeneous slab phantom including bones was made. Paired cubes in the phantom representing bladder and prostate and a cylindrical container representing rectum were filled with MAGIC gel and placed in the anthropomorphic pelvic phantom. The phantom was irradiated with four beams as planned using a treatment planning system [TPS]. Magnetic resonance transverse relaxation rate images were acquired and turned into dose distribution maps using a calibration curve. This calibration curve was obtained by linear fitting to R2 values of 4 test tubes against their given known doses. Image processing and data analysis were preformed in MATLAB 7 software. The gel dosimeter was validated using an ionization chamber. Dose maps and dose volume histograms [DVHs] were compared with dose distributions and DVHs of the TPS. Mean "distance-to-agreement" and mean "does difference" were 2.98 mm and 6.2%, respectively, in the comparison of profiles obtained from ionization chamber and gel dostimetry. Mean relative difference of DHVs between gel dosimetry and TPs data were 3.04%, 10.4% and 11.7%,for prostate, bladder and rectum, respectively. Gel dosimetry is a good method for three dimensional dosimetry although it has a low precision in high close gradient regions. This method can be used for evaluation of complicated dose distribution accuracy in 3D conformal radiotherapy, especially in presence of heterogeneities