[en] At high radiation doses, breaks in the DNA are considered the critical lesions in initiation of radiation- induced cancer. However, at the very low radiation doses relevant for the general public, the induction of such breaks will be rare, and other changes to the DNA such as DNA methylation may play a role in radiation responses. DNA methylation is the addition of a methyl group to cytosine in the DNA, usually where a cytosine is adjacent to a guanine (CpG). Methylation affects the way in which genes are read, and is inherited from cell to cell on replication. It is known that high dose radiation can cause changes in methylation in the genome but less is known about the effect of low dose radiation on methylation. We developed a sensitive assay to measure the levels of DNA methylation across the mouse genome by analysing a stretch of DNA sequence within Long Interspersed Nuclear Elements-1(LINE1) that comprise a very large proportion of the mouse and human genomes. Using bisulphite modification followed by quantitative real-time polymerase chain reaction (PCP) and high- resolution melt analysis, a very large pool of DNA sequences from throughout the genome can be studied indicating gain or loss of methylation. We validated the assay in vitro using the chemical demethylating agent 5'-aza-2' -deoxycytidine with changes at as few as 3% of CpG's being reproducibly detected. We have demonstrated a difference in the baseline levels of in vivo DNA methylation between male and female mice and between different tissues. Our initial results suggest no significant short-term or long-term changes in global DNA methylation after low dose whole-body X-radiation of 10 -Gy or 10 mGy, with a significant transient increase in DNA methylation observed 1 day after a high dose of 1 Gy. If the low radiation doses tested are inducing changes in global DNA methylation, these would appear to be smaller than the natural variation observed between the sexes and following the general stress of the sham-irradiation procedure itself.

[en] Conventional advice for minimising radiation exposure in interventional radiology is to use techniques such as low-dose fluoroscopy, lowest frame-rate cine, keeping the patient close to the image receptor, minimise the patient thickness intercepting the x-ray beam and using the largest field-of-view practicable. In the modern interventional environment not all of these strategies are feasible, and the expected dose-saving benefit from those that can be applied is not completely understood by the operators. To help increase understanding of the potential achievable dose savings a case with multiple extended interventional procedures was reviewed with detailed dose information taken from each cine run performed together with and additional data from the DICOM header. The impact of the chosen dose-reduction strategies was then assessed. This assessment showed that the use of low-dose fluoroscopy provided a 60% reduction in skin entrance dose during the fluoroscopy component of the exam and the use of the largest practical field size provided an additional 50% reduction in skin entrance doses in both the cine and general fluoroscopic modes. Knowledge gained from this assessment has allowed for a set of specific dose reduction strategies to be developed. These strategies have subsequently been applied to a case where an individual patient has required multiple, extended interventional procedures in a 6 month period.

[en] Objective: This study was carried out with the objective of determining the exposure rate from the patients to the one to conclude a study PET CT of our unit and to contrast them with the international recommendations. materials and methods: 100 patients were evaluated those that were practiced an exam of PET CT with F18-FDG, of which 54 were of feminine sex and 46 of masculine sex, the ages fluctuated among 9 to 90 years and the pesos among 20 to 100 kg, the stature of the patients fluctuated among 1.3-1.9 mt. A Ludlum, area monitor, Model 272D Remote, calibrated from the year 2017 was used.Exposure rate elaborated for this purpose and Excel 2016 program . Results: The exposure rate with which the patients retire when concluding its study PET CT is inside the one range of 10.1-11.1 uSv/h (3 patient) 6.1-10.9 uSv/h (46 patients) and of 0.8-5.9 uSv/h (51 patients); the which was not influenced by the age, weight, neither the patient's sex. Conclusions: the rate values of exposure with which the patients retire when concluding its study PET CT is very for under the international reference levels.

[en] According to study, Gafchromic films (XR-QA2) were found to be practical to measure radiation irradiated area over the surface of a phantom. The obtained results seem to agree with other published dosimetric studies covering other types of dental cone beam computed tomography (DCBCT) scanners. The dosimetry results are important in order to document and audit radiation doses delivered to patients undergoing imaging studies using DCBCT. Patient dosimetry is a central part of the medical physics biannual quality assurance testing in DCBCT

[en] During January 2015, gamma-absorbed dose rates of natural radionuclides above ground were calculated throughout different areas of the Peruvian Antarctic Station 'Machu Picchu'. The median outdoor gamma dose rate in air was determined as 43 ± 5 nGy/h. Using the data obtained in this study the median annual dose was found to be about 376 ± 44 μGy. These dose values are far below the doses reported in Peruvian territory due to the geographical location of the station. (author)

[en] To determine the patterns of dose rate reduction in single and multiple radioiodine (I-131) therapies in cases of well differentiated thyroid cancer patients. Study Design: Analytical series. Place and Duration of Study: Department of Nuclear Medicine and Radiation Physics, Multan Institute of Nuclear Medicine and Radiotherapy (MINAR), Multan, Pakistan, from December 2006 to December 2013. Methodology: Ninety three patients (167 therapies) with well differentiated thyroid cancer treated with different doses of I-131as an in-patient were inducted. Fifty four patients were given only single I-131 herapy dose ranging from 70 mCi (2590 MBq) to 150 mCi (5550 MBq). Thirty nine patients were treated with multiple I-131radioisotope therapy doses ranging from 80 mCi (2960 MBq) to 250 mCi (9250 MBq). T-test was applied on the sample data showed statistically significant difference between the two groups with p-value (p < 0.01) less than 0.05 taken as significant. Results: There were 68 females and 25 males with an age range of 15 to 80 years. Mean age of the patients were 36 years. Among the 93 cases of first time Radio Active Iodine (RAI) therapy, 59 cases (63%) were discharged after 48 hours. Among 39 patients who received RAI therapy second time or more, most were discharged earlier after achieving acceptable discharge dose rate i.e 25 micro r; 2 out of 39 (5%) were discharged after 48 hours. In 58% patients, given single I-131 therapy dose, majority of these were discharged after 48 hours without any major complications. Conclusion: For well differentiated thyroid cancer patients, rapid dose rate reduction is seen in patients receiving second or subsequent radioiodine (RAI) therapy, as compared to first time receiving RAI therapy. (author)

[en] Breast cancer is the most common malignancy among the women in the world, synchronous bilateral breast cancer is uncommon with the incidence of 2.1%. Bilateral Breast planning is time consuming and challenging because of the huge volume and nearby critical structures. Helical Tomotherapy (HT) is capable to deliver well tolerated homogeneous dose to bilateral breast without field overlapping

[en] In chest CT Image acquisition protocols should be based on research to maintain or improve the image quality and reduce risks due to the use of ionizing radiation For this reason, evaluation of the patient’s mass and volume needs to be observed, the analysis of the optical density, the dose measurement and contrast are some factors to be considered to optimize the parameters for image acquisition with diagnostic quality. The Study to determine the low dose study using radio chromic film Low dose chest CT- dose chamber assessment by using CTDI head and body phantom with ionization chamber and radio chromic film CTDI phantom will undergo CT acquisition with low dose protocols containing changes in: Kvp, mAs, Gantry rotation In the study it was compared the dose index values obtained by the pencil chamber measurement to the dose longitudinal profiles recorded by the film strips. Absorbed dose records by the radio chromic film strips for each position of measurement in the phantom were similar to the values obtained by the pencil ionization chamber. Film strips may be used as a reliable tool in the analysis of absorbed dose, in the search for optimizing the acquisition protocols for HRCT scan

[en] Use of diagnostic reference levels (DRLs) is an important tool for patient dose optimization in interventional radiology. DRLs are normally expressed in terms of kerma-area product (P_ka). However, no direct method is available to estimate the probability of skin reactions using system displayed quantities. The aim of this work was to measure skin entrance doses (SEDs) in patients undergoing coronary angiography (CA) and percutaneous coronary interventions (PCI) using Gafchromic films and establish DRLs. The details of patients, exposure parameters, and dose quantities were recorded for 572 patients. Out of these, skin doses were measured for selected 64 patients using Gafchromic film. Measured SEDs are in the range of 48.2–740 mGy and 84–1242 mGy for CA and PCI, respectively. The data of 572 patients were analyzed, and 75^th percentile of P_ka was calculated. DRLs for CA and PCI in terms of P_ka are found to be 34 and 134 Gy.cm², respectively. DRLs for CA and PCI in terms of cumulative air kerma (K_a) at reference point are found to be 590 mGy and 1930 mGy, respectively. SED has a good correlation with K_a, however, it does not correlate well with P_ka. (author)

[en] Ionizing radiation induces a spectrum of DNA damages which include single and clustered lesions in human cells. DNA damage response (DDR) activates various DNA-repair pathways to maintain the integrity of the genome. It may lead to alteration in transcription profile of genes. miRNAs and proteins. MicroRNAs are small single-stranded RNAs of 20-25 nt in length that regulate gene expression at post-transcriptional level. These are emerging regulators of various cellular responses, such as, DDR, cell signalling, apoptosis, carcinogenesis and cell death in response to radiation. Attempts have been made to study the expression pattern of selected miRNAs involved in DDR and repair pathways and their target genes in resting human peripheral blood mononuclear cells (PBMCs) exposed to low and high doses of γ radiation. Venous blood samples were collected from random and healthy individuals residing in normal and high level natural radiation areas of Kerala coast, and baseline expression was analyzed. Blood samples were also collected from Mumbai and PBMCs were exposed to acute doses of γ radiation from 10 20 cGy at a dose rate of 1.0 Gy/min using "6"0Co γ-rays. Total RNA and nuclear protein extract was prepared from irradiated PBMCs. mRNA and miRNA expression was studied by quantitative real time PCR and protein expression by Western blot. Our results showed a significant (p≤0.05) downregulation of miR 18 and upregulation of miR 155 in HNLRA individuals. Similarly, ERCC3, hRad23B, hMSH2 and hMSH6 showed a significant (p≤0.05) increased expression in HLNRA individuals as compared to NLNRA. In acute exposure, miR 155 showed a significantly (p≤0.01) increased expression across all the doses (0.1 2.0 Gy) after 4 h and 24 h as compared to control. The increase in miR 155 was correlated with downregulation of one of its target genes hMSH2 at protein level. (author)