Assessment of Potentially Malignant Disorders among Men and Women in South Bihar Population.

Oral cancer is detected in 270,000 people per annum or around 3% of all malignancies. It ranks sixth among males and twelve among females in terms of prevalence. Mostly, all oral squamous cell carcinomas (OSCC) are responsible for 92-95% of cases. Oral carcinoma starts five years before the average age of PMD patients, who range in age from 5th to 6th decade of life. Thus, the goal of this study is to identify any relevant risk factors and assess the incidence of oral possibly malignant disorders in both men and women living in rural Bhojpur District, Bihar. A cross-sectional study has been carried out at the Sadar Hospital in Bhojpur by surveying volunteers at various oral health screening and treatment camps held from January 2022 to July 2022. A pre-validated questionnaire adapted and modified from Kumar S et al. was utilized to collect data in a qualitative interview. It was discovered that (17%) of all people had an oral possibly malignant disease. OSMF was the lesion with the greatest prevalence (7%) and lichen planus having the smallest prevalence (1%). Malignancy frequently develops from oral potential malignant diseases. Diabetes and BMI were inversely related, which is expected provided the socioeconomic position.

Protocol for the isolation of tumor cell-derived extracellular vesicles followed by in vivo metastasis assessment in a murine ovarian cancer model.

Extracellular vesicles (EVs) play a crucial role in facilitating communication between cancer cells and their immediate or remote microenvironments, thereby promoting the extensive spread of cancer throughout the body. In this context, we present a protocol for the isolation of tumor cell-derived EVs followed by in vivo metastasis assessment in a murine ovarian cancer model. We describe steps for the isolation and characterization of EVs from ID8 cells, development of a metastatic mouse model, and sample preparation for flow cytometry. For complete details on the use and execution of this protocol, please refer to Gupta et al.1.

Quality of life assessment in testicular non-seminomatous germ cell tumour survivors.

PURPOSE: Patients with Germ cell tumours (GCT) are at risk of long-term toxicities due to multimodality therapy. It is debatable whether there is an impact on the quality of life(QoL) of GCT survivors. METHODS: A case-control study was conducted at a tertiary care centre in India, using the EORTC QLQ C30 questionnaire, to compare the QoL between GCT survivors(disease free > 2 years) and healthy matched controls. A multivariate regression model was used to identify factors affecting QoL. RESULTS: A total of 55 cases and 100 controls were recruited. Cases had a median age of 32 years (interquartile range, IQR 28-40 years), ECOG PS of 0-1(75%), advanced stage III (58%), chemotherapy (94%) and 66% were > 5 years from diagnosis. The median age of controls: 35 years (IQR 28-43 years). A statistically significant difference was seen for emotional (85.8 ± 14.2 vs 91.7 ± 10.4, p 0.005), social(83.0 ± 22.0 vs 95.2 ± 9.6, p < 0.001) and global scales (80.4 ± 21.1 vs 91.3 ± 9.7, p < 0.001). Cases had more nausea and vomiting(3.3 ± 7.4 vs 1.0 ± 3.9, p 0.015), pain(13.9 ± 13.9 vs 4.8 ± 9.8, p < 0.001), dyspnea(7.9 + 14.3 vs 2.7 ± 9.1, p 0.007), and appetite loss(6.7 ± 14.9 vs 1.9 ± 7.9, p 0.016) and greater financial toxicity(31.5 ± 32.3 vs 9.0 ± 16.3, p < 0.001). Adjusting for age, performance status, BMI, stage, chemotherapy, RPLND, recurrent disease, and time since diagnosis, no predictive variables were significant. CONCLUSION: There is a detrimental impact of history of GCT in long term survivors of GCT.

Spatial variation in groundwater quality and health risk assessment for fluoride and nitrate in Chhotanagpur Plateau, India.

The evaluation of groundwater quality is vital to assess the risk to human health. The present study assesses groundwater quality for drinking purposes and human health risks due to ingestion of fluoride and nitrate through drinking water in Chhotanagpur Plateau, India, using geoinformation techniques. For drinking water quality assessment, analyzed parameters were compared with World Health Organization (WHO) standards, and water quality index (WQI) was used. Results reveal that most of the samples come within the desired limit suggested by WHO. In a few samples, conductivity, hardness, chloride, sulfate, and calcium are higher than the desirable limit, whereas fluoride and nitrate are beyond the permissible limit in 70% and 27% of the samples, respectively. WQI highlights that poor to very poor water is present in 25% of the samples. Anthropogenic activities have played a critical role in deteriorating groundwater quality, resulting in harmful impacts on human health. To assess non-carcinogenic health risks, the hazard quotient (HQ) and total hazard index (THI) were computed. THI ranges from 0.01 to 7.46, 0.01 to 7.05, and 0.01 to 9.05 for males, females, and children, respectively. THI is greater than the allowable limit in 84%, 78%, and 89% of the samples for males, females, and children, respectively, indicating high risk to human health, particularly children. The study advocates proper water management strategies. Knowledge of spatial variation and anomalous concentration is vital for groundwater management as well as health risk assessment. The findings of this study will be helpful to government officials, policy planners, and local communities.

The elimination of an artifact in the FLURZnrc-derived electron-fluence spectrum close to the Spencer-Attix-Nahum cut-offΔ.

Objective. An artifact in the electron fluence, differential in energy,ΦE, computed by the EGSnrc Monte-Carlo user-code FLURZnrc, was identified and a methodology has been developed to eliminate it. This artifact manifests itself as an 'unphysical' increase inΦEat energies close to the production threshold for knock-on electrons,AE; this in turn causes an over-estimation of the Spencer-Attix-Nahum (SAN) 'track-end' dose by a factor ∼1.5, thereby inflating the dose derived from the SAN cavity integral. For SAN cut-offΔSAN =1 keV for 1 MeV and 10 MeV photons in water, aluminium and copper, withmaximum fractional energy loss per step ESTEPE= 0.25 (default value), this anomalous increase in the SAN cavity-integral dose is of the order of 0.5%-0.7%.Approach. The dependence ofΦEon the value ofAE(the maximum energy loss involved in the restricted electronic stopping power (dE/ds)AE) at or close toΔSANwas investigated; this was done for different values ofESTEPE.Main results.The error in the electron-fluence spectrum occurs whenΔSANis setclose toorequal to AE; this error disappears (at the 0.1% level or better) ifAEis set ≤ 0.5 ×ΔSAN. However, ifESTEPE≤ 0.04 the error in the electron-fluence spectrum is negligible even whenΔSAN=AE.Significance. An artifact in the FLURZnrc-derived electron fluence, differential in energy, at or close to electron energyAEhas been identified. It is shown how this artifact can be avoided, thereby ensuring the accurate evaluation of the SAN cavity integral.

The PTW microSilicon diode: Performance in small 6 and 15 MV photon fields and utility of density compensation.

PURPOSE: We have experimentally and computationally characterized the PTW microSilicon 60023-type diode's performance in 6 and 15 MV photon fields ≥5 × 5 mm2 projected to isocenter. We tested the detector on- and off-axis at 5 and 15 cm depths in water, and investigated whether its response could be improved by including within it a thin airgap. METHODS: Experimentally, detector readings were taken in fields generated by a Varian TrueBeam linac and compared with doses-to-water measured using Gafchromic film and ionization chambers. An unmodified 60023-type diode was tested along with detectors modified to include 0.6, 0.8, and 1.0 mm thick airgaps. Computationally, doses absorbed by water and detectors' sensitive volumes were calculated using the EGSnrc/BEAMnrc Monte Carlo radiation transport code. Detector response was characterized using k Q c l i n , 4 cm f c l i n , 4 cm , a factor that corrects for differences in the ratio of dose-to-water to detector reading between small fields and the reference condition, in this study 5 cm deep on-axis in a 4 × 4 cm2 field. RESULTS: The greatest errors in measurements of small field doses made using uncorrected readings from the unmodified 60023-type detector were over-responses of 2.6% ± 0.5% and 5.3% ± 2.0% determined computationally and experimentally, relative to the reading-per-dose in the reference field. Corresponding largest errors for the earlier 60017-type detector were 11.9% ± 0.6% and 11.7% ± 1.4% over-responses. Adding even the thinnest, 0.6 mm, airgap to the 60023-type detector over-corrected it, leading to under-responses of up to 4.8% ± 0.6% and 5.0% ± 1.8% determined computationally and experimentally. Further, Monte Carlo calculations indicate that a detector with a 0.3 mm airgap would read correctly to within 1.3% on-axis. The ratio of doses at 15 and 5 cm depths in water in a 6 MV 4 × 4 cm2 field was measured more accurately using the unmodified 60023-type detector than using the 60017-type detector, and was within 0.3% of the ratio measured using an ion chamber. The 60023-type diode's sensitivity also varied negligibly as dose-rate was reduced from 13 to 4 Gy min-1 by decreasing the linac pulse repetition frequency, whereas the sensitivity of the 60017-type detector fell by 1.5%. CONCLUSIONS: The 60023-type detector performed well in small fields across a wide range of beam energies, field sizes, depths, and off-axis positions. Its response can potentially be further improved by adding a thin, 0.3 mm, airgap.

Monte-Carlo-computed dose, kerma and fluence distributions in heterogeneous slab geometries irradiated by small megavoltage photon fields.

Small-field dosimetry is central to the planning and delivery of radiotherapy to patients with cancer. Small-field dosimetry is beset by complex issues, such as loss of charged-particle equilibrium (CPE), source occlusion and electron-scattering effects in low-density tissues. The purpose of the present research is the elucidation of the fundamental physics of small fields through the computation of absorbed dose, kerma and fluence distributions in heterogeneous media using the Monte-Carlo (MC) method. Absorbed dose and kerma were computed using the DOSRZnrc MC user-code for beams with square field sizes ranging from 0.25 × 0.25 to 7 × 7 cm2 (for 6 MV 'full linac' geometry) and 0.25 × 0.25 to 16 × 16 cm2 (for 15 MV 'full linac' geometry). In the bone inhomogeneity the dose increases (vs. homogeneous water) for field sizes <1 × 1 cm2 at 6 MV and ⩽3 × 3 cm2 at 15 MV and decreases (vs. homogeneous water) for field sizes ⩾3 × 3 cm2 at 6 MV and ⩾5 × 5 cm2 at 15 MV. In the lung inhomogeneity there is negligible decrease in dose compared to in uniform water for field sizes >5 × 5 cm2 at 6 MV and ⩾16 × 16 cm2 at 15 MV, consistent with the Fano theorem. The near-unity value of the absorbed-dose to collision-kerma ratio, D/K col, at the centre of the bone and lung slabs in the heterogeneous phantom demonstrates that CPE is achieved in bone for field sizes >1 × 1 cm2 at 6 MV and ⩾5 × 5 cm2 at 15 MV; CPE is achieved in lung at field sizes >5 × 5 cm2 at 6 MV and ⩾16 × 16 cm2 at 15 MV. Electron-fluence perturbation factors for the 0.25 × 0.25 cm2 field were 1.231 and 1.403 for bone-to-water and 0.454 and 0.333 for lung-to-water at 6 and 15 MV, respectively. For field sizes large enough for quasi-CPE, the MC-derived dose-perturbation factors, lung-to-water, [Formula: see text] were close to unity; electron-fluence perturbation factors, lung-to-water, [Formula: see text] were ∼1.0, consistent with the Fano theorem. At 15 MV in the lung inhomogeneity the magnitude and also the 'shape' of the primary electron-fluence spectrum differ significantly from that in water. Beam penumbrae relative to water are narrower in the bone inhomogeneity and broader in the lung inhomogeneity for all field sizes.

Density compensated diodes for small field dosimetry: comprehensive testing and implications for design.

PURPOSE: In small megavoltage photon fields, the accuracies of an unmodified PTW 60017-type diode dosimeter and six diodes modified by adding airgaps of thickness 0.6-1.6 mm and diameter 3.6 mm have been comprehensively characterized experimentally and computationally. The optimally thick airgap for density compensation was determined, and detectors were micro-CT imaged to investigate differences between experimentally measured radiation responses and those predicted computationally. METHODS: Detectors were tested on- and off-axis, at 5 and 15 cm depths in 6 and 15 MV fields ≥ 0.5 × 0.5 cm2. Computational studies were carried out using the EGSnrc/BEAMnrc Monte Carlo radiation transport code. Experimentally, radiation was delivered using a Varian TrueBeam linac and doses absorbed by water were measured using Gafchromic EBT3 film and ionization chambers, and compared with diode readings. Detector response was characterized via the [Formula: see text] formalism, choosing a 4 × 4 cm2 reference field. RESULTS: For the unmodified 60017 diode, the maximum error in small field doses obtained from diode readings uncorrected by [Formula: see text] factors was determined as 11.9% computationally at +0.25 mm off-axis and 5 cm depth in a 15 MV 0.5 × 0.5 cm2 field, and 11.7% experimentally at -0.30 mm off-axis and 5 cm depth in the same field. A detector modified to include a 1.6 mm thick airgap performed best, with maximum computationally and experimentally determined errors of 2.2% and 4.1%. The 1.6 mm airgap deepened the modified dosimeter's effective point of measurement by 0.5 mm. For some detectors significant differences existed between responses in small fields determined computationally and experimentally, micro-CT imaging indicating that these differences were due to within-tolerance variations in the thickness of an epoxy resin layer. CONCLUSIONS: The dosimetric performance of a 60017 diode detector was comprehensively improved throughout 6 and 15 MV small photon fields via density compensation. For this approach to work well with good detector-to-detector reproducibility, tolerances on dense component dimensions should be reduced to limit associated variations of response in small fields, or these components should be modified to have more water-like densities.

Reply to comment on 'origins of the changing detector response in small megavoltage photon radiation fields'.

Andreo and Benmakhlouf (2017 Phys. Med. Biol. 62 1518-32) have disputed a finding of Scott et al (2012 Phys. Med. Biol. 57 4461-76) that the variation with field-size of the response of small ion chambers and solid-state dosimeters in small megavoltage photon radiation fields can largely be attributed to density. Further evidence for this finding was provided by Fenwick et al (2018 Phys. Med. Biol. 63 125003), but Andreo and Benmakhlouf (2018 Phys. Med. Biol. 63 125003) have now challenged the methodology used in that study. Specifically, Andreo and Benmakhlouf suggest that mass stopping-powers of fictitious materials used in Monte Carlo radiation transport calculations should be adjusted with material density according to the polarization effect, as if the materials were real and created by compressing other real materials. In this reply, we observe that fictitious materials are not real, and therefore their densities, mass stopping-powers and microscopic radiation interaction cross-sections can be freely and independently chosen to provide the clearest answers to the questions being studied. And we note that the key role played by density in small field detector response was further confirmed by our group back in 2013, using fictitious materials in which mass stopping-powers were adjusted with density, as preferred by Andreo and Benmakhlouf, as well as being held fixed, with very similar results being obtained in both circumstances (Underwood et al 2013a Med. Phys. 40 082102).

Origins of the changing detector response in small megavoltage photon radiation fields.

Differences in detector response between measured small fields, f clin, and wider reference fields, f msr , can be overcome by using correction factors [Formula: see text] or by designing detectors with field-size invariant responses. The changing response in small fields is caused by perturbations of the electron fluence within the detector sensitive volume. For solid-state detectors, it has recently been suggested that these perturbations might be caused by the non-water-equivalent effective atomic numbers Z of detector materials, rather than by their non-water-like densities. Using the EGSnrc Monte Carlo code we have analyzed the response of a PTW 60017 diode detector in a 6 MV beam, calculating the [Formula: see text] correction factor from computed doses absorbed by water and by the detector sensitive volume in 0.5 × 0.5 and 4 × 4 cm2 fields. In addition to the 'real' detector, fully modelled according to the manufacturer's blue-prints, we calculated doses and [Formula: see text] factors for a 'Z → water' detector variant in which mass stopping-powers and microscopic interaction coefficients were set to those of water while preserving real material densities, and for a 'density → 1' variant in which densities were set to 1 g cm-3, leaving mass stopping-powers and interaction coefficients at real levels. [Formula: see text] equalled 0.910 ± 0.005 (2 standard deviations) for the real detector, was insignificantly different at 0.912 ± 0.005 for the 'Z → H2O' variant, but equalled 1.012 ± 0.006 for the 'density → 1' variant. For the 60017 diode in a 6 MV beam, then, [Formula: see text] was determined primarily by the detector's density rather than its atomic composition. Further calculations showed this remained the case in a 15 MV beam. Interestingly, the sensitive volume electron fluence was perturbed more by detector atomic composition than by density; however, the density-dependent perturbation varied with field-size, whereas the Z-dependent perturbation was relatively constant, little affecting [Formula: see text].

Assessment of anti-CarP antibodies, disease activity and quality of life in rheumatoid arthritis patients on conventional and biological disease-modifying antirheumatic drugs.

OBJECTIVE: Good biomarkers are important to guide decisions in the clinical management of rheumatoid arthritis (RA). RA patients harbor antibodies directed against carbamylated proteins which may predict joint damage. This study investigated whether antibodies against carbamylated proteins (anti-CarP) may serve as surrogate prognostic markers. MATERIAL AND METHODS: Fifty-three patients with a diagnosis of rheumatoid arthritis according to ACR 1987 criteria were included. Blood samples were analyzed for CarP antibody levels using the ELISA method. Quality of life (QoL) was assessed by the WHO SF-36 questionnaire, and disease activity was assessed using the DAS28 calculator. Newly diagnosed patients were assessed at the first visit and at 12 weeks of treatment, while a single assessment was made for patients already on maintenance therapy. RESULTS: Out of 53 patients, 22 had titers of anti-CarP above the cut-off range and considered as positive for anti-CarP antibodies. Anti-CarP antibody serum level was significantly higher in patients with deformity of joints and with erosions in comparison to those without any destructive changes (p < 0.05). There was a weak positive correlation between anti-CarP and DAS 28 (p > 0.05). Also there was a weak negative correlation in all domains of quality of life with anti-CarP antibody titers (p > 0.05). There was no significant correlation between titers of anti-CarP antibodies and presence or absence of rheumatoid factor. CONCLUSIONS: Serum levels of anti-CarP antibodies in RA patients with joint erosions/deformities were much higher than in those without any joint damage. Anti-CarP antibodies may have good prognostic value in RA patients with erosions. Disease activity and QoL of RA patients improved during treatment, but no correlation was found between DAS 28/QoL and anti-CarP antibody serum levels.

Breakdown of Bragg-Gray behaviour for low-density detectors under electronic disequilibrium conditions in small megavoltage photon fields.

In small photon fields ionisation chambers can exhibit large deviations from Bragg-Gray behaviour; the EGSnrc Monte Carlo (MC) code system has been employed to investigate this 'Bragg-Gray breakdown'. The total electron (+positron) fluence in small water and air cavities in a water phantom has been computed for a full linac beam model as well as for a point source spectrum for 6 MV and 15 MV qualities for field sizes from 0.25 × 0.25 cm(2) to 10 × 10 cm(2). A water-to-air perturbation factor has been derived as the ratio of total electron (+positron) fluence, integrated over all energies, in a tiny water volume to that in a 'PinPoint 3D-chamber-like' air cavity; for the 0.25 × 0.25 cm(2) field size the perturbation factors are 1.323 and 2.139 for 6 MV and 15 MV full linac geometries respectively. For the 15 MV full linac geometry for field sizes of 1 × 1 cm(2) and smaller not only the absolute magnitude but also the 'shape' of the total electron fluence spectrum in the air cavity is significantly different to that in the water 'cavity'. The physics of this 'Bragg-Gray breakdown' is fully explained, making reference to the Fano theorem. For the 15 MV full linac geometry in the 0.25 × 0.25 cm(2) field the directly computed MC dose ratio, water-to-air, differs by 5% from the product of the Spencer-Attix stopping-power ratio (SPR) and the perturbation factor; this 'difference' is explained by the difference in the shapes of the fluence spectra and is also formulated theoretically. We show that the dimensions of an air-cavity with a perturbation factor within 5% of unity would have to be impractically small in these highly non-equilibrium photon fields. In contrast the dose to water in a 0.25 × 0.25 cm(2) field derived by multiplying the dose in the single-crystal diamond dosimeter (SCDDo) by the Spencer-Attix ratio is within 2.9% of the dose computed directly in the water voxel for full linac geometry at both 6 and 15 MV, thereby demonstrating that this detector exhibits quasi Bragg-Gray behaviour over a wide range of field sizes and beam qualities.

Determination of surface dose rate of indigenous (32)P patch brachytherapy source by experimental and Monte Carlo methods.

Isotope production and Application Division of Bhabha Atomic Research Center developed (32)P patch sources for treatment of superficial tumors. Surface dose rate of a newly developed (32)P patch source of nominal diameter 25 mm was measured experimentally using standard extrapolation ionization chamber and Gafchromic EBT film. Monte Carlo model of the (32)P patch source along with the extrapolation chamber was also developed to estimate the surface dose rates from these sources. The surface dose rates to tissue (cGy/min) measured using extrapolation chamber and radiochromic films are 82.03±4.18 (k=2) and 79.13±2.53 (k=2) respectively. The two values of the surface dose rates measured using the two independent experimental methods are in good agreement to each other within a variation of 3.5%. The surface dose rate to tissue (cGy/min) estimated using the MCNP Monte Carlo code works out to be 77.78±1.16 (k=2). The maximum deviation between the surface dose rates to tissue obtained by Monte Carlo and the extrapolation chamber method is 5.2% whereas the difference between the surface dose rates obtained by radiochromic film measurement and the Monte Carlo simulation is 1.7%. The three values of the surface dose rates of the (32)P patch source obtained by three independent methods are in good agreement to one another within the uncertainties associated with their measurements and calculation. This work has demonstrated that MCNP based electron transport simulations are accurate enough for determining the dosimetry parameters of the indigenously developed (32)P patch sources for contact brachytherapy applications.

Monte-Carlo-derived insights into dose-kerma-collision kerma inter-relationships for 50 keV-25 MeV photon beams in water, aluminum and copper.

The relationships between D, K and Kcol are of fundamental importance in radiation dosimetry. These relationships are critically influenced by secondary electron transport, which makes Monte-Carlo (MC) simulation indispensable; we have used MC codes DOSRZnrc and FLURZnrc. Computations of the ratios D/K and D/Kcol in three materials (water, aluminum and copper) for large field sizes with energies from 50 keV to 25 MeV (including 6-15 MV) are presented. Beyond the depth of maximum dose D/K is almost always less than or equal to unity and D/Kcol greater than unity, and these ratios are virtually constant with increasing depth. The difference between K and Kcol increases with energy and with the atomic number of the irradiated materials. D/K in 'sub-equilibrium' small megavoltage photon fields decreases rapidly with decreasing field size. A simple analytical expression for X̅, the distance 'upstream' from a given voxel to the mean origin of the secondary electrons depositing their energy in this voxel, is proposed: X̅(emp) ≈ 0.5R(csda)(E̅(0)), where E̅(0) is the mean initial secondary electron energy. These X̅(emp) agree well with 'exact' MC-derived values for photon energies from 5-25 MeV for water and aluminum. An analytical expression for D/K is also presented and evaluated for 50 keV-25 MeV photons in the three materials, showing close agreement with the MC-derived values.

Informal e-waste recycling: environmental risk assessment of heavy metal contamination in Mandoli industrial area, Delhi, India.

Nowadays, e-waste is a major source of environmental problems and opportunities due to presence of hazardous elements and precious metals. This study was aimed to evaluate the pollution risk of heavy metal contamination by informal recycling of e-waste. Environmental risk assessment was determined using multivariate statistical analysis, index of geoaccumulation, enrichment factor, contamination factor, degree of contamination and pollution load index by analysing heavy metals in surface soils, plants and groundwater samples collected from and around informal recycling workshops in Mandoli industrial area, Delhi, India. Concentrations of heavy metals like As (17.08 mg/kg), Cd (1.29 mg/kg), Cu (115.50 mg/kg), Pb (2,645.31 mg/kg), Se (12.67 mg/kg) and Zn (776.84 mg/kg) were higher in surface soils of e-waste recycling areas compared to those in reference site. Level exceeded the values suggested by the US Environmental Protection Agency (EPA). High accumulations of heavy metals were also observed in the native plant samples (Cynodon dactylon) of e-waste recycling areas. The groundwater samples collected form recycling area had high heavy metal concentrations as compared to permissible limit of Indian Standards and maximum allowable limit of WHO guidelines for drinking water. Multivariate analysis and risk assessment studies based on total metal content explains the clear-cut differences among sampling sites and a strong evidence of heavy metal pollution because of informal recycling of e-waste. This study put forward that prolonged informal recycling of e-waste may accumulate high concentration of heavy metals in surface soils, plants and groundwater, which will be a matter of concern for both environmental and occupational hazards. This warrants an immediate need of remedial measures to reduce the heavy metal contamination of e-waste recycling sites.

Using cavity theory to describe the dependence on detector density of dosimeter response in non-equilibrium small fields.

The dose imparted by a small non-equilibrium photon radiation field to the sensitive volume of a detector located within a water phantom depends on the density of the sensitive volume. Here this effect is explained using cavity theory, and analysed using Monte Carlo data calculated for schematically modelled diamond and Pinpoint-type detectors. The combined impact of the density and atomic composition of the sensitive volume on its response is represented as a ratio, Fw,det, of doses absorbed by equal volumes of unit density water and detector material co-located within a unit density water phantom. The impact of density alone is characterized through a similar ratio, Pρ -, of doses absorbed by equal volumes of unit and modified density water. The cavity theory is developed by splitting the dose absorbed by the sensitive volume into two components, imparted by electrons liberated in photon interactions occurring inside and outside the volume. Using this theory a simple model is obtained that links Pρ - to the degree of electronic equilibrium, see, at the centre of a field via a parameter Icav determined by the density and geometry of the sensitive volume. Following the scheme of Bouchard et al (2009 Med. Phys. 36 4654-63) Fw,det can be written as the product of Pρ -, the water-to-detector stopping power ratio [L[overline](Δ)/ρ](w)(det), and an additional factor Pfl -. In small fields [L[overline](Δ)/ρ](w)(det) changes little with field-size; and for the schematic diamond and Pinpoint detectors Pfl - takes values close to one. Consequently most of the field-size variation in Fw,det originates from the Pρ - factor. Relative changes in see and in the phantom scatter factor sp are similar in small fields. For the diamond detector, the variation of Pρ - with see (and thus field-size) is described well by the simple cavity model using an Icav parameter in line with independent Monte Carlo estimates. The model also captures the overall field-size dependence of Pρ - for the schematic Pinpoint detector, again using an Icav value consistent with independent estimates.

Assessment of health risks with reference to oxidative stress and DNA damage in chromium exposed population.

Trivalent chromium [Cr(III)] is widely used in tanning industrial processes. The population living in tanning industrial area is continuously exposed to Cr(III) which appears to be associated with both acute and chronic health problems. Therefore, the aim of this study was to evaluate the health risk with special reference to oxidative stress parameters (malondialdehyde - MDA, glutathione - GSH, and superoxide dismutase - SOD) and DNA damage in 100 Cr-exposed and 100 unexposed populations. The total blood Cr level, SOD level, MDA level and DNA damage were significantly (p<0.05) higher and GSH level was significantly (p<0.05) lower in exposed group as compared to the unexposed group. The altered oxidative stress parameters and DNA damage were found to be slightly higher in female population of both groups. In simple and multiple correlation analyses (adjusted with potential confounders), blood Cr level showed negative significant correlation with GSH level and positive significant correlation with level of MDA, SOD and DNA damage in both groups. The overall prevalence of morbidity was found to be significantly (p<0.05) higher in the exposed group as compared to the unexposed group. In the exposed group, the prevalence of respiratory illness is highest, followed by diabetes, gastrointestinal tract problems and dermal problems respectively. Our results concluded that the Cr(III) exposed population is at high risk for health hazards and the female population is slightly more susceptible to Cr(III) exposure.

Establishment of air kerma reference standard for low dose rate Cs-137 brachytherapy sources.

A guarded cylindrical graphite ionization chamber of nominal volume 1000 cm3 was designed and fabricated for use as a reference standard for low-dose rate 137Cs brachytherapy sources. The air kerma calibration coefficient (N(K)) of this ionization chamber was estimated analytically using Burlin's general cavity theory, as well as by the Monte Carlo simulation and validated experimentally using Amersham CDCS-J-type 137Cs reference source. In the analytical method, the N(K) was calculated for 662 keV gamma rays of 137Cs brachytherapy source. In the Monte Carlo method, the geometry of the measurement setup and physics-related input data of the 137Cs source and the surrounding material were simulated using the Monte Carlo N-Particle code. The photon energy fluence was used to arrive at the reference air kerma rate (RAKR) using mass energy absorption coefficient. The energy deposition rates were used to simulate the value of charge rate in the ionization chamber, and the N(K) was determined. The analytical and Monte Carlo values of N(K) of the cylindrical graphite ionization chamber for 137Cs brachytherapy source are in agreement within 1.07%. The deviation of analytical and Monte Carlo values from experimental values of N(K) is 0.36% and 0.72%, respectively. This agreement validates the analytical value, and establishes this chamber as a reference standard for RAKR or AKS measurement of 137Cs brachytherapy sources.

A case study: biomedical waste management practices at city hospital in Himachal Pradesh.

Proper management of biomedical waste is a crucial issue for maintaining human health and the environment. The waste generated in the hospitals has the potential for spreading infections and causing diseases. The study was conducted by visiting a near by hospital in order to get acquainted with the generation of the biomedical waste and their disposal strategies. The study includes an assortment of details about the quantity of different types of waste generated, their handling, treatment, final disposal and various management strategies adopted by the hospital. The survey was conducted by asking various questions regarding the issue by the waste management team and the workers involved in managing the waste.