Lakhwant Singh

Indoor radon measurements in dwellings of Kulu area, Himachal Pradesh, using solid state nuclear track detectors

Abstract In the present paper, the results of radon activity recorded in domestic regions of the Kulu area (Himachal Pradesh, India) known for uranium mineralisation are reported. Time integrated track etch technique has been used for the measurement of indoor radon levels. Bare cellulose nitrate LR-115 type II films have been used as detectors in the survey of radon. The calibration constant of 4.8×10 2 tracks cm −2 day −1 per WL of radon at equilibrium (which corresponds to 12.97×10 −2 tracks cm −2 d −1 per Bq m −3 ) determined by Subba Ramu et al. (Sci. Total Environ. 73 (1988) 245) has been used to express radon activity in Bq m −3 . In some of the dwellings the levels of radon activity are found to be quite high giving an annual exposure dose that crosses the safety limits set by the International Commission on Radiological Protection (ICRP, Protection against radon-222 at home and at work, ICRP Publication 65, Annals of the ICRP, 23 (2), 1993). A study of seasonal variations of indoor radon in some of the dwellings has also been carried out.

High U-contents observed in some drinking waters of Punjab, India

Abstract Uranium estimation has been carried out for some water samples collected from Bathinda and Amritsar, which are cities of the Punjab state, India, by using a track etch technique. The range of U-concentration present in water samples taken from Amritsar was 17.87 ± 0.18 to 20.23 ± 0.20 ppb while that in Bathinda samples was 11.71 ± 0.15 to 113.70 ± 0.46ppb. The daily intake of uranium by the population through drinking water has also been assessed. The high U-concentrations observed in the Bathinda area suggests that this area might warrant further investigation for uranium exploration purposes as well as for its potential health hazard effects.

Uranium analysis of geological samples, water and plants from Kulu Area, Himachal Pradesh, India

This paper deals with the measurement of uranium content in soil, rock, water and plant samples collected from some areas of Kulu district, Himachal Pradesh, India. The anomalous uranium values have been observed in soil, rock and plant samples belonging to Balsari village of the area. Uranium concentration in water samples is quite low and is thus safe for drinking. The aim of the work is to explore the possibility of uranium exploration and for the health risk assessment in the area.

Dose volume histogram analysis and comparison of different radiobiological models using in-house developed software.

The purpose of this study is to compare Lyman-Kutcher-Burman (LKB) model versus Niemierko model for normal tissue complication probability (NTCP) calculation and Niemierko model versus Poisson-based model for tumor control probability (TCP) calculation in the ranking of different treatment plans for a patient undergoing radiotherapy. The standard normal tissue tolerance data were used to test the NTCP models. LKB model can reproduce the same complication probability data of normal tissue response on radiation, whereas Niemierko model cannot reproduce the same complication probability. Both Poisson-based and Niemierko models equally reproduce the same standard TCP data in testing of TCP. In case of clinical data generated from treatment planning system, NTCP calculated using LKB model was found to be different from that calculated using Niemierko model. When the fractionation effect was considered in LKB model, the calculated values of NTCPs were different but comparable with those of Niemierko model. In case of TCP calculation using these models, Poisson-based model calculated marginally higher control probability as compared to Niemierko model.

Annealing kinetics of heavy ion radiation damage in crystalline minerals

Abstract Studies have been made concerning the annealing behaviour of radiation damage due to heavy ion beams in some crystalline minerals, namely chlorite, biotite, phlogopite, apatite and zircon. Annealing experiments were carried out in the temperature range 200–950° C. The activation energy, E a , for track annealing is determined in the frame of a model involving a unique value of E a for a given detector.

Verification of IMRT dose calculations using AAA and PBC algorithms in dose buildup regions

The purpose of this comparative study was to test the accuracy of anisotropic analytical algorithm (AAA) and pencil beam convolution (PBC) algorithms of Eclipse treatment planning system (TPS) for dose calculations in the low‐ and high‐dose buildup regions. AAA and PBC algorithms were used to create two intensity‐modulated radiotherapy (IMRT) plans of the same optimal fluence generated from a clinically simulated oropharynx case in an in‐house fabricated head and neck phantom. The TPS computed buildup doses were compared with the corresponding measured doses in the phantom using thermoluminescence dosimeters (TLD 100). Analysis of dose distribution calculated using PBC and AAA shows an increase in gamma value in the dose buildup region indicating large dose deviation. For the surface areas of 1, 50 and 100cm2, PBC overestimates doses as compared to AAA calculated value in the range of 1.34%–3.62% at 0.6 cm depth, 1.74%–2.96% at 0.4 cm depth, and 1.96%–4.06% at 0.2 cm depth, respectively. In high‐dose buildup region, AAA calculated doses were lower by an average of ‐7.56%(SD=4.73%), while PBC was overestimated by 3.75%(SD=5.70%) as compared to TLD measured doses at 0.2 cm depth. However, at 0.4 and 0.6 cm depth, PBC overestimated TLD measured doses by 5.84%(SD=4.38%) and 2.40%(SD=4.63%), respectively, while AAA underestimated the TLD measured doses by ‐0.82%(SD=4.24%) and ‐1.10%(SD=4.14%) at the same respective depth. In low‐dose buildup region, both AAA and PBC overestimated the TLD measured doses at all depths except ‐2.05%(SD=10.21%) by AAA at 0.2 cm depth. The differences between AAA and PBC at all depths were statistically significant (p<0.05) in high‐dose buildup region, whereas it is not statistically significant in low‐dose buildup region. In conclusion, AAA calculated the dose more accurately than PBC in clinically important high‐dose buildup region at 0.4 cm and 0.6 cm depths. The use of an orfit cast increases the dose buildup effect, and this buildup effect decreases with depth. PACS number: 87.53.Bn

A comparison of fission track and laser fluorometry techniques for uranium analysis in water samples

Water samples were collected from different areas of the states of Himachal Pradesh and Punjab in India for uranium analysis. The sources of these samples comprise of drains ponds, springs, dug wells, handpumps, municipal committee supply and tube wells. Initially, the fission track technique was used for the estimation U-content. As some of the samples showed high values of U-content, all these samples along with some new samples were also analysed using the laser fluorometry technique in order to confirm the results. A comparative analysis of the results obtained from these two different techniques has been made. The comparison confirmed high U-content in some of the samples. It is observed that the laser fluorometry technique is more suitable for analysis of the water samples having high U-content than the fission track technique.

Temperature dependent electrical transport characteristics of BaTiO3 modified lithium borate glasses

The glass samples with composition (70B2O3-29Li2O-1Dy2O3)-xBT; x = 0, 10 and 20 weight percent, have been prepared by conventional melt quench technique. The dielectric measurements as a function of temperature have been carried out on these samples in the frequency range 1 Hz-10 MHz. The dielectric relaxation characteristics of these samples have been studied by analyzing dielectric spectroscopy, dielectric loss, electric modulus formulation and electrical conductivity spectroscopy. It is found that the dielectric permittivity of the samples increases with an increase in the temperature and BT content. The frequency dependent ac conductivity has been analyzed using Jonscher’s universal power law whereas non exponential KWW function has been invoked to fit the experimental data of the imaginary part of the electric modulus. The values of the activation energy determined from the electric modulus and that from dc conductivity have been found to be quite close to each other suggesting that the same type of charge barriers are involved in the relaxation and the conduction mechanisms. The stretched exponent (β) and the power exponent (n) have been found to be temperature and composition dependent. The decrease in n with an increase in temperature further suggested that the ac conduction mechanism of the studied samples follows the correlated barrier hopping (CBH) model.

Etching and annealing kinetics of heavy ion tracks in quartz crystal

Abstract Swift heavy ions of sufficient size and energy produce stable latent tracks in most of the solid state nuclear track detectors. The etching and annealing kinetics of 208Pb (13.8 MeV/n) ion tracks in natural quartz crystal were investigated. The values of various etching parameters, viz. track etch rate VT, bulk etch rate VB, etching efficiency η and activation energy for track etching ET, are reported. The activation energy for annealing of latent tracks using a modified empirical formulation is determined.

CT and MR image fusion of tandem and ring applicator using rigid registration in intracavitary brachytherapy planning

The purpose of this study is to find the uncertainties in the reconstruction of MR compatible ring‐tandem intracavitary applicators of high‐dose rate image‐based brachytherapy treatment planning using rigid registration of 3D MR and CT image fusion. Tandem and ring reconstruction in MR image based brachytherapy planning was done using rigid registration of CT and MR applicator geometries. Verifications of registration for applicator fusion were performed in six verification steps at three different sites of tandem ring applicator set. The first site consists of three errors at the level of ring plane in (1) cranio–caudal shift (Cranial Shift) of ring plane along tandem axis, (2) antero–posterior shift (AP Shift) perpendicular to tandem axis on the plane containing the tandem, and (3) lateral shift (Lat Shift) perpendicular to the plane containing the tandem at the level of ring plane. The other two sites are the verifications at the tip of tandem and neck of the ring. The verification at the tip of tandem consists of two errors in (1) antero–posterior shift (AP Shift) perpendicular to tandem axis on the plane containing the tandem, and (2) lateral shift (Lat Shift) perpendicular to the plane containing the tandem. The third site of verification at the neck of the ring is the error due to the rotation of ring about tandem axis. The impact of translational errors from −5 mm to 5 mm in the step of 1 mm along x‐, y‐, and z‐axis and three rotational errors about these axes from −19.1° to 19.1° in the step of 3.28° on dose‐volume histogram parameters (D2cc,D1cc,D0.1cc, and D5cc of bladder, rectum, and sigmoid, and D90 and D98 of HRCTV were also analyzed. Maximum registration errors along cranio–caudal direction was 2.2 mm (1 case), whereas the errors of 31 out of 34 cases of registration were found within 1.5 mm, and those of two cases were less than 2 mm but greater than 1.5 mm. Maximum rotational error of ring about tandem axis was 3.15° (1.1 mm). In other direction and different sites of the ring applicator set, the errors were within 1.5 mm. The impacts of registration errors on DVH parameters of bladder, rectum, and sigmoid were very sensitive to antero–posterior shift. Cranio‐caudal errors of registration also largely affected the rectum DVH parameters. Largest change of 17.95% per mm and 20.65% per mm in all the DVH parameters of all OARs and HRCTV were observed for ϕ and Ψ rotational errors as compare to other translational and rotational errors. Catheter reconstruction in MR image using rigid registration of applicator geometries of CT and MR images is a feasible technique for MR image‐based intracavitary brachytherapy planning. The applicator registration using the contours of tandem and neck of the ring of CT and MR images decreased the rotational error about tandem axis. Verification of CT MR image fusion using applicator registration which consists of six steps of verification at three different sites in ring applicator set can report all the errors due to translation and rotational shift along θ,ϕ, and Ψ. ϕ and Ψ rotational errors, which produced potential changes in DVH parameters, can be tackled using AP Shift and Lat Shift at the tip of tandem. The maximum shift was still found along the tandem axis in this technique. PACS number: 87.55.km