Comparison of 126 MeV antiproton and proton-a FLUKA-based microdosimetric approach.

Objective. This study aims at comparing dosimetric parameters of 126 MeV antiprotons and protons using microdosimetric approach.Approach. Microdosimetric distributions of 126 MeV proton and antiproton beams at 1µm site size are calculated using the Monte Carlo-based FLUKA code. The distributions are calculated at various depths along the central axis in water phantom as well as at different off-axis locations. The study also includes calculations of secondary radiations produced by antiprotons and protons. Mean quality factor,Q¯is calculated using the ICRP 60 and ICRU 40 recommendations. The Relative Biological Effectiveness (RBE) of HSG tumour cell at 10% survival level is calculated based on Microdosimetric Kinetic Model.Main results.Q¯ICRP,Q¯ICRUand RBE for antiprotons are higher by a factor of about 3.60, 3.41 and 1.24, respectively, at Bragg-peak and higher by a factor of about 1.41, 1.76 and 1.05, respectively, at plateau region of depth-dose profile when compared to protons. At 15 cm depth along the central axis,Q¯ICRP,Q¯ICRUand RBE for protons are higher by a factor of about 1.42, 1.66 and 1.26, respectively, when compared to antiprotons. At the off-axis distance (Ld) of 6 cm (at 11.5 cm depth in water),Q¯ICRPandQ¯ICRUof protons are higher than that of antiproton whereas the trend is opposite at off-axis distance of 4 cm. AtLd= 4 cm (at 11.5 cm depth in water), RBE of antiprotons is higher by about 4% than protons whereas atLd= 6 cm, RBE of protons is higher by about 13% than antiprotons.Significance. The study shows that antiproton radiotherapy is advantageous as compared to protons considering enhancements in the absorbed dose and RBE-weighed dose values at the Bragg-peak.

MAPPING OF WORKPLACE RADIATION FIELDS IN DIAGNOSTIC RADIOLOGY FACILITIES USING PERSONNEL MONITORING TLD BADGES.

The radiation protection programme is aimed at safe usage of radiation at workplace, ensuring minimum possible dose to radiation workers, patients and members of the public. Verification of the adequacy of protective measures in actual workplace is important, especially for diagnostic radiology facilities, as a substantial number of suspected overexposures are reported from these facilities. To address this issue, a study was conducted for mapping workplace radiation field at various locations in nine Diagnostic Radiology Facilities of two hospitals in India. The cumulative doses were measured for a period of 1-3 months, using personnel monitoring TLD badges. The dosemeters were placed at positions representative of two exposure situations: (1) probable locations of workers during procedures, leading to genuine exposure and (2) inappropriate storage locations of personal dosemeters at user end for probing claims of nongenuine exposures. The results indicate that the measured doses at locations (1) were just a fraction of the permissible dose, provided all safety practices are adhered to. However, the measured doses at certain locations (2) exceeded the investigation levels and indicate that any inadvertent storage of the dosemeters at such locations could lead to reporting of the overexposure from these radiology facilities. The outcome of the study will be useful for the investigation of such exposures and better understanding of the readout patterns of TLD badges in radiology workplaces.

Synthesis and structure-activity relationship study of 2-(substituted benzylidene)-7-(4-fluorophenyl)-5-(furan-2-yl)-2H-thiazolo[3,2-a]pyrimidin-3(7H)-one derivatives as anticancer agents.

The synthesis and structure-activity relationship (SAR) study of a series of 2-(substituted benzylidene)-7-(4-fluorophenyl)-5-(furan-2-yl)-2H-thiazolo[3,2-a]pyrimidin-3(7H)-one (4a-4j) derivatives as anticancer agents are described. This series of thiazolopyrimidines were synthesized by the reaction of 7-(4-fluoro phenyl)-5-(furan-2-yl)-2H-thiazolo[3,2-a] pyrimidin-3(7H)-one (3) with appropriate substituted aldehydes in the presence of anhydrous sodium acetate and glacial acetic acid. Their structures were confirmed by IR, (1)H-NMR, mass, and elemental analyses. These novel thiazolopyrimidine derivatives were screened for their anticancer activity on the U937 human histocytic lymphoma cell line by 3-(4,5-dimethyl thiazole-2-yl)-2,5-diphenyltetrazoliumbromide (MTT) assay. The comparison of anticancer activity of thiazolopyrimidine was performed considering their structures. This study was done using 2-(substituted benzylidene)-7-(4-fluorophenyl)-5-(furan-2-yl)-2H-thiazolo[3,2-a]pyrimidin-3(7H)-one (4a-4j) as a basic model, showing that i) presence of a hydrogen donor/acceptor domain [thiazolo[3,2-a]pyrimidin-3(7H)-one] on the thiazolopyrimidine ring; ii) presence of a hydrophobic [(4-fluorophenyl)] aryl ring system on the thiazolopyrimidine ring; iii) presence of an electron donor moiety [5-(furan-2-yl)] on the thiazolopyrimidine ring; iv) ortho and para substitution of the distal aryl ring [2-(substituted benzylidene)] function strongly influenced anticancer activity. Among these compounds (4a-4j) para substituted derivatives 4c, 4e, 4f, 4g, 4h, and 4j showed significant anticancer activity.

Synthesis, characterization, and anthelmintic activity of novel 6,7,8,9-tetrahydro-5H-5-phenyl-2-benzylidine-3-substituted hydrazino thiazolo (2,3-b) quinazoline derivatives and analogues.

Several novel 6,7,8,9-tetrahydro-5H-5-phenyl-2-benzylidine-3-substituted hydrazine thiazolo (2,3-b) quinazoline derivatives were synthesized and evaluated for their anthelmintic activity in a passive avoidance test. Chemical structures of all of the newly synthesized compounds were confirmed by infrared spectroscopy, (1)H-nuclear magnetic resonance, mass spectroscopy, and elemental analyses. Out of 15 compounds, only 6e and 6o had good anthelmintic activity. Experimental data led to the conclusion that the synthesized compounds have anthelmintic activity.

Monte Carlo aided room scatter studies in the primary air kerma strength standardization of a remote afterloading 192Ir HDR source.

Corrections for room scatter, [ksc(d, H)]RM, were derived using Monte Carlo methods for rooms of various sizes, including the brachytherapy treatment room, in which primary air kerma strength standardization of a remote afterloading microSelectron 192Ir HDR source was carried out, using a 60 cm3 spherical graphite ion chamber. It was observed that for a given source-to-floor height, H, the air kerma rate due to room scatter was found to be decreasing with increase in source-to-detector distance, d, whereas it is assumed to be constant in the experimental determination (multiple-distance method) of the air kerma strength (AKS). Irrespective of the room size considered in the present study and when H = 100 cm, the assumption of 'constant room scatter' for d = 50, 75 and 100 cm resulted in overestimation of the AKS by about 1%. However, when d was in the range 13-25 cm, it was only 0.20%. The room scatter correction for the shadow cone method was also computed and the result showed that no additional correction was required on account of forward scatter from the cone. Further, at larger d (50-100 cm), the number of low-energy photons (40-200keV) relative to the total number of photons was found to be very significant, which may be useful to revisit the Spencer-Attix cavity theory.