An empirical method for splitting arcs in VMAT.

PURPOSE: We present a new approach to determine the optimal arc split for VMAT beams which is an extension of our recently published algorithm for selecting optimal beam angles in Intensity Modulated Radiation Therapy (IMRT) MATERIAL AND METHODS: The proposed approach uses an objective function based scoring method called "ψ - score" to determine optimal arc splitting strategy. To validate our approach, we applied it in different clinical cases: Abdomen-Para aortic node, Lung, Pancreas and Prostate. Basically, for all clinical cases, two set of plans were created, namely VMAT plan and VMAT_S plan using Pinnacle3 (V16.2, Philips Medical Systems (Cleveland), Inc.). In the VMAT plans, full arc (360°) with 4-degree gantry spacing was used during optimization to compute the "ψ - score". Subsequently the avoidable arc portions were identified and removed using the ψ - score plot followed by the final optimization (VMAT_S). RESULTS: Equivalent or better OAR sparing, and similar target coverage were achieved in VMAT_S plans compared to VMAT plans. VMAT_S reduced the number of control points and monitor units by 24.2% and 12.9% respectively. On the average, beam on time was reduced by 21.9% and low dose volume (5 Gy isodose volume) to healthy tissues was reduced by 4.9% in VMAT_S compared to VMAT plans. CONCLUSION: The results demonstrated that the proposed method is useful for reducing the monitor units, beam on time and low dose volume without significantly compromising plan quality and most useful for non-centrically located targets.

Objective function based ranking method for selection of optimal beam angles in IMRT.

We propose a novel method for the selection of optimal beam angles in Intensity Modulated Radiation Therapy (IMRT). The proposed approach uses an objective function based metric called "target-to-critical organ objective function ratio" to find out the optimal gantry angles. The beams are ranked based on this metric and are accordingly chosen for IMRT optimization. We have used the Pinnacle TPS (Philips Medical System V 16.2) for performing the IMRT optimization. In order to validate our approach, we have applied it in four clinical cases: Head and Neck, Lung, Abdomen and Prostate. Basically, for all clinical cases, two set of plans were created with same clinical objectives, namely Equal angle plan (EA Plan) and Suitable angle Plan (SA Plan). In the EA plans, the beam angles were placed in an equiangular manner starting from the gantry angle of 0°. In the corresponding SA plans, the beam angles were decided using the guidance provided by the algorithm. The reduction in OAR mean dose and max dose obtained in SA plans is about 3 to 16% and 3 to 15% respectively depending upon the treatment site while obtaining equal target coverage as compared to their EA counterparts. It takes approximately 15-25 min to find the optimal beam angles. The results obtained from the clinical cases indicate that the plan quality is considerably improved when the beam angles are optimized using the proposed method.

Crystal structure of 4,5,6,7,8,8-hexa-chloro-2-(3,4-di-meth-oxy-pheneth-yl)-3a,4,7,7a-tetra-hydro-1H-4,7-methano-iso-indole-1,3(2H)-dione [+solvent].

In the title compound, C19H15Cl6NO4 [+solvent], the six-membered ring of the norbornene moiety adopts a boat conformation and the two five-membered rings have envelope conformations. The pyrrolidine ring makes a dihedral angle of 14.83 (12)° with the 3,4-di-meth-oxy-phenyl ring, which are attached to each other by an extended N-CH2-CH2-Car bridge. In the crystal, the structure features C-H⋯O inter-molecular hydrogen bonds, an offset π-π inter-action [inter-centroid distance = 3.564 (1) Å] and a C-Cl⋯π inter-action. The contribution of some disordered solvent to the scattering was removed using the SQUEEZE routine [Spek (2015 ▸). Acta Cryst. C71, 9-18] of PLATON. The solvent contribution was not included in the reported mol-ecular weight and density.

Rhizopus stolonifer mediated biosynthesis of biocompatible cadmium chalcogenide quantum dots.

We report an efficient method to biosynthesize biocompatible cadmium telluride and cadmium sulphide quantum dots from the fungus Rhizopus stolonifer. The suspension of the quantum dots exhibited purple and greenish-blue luminescence respectively upon UV light illumination. Photoluminescence spectroscopy, X-ray diffraction, and transmission electron microscopy confirms the formation of the quantum dots. From the photoluminescence spectrum the emission maxima is found to be 424 and 476nm respectively. The X-ray diffraction of the quantum dots matches with results reported in literature. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay for cell viability evaluation carried out on 3-days transfer, inoculum 3×105 cells, embryonic fibroblast cells lines shows that more than 80% of the cells are viable even after 48h, indicating the biocompatible nature of the quantum dots. A good contrast in imaging has been obtained upon incorporating the quantum dots in human breast adenocarcinoma Michigan Cancer Foundation-7 cell lines.

Purification, crystallization, preliminary X-ray diffraction and molecular-replacement studies of great cormorant (Phalacrocorax carbo) haemoglobin.

Haemoglobin is the iron-containing oxygen-transport metalloprotein that is present in the red blood cells of all vertebrates. In recent decades, there has been substantial interest in attempting to understand the structural basis and functional diversity of avian haemoglobins. Towards this end, purification, crystallization, preliminary X-ray diffraction and molecular-replacement studies have been carried out on cormorant (Phalacrocorax carbo) haemoglobin. Crystals were grown by the hanging-drop vapour-diffusion method using PEG 3350, NaCl and glycerol as precipitants. The crystals belonged to the trigonal system P3121, with unit-cell parameters a=b=55.64, c=153.38 Å, ß=120.00°; a complete data set was collected to a resolution of 3.5 Å. Matthews coefficient analysis indicated that the crystals contained a half-tetramer in the asymmetric unit.

Erratum: 6'-Amino-3'-methyl-2-oxo-1'-phenyl-1',3a',4',7a'-tetra-hydrospiro-[1H-indole-3(2H),4'-pyrano[2,3-d]pyrazole]-5'-carbonitrile. Corrigendum.

The title and chemical structural diagram in Etti, Shanmugam & Perumal [Acta Cryst. (2008), E64, o341] are corrected.[This corrects the article DOI: 10.1107/S1600536807064926.].

6'-Amino-3'-methyl-2-oxo-1'-phenyl-1',3a',4',7a'-tetra-hydrospiro-[1H-indole-3(2H),4'-pyrano[2,3-d]pyrazole]-5'-carbonitrile.

In the crystal structure of the title compound, C(21)H(15)N(5)O(2), the planar indolone unit and the pyran ring are almost perpendicular to each other [dihedral angle = 89.41 (2)°], and the pyrazole and phenyl rings are oriented at an angle of 25.74 (1)°. The mol-ecular packing is stabilized by inter- and intra-molecular C-H⋯O, N-H⋯O and C-H⋯π hydrogen bonds.

3-[3-(4-Bromo-phen-yl)-1-phenyl-1H-pyrazol-4-yl]-5-eth-oxy-2-phenyl-isoxazolidine.

In the title compound, C(26)H(24)BrN(3)O(2), the isoxazolidine ring adopts an envelope conformation, the ring N atom deviating from the mean plane of the other four atoms by an angle of 0.286°. The orientation of the phenyl ring is +sp and the bromophenyl ring is +sc relative to the attached pyrazole ring; the dihedral angles between the least-squares planes of the pyrazole and the attached phenyl and bromophenyl rings are 21.8 (3) and 41.8 (3)°.

Association of Borrelia afzelii with rodents in Europe.

Borrelia burgdorferi sensu lato (s.l.) is maintained in nature by complex zoonotic transmission cycles, involving a large variety of vertebrates as hosts and hard ticks of the genus Ixodes as vectors. Recent studies suggest that the genospecies of B. burgdorferi s.l. and sometimes their subtypes are propagated by different spectra of hosts, mainly birds and rodents. In order to test the concept of host-association, we analysed the relationships between Borrelia genospecies, rodent hosts and I. ricinus ticks in an endemic focus of Lyme borreliosis in western Slovakia. Rodents and questing ticks were collected at a forested low land locality near Bratislava. Tick infestation levels on rodents were determined, and spirochaete infections in ticks and in ear punch biopsies were analysed by PCR followed by genotyping. Mice were more heavily infested with ticks than bank voles, and a higher proportion of mice was infected with spirochactes than voles. However, the infectivity of soles was much higher than that of mice. The vast majority of infections detected in the skin and in ticks feeding on the rodents represented B. afzelii. In contrast, more than half of all infections in questing ticks collected in the same region of Slovakia were identified as B. valaisiana and B. garinii. In conclusion, whilst the study reveals that mice and voles play different quantitative roles in the ecology of Lyme borreliosis, it demonstrates that B. afzelii is specifically maintained by European rodents, validating the concept of host-association of B. burgdorferi s.l.

Distinct combinations of Borrelia burgdorferi sensu lato genospecies found in individual questing ticks from Europe.

The genetic diversity of Borrelia burgdorferi sensu lato was assessed in individual adult Ixodes ricinus ticks from Europe by direct PCR amplification of spirochetal DNA followed by genospecies-specific hybridization. Analysis of mixed infections in the ticks showed that B. garinii and B. valaisiana segregate from B. afzelii. This and previous findings suggest that host complement interacts with spirochetes in the tick, thereby playing an important role in the ecology of Lyme borreliosis.