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Purpose: Previous studies have introduced gold nanoparticles as vascular-disrupting agents during radiation therapy. Crucial to this concept is the low energy photon content of the therapy radiation beam. The authors introduce a new mode of delivery including a linear accelerator target that can toggle between low Z and high Z targets during beam delivery. In this study, the authors examine the potential increase in tumor blood vessel endothelial cell radiation dose enhancement with the low Z target. Methods: The authors use Monte Carlo methods to simulate delivery of three different clinical photon beams: (1) a 6 MV standard (Cu/W) beam, (2) a 6 MV flattening filter free (Cu/W), and (3) a 6 MV (carbon) beam. The photon energy spectra for each scenario are generated for depths in tissue-equivalent material: 2, 10, and 20 cm. The endothelial dose enhancement for each target and depth is calculated using a previously published analytic method. Results: It is found that the carbon target increases the proportion of low energy (<150 keV) photons at 10 cm depth to 28% from 8% for the 6 MV standard (Cu/W) beam. This nearly quadrupling of the low energy photon content incident on a gold nanoparticle results in 7.7 times the endothelial dose enhancement as a 6 MV standard (Cu/W) beam at this depth. Increased surface dose from the low Z target can be mitigated by well-spaced beam arrangements. Conclusions: By using the fast-switching target, one can modulate the photon beam during delivery, producing a customized photon energy spectrum for each specific situation. C 2016 American Association of Physicists in Medicine. [http://dx

The effect of minor changes in lattice parameters and Mn 3+ /Mn 4+ ratios on the magnetoresistive and related properties of the La-Er-Ca-Mn-O perovskite system have been investigated. The latter is found to be the more important factor in determining the magnetotransport properties of these materials. One composition has been prepared by both the standard ceramic method as well as a sol-gel technique. Although the general features of the magnetotransport properties of these two samples were very similar, the magnetic properties showed significant differences. Experimental results are explained on the basis of a spindependent mechanism which is related to lattice distortion.

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This study was designed to evaluate skin dose in both VMAT and tangent treatment deliveries for the purpose of identifying suitable bolus use protocols that should produce similar superficial doses. Methods: Phantom measurements were used to investigate skin dose in chest wall radiotherapy with and without bolus for 3D and rotational treatment techniques. Optically stimulated luminescence dosimeters (OSLDs) with and without housing and EBT3 film were used. Superflab (3, 5, and 10 mm) and brass mesh were considered. Measured doses were compared with predictions by the Eclipse treatment planning system. Patient measurements were also performed and the bolusing effect of hospital gowns and blankets were highlighted. The effect of flash for VMAT plans was considered experimentally by using 2 mm couch shifts. Results: For tangents, average skin doses without bolus were 0.64 (EBT3), 0.62 (bare OSLD), 0.77 (jacketed OSLD), and 0.68 (Eclipse) as a fraction of prescription. For VMAT, doses without bolus were 0.53 (EBT3), 0.53 (bare OSLD), 0.64 (jacketed OSLD), and 0.60 (Eclipse). For tangents, the average doses with different boluses as measured by EBT3 were 0.99 (brass mesh), 1.02 (3 mm), 1.03 (5 mm), and 1.07 (10 mm). For VMAT with bolus, average doses as measured by EBT3 were 0.83 (brass), 0.96 (3 mm), 1.03 (5 mm), and 1.04 (10 mm). Eclipse doses agreed with measurements to within 5% of measurements for all Superflab thicknesses and within 15% of measurements for no bolus. The presence of a hospital gown and blanket had a bolusing effect that increased the surface dose by approximately 10%. Conclusions: Results of this work allow for consideration of different bolus thicknesses, materials, and usage schedules based on desired skin dose and choice of either tangents or an arc beam techniques.

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The thermal and electronic properties of amorphous Al87Y8Ni3TM2 (TM=Mn, Fe, Co, Ni, Cu) and Al87Y8Ni5-xFex (x=0, 2, 3, 5) alloys have been investigated. Thermal analysis studies have shown that all alloys studied, except Al87Y8Fe5, undergo a primary crystallization process which involves a precipitation of FCC-Al followed by a eutectic crystallization process to an intermetallic compound. Al87Y8Fe5 undergoes eutectic crystallization directly and shows the highest crystallization temperature, 593 K, of the alloys studied. Alloys which do not contain Fe show resistivities which are well described by the Ziman-Faber model for structurally disordered materials. Fe-containing alloys show electronic properties which suggest the influence of magnetic interactions. The magnitude and temperature dependence of the resistivity show compositional variations which can be related to thermal stability.