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Using atomic force microscopy (AFM), we have investigated neutron-induced DNA double-strand breaks in plasmids in aqueous solution. AFM permits direct measurement of individual DNA molecules with an accuracy of a few nanometers. Furthermore, the analysis of the DNA fragment size distribution is non-parametric, whereas other methods are dependent on the(More)
Published by the American Association of Physicists in Medicine DISCLAIMER: This publication is based on sources and information believed to be reliable, but the AAPM and the editors disclaim any warranty or liability based on or relating to the contents of this publication. The AAPM does not endorse any products, manufacturers, or suppliers. Nothing in(More)
Chars, a form of environmental black carbon resulting from incomplete burning of biomass, can immobilize organic contaminants by both surface adsorption and partitioning mechanisms. The predominance of each sorption mechanism depends upon the proportion of organic to carbonized fractions comprising the sorbent. Information is currently lacking in the(More)
A common radiotherapeutic technique for treating breast cancer is the combination of external beam radiation with an interstitial iridium-192 boost. When smaller tumors (T1 and T2) are treated using this technique, the soft tissue complication rate is small. However, with treatment of more advanced stages of disease, where large volumes of breast tissue(More)
Digital image processing has the potential to enhance and improve several functions of a modern radiation oncology department. These functions may include improving perception of information for low contrast films, electronic transfer of images to remote facilities and back, and reducing storage space requirements for archiving once treatment is finished.(More)
BACKGROUND Resection of liver metastases from colorectal carcinoma can be curative. Unresectable but liver-confined metastases might be ablated by high-dose radiation with a similar curative result. METHODS At Georgetown University Hospital, 22 patients with unresectable hepatic metastases from colorectal carcinoma underwent 24 interstitial irradiation(More)
PURPOSE To determine the effects of a lucite beam spoiler on the dose distribution to points inside and outside the primary beam for head and neck irradiation with a 10-MV photon beam. METHODS AND MATERIALS Build-up and depth-dose measurements were performed with a parallel-plate ionization chamber for 5 x 5, 10 x 10, and 15 x 15-cm field sizes using(More)
The use of non-circular collimators is considered on all or some of the arcs used for radiosurgery on a linear accelerator in order to obtain conformal dose distribution for non-spherical lesions using a single isocenter. An extension of software to allow for use of non-circular collimators and a mathematical optimization based on prescribed doses on the(More)
Atomic force microscopy (AFM) has been used to directly visualize, size and compare the DNA fragments resulting from exposure to low- and high-LET radiation. Double-stranded pUC-19 plasmid ("naked") DNA samples were irradiated by electron-beam or reactor neutron fluxes with doses ranging from 0.9 to 10 kGy. AFM scanning in the tapping mode was used to image(More)