The purpose of this study is to describe four new delivery schemes for intensity-modulated radiation therapy (IMRT). In the first two schemes the order in which segments are delivered is varied from fraction to fraction. The last two delivery schemes employ fixed order of segments. The obtained results indicate that the suggested approaches can significantly reduce the so-called "overshoot" and "undershoot" phenomena and the associated discrepancies between planned and delivered monitor units.
We have measured the energies and widths of the x-ray lines from the 4f~* 3d transition in antiprotonic atoms of 14 N and t6 0. The results are discussed in terms of a phenomenological optical potential. We have also observed the x-ray line from the 3d -~ 4p transition in the antiprotonic 4 He atom.
An on-line electronic portal imaging system was used in a quantitative measurement of field placement errors in external beam radiotherapy. Data from 30 patients, giving a total of 150 portals with 66% in the thoracic region and 34% in the abdominal region, were analysed. Displacements from the prescription delineated by physicians were measured. The displacements included errors to block malposition, field malposition, field malrotation and patient malposition, and these were classified in two categories of displacements, those associated with the portal boundary and those with anatomic structures. Except for one rotational error, only translational errors were found. Displacements greater than 1 cm amounted to 17% with respect to the portal boundary and between 10% and 46% with respect to anatomic landmarks within the portal. From the results of the study, a margin of 1 cm around the tumour is barely sufficient if a 5% accuracy in dose delivery is desired.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.