Structural and Functional Characteristics of Protein Phosphorylation Revealed by Bioinformatic Approaches

Abstract

The purpose of this study was to investigate beam output factors (OFs)forconformal radiation therapy and to compare the OFs measured with differentdetectors with those simulated with Monte Carlo methods. Four differentdetectors (diode, diamond, pinpoint and ionization chamber) were usedtomeasure photon beam OFs in a water phantom at a depth of 10 cm withasource–surface distance (SSD) of 100 cm. Square ?elds with widthsrangingfrom 1 cm to 15 cm were observed; the OF for the different ?eld sizeswasnormalized to that measured at a 5 cm × 5cm?eldsizeatadepthof10 cm.The BEAM/EGS4 programwas used to simulate the exact geometry of a6MVphoton beam generated by the linear accelerator, and the DOSXYZ-codewas implemented to calculate the OFs for all ?eld sizes. Two resolutions(0.1 cm and 0.5 cm voxel size) were chosen here. In addition, to modelthedetector four kinds of material, water, air, graphite or silicon,were placed inthe corresponding voxels.Pro?les and depth dose distributions resulting from the simulationshowgood agreement with the measurements. Deviations of less than 2% canbeobserved. TheOFmeasuredwith different detectors in water vary bymorethan35% for 1 cm × 1 cm ?elds. This result can also be found for the simulatedOF with different voxel sizes and materials. For ?eld sizes of atleast 2 cm ×2 cm the deviations between all measurements and simulations are below3%. This demonstrates that very small ?elds have a bad effect on dosimetricaccuracy and precision. Finally, Monte Carlo methods can be signi?cantindetermining the OF for small ?elds.