This is a theoretical study of the inherent spatial resolution of the latent image on the surface of an amorphous selenium (a-Se) plate used for diagnostic x-ray imaging. The following effects are considered: (A) ranges of primary photoelectrons; (B) reabsorption of K fluorescence; (C) reabsorption of Compton scattered photons; (D) diffusion; (E) the geometric effect due to oblique incidence of x rays; (F) electrostatic effect; and (G) the space charge effect. The modulation transfer function of a-Se in the diagnostic x-ray energy range has been estimated. In conclusion, (A) and (E) are the main factors limiting the resolution, and for diagnostic x rays, the inherent spatial resolution of a-Se plates is much better than that of CsI layers used in x-ray image intensifiers.
In the "stop and shoot" method of intensity modulated radiation therapy, it is desirable to use an efficient multileaf collimator (MLC) field segmentation algorithm in the sense that it translates beam intensity maps into the least number of MLC field segments. In this work, we compare the performance of eight different algorithms, including the ones by Bortfeld et al., Galvin et al., Xia and Verhey, the Siemens IMFAST algorithm, and four other algorithms which have not been studied before. We find that the algorithm of Xia and Verhey is most frequently the algorithm that needs the least MLC field segments. However, no single algorithm is the most efficient for all clinical cases or intensity maps. This suggests that it is desirable to have multiple algorithms available in a clinical treatment planning system which will search through all algorithms automatically and find the most efficient delivery sequence for a given treatment. Each intensity map in a treatment could be delivered by a different algorithm, whichever is the most efficient for that map. It is pointed out that when the background intensity level is not zero, it is not always efficient to deliver a segment to bring the background level down to zero.
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.