Radiation skyshine from a 6 MeV medical accelerator
This study assesses the dose level from skyshine produced by a 6 MeV medical accelerator. The analysis of data collected on skyshine yields professional guidance for future investigators as they attempt to quantify and qualify radiation protection concerns in shielding therapy vaults. Survey measurements using various field sizes and at varying distances from a primary barrier have enabled us to identify unique skyshine behavior in comparison to other energies already seen in literature. In order to correctly quantify such measurements outside a shielded barrier, one must take into consideration the fact that a skyshine maximum may not be observed at the same distance for all field sizes. A physical attribute of the skyshine scatter component was shown to increase to a maximum value at 4.6 m from the barrier for the largest field size used. We recommend that the largest field sizes be used in the field for the determination of skyshine effect and that the peak value be further analyzed specifically when considering shielding designs. PACS numbers: 87.52.‐g, 87.52.Df, 87.52.Tr, 87.53.‐j, 87.53.Bn, 87.53.Dq, 87.66.‐a, 89., 89.60.+x
Effect of the skyshine approach on the total cost of concrete shielding in a conventional radiotherapy facility room
Photon beams produced in large linear accelerators are widely used in medicine for the treatment of cancer. Nevertheless, the use of these medical purpose machines in radiotherapy bring some interesting questions as for example how to evaluate the thicknesses of the walls of the facility room housing them in order to guarantee that their vicinities do not receive a radiation dose above the permissible levels. The aim of work is to present a simplified general formalism for the estimation of wall thicknesses of a facility room housing linear accelerators that generate photons with energies in the range 4-30 MeV and using ordinary concrete as the material of shielding. A computer code based on FORTRAN programming language was developed in order to handle with all the input parameters. The roof thickness was calculated according to the skyshine approach, and the overall results have shown a lower total volume and associated cost of concrete shielding as compared with the primary approach.
An automated retinal image quality grading algorithm
This paper introduces an algorithm for the automated assessment of retinal fundus image quality grade. Retinal image quality grading assesses whether the quality of the image is sufficient to allow diagnostic procedures to be applied. Automated quality analysis is an important preprocessing step in algorithmic diagnosis, as it is necessary to ensure that images are sufficiently clear to allow pathologies to be visible. The algorithm is based on standard recommendations for quality analysis by human screeners, examining the clarity of retinal vessels within the macula region. An evaluation against a reference standard data-set is given; it is shown that the algorithm's performance correlates closely with that of clinicians manually grading image quality.