During interventional procedures, the vast majority of scatter radiation originates from the patient and table and travels in all directions in straight lines. Because the operator's head is much higher than the patient and at an angle upward and to the side of the patient (not directly above), the scatter received by the operator's head is projected in an upward angle. Thus a face shield could potentially be lower than the object it is shielding, e.g., below the eyes. This principle may be used as an advantage to design the lowest shield that effectively protects the head while providing optimum vision, appearance, acoustics, low weight, and sense of openness. A flat acrylic plate shield, 0.5 mm Pb equivalence, was suspended vertically in front of a 451P dosimeter. A phantom patient created scatter in an interventional suite while the dosimeter was placed at the level of the crowns of different operators' heads. Many different configurations were tested to determine which ones would provide effective shielding. The results confirmed that the top of the shield may reside several centimeters below the vertical height of the dosimeter (operator's crown), allowing line of sight to monitor above the shield, and still provide effective shielding equivalent to when the dosimeter is positioned directly behind the center of the shield. The image receptor functioned as an effective shield against scatter. Factors increasing the minimum height of effective shielding included shorter operator, opposite oblique projection of image receptor, and shield closer to the face (in horizontal direction).
The "Levels of Digital Preservation" being refined now by the National Digital Stewardship Alliance (NDSA), is a tiered set of recommendations on how organizations should begin to build or enhance their digital preservation activities. A work in progress, it is intended to be a relatively easy-to-use set of guidelines useful not only for those just beginning to think about preserving their digital assets, but also for institutions planning the next steps in enhancing their existing digital preservation systems and workflows. It allows institutions to assess the level of preservation achieved for specific materials in their custody. It is not designed to assess the robustness of digital preservation programs as a whole since it does not cover such things as policies, staffing, or organizational support. The guidelines are organized into five functional areas that are at the heart of digital preservation systems: storage and geographic location, file fixity and data integrity, information security, metadata, and file formats. This paper presents the Levels, explains the context of the project's development within the NDSA, describes the rationale behind each of the guidelines and why they were prioritized the way they were, suggests how the guidelines may be used, and compares and contrasts the Levels to other ways of assessing stages of digital preservation. Other assessment models include
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