DigiBit: A System for Adjusting Radiographic Exposure Factors in the Digital Era.

OBJECTIVE: To develop an exposure adaptation system for direct radiography that can accurately adjust exposure factors such as milliampere seconds (mAs), kilovoltage peak, and source-to-image distance for patients of differing size. METHODS: The DuPont Bit System was used to select the mAs for 60 combinations of exposure factors for an anthropomorphic pelvic phantom. The exposure index (EI) with a target value of 1500 ± 2% was used to evaluate whether each image was exposed correctly. The DuPont Bit System was then adapted for direct radiography so the mAs could be adjusted to achieve both the target bit value and the target EI. RESULTS: With the DuPont Bit System, an EI of 1500 ± 21.6% was achieved in all 60 radiographs, whereas the target EI of 1500 ± 2% was achieved in 16 radiographs. With the modified version of the DuPont Bit System, "the DigiBit system," achieving the target EI increased to 38 out of 60 radiographs. DISCUSSION: The DigiBit system is an exposure adjustment system designed for direct radiography. In situations where automatic exposure control is not available, the Digibit system allows adjustment of radiographic exposure. It is potentially a valuable tool for radiography. CONCLUSION: The DigiBit system provides an accurate method of adjusting exposure factors for direct radiography.

Patient-based radiographic exposure factor selection: a systematic review.

INTRODUCTION: Digital technology has wider exposure latitude and post-processing algorithms which can mask the evidence of underexposure and overexposure. Underexposure produces noisy, grainy images which can impede diagnosis and overexposure results in a greater radiation dose to the patient. These exposure errors can result from inaccurate adjustment of exposure factors in response to changes in patient thickness. This study aims to identify all published radiographic exposure adaptation systems which have been, or are being, used in general radiography and discuss their applicability to digital systems. METHODS: Studies in EMBASE, MEDLINE, CINAHL and SCOPUS were systematically reviewed. Some of the search terms used were exposure adaptation, exposure selection, exposure technique, 25% rule, 15% rule, DuPont™ Bit System and radiography. A manual journal-specific search was also conducted in The Radiographer and Radiologic Technology. Studies were included if they demonstrated a system of altering exposure factors to compensate for variations in patients for general radiography. Studies were excluded if they focused on finding optimal exposures for an 'average' patient or focused on the relationship between exposure factors and dose. RESULTS: The database search uncovered 11 articles and the journal-specific search uncovered 13 articles discussing systems of exposure adaptation. They can be categorised as simple one-step guidelines, comprehensive charts and computer programs. CONCLUSION: Only two papers assessed the efficacy of exposure adjustment systems. No literature compares the efficacy of exposure adaptations system for film/screen radiography with digital radiography technology nor is there literature on a digital specific exposure adaptation system.

MMP2-9 cleavage of dystroglycan alters the size and molecular composition of Schwann cell domains.

Myelinating glial cells exhibit a spectacular cytoarchitecture, because they polarize on multiple axes and domains. How this occurs is essentially unknown. The dystroglycan-dystrophin complex is required for the function of myelin-forming Schwann cells. Similar to other tissues, the dystroglycan complex in Schwann cells localizes with different dystrophin family members in specific domains, thus promoting polarization. We show here that cleavage of dystroglycan by matrix metalloproteinases 2 and 9, an event that is considered pathological in most tissues, is finely and dynamically regulated in normal nerves and modulates dystroglycan complex composition and the size of Schwann cell compartments. In contrast, in nerves of Dy(2j/2j) mice, a model of laminin 211 deficiency, metalloproteinases 2 and 9 are increased, causing excessive dystroglycan cleavage and abnormal compartments. Pharmacological inhibition of cleavage rescues the cytoplasmic defects of Dy(2j/2j) Schwann cells. Thus, regulated cleavage may be a general mechanism to regulate protein complex composition in physiological conditions, whereas unregulated processing is pathogenic and a target for treatment in disease.