Comparison of micro-CT and cone beam CT-based assessments for relative difference of grey level distribution in a human mandible.

OBJECTIVES: The purpose of this study was to examine the ability of CT to assess the relative difference of degree of bone mineralization (grey level) parameters in a human mandible. METHODS: Ten mandibular sections from cadavers (81.5 ± 12.1 years) were scanned using micro-CT with 27.2 µm voxel size and cone beam CT (CBCT) with 200 µm, 300 µm, and 400 µm voxel sizes. In addition, 15 clinical CBCT images from young patients (mean age 18.9 ± 3.3 years) were identified. After segmentation of bone voxels, alveolar bone and basal cortical bone regions were digitally isolated. A histogram of grey level, which is equivalent to degree of bone mineralization, was obtained from each region of the CT images. Mean, standard deviation (SD), coefficient of variation (COV), fifth percentile low (Low(5)) and high (High(5)) of alveolar bone and basal cortical bone regions were obtained. Percentage differences of grey level parameters between alveolar and basal cortical bones were computed. RESULTS: The alveolar bone region had significantly lower Mean, Low(5) and High(5) values but significantly higher SD and COV than the basal cortical bone region for all CT images (p < 0.05). All parameters were significantly lower for the old cadaver group than for the young patient group (p < 0.05). CONCLUSIONS: CBCT and micro-CT provide comparable results in the assessment of relative difference in grey level distribution between alveolar and basal cortical bone regions in the human mandible. The percentage difference relative to an internal reference (basal cortical bone) can be a reliable method when assessing the degree of bone mineralization using CBCT images for both cross-sectional and longitudinal comparisons.

Cost effective nursing under prospective reimbursement.

The implications of the prospective payment system are far-reaching and have specific impact on nurses. It is essential that nurses fully understand the ramifications of this system and appreciate their critical role in making health care most cost-effective for both the patient and the institution. This article will compare a retrospective, cost-based reimbursement system with a prospective reimbursement system. The role of the nurse as a Patient Advocate under prospective reimbursement will be examined. A case presentation will demonstrate the types of choices nurses must make to balance technology with cost-containment measures.

Avian cholera in common crows, Corvus brachyrhynchos, from the central Texas panhandle.

An epornitic of avian cholera involving approximately 150 birds is described from a flock of common crows, Corvus brachyrhynchos, on a single playa lake utilized as a roost in Castro County, Texas, during early spring of 1980. There was a concomitant epornitic of avian cholera involving several hundred ducks and geese of several species on adjacent lakes in he same area. Crows scavenged extensively on waterfowl carcasses. Gross and histopathologic lesions in waterfowl were typical of acute avian cholera. Crows had a more chronic form of the disease, especially neurological involvement with the most common lesion consisting of a hemorrhagic meningitis. Other endemic species from which Pasteurella multocida was isolated included the short-eared owl, Asio flammeus, and cottontail rabbit, Silvilagus sp. The role of crows in the dissemination and maintenance of avian cholera is discussed.