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 6 12.1 years) were scanned using micro-CT with 27.2 mm voxel size and cone beam CT (CBCT) with 200 mm, 300 mm, and 400 mm voxel sizes. In addition, 15 clinical CBCT images from young patients (mean age 18.9 6 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.

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always first on the face, it followed in a few hours on the arms and legs, with a few spots on the back; the chest and abdomen were nearly free, in many mild cases absolutely free, the picture so formed being very striking in its contrast to varicella; on the limbs the rash was always centrifugal. There was no succession of crops as in varicella, all the spots in a given part of the body being of the same age. The individual spots were in the deeper layers of the skin as opposed to the superficial vesicles of varicella, and passed through the classical stages on the face in about ten days; in the limbs much longer was required, unbroken pustules being often present after the face was clear; the last to clear up were always round the ankles and on the soles of the feet. A few of the largest spots were punctured and found to be unilocular; umbilication was frequent but not universal. So uniform was the rash in its essential features as regards both its nature and distribution that the diagnosis rarely gave any anxiety once the rash was well out.Secondary rise of temperature occurred in all but one of the semiconfluent cases and in 10 of the mild casestwenty-three times in all. It was invariably septic in type, and while it lasted patients always felt worse than during the early days of the rash, though usually not so ill as in the prodromal period. It commenced on the third or fourth day of the rash and lasted for one day only in 7 cases, for two days in 4 cases, for three days in 2 cases, for four days in 7 cases, and for five, six, and nine days in one case each. In only 10 cases did it exceed 1000, the highest recorded being 101.60.Conjunctivitis occurred during pustulation in 6 cases and appeared to be caused by pustules on the eyelids; arthritis of the knee occurred once during convalescence, in a man of 55 not previously subject to " rheumatism." There were no other complications; one case each of imperfectly compensated mitral disease and of six months' pregnancy were unaffected, both being cases of " mild " type.Treatment was symptomatic only. From the period of scabbing onwards all patients we're liberally treated with olive oil and hot baths; the nursing staff as well as the author were convinced that this materially shortened convalescence.Dutration of Infectivity.-After the scab had fallen off a purple scar remained, at first slightly raised; around its edge was ofteni attached some dry skin, the remaining circumferential part of the skin originally covering the vesicle. Until this had disappeared from all the spots the patient was regarded as still infectious. The last part to clear was invariably the ankles and soles of the feet, and the process was completed within three weeks of the appearance of the rash in 23 cases; in 20 cases infection persisted to the fourth week, in 3 cases to the fifth, in 3 cases to the sixth, and once to the seventh week. Liberal applications of olive oil and hot baths materially assisted the removal of this dry skin; premature picking off of the scabs, on the othier hand,...

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