Performance for obtaining maximal gain from a program for digital subtraction radiography

Abstract – The aim of this study was to evaluate the effect on subtraction image quality of number of a) gray shades sampled during camera recording, and b) reference points positioned in the two images to be subtracted. Intraoral radiographs were obtained in each of 12 patients, one at 0° and one at 15° horizontal angulation in a standardized recording procedure. The radiographs were videorecorded twice sampling 1) 160–180 and 2) 200–220 shades of gray. The 0° radiographic image was digitally copied. Subtractions were performed between the identical (0°/0°) and the non-identical (0°/15°) radiographs from both gray shade samples after positioning 5, 10, 15, and 20 reference points, respectively, in each of the images to be subtracted. The standard deviation in the subtraction image histogram was used as the test parameter for image quality. No differences existed between image quality obtained from the radiographs sampled using 160–180 and 200–220 shades of gray (P>0.05). The standard deviation fell continuously, the more reference points were positioned in the images. For the 0°/0° images the difference was statistically significant between the 5 and 10 point images ( F= 0.045) while for the 0°/15° images differences existed between 5 and 10 point images (P = 0.077) and the 10 and 15 point images ( P= 0.048). The precision of reference point positioning as evaluated in the two identical images was satisfactory, the divergence being on average 1.4 pixels. The conclusion from cost/benefit analysis was that, when working with subtraction radiography, time should not be spent adjusting camera diaphragm to utilize the full range of gray shades but rather on a precise positioning of 10–15 reference points in the images to be subtracted.     

Influence of projection angles upon position of cementoenamel junction on radiographs

Abstract — The CEJ on radiographs is often used as a reference point in the assessment of alveolar bone loss. The aim of the present study was to test the stability of the radiographic CEJ ("RCEJ") in relation to the alveolar west under varying angulations of the central X-ray beam. In an experimental model four types of extracted teeth were radicrgraphed al 0° and 20° vertical angulation and at 15 horizontal angulations varying from a 17.5° mesial view to a 17.5° distal view. The buccal alveolar bone margin was simulated by a steel needle. RCEJ-"crest" distances were read at a × 10 magnification. Changing the vertical angutation from 0° to 20° reduced the RCEJ-"crest" distances far all tooth types (range ofaverage reduction 2.2–4.1 mm). HorizontaE angulations without concomitant vertical angularion had a significant effect but where without clinical significance. Horizontal anglslations in combination with a 20° vertical angulation bad a considerable influence; in a mesial view, mesial RCEJ-"crest" distances decreas-ed and distal ones increased, and vice wna in a distal view. The deviations from the true CEJ-crest distance demonstrated may be of clinical significance, and a critical attitude to alveolar bone loss measures on radiographs using the RCEJ as reference point is recommended.     

Influence of spatulation time upon the radio-graphic homogeneity of Adaptic Radiopaque® fillings

Abstract— Twelve test cavities were filled with Adaptic Radiopaque by die author, varying the spatulation times from 5 s to 60 s at 5-s intervals but using the same mixing technique. Fillings spatulated for less than 20 s appeared inhornogeneous on radiographs. 2) Twenty-eight dentists produced 84 test fillings determining themselves their spatulation time and applying their own mixing technique. Spatulation times varied! froira 10 to 35 s. The fillings were radiographed under standardized conditions. Twenty-five were classified as radio graphically homogeneous, 35 as partly iniiomogeneous, and 24 as inhomogeneous. Short spatulation times were correlated with a high frequency ofinhomogeiieous fillings. Only 15% of fillings spatula ted for less than 30 s were radiographically homogeneous. The observed inhomogeneities imply a risk of false positive diagnoses of secondary carious lesions.     

Raised bile acid concentrations in SIDS lungs at necropsy

Previous studies of the abnormal physical properties of lung surfactant derived from infants experiencing prolonged expiratory apnoea, or who have died of sudden infant death syndrome (SIDS), have led to a search for the agent responsible. Bronchoalveolar lavage (BAL) has been performed upon 12 infants under 12 months at necropsy and the rinsings analysed for up to 26 bile acids using high performance liquid chromatography, which requires nanomolar quantities. They were also analysed for simultaneously retrieved phospholipid and proteolipid-a minor component of lung surfactant-as markers of lavage efficiency. Total bile acid (TBA) was found to be higher in six SIDS cases, reaching a mean (SE) 8.54 (2.24) mumol/l in the BAL fluid compared with 4.66 (1.47) mumol/l in the six controls of similar age. When related to the concomitant surfactant yield, the TBA/ proteolipid and TBA/phospholipid ratios both showed highly significant differences between index lungs and controls, providing another postmortem marker of SIDS with potential for development as a test of risk. Since the bile:phospholipid ratio determines whether phospholipase A2 synthesises or hydrolyses phospholipid, the raised TBA/phospholipid ratio could be highly significant, causing this enzyme to function more like its role in the gut than in the lung.     

Radiographic control of fixture-abutment connection in Brånemark implant technique

Abstract— In the treatment with osseointegrated implants ad modum Brånemark a radiographic control of the fixture-abutment connection is recommended. The purpose of the present study was to analyze the possibilities of detecting incomplete connection by radiography using the recommended technique. In an experimental model the influence of film density, orientation of the fixture hexagon, angulation between film plane and fixture axis, leakage width, and partial connection were analyzed. Slits of 0.05 mm were detectable under optimum projection conditions. On the other hand, slits of 0.1 mm were obscured even at deviations of 5°. A number of factors, e.g. low density level and "unfavorable" orientation of the hexagon in relation to the X-ray beam, reduce the possibilities of detecting slits. It is concluded that in clinical cases a demonstration of incomplete fixture-abutment connection by the use of the recommended radiographic technique radiography to some extent is fortuitous, and that radiographic control has certain limitations.     

Which Carbohydrates Should We Recommend for Intravenous Nutrition?

In a short review solutions of glucose, fructose and invertose have been compared in regard to proteinsparing effects, side effects and infusion rates. It is concluded that fructose alone offers no advantage to glucose neither in the normal nor in the stressed organism. Compared with pure glucose and fructose solutions, higher amounts of carbohydrate can be administered as invertose, without increasing the risk of side effects.     

THE PSYCHOLOGICAL EFFECTS OF BREAST SCREENING IN TERMS OF PATIENTS' PERCEIVED HEALTH ANXIETIES

SUMMARY This study aimed to assess and compare the impact of letter of invitation, initial breast screening mammography, and subsequent recall procedures on the level of anxiety over breast problems. The survey of females undergoing routine breast screening procedures in a primary care setting is part of the first wave of a national breast screening programme in the UK. Women aged 50-64 registered with six general practices (n=2618) were invited by letter to attend for screening. Their self-perceived impact of receipt of invitation letter, attendance at initial screening, and recall, in terms of anxiety and concern about breast problems, was measured by a self-report questionnaire and the physical, emotional and social dysfunction subscales of the Psychological Consequences of Screening Mammography Questionnaire (PCQ). Overall, subjects' anxiety levels diminished between the receipt of their invitation letter and the completion of their screening examination. Subjects did not, however, respond to the letter of invitation and screening procedure in a homogeneous manner. In a sample of 1253, the letter of invitation reduced anxiety about breast problems in 39.7%, increased anxiety in 24.6%, and had no appreciable effect in 35.7%. In the 1280 who attended for breast screening, the examination procedure reduced anxiety about breast problems in 55.9%, increased anxiety in 12.8%, and had no appreciable effect in 31.3%. In a smaller sample (n=33) who completed questionnaires at recall, there were significant increases in PCQ-measured anxiety. Throughout the study, the PCQ was sensitive to change in anxiety over breast problems. We conclude that screening procedures can either increase or reduce anxiety about breast problems, or have no appreciable effect. Subjects' perception of the impact of receiving the letter of invitation and undergoing the screening examination procedure is related to previous levels of concern over breast problems. Conclusions about the psychological effect of breast screening cannot be drawn without consideration of the time and place of the baseline assessment. Participants in breast screening programmes therefore cannot be considered a homogeneous entity. Caution should be exercised when assessing the impact of screening procedures on entire populations as this approach might mask an important diversity of response.