An evaluation of a noninvasive method of assessing alveolar bone levels in an experimental model of cleft lip and palate.

OBJECTIVE: The purpose of this study was to evaluate an ultrasound mucous-membrane-thickness-measuring device as a noninvasive, nonionizing alternative to radiography in the assessment of alveolar bone grafting. DESIGN: This was a prospective experimental study on porcine cadaver models. METHOD: An ultrasound technique (Krupp SDM) was assessed ex vivo on three specially developed porcine cadaver models in comparison to radiography and ridge-mapping. Direct measurement of the mucosal thickness provided a standard for comparison. In each model, 30 measurement sites were identified for comparison of the techniques. RESULTS: All measurement techniques demonstrated clinically acceptable reproducibility. Of the clinical measurement techniques, radiography proved to be the most reliable, showing a small, nonsignificant statistical difference from direct measurement. Both the ultrasound technique and ridge-mapping showed significant tendencies to underestimate mucosal thickness that became greater with increasing mucosal thickness. At sites where mucosal thickness was less than 6 mm, the ultrasound technique underestimated mucosal thickness by 0.6 mm on average. At sites where mucosal thickness exceeded 6 mm, ultrasonic artifacts rendered the ultrasound technique unreliable. CONCLUSION: The ultrasound technique could prove to be a useful clinical adjunct to radiography in the assessment of alveolar bone grafts, but in this particular application, care should be taken when using it to assess deeper alveolar defects.

Aortic injury: comparison of supine and upright portable chest films to evaluate the widened mediastinum.

Despite many reports of radiologic findings that may be suggestive of aortic injury, most authors believe the recognition of a widened mediastinum on chest film remains the sine qua non. Few studies have confirmed the widely held belief that the supine AP chest film is inaccurate in assessing the width of the mediastinal structures, and that one should use only the upright or sitting chest films. This study was undertaken to assess the accuracy of both upright and supine chest films in the evaluation of mediastinal widening after blunt deceleration chest injury. Both supine and upright sitting chest films were obtained immediately on arrival in the resuscitation areas for 55 patients. Twenty-one (38%) exhibited a mediastinum that appeared wide on supine view but within normal limits on the upright view, as attested by two radiologists. Aortography was not performed on any of these patients. Daily upright chest films, repeated until discharge, failed to demonstrate any change in mediastinal anatomy, and all patients recovered without incident. Twelve patients' films (22%) demonstrated widened mediastinum on both views, and these 12 patients underwent immediate aortography. Aortic rupture was revealed in four (33%). This study clarifies the diagnostic value of the upright chest film in assessing the mediastinum after blunt injury. It confirms the belief that supine films are not accurate, and that they may lead to numerous false positives and unnecessary aortograms. The initial upright or sitting chest film is accurate, and its use is cost-effective and time-saving for patient and physician.(ABSTRACT TRUNCATED AT 250 WORDS)

Visual masking of targets displayed against two- and three-dimensional backgrounds.

Detection thresholds for targets displayed against two- and three-dimensional backgrounds were measured under backward masking and non-masking conditions. The results indicate that planar ring targets displayed against a two-dimensional ground are easier to mask than identical targets portrayed against a three-dimensional background. Also, the detectability of a planar ring target is enhanced when it is included within a three-dimensional rather than an identical but two-dimensional visual display. These results confirm and extend previous findings and suggest a processing asymmetry biased toward three-dimensional visual displays.

The Poggendorf illusion in stereoscopic space.

The stereoscopic depth separation between the bisecting rectangle and the oblique line of a Poggendorf configuration was manipulated by varying the direction and magnitude of disparity carried by the rectangle. Based upon data of 6 subjects, the magnitude of the illusion decreased with increasing depth separation regardless of the direction of disparity. Depth separation varied directly with disparity. These findings make plain that depth adjacency can operate symmetrically in stereoscopic space.