Motion artifact seen on slot-scanning direct digital mammography

OBJECTIVE: Our goal was to determine the appearance of motion artifact when imaging an anthropomorphic breast phantom using a digital slot-scanning system compared with a screen-film system. MATERIALS AND METHODS: Digital and screen-film images were obtained during both brief and continuous manually induced motion of an anthropomorphic phantom in four directions. Continuous motion was further characterized using a syringe pump to induce motion artifact. RESULTS: On screen-film images, brief motion caused degradation of the entire image, simulating a double exposure. Conversely, on digital images using a slot-scanning system, brief motion caused degradation of only a small portion of the image. Continuous motion resulted in smearing of phantom details with both systems, although the smearing was more strongly influenced by the direction of motion when the slot-scanning system was used. With the slot-scanning system, motion in the direction of the detector sweep resulted in elongated distortion, whereas motion in the opposite direction resulted in foreshortening; diagonal smearing was seen with perpendicular phantom motion. The magnitude of distortion for continuous motion at a set velocity was substantially less with the slot-scanning system. CONCLUSION: Motion artifact with a slot-scanning direct digital mammography unit differs significantly from that seen with a conventional screen-film unit and, despite a relatively long overall exposure, may prove to be less of a problem than with conventional units because any given part of an object is exposed only briefly.     

Physician integration into mass gathering medical care. The United States Air Show

INTRODUCTION: Limited information exists concerning physician staffing at mass gathering events. METHODS: A retrospective review of the preparation, planning, and provision of medical care for the United States Air Show was performed. Patient encounters from the air show for the years 1981-1991 also were evaluated. RESULTS: The frequency rate of overall encounters was 8.45 patients/10,000 spectators and hospital transport rate was 0.6/10,000 spectators. The majority of complaints were related to heat or minor injuries. During this period, emergency physicians played a vital role in both medical planning and on-site staffing. Emergency medicine residents also participated. A small patient population received direct benefit from on-site physician intervention. CONCLUSION: The on-site emergency physician is of benefit in event preplanning and reducing the burden on the EMS system during mass gathering events.     

A rejoinder to Professor Bruening

Point and Counterpoint

A rejoinder to Professor Bruening     

Further thoughts on double effect: some preliminary responses

Since the papers in this issue by Alan Donagan, Don Marquis, William Nelson and Warren Quinn raise complex and challenging questions about almost every aspect of my "Who is Entitled to Double Effect", I cannot, in the present context, provide more than preliminary responses to some of the more important issues they raise in the hope that this might contribute to further clarification of the doctrine of double effect (DDE).