Recognizing the Toxicodendrons (poison ivy, poison oak, and poison sumac).
Poison ivy, poison oak, and poison sumac are now classified in the genus Toxicodendron which is readily distinguished from Rhus. In the United States, there are two species of poison oak, Toxicodendron diversilobum (western poison oak) and Toxicodendron toxicarium (eastern poison oak). There are also two species of poison ivy, Toxicodendron rydbergii, a nonclimbing subshrub, and Toxicodendron radicans, which may be either a shrub or a climbing vine. There are nine subspecies of T. radicans, six of which are found in the United States. One species of poison sumac, Toxicodendron vernix, occurs in the United States. Distinguishing features of these plants and characteristics that separate Toxicodendron from Rhus are outlined in the text and illustrated in color plates.
Recognition of Poison Ivy During Winter with Emphasis on Midwestern Plants
An important factor in the management of poison ivy dermatitis, as in that of other types of allergic contact dermatitis, is the recognition and avoidance of the causative agent. However, this is not always easy. In the United States, there are five species of Toxicodendron, including six of the nine subspecies of Toxicodendron rac/fcans.' There are also other toxic plants that are regionally important, eg, poisonwood and "Florida holly" in Florida. However, for most of the United States, poison ivy is by far the most important of these plants. Patients and physicians assume that everyone instinctively knows how to recognize poison ivy. Consequently, many people are ashamed to ask how this is done. So few reliable sources of information are available for some species and subspecies that pictures and models of one Atlantic Coast subspecies have been used to teach patients living in areas where that plant does not exist. In the summer, even knowledgeable individuals use leaf morphology as their principal, if not exclusive, criterion for identification of poison ivy: in the winter, there are few who can recognize the plant at all.
Mottle on computed radiographs of the chest in pediatric patients.
PURPOSE
To investigate the relationship between radiation exposure and perceived mottle at bedside pediatric chest examinations performed with screen-film and computed radiographic techniques.


MATERIALS AND METHODS
In a pediatric intensive care unit, chest radiographs were obtained with both computed radiography (60 radiographs) and a 600-speed screen-film system (14 radiographs). The relative radiation exposure was estimated by using the sensitivity value obtained in the processing of each computed radiograph. Five radiologists assessed the mottle present in the computed radiographs and screen-film images.


RESULTS
For computed radiographs, the perceived level of mottle was inversely related to radiation exposure. For the same radiation exposure, the perceived mottle on computed radiographs was significantly higher than that on screen-film images (P < .001 for small cassettes; P < .01 for large cassettes).


CONCLUSION
Pediatric computed radiography of the chest requires approximately twice the exposure of a 600-speed screen-film system to attain the same level of mottle.