No abstract

No abstract

The effect of temperature on the Schumann‐Runge ultraviolet absorption continuum of oxygen has been investigated, using photoelectric techniques, over a temperature range from 300 to 900°K and in the wavelength interval from 1580 to 1950 A. The monochromator bandwidth was 0.075 A. Absolute absorption cross sections were obtained and curves are presented showing the variation of the cross section with wavelength for the temperatures 300, 600, and 900°K.

No abstract

No abstract

Quantitative dual-energy radiographic absorptiometry (DRA) and dual-photon absorptiometry (DPA) were compared to determine the best means of assessing bone density. Both methods were used to evaluate the lumbar spine in 107 women (aged 35-84 years [mean, 64 years]) referred for evaluation of osteoporosis risk. High correlation was documented between measurements derived by the two techniques, with a .95 linear regression coefficient for the total spine density measurement. Age-related regression equations were similar in slope but manifested different intercepts. Bone mineral density values derived with DRA were consistently lower than those obtained with DPA (conversion equation: DPA density = [1.067 X DRA density] + 0.163). Besides the inherent imperfections of each system, it was found that inaccurate identification of intervertebral spaces on the low-resolution DPA images introduced errors in patient data. DRA may replace DPA as the dedicated projectional densitometric procedure of choice for technical reasons, but at present a conversion equation must be used to compare DRA data to DPA data.

No abstract

An x-ray imaging system that makes use of a rapidly scanning pencil beam of x rays to acquire images of any part of the body has been developed. The system is capable of generating and displaying images in 15 seconds, using extremely low radiation exposures. The principle of its operation, its unique imaging properties, and its possible applications are discussed.