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At least 1,621 records · Page 90Linked to original sources
PubMed2004

Spatial and temporal variations of atmospheric 85Kr observed during 1995-2001 in Japan: estimation of atmospheric 85Kr inventory in the Northern Hemisphere.

Atmospheric 85Kr concentrations have been continuously monitored since 1995 at the Meteorological Research Institute (MRI) in Tsukuba, Japan. They have also been observed once a year at several stations over the Japanese islands since 1995. The annual growth rate of the background atmospheric 85Kr concentrations in Tsukuba was 0.03 Bq x m(-3) x yr(-1) during 1996-2001. The atmospheric 85Kr concentrations at several stations over Japan were within the range of the annual variations in Tsukuba. However, higher and lower 85Kr concentrations in early winter, compared with those in Tsukuba (36.1 degrees N, 140.1 degrees E), occurred in Sapporo (43.1 degrees N, 141.3 degrees E) and Ishigaki (24.3 degrees N, 124.2 degrees E), respectively. The reason for this is that Sapporo is covered by a continental air mass, some from European sources, whereas Ishigaki is still covered by a subtropical air mass. The Northern Hemispheric background 85Kr concentrations from 1994 to 2001 was calculated from the 85Kr inventory and the release rate of 85Kr from the nuclear fuel reprocessing plants in Europe. Calculated 85Kr concentrations in surface air were in good agreement with annual average observed values at the MRI, Tsukuba. The global atmospheric inventory of 85Kr in December 2001 was also estimated to be approximately 5 EBq by using observed data in Tsukuba.

Air Pollutants, Radioactive↗
PubMed2003

Regional ventilation by electrical impedance tomography: a comparison with ventilation scintigraphy in pigs.

STUDY OBJECTIVE: The validation of electrical impedance tomography (EIT) for measuring regional ventilation distribution by comparing it with single photon emission CT (SPECT) scanning. DESIGN: Randomized, prospective animal study. SETTINGS: Animal laboratories and nuclear medicine laboratories at a university hospital. PARTICIPANTS: Twelve anesthetized and mechanically ventilated pigs. INTERVENTIONS: Lung injury was induced by central venous injection of oleic acid. Then pigs were randomized to pressure-controlled mechanical ventilation, airway pressure-release ventilation, or spontaneous breathing. MEASUREMENTS AND RESULTS: Ventilation distribution was assessed by EIT using cross-sectional electrotomographic measurements of the thorax, and simultaneously by single SPECT scanning with the inhalation of (99m)Tc-labeled carbon particles. For both methods, the evaluation of ventilation distribution was performed in the same transverse slice that was approximately 4 cm in thickness. The transverse slice then was divided into 20 coronal segments (going from the sternum to the spine). We compared the percentage of ventilation in each segment, normalized to the entire ventilation in the observed slice. Our data showed an excellent linear correlation between the ventilation distribution measured by SPECT scanning and EIT according to the following equation: y = 0.82x + 0.7 (R(2) = 0.92; range, 0.86 to 0.97). CONCLUSION: Based on these data, EIT seems to allow, at least in comparable states of lung injury, real-time monitoring of regional ventilation distribution at the bedside.

Animals↗
PubMed1982

Dynamic imaging of the respiratory cycle with 81mKr.

To define the regional ventilation of the human lung, subjects were monitored with a gamma camera, while breathing air labeled with radioactive 81mKr which is being continuously eluted from a generator. The information observed is displayed as a reiterated multiframe moving picture. This is accomplished by storing the information from multiple breaths, selecting acceptable cycles (determined by the duration of inspiration and expiration and the amplitude to extremes of the cycles), and normalizing the usable information and converting the summed data into sequential frames, which are repeatedly shown on a video screen from computer memory.

Computers↗
PubMed1978

81mKr ventilation and 99mTc perfusion scans in chest disease: comparison with standard radiographs.

In 75 patients with various pulmonary disorders, ventilation and perfusion scans were obtained in multiple views with the 81mKr/99mTc technique and compared with an evaluation of regional ventilation and perfusion derived from the standard chest radiograph. In emphysema, the chest film correlated poorly with ventilation-perfusion scans, showing a trend to underestimate the functional impairment. In chronic bronchitis and asthma, large segmental defects observed on both ventilation and perfusion scans were associated with a normal chest radiograph. Typical findings in pulmonary embolism were segmental defects on perfusion scan with normal ventilation scan and clear lung fields on the chest film. In chronic left heart disease, plain films were inaccurate in predicting alteration of the base-to-apex perfusion gradient observed on the scan.

Airway Obstruction↗
PubMed1996

A study of laser-based removal of polymethylmethacrylate bone cement.

Complications are often produced with the removal of bone cement from the femoral cavity in the treatment of a failed hip prosthesis. Apart from being slow and difficult the conventional process runs the risk of producing damage to the femur. Ultrasonic techniques have been suggested to achieve these ends but removal of the cement by this approach is not entirely easy. The alternative laser-based approach would seem to have significant advantages over conventional techniques. The laser is capable of delivering energy to a specific region or surface under close control. The choice of laser is determined by its ability to ablate the cement and the ease with which it can be delivered to the base of the femur cavity. This paper examines several laser wavelengths: CO2 (10.6 microns), excimer (248 nm), Hol:YAG (2.12 microns), and presents polymethylmethacrylate (PMMA) vaporization thresholds for each laser.

Absorption↗