Biomedical subjects
Publications and source records attributed to A Thorsen.
Fluorine-18-2-fluro-2-deoxy-D-glucose-positron emission tomographic tumor imaging was employed to aid in the diagnosis of a patient with a right hilar mass. Based on preoperative imaging and intraoperative findings, a right pneumonectomy was performed for what proved to be a pulmonary artery sarcoma.
OBJECTIVE: To better define the effectiveness of abdominal computed tomographic scanning (ACTS) in adult patients with suspected appendicitis. DESIGN: Retrospective analysis. SETTING: A community teaching hospital. PATIENTS: Ninety-seven patients with appendicitis in the differential diagnosis, whose clinical findings were insufficient to perform surgery or to discharge from the hospital, during a 14-month period. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Accuracy of ACTS, rate of appendectomies that show no appendicitis (negative appendectomy rate), and frequency of ACTS as a definitive diagnostic test. RESULTS: Forty-nine of the 50 patients with appendicitis were correctly diagnosed by ACTS. Forty-three of the 47 patients without appendicitis were correctly diagnosed by ACTS. Positive predictive value was 92%, negative predictive value was 98%, and accuracy was 96%. The ACTS group had a negative appendectomy rate of 5.8% (3/52), lower than the hospital rate of 14% for the preceding 3 years. The ACTS established an alternative diagnosis in 16 patients, allowed 10 other patients to be discharged early or not admitted, and was the critical diagnostic test in 30 of the patients with appendicitis. Therefore, the ACTS played a definitive role in the treatment of 56 (57.7%) of the 97 patients. CONCLUSIONS: The ACTS was an accurate test in the diagnosis of appendicitis and was of significant benefit in 57.7% of the patients studied. However, it was difficult to predict which patients were most likely to benefit. Expanded selective use of ACTS for patients with clinically indeterminate appendicitis may result in a lower negative appendectomy rate and fewer patient admissions for observation.
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Conventional transmission electron microscopy requires an effective dehydration of the tissue specimens under investigation. This dehydration, for which ethanol most often is used, may influence the solubility of the slightly soluble calcium phosphates. To study the behavior of calcium phosphates in ethanol, stable neutral aqueous solutions containing the ions were mixed with ethanol in various ratios at 20 degrees C. After 24 hours, the precipitates formed wee identified by x-ray diffraction to be either apatite, brushite, or amorphous calcium phosphate. The results are discussed with reference to possible formation of calcium phosphate artifacts.
In a liquid (22 degrees C) saturated with and in contact with powdered bone apatite, the fluoride ion activity was adjusted to 1-10 parts/10(6). Due to the fluorapatite (FAP) supersaturation produced hereby, a rapid formation of this salt occurred leading to a decrease of the concentration of the ions involved. When no more fluoride was available in the liquid, the concentrations of calcium and phosphate increased again, due to dissolution of presumably hydroxyapatite (HAP). Fifty four rats were given either 10, 20, or 40 mg NaF per kg body weight intraperitoneally. The animals were sacrificed from 5 min to 96 h after the injection. The fluoride concentration in plasma increased to a peak, after which it decreased. Plasma calcium decreased and remained low until the fluoride had attained normal levels. The intensity of mineralization of the growing dental hard tissue was monitored on microradiographs. Corresponding to the plasma fluoride peak and the decrease of plasma calcium, a hypermineralized layer was formed while a hypomineralized zone was formed during plasma calcium increase after disappearance of fluoride. Similarities and dissimilarities between the in vitro and the in vivo experiments are discussed.
Human dental enamel was exposed to a pH 4 buffer containing 150 parts/10(6) fluoride. It was found that due to the arising degrees of saturation with respect to calcium fluoride and apatites, surface enamel dissolved coincident with a formation of calcium fluoride. The calcium fluoride redissolved while it kept the liquid saturated with respect to this salt. During this second period, fluorapatite was formed while hydroxyapatite dissolved. Finally, all calcium fluoride was dissolved and the unreacted fluoride was taken up in the apatitic lattice. The results are discussed with reference to the conditions of the oral cavity and enamel solubility experiments.
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