In all patients, 1.5 mCi of thallium was injected intravenously at peak exercise and exercise was continued for a further 1 min. Initial thallium scanning was begun within 8 min of cessation of exercise, following removal of the BSPM leads. Images were obtained in the 45° left anterior oblique positiqn, as well as in the anterior and left lateral positions, using an Ohio Nuclear Series 420 scintillation camera and a high sensitivity, parallel hole collimator. Images were continued until 300,000 total counts were recorded in each view. Scanning was repeated in the same fashion 4 h postexercise.
Analog images were interpreted from x-ray transparent film without computer enhancement or background subtraction, independent of other clinical and study data. Exercise and 4-h redistribution scans were analyzed in pairs for the presence or absence of a thallium defect. Exercise defects were classified as fixed (unchanged at redistribution) or reversible (reduced or absent at redistribution). Reversible defects were considered positive scintigraphic evidence of exercise-induced ischemia. birth control pills
Scans were further classified in a semiquantitative manner, according to the method of Atwood et al. Defect size was graded on a scale of 1 to 5, with 10^20 percent of myocardial area scored as 1; 20^30 percent, 2; 30<40 percent, 3; 40^50 percent, 4; and, >50 percent, scored as 5. Defect intensity was graded as follows: 1 = normal uptake; 2= just less than normal; 3=just greater than background; and 4 = equivalent to background activity. Size and intensity scores from all three views were summed at both exercise and 4-h redistribution. Patients with reversible defects then had a net severity score calculated as the exercise score minus the redistribution score. This net score was utilized as a quantitative reflection of exercise-induced perfusion deficit and myocardial ischemia (Table 2).
Blog invites submissions of review articles, reports on clinical techniques, case reports, conference summaries, and articles of opinion pertinent to the control of pain and anxiety in dentistry.