DEADTIME MEASUREMENTS IN SCINTILLATION CAMERAS UNDER SCATTER CONDITIONS SIMULATING QUANTITATIVE NUCLEAR CARDIOGRAPHY

  • 1 January 1978
    • journal article
    • research article
    • Vol. 19  (5) , 538-544
Abstract
Deadtime performance of scintillation cameras is sensitive to such factors as scatter fraction and analyzer window width. Data from manufacturers and previous investigators do not predict counting-rate losses under clinical conditions. Scintillation cameras used with 99mTc for quantitative nuclear cardiology in humans should be evaluated for deadtime performance by the 2-source method using a scatter phantom designed to simulate the spectrum from 99mTc in the heart. Under these conditions, scintillation cameras were found to follow the paralyzable model; accurate estimates could be obtained for data losses and maximum useful counting rates in a clinical setting. A survey of 39 contemporary scintillation cameras yielded a range of paralyzing deadtime values of 4.3-10 .mu.s, with a 20% window centered on the 99mTc photopeak. For an average deadtime of 6 .mu.s, counting rates should be maintained below 36,000 cps to avoid undue data losses in excess of 25%.

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