Postexercise lung uptake of Tc-99m-sestamibi determined by a new automatictechnique: Validation and application in detection of severe and extensivecoronary artery disease and reduced left ventricular function

This study validated a new automatic algorithm for assessment of lung-to-he art ratio (UH) of radiotracers in myocardial perfusion SPECT and assessed t he diagnostic value of Tc-99m-sestamibi UH after exercise. Methods: The new technique extracts a left ventricular region of interest (ROI) from a summ ed anterior projection image and generates a lung ROI by reshaping and tran slating the left ventricular ROI. This algorithm was applied to 230 patient s who underwent exercise Tc-99m-sestamibi SPECT (gated SPECT, n = 88) with first-pass ventriculography. Normal values were established in 26 patients in whom the likelihood of coronary artery disease (CAD) was 5% or less. An abnormality threshold for detecting severe and extensive CAD was defined in a subgroup of 109 patients who underwent coronary angiography and was vali dated in a prospective group (n = 72). Results: The success rate of the aut omatic algorithm was 97%. Excellent correlation was found between automatic and manual UH values (r = 0.95; P < 0.001). The mean VH was higher in pati ents with a peak exercise ejection fraction (EF) less than 40% versus 40% o r more (0.51 +/- 0.07 versus 0.43 +/- 0.05, P < 0.001) and in patients with a poststress EF less than 40% versus 40% or more (0.50 +/- 0.07 versus 0.4 4 +/- 0.06, P < 0.01). A threshold of UH greater than 0.44 yielded a sensit ivity and specificity of 63% and 81%, respectively, for identifying severe and extensive CAD in the prospective group and a sensitivity of 86% in iden tifying stenosis of 90% or more in the proximal left anterior descending ar tery. Conclusion: The new automatic algorithm for assessing VH correlated w ell with manually derived UH for Tc-99m-sestamibi as well as (TI)-T-201 SPE CT. An increased postexercise Tc-99m-sestamibi VH adds significant diagnost ic value to study myocardial perfusion SPECT as a marker of severe and exte nsive CAD and reduced ventricular function.