title: Evaluation and clinical use of early washout ratio of thallium-201 in normal and ischemic myocardium after dipyridamole-induced vasodilation using ring-type emission computed tomography.
abstract: Using newly developed ring-type emission computed tomography (SPECT), we investigated the washout ratio (WR) of T1-201 in the myocardium quantitatively with fast dynamic scanning after infusion of dipyridamole (0.57 mg/kg), and assessed the feasibility of early WR as a marker to detect coronary artery disease. Twenty-three patients with and 8 patients without coronary artery disease had serial SPECT images obtained every 5 min for 45 min and at 180 min after dipyridamole and subsequent T1-201 injection. The best appropriate transaxial slice was selected for WR analysis. Most appropriate diagnostic time was 25 min after infusion of T1-201 (WR-25). Normal WR-25 was 7.1 +/- 4.0%, 5.9 +/- 3.1% and 7.1 +/- 2.3% at the septum, anterior and lateral wall, respectively. Sensitivity, specificity and accuracy to identify coronary stenosis greater than 50% with a usage of abnormal WR-25, defined as WR-25 less than (mean of normals--1SD) in each region of inferest of the left ventricle (LV), were 96%, 100% and 97%, respectively. These results were better than those achieved by visual analysis (sensitivity 78%, specificity 100%, accuracy 84%). In patients with single as well as multivessel disease, the regional accuracy in assessing stenosis of more than 50% in the left anterior descending artery (LAD) and left circumflex artery (LCX) by WR-25 was 94% and 83%, respectively, which was significantly better than using visual methods (LAD 72% and LCX 50%; p less than 0.05). Thus, evaluation of early washout ratios (WR-25) after dipyridamole injection is a valuable method to increase sensitivity in assessing regional myocardial perfusion abnormality and is helpful in detection of ischemic heart disease, even with multivessel disease.
authors.affiliation: Department of Internal Medicine, Kyoto University Hospital, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Hayashi
authors.forename: H
authors.initials: H
authors.lastname: Kambara
authors.forename: R
authors.initials: R
authors.lastname: Nohara
authors.forename: T
authors.initials: T
authors.lastname: Fudo
authors.forename: T
authors.initials: T
authors.lastname: Hashimoto
authors.forename: C
authors.initials: C
authors.lastname: Kawai
authors.forename: N
authors.initials: N
authors.lastname: Tamaki
authors.forename: Y
authors.initials: Y
authors.lastname: Yonekura
authors.forename: J
authors.initials: J
authors.lastname: Konishi
mesh_terms: D000328:Adult; D000368:Aged; D003327:Coronary Disease / Q000000981:diagnostic imaging*; D004176:Dipyridamole / Q000494:pharmacology*; D005260:Female; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D008297:Male; D008875:Middle Aged; D013794:Thallium Radioisotopes / Q000378:metabolism*; D014055:Tomography, Emission-Computed / Q000379:methods*; D014664:Vasodilation / Q000187:drug effects*
chemical_list: D013794:Thallium Radioisotopes; D004176:Dipyridamole