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A Multicenter Trial on Interobserver and Intraobserver Reproducibility of Segmental Scoring of Thallium-201 Planar Myocardial Imaging Before and After Reinjection

Department of Nuclear Medicine, Ospedale Maggiore, Novara
Department of Nuclear Medicine, Montescano Hospital
Department of Nuclear Medicine, Faenza Hospital, Faenza
Department of Nuclear Medicine, Messina University, Messina
Department of Nuclear Medicine, Milan University
Department of Nuclear Medicine, Niguarda Hospital, Milan, Italy

Correspondence: For correspondence or reprints contact: Marco Brambilla, Dept. of Nuclear Medicine, Ospedale Maggiore della Carità, corso Mazzini 18, 28100 Novara, Italy.

ABSTRACT

Inter- and intraobserver reproducibility (R) of segmental ²⁰¹Tl scores after stress (ST), redistribution (RD) and reinjection (RI) planar imaging were evaluated. Methods: Images were examined from 396 patients with suspected coronary artery disease, demonstrated by means of post-ST imaging of at least one perfusion defect. To eliminate external sources of variability, the same gamma camera, acquisition protocol and computer software were used in this multicenter study. Thallium-201 images of the anterior, left anterior oblique and left lateral projections were obtained immediately, 4 hr after exercise and 30 min after the injection of additional ²⁰¹Tl either on the same day or on a different day. The left ventricle was divided into 15 segments and evaluated by three independent observers, blinded to clinical data, according to a five-point scale. Results: The R score for ST, RD and RI images, expressed as an intraclass correlation coefficient, was 0.76, 0.74 and 0.72, respectively. After averaging multiple observer scores, R increased to 0.91, 0.90 and 0.89, respectively. Individual observer measurement of the R score was 0.48, 0.51 and 0.32 for ST-AD, ST-RI and RD-RI image pairs, respectively, and multiple observer scores showed R increases to 0.74, 0.76 and 0.58. Conclusion: This qualitative scale reliably assesses the severity of ²⁰¹Tl perfusion defects, particularly when multiple-observer scores are averaged. Individual observer change scores should be taken with great caution, especially in studies involving the visual evaluation of RD-RI image changes.

Key Words: multicenter trial • thallium-201 • planar myocardial imaging