RESUMEN
OBJECTIVE: Extracardiac activity (ECA) may affect interpretation of gated SPECT myocardial perfusion studies (MPSs). To solve this problem, available softwares include myocardial edge delimitation. PURPOSE: To evaluate the influence of ECA in automatic myocardial edge detection under normal conditions and with abnormal perfusion and also evaluate the reproducibility of semi-automatic processing. METHODS: A total of 100 MPSs, 50 with ECA, were analyzed. Each subgroup included 25 cases with perfusion abnormalities. The cases were processed automatically and by 4 independent operators with different levels of experience. Commercial QGS and QPS softwares were used with tools to mask and relocate the left ventricle area. Functional parameters (final diastolic and systolic volumes and ejection fraction) and perfusion parameters such as the reversibility perfusion score and rest perfusion defect extension were analyzed. The data were compared with Pearson's correlation and Student's test. RESULTS: Interobserver correlation significantly worsened with the presence of ECA and was moderately affected by perfusion abnormalities. More experienced observers presented better correlation. Reproducibility was greater for the functional perfusion parameters, independently of the observer's experience. CONCLUSIONS: ECA significantly affects automatic edging delimitation, affecting the MPS values. Interobserver reproducibility with manual processing was more altered regarding functional parameters than in the perfusion scores. Perfusion abnormalities did not interfere with software reproducibility, and when present, better correlation was found. If ECA is not present, manual intervention should be avoided.
Asunto(s)
Artefactos , Tomografía Computarizada por Emisión de Fotón Único Sincronizada Cardíaca , Isquemia Miocárdica/diagnóstico por imagen , Imagen de Perfusión Miocárdica , Variaciones Dependientes del Observador , Radiofármacos , Tecnecio Tc 99m Sestamibi , Anciano , Automatización , Femenino , Humanos , Intestinos/diagnóstico por imagen , Hígado/diagnóstico por imagen , Masculino , Persona de Mediana Edad , Isquemia Miocárdica/patología , Radiofármacos/farmacocinética , Reproducibilidad de los Resultados , Programas Informáticos , Volumen Sistólico , Tecnecio Tc 99m Sestamibi/farmacocinética , Radioisótopos de Talio/farmacocinética , Distribución TisularAsunto(s)
Corazón/diagnóstico por imagen , Radioisótopos de Talio , Ventrículos Cardíacos/diagnóstico por imagen , Ventrículos Cardíacos/metabolismo , Humanos , Isquemia Miocárdica/diagnóstico por imagen , Isquemia Miocárdica/metabolismo , Cintigrafía , Radioisótopos de Talio/administración & dosificación , Radioisótopos de Talio/farmacocinética , Factores de Tiempo , Distribución TisularRESUMEN
Normal myocardial cells actively uptake the radioisotope Thallium-201 and its myocardial distribution is a reflection of the existent regional coronary artery blood flow at the moment of the examination. Thallium-201 reaches quickly a high intracellular concentration and then leaves myocardial cells in a mean time of 4 to 8 h. In the presence of significant coronary artery disease, uptake and elimination rates of Thallium-201 are delayed in ischemic tissue, compared to normal tissue. This leads to regional differences in relative concentrations which allow to identify viable areas with insufficient coronary flow in conditions of vasodilatation induced by exercise or pharmacologic means. This phenomenon does not occur in the irreversibly damaged myocardium, and affected areas fail to uptake the radioisotope. Clinical applications of this test are: 1.--Search for coronary artery disease. 2.--Assessment of patients with known coronary artery disease. 3.--Evaluation of patients after revascularization procedures. 4.--Assessment of coronary risk before peripheral vascular surgery. 5.--Detection of viable myocardium. 6.--Assessment of coronary reserve in patients with angor and normal coronary vessels.