The impact of number of steps on gastrointestinal activity-related artifacts in myocardial perfusion scintigraphy

Abstract

Abstract Objective. Various techniques have been used to reduce interfering extracardiac activity in myocardial perfusion imaging (MPI) with inconsistent results. The aim of this study was to investigate the effect of previously not specifically addressed monitored walking on the reduction of infracardial artifacts in the pharmacological stress Tc-99m tetrofosmin MPI with single-photon emission computed tomography (SPECT) to improve image quality. Methods. The study was performed in 199 patients who were referred for routine 2-day stress/rest MPI and underwent pharmacological stress test. Patients were randomized into group A (n=95) and group B (n=104). Both groups were provided with a step-counter immediately after the radiotracer injection, but only group A was instructed to take at least 1000 steps before the imaging. Study participants received intervention only on stress day. Images were evaluated qualitatively and quantitatively for the interfering extracardiac artifacts. Myocardial and abdominal activity were quantitatively assessed on raw planar images, and the mean myocardium-to-abdomen count ratios were calculated. In addition, the presence of interfering activity was assessed visually on reconstructed SPECT images. The amount of extracardiac tracer activity was scored from “no tracer activity” to “severe.” Moderate and severe subdiaphragmatic tracer activity was considered relevant for the interpretation of the myocardial perfusion scan. Results. There were no differences in clinical characteristics between the two groups. Patients in group A walked more steps than those in group B, but there were no differences in acceptance rate between the two groups. There were also no differences in proportion of subdiaphragmatic activity with a score 2 or 3 between the groups. Number of steps had no effect on acceptance rate. Conclusions. Walking at least 1000 steps while waiting on acquisition has no impact on the gastrointestinal activity related artifacts and acceptance rate of the scans after pharmacological stress in comparison to walking on own discretion. However, the use of pedometers encourages patients to walk while waiting for imaging. Further larger studies, which would compare a group with a higher number of steps (at least 3000 steps) and a sedentary control group, are needed, to address the impact of walking on gastrointestinal artifacts in MPI.