Subdiaphragmatic activity-related artifacts in myocardial perfusion scintigraphy

Abstract

Background: Myocardial perfusion imaging (MPI) with single photon emission computed tomography is an established non-invasive technique for assessing myocardial ischemia. This method involves the intravenous administration of a radiopharmaceutical that accumulates in the heart muscle proportional to regional blood flow. However, image quality and diagnostic accuracy can be compromised by various technical and patient-related factors, including high non-specific radiopharmaceutical uptake in abdominal organs such as the stomach, intestines, liver, and gall-bladder, leading to subdiaphragmatic artifacts. These artifacts are particularly problematic for evaluating inferior wall perfusion and often necessitate repeated imaging, which decreases gamma camera availability and prolongs imaging times.

Conclusions: Despite numerous investigated techniques to reduce interfering gastrointestinal activity, results have been inconsistent, and current MPI guidelines provide scant information on effective procedures to mitigate this issue. Based on our experience, some possible approaches to reducing artifacts include choosing stress testing with an exercise stress test, when possible, late imaging, fluid intake, and consuming carbonated water immediately before imaging.

Keywords: artifacts, subdiaphragmatic activity; intervention; myocardial perfusion imaging; single photon emission computed tomography.

FIGURE 1.

Interfering subdiaphragmatic activity (yellow arrow) on short and vertical long axis images of the left ventricle with (upper raw) and without attenuation correction (lower raw).

FIGURE 2.

An example of manually drawn regions of interests (ROIs) over the midportion of the inferior wall of the myocardium and the adjacent underlying abdominal regions on multiple projections on raw planar images of the stress study. After pixel counts were obtained for every ROI, the mean myocardial and extracardiac counts were used to calculate the ratio of myocardial to extracardiac activity (MYO:EXT ratio).

FIGURE 3.

By administering carbonated water before imaging, carbon dioxide gas may additionally expand the stomach. The upper part of the stomach adjacent to the inferior wall of the heart is mainly filled with gas instead of water. By distending the stomach, we increase the distance between the gut and the heart, thereby reducing imaging artifacts (yellow arrow).