What is the optimal activity ratio for same-day myocardial perfusion SPECT?
- PDF / 285,939 Bytes
- 4 Pages / 593.972 x 792 pts Page_size
- 39 Downloads / 164 Views
a
Nuclear Medicine, Manchester University NHS Foundation Trust, Manchester, UK
Received Sep 11, 2020; accepted Sep 11, 2020 doi:10.1007/s12350-020-02386-9
See related article, https://doi.org/10.10 07/s12350-020-02290-2 Myocardial perfusion SPECT with the Tc-99m tracers sestamibi (MIBI) and tetrofosmin has been performed clinically for decades and forms the backbone of nuclear cardiac imaging for patients with coronary artery disease (CAD). The favorable physical characteristics of Tc-99m, compared with Tl-201, leads to improved image quality and reduced patient radiation exposure. For Tc-99m tracers, practice is split among sameday and two-day imaging protocols and there are advantages and disadvantages for both approaches. Same-day imaging protocols provide the convenience of a single visit to the center, which is particularly advantageous for patients traveling substantial distance. However, the lack of significant tracer redistribution for both MIBI and tetrofosmin mandates the need for a second injection of tracer to show differences of perfusion during resting and stress conditions. As the second imaging session is typically performed 3 to 4 hours after the first imaging session, the inevitable presence of residual tracer within the myocardium due to the 6-hour Tc-99m half-life requires the activity in the second injection to be greater to reduce the appearances of the residual activity distribution from the first injection—a phenomenon that been referred to as ‘‘shine-through’’ or ‘‘ghosting’’.
Reprint requests: Ian S. Armstrong, PhD, Nuclear Medicine, Manchester University NHS Foundation Trust, Oxford Road, Manchester M13 9WL; [email protected] J Nucl Cardiol 1071-3581/$34.00 Copyright Ó 2020 American Society of Nuclear Cardiology.
HISTORY AND PRACTICE The first use of MIBI in the late 1980s1 predates the introduction of tetrofosmin2 and hence it is these preliminary studies using MIBI that set the precedent for the same-day regime of activity ratios. Over the following decade, several studies were published that evaluated the use of both MIBI and tetrofosmin in sameday imaging. A summary of a selection of these studies is given in Table 1. As can be seen from the data in the table, the earlier studies with MIBI focused on a reststress protocol opposed to a stress-rest protocol, with the former being shown to provide the superior ability to identify areas of ischemia.3,4 The increased focus on reducing radiation dose to patients advocates the use of stress-first, stress-only protocols where the follow-on resting acquisition, which carries a greater radiation burden, can be canceled if not required.5 Hence modern practice is likely to perform the stress imaging first, which will facilitate the use of stress-first, stress-only imaging. This requires perfusion in the follow-on resting image to fully mask any regional tracer reduction in the stress images to differentiate reversible ischemia from non-reversible infarct. While early studies have evaluated the order in which to perform rest and stress
Data Loading...
