Time from Tc-99m Sestamibi Injection to Imaging Scan for Rest and Stress Myocardial Perfusion Imaging

Introduction: The 2016 American Society of Nuclear Cardiology (ASNC) Imaging Guidelines for SPECT Nuclear Cardiology Procedures recommend the times between injection and imaging using Tc-99m Sestamibi are as follows: minimum delay for a rest study is 45 to 60 minutes, 15 to 20 minutes for an exercise stress study, and 60 minutes for pharmacologic stress exam. After a recent review within our Nuclear Cardiology Department at Northwestern Memorial Hospital (NMH), our physicians were unsure if the department was following published guidelines. The purpose of this project was to evaluate rest and stress injection times vs. imaging time to see if NMH was following published ASNC guidelines for Tc-99m Sestamibi myocardial perfusion imaging.

Methods: Data from 210 Nuclear Cardiology patient studies were collected using Visage Imaging software from October to November 2022. Injection time, scan time and the type of stress test were recorded for each patient. The injection times were compared along with the scan times for both rest and stress studies. Based on the aforementioned times from injection to imaging, it was noted whether the study adhered to published recommendations.

Results: Based on the data collection, the average uptake time for rest studies was 39.7 minutes with a standard deviation of 12.6 minutes. The average uptake time for an exercise stress study was 41.2 minutes with a standard deviation of 21.2 minutes. The average uptake time for pharmacologic stress study was 73.2 minutes with a standard deviation of 19.8 minutes.

Conclusions: The results revealed that rest and exercise stress studies at NMH were not within range of ASNC’s published guidelines. In particular, the average time from rest injection to imaging was shorter than the recommended minimum uptake time. Shorter uptake time from rest injection to imaging may adversely impact image quality due to increased subdiaphragmatic activity, and merits further investigation. Many factors may be affecting these results, such as camera availability and patient stability after stress testing. However, the results revealed that the average pharmacologic stress uptake times were within range of the published guidelines. In order to establish compliance with ASNC’s SPECT Nuclear Cardiology Guidelines, NMH may need to increase their patient appointment times to allow for appropriate timing on the cameras and educate the nuclear cardiology staff members on the ASNC recommendations.