Objective:
Myocardial Perfusion Imaging (MPI) with radiotracers is an integral component in
evaluation of the patients with known or suspected coronary artery diseases (CAD). 99mTc-Sestamibi
and 99mTc-Tetrofosmin are commercial radiopharmaceuticals for MPI by single photon-emission computed
tomography (SPECT). Despite their widespread clinical applications, they do not meet the requirements
of an ideal perfusion imaging agent due to their inability to linearly track the regional myocardial
blood flow rate at >2.5 mL/min/g. With tremendous development of CZT-based SPECT cameras
over the past several years, the nuclear cardiology community has been calling for better perfusion radiotracers
with improved extraction and biodistribution properties.
Methods:
This review will summarize recent research efforts on new cationic and neutral 99mTc radiotracers
for SPECT MPI. The goal of these efforts is to develop a 99mTc radiotracer that can be used to
detect perfusion defects at rest or under stress, determine the regional myocardial blood flow, and measure
the perfusion and left ventricular function.
Results:
The advantage of cationic radiotracers (e.g. 99mTc-Sestamibi) is their long myocardial retention
because of the positive molecular charge and fast liver clearance kinetics. 99mTc-Teboroxime derivatives
have a high initial heart uptake (high first-pass extraction fraction) due to their neutrality. 99mTc-
3SPboroxime is the most promising radiotracer for future clinical translation considering its initial heart
uptake, myocardial retention time, liver clearance kinetics, heart/liver ratios and SPECT image quality.
Conclusion:
99mTc-3SPboroximine is an excellent example of perfusion radiotracers, the heart uptake of
which is largely relies on the regional blood flow. It is possible to use 99mTc-3SPboroximine for detection
of perfusion defect(s), accurate quantification and determination of regional blood flow rate. Development
of such a 99mTc radiotracer is of great clinical benefit for accurate diagnosis of CAD and
assessing the risk of future hard events (e.g. heart attack and sudden death) in cardiac patients.