Abstract
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Objectives Dynamic SPECT/CT (dSPECT/CT) previously has been reported as an accurate method to measure absolute Tc99m activity concentration in phantom and was utilized to characterize Tc99m-Sestamibi (MIBI) time activity curves (TACs) in patients (SNM 2011). This study further demonstrates measurement of MBF and coronary flow reserve (CFR) in normal subjects.
Methods Five consecutive patients (male=4, age=61±8 yr) with low likelihood of coronary artery disease (<5%) were recruited for rest/dipyridamole-stress (DS) MIBI dSPECT/CT scan using Symbia T2 system. At rest, multiple rapid gantry rotations within 180° arc (10x10sec+ 5x20sec+4x60sec+280sec) was set up to acquire dynamic raw data 10 sec prior to 10mCi MIBI injection and followed by a low dose CT (ldCT). After 3 hours, the scan was repeated post the standard DS and 10 sec prior to 25 mCi MIBI injection, then followed by another ldCT. All dynamic SPECT images were reconstructed with 3D-OSEM, physical correction and noise filtration with the matched projection method. TACs were manually generated for regions of blood-pool and myocardium (M). A simple net-retention flow model was employed to calculate K1 and MBF values with correction for partial volume (recover coefficient=1.83) in M and MIBI extraction fraction: 1- a*exp[-b/MBF] (a=0.87, b=0.44). CFR was then computed by taking the ratio of stress and rest MBF values.
Results Mean MBF at rest for normal subjects was 0.57±0.14 (ml/g/min) and increased to 2.69±0.57 with DS. Mean CFR value was 4.67±13.0% which matched closely with the known CFR value of N13-Ammonia PET (4.3±37.2%).
Conclusions Quantitative dynamic SPECT/CT incorporated with the net-retention flow model can be a feasible approach to quantify myocardial blood flow with Tc99m-Sestamibi injection.
Research Support Internal grant support, Chang Bing Show Chwan Memorial Hospita
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