Institute of Nuclear Medicine


Service development for dynamic myocardial perfusion SPECT (MPS) on a solid-state dedicated cardiac camera: methodology and implementation in the clinical workflow

Objectives: MPS is well established for the assessment of coronary artery disease (CAD). However, it often uncovers only the coronary territory supplied by the most severe stenosis and in patients with multi-vessel disease it may underestimate the extent of underlying obstructive CAD. Quantitative assessment of myocardial blood flow and myocardial perfusion reserve is useful for further analysis and is well established using dynamic PET imaging. Recent developments in dedicated cardiac cameras enable dynamic acquisitions. We evaluated the feasibility of dynamic tomographic imaging and quantification of global and regional myocardial perfusion reserve using a solid-state dedicated cardiac camera (D-SPECT, Spectrum-Dynamics, Caesarea, Israel).

Methods: Rest/stress Tc-MIBI MPS (250-350 MBq rest, 750-850 MBq stress) were performed. An IV test dose of 40-50MBq was used for a pre-scan of 60 sec, to enable localization of the left ventricle. The remainder of the rest dose was housed in a lead syringe box, connected to a contrast injector (Quickfit, MEDRAD) with a saline-filled syringe (100mls), attached to CT extension tubing. The dose was infused into the patient and dynamic SPECT images were obtained for 6 minutes (6sec/frame for 60 frames). Routine gated MPI SPECT followed. This procedure was repeated for the STRESS acquisition. The data were reconstructed with OSEM with 4 iterations and 32 subsets. Factor analysis was applied to generate right and left ventricular (LV) curves. The LV blood pool curve was used as the input function in a one-tissue compartment kinetic model. K1 values, corresponding to Tc-MIBI uptake, were calculated for stress and rest and 99mTc washout (K2) was set to zero. The Myocardial Perfusion Reserve Index (MPRI) was calculated as the quotient of K1 stress and rest for the myocardium as a whole, as well as individual arterial tributaries.

Results: The data of the first 34 patients (M=26, age 63.7+11.5 yrs, BMI 28.2+5) were analyzed.  16 patients (47%) had known coronary artery disease (CAD). There were 18 normal and 16 abnormal scans (10 fixed, 12 reversible defects). Global MPRI was 1.45+0.4 and the regional values were 1.43+0.36(LAD), 1.63+0.69 (RCA) and 1.44+0.43 (LCX). Global MPRI correlated with age (p = 0.01) and was lower in patients with known CAD (p = 0.03). MPRI was 1.27+0.32 in regions with abnormal perfusion vs. 1.6+0.4 in regions with normal perfusion (p=0.008). In 3/4 patients with known multi-vessel disease MPS underestimated the extent of disease, whereas MPRI was reduced in all obstructed territories.

Conclusion: Dynamic tomographic imaging is feasible using a solid state dedicated cardiac camera. Our preliminary results show that MPRI estimates can be obtained from the dynamic tomograms and are lower in patients with CAD and in regions with abnormal perfusion. Furthermore, MPRI estimates may have an advantage over MPS alone in the detection of multi-vessel CAD. More data are needed to establish the role of this technique in the diagnostic clinical workup.