Methods: Patients referred for vasodilator stress MPI were randomly selected for dynamic imaging on a DSPECT camera. The patient population was reflective of referral patterns for MPI or post-heart transplant (HT)evaluation. Patient positioning was accomplished with a hand-injected 1mCi Tc-99m sestamibi (MIBI) pre-scan. Vasodilator stress, and rest/ stress MIBI injection using an automated syringe pump, were performed with the patient under the camera. The protocol consists of 9mCi and 30mCi of MIBI in 2ml saline followed by a 40 mL saline flush for the rest and stress studies, respectively, with the tracer injection performed 50s after Regadenoson stress. Data acquired in list mode were processed on the INVIA 4DM platform. Significant manual adjustments were made to the blood pool and tissue ROI positions for input and myocardial activity curve derivation.
Results: Of 104 non-transplant patients, 83 had normal MPI. Global myocardial flow reserve (MFR), peak stress flow (PSF) and rest flow (RF) were compared between patients with normal and abnormal MPI (2.17 vs 1.89, p = .16; 2.91 vs 1.91, p= .00; and 1.5 vs 1.1, p= .028, respectively). Among patients with normal MPI, MFR (2.1 vs 2.01, p= .287), PSF (3.1 vs 2.7, p= .044), and RF (1.6 vs 1.5, p=.48) were compared between men and women. Among 16 HT patients the RF was higher compared to non-transplant patients (1.8 vs 1.4, p=.032) while MF and PSF were similar.
Conclusion: Myocardial flow quantification with dynamic SPECT is feasible in the clinical setting and provides physiologically tenable values. Further studies are needed to evaluate its additive value to relative perfusion imaging.