Comparison of Manual and Automatic ^99mTc-Sestamibi Dose Injections on Dynamic SPECT Measurements

Introduction: Absolute measurements of myocardial blood flow (MBF) and coronary flow reserve (CFR) using dynamic SPECT have been shown to provide incremental diagnostic and prognostic information over traditional MPI SPECT. Unfortunately, the dose injection protocol (which is performed during data acquisition within the apparatus) is site-specific and it is not clear if the MBF measurements are dependent on it.

Objectives: To compare MBF measurements obtained using manual and automatic ^99mTc-SESTAMIBI bolus injections on a single site.

Methods: Thirteen patients underwent a stress-first dynamic SPECT study. For the first 7 patients, the injection was performed using a manual syringe injection (3-5 seconds) followed by a saline flush (5 seconds), while for the remaining 6 patients an automatic injector was used (30 seconds injection + 20 seconds saline flush). Injection dose remained the same for both types of injections. MBF at stress and rest were computed using INVIA 4DM and comparison of the obtained time-activity curves and MBF values was then performed.

Results: Mean MBF values at rest obtained using both methods were almost identical: 0.61±0.26 for manual injections and 0.63±0.15 ml/min/g for automatic injections. Mean MBF values at stress were: 1.68±0.08 and 1.39±0.40 ml/min/g for manual and automatic injections, respectively. For both rest and stress mean MBF, no significant difference was observed between the two injection methods (p=0.87 for rest; p=0.40 for stress). However, it should be noted that only the patients who subsequently were found to be without ischemia on the standard MPI were included in the stress MBF calculations (3 with manual injection and 6 with automatic).

Conclusions: These initial promising results demonstrate the feasibility of CFR measurements using ^99mTc-SESTAMIBI CZT-SPECT using both manual and automatic injections. Moreover, mean MBF values remained practically the same for both types of injections, thus confirming equivalence of the two methods.