Objectives: To compare MBF measurements obtained using manual and automatic 99mTc-SESTAMIBI bolus injections in the context of a clinical study for the detection of CAD using a SPECT system.
Methods: Thirteen patients underwent a stress-first 99mTc-SESTAMIBI dynamic SPECT study. While the protocol is similar to the standard MPI protocol, the injection is performed within the apparatus. 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 with a pre-defined injection profile (30 second injection followed by a 20 second saline flush). The injection dose remained the same for both types of injections. MBF at stress and rest was computed using commercial dynamic SPECT software and comparison of the obtained time-activity curves (TACs) and MBF values was performed. Finally, CFR, defined as the ratio between MBF at stress and rest, was computed.
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 and 0.40, for rest and stress MBF, respectively). 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, i.e. three patients from the manual injection cohort and six patients from the automatic injection cohort. Moreover, the qualitative behavior of TACs was similar for both injection methods, except that the 99mTc-SESTAMIBI bolus was observed in the left ventricle cavity for a shorter period in the manual injection than in the automatic injection (~20 and ~40 seconds, respectively) as expected due to the faster manual injection.
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 the two methods.