Absolute myocardial blood flow (MBF) and myocardial flow reserve (MFR) provide incremental diagnostic and prognostic information over relative perfusion alone. Recent development of dedicated cardiac SPECT cameras with better sensitivity and temporal resolution make dynamic SPECT imaging more practical. In this study, we evaluate the measurement of MBF using a multipinhole dedicated cardiac SPECT camera in a pig model of rest and transient occlusion at stress using 3 common tracers: 201 Tl, 99m Tc-tetrofosmin, and 99m Tc-sestamibi. Methods: Animals (n 5 19) were injected at rest/stress with 99m Tc radiotracers (370/1,100 MBq) or 201 Tl (37/110 MBq) with a 1-h delay between rest and dipyridamole stress. With each tracer, microspheres were injected simultaneously as the gold standard measurement for MBF. Dynamic images were obtained for 11 min starting with each injection. Residual resting activity was subtracted from stress data and images reconstructed with CT-based attenuation correction and energy window-based scatter correction. Dynamic images were processed with kinetic analysis software using a 1-tissue-compartment model to obtain the uptake rate constant K 1 as a function of microsphere MBF. Results: Measured extraction fractions agree with those obtained previously using ex vivo techniques. Converting K 1 back to MBF using the measured extraction fractions produced accurate values and good correlations with microsphere MBF: r 5 0.75-0.90 (P , 0.01 for all). The correlation in the MFR was between r 5 0.57 and 0.94 (P , 0.01). Conclusion: Noninvasive measurement of absolute MBF with stationary dedicated cardiac SPECT is feasible using common perfusion tracers. St udies using PET have demonstrated that absolute myocardial blood flow (MBF) and myocardial flow reserve (MFR 5 stress/ rest MBF) provide incremental diagnostic and prognostic information over relative perfusion alone (1-4). Imaging of myocardial perfusion is much more commonly performed with SPECT than with PET, but MBF measurements are not typically acquired.Measuring MBF is difficult with standard SPECT cameras because of the need for attenuation and scatter correction and the need to rotate around the patient for 3-dimensional imaging. Recent studies have shown that it is possible to obtain an index of the MFR without a direct measure of MBF using a combination of dynamic planar followed by static SPECT acquisitions (5) and that this can provide some prognostic information (6). Other studies have demonstrated that rapid camera rotation can provide dynamic tomographic data and hence a measure of MFR (7) and the arterial input function (8), suggesting that accurate measures of MBF could be possible (9). The practicality of measuring MBF has increased greatly, however, with the advent of dedicated cardiac cameras.Dedicated cardiac cameras such as the DSPECT system (Spectrum Dynamics Medical Inc.) or the Discovery NM 530c/ 570c cameras (GE Healthcare) have greatly improved sensitivity and do not rotate around the patient (10). These features allow d...

Myocardial blood flow (MBF) and myocardial flow reserve (MFR) measured with PET have clinical value. SPECT cameras with solid-state detectors can obtain dynamic images for measurement of MBF and MFR. In this study, SPECT measurements of MBF made using Tc-tetrofosmin were compared with PET in the same patients. Thirty-one patients underwent PET MBF rest-stress studies performed with Rb orN-ammonia within 1 mo of their SPECT study. Dynamic rest-stress measurements were made using a SPECT camera. Kinetic parameters were calculated using a 1-tissue-compartment model and converted to MBF and MFR. Processing with and without corrections for attenuation (+AC and -AC), patient body motion (+MC and -MC), and binding of the tracer to red blood cells (+BB and -BB) was evaluated. Both +BB and +MC improved the accuracy and precision of global SPECT MBF compared with PET MBF, resulting in an average difference of 0.06 ± 0.37 mL/min/g. Global MBF and detection of abnormal MFR were not significantly improved with +AC. Global SPECT MFR with +MC and +BB had an area under the receiver-operating curve of 0.90 (+AC) to 0.95 (-AC) for detecting abnormal PET MFR less than 2.0. Regional analysis produced similar results with an area under the receiver-operating curve of 0.84 (+AC) to 0.87 (-AC). Solid-state SPECT provides global MBF and MFR measurements that differ from PET by 2% ± 32% (MBF) and 2% ± 28% (MFR).

Background: Measurement of myocardial blood flow (MBF) with single photon emission computed tomography (SPECT) is feasible using cardiac cameras with solid-state detectors. SPECT MBF has been shown to be accurate when compared with positron emission tomography MBF measured in the same patients. However, the value of a test result applied to an individual patient depends strongly on the precision or repeatability of the test. The purpose of our study is to measure the precision of SPECT MBF measurements using 99m Tc-tetrofosmin and a solid-state cardiac camera. Methods: SPECT MBF was measured in 30 patients and repeated at a mean interval of 18 days. MBF was evaluated from images with and without attenuation correction based on a separately acquired CT scan. The dynamic images were processed independently by 2 operators using in-house kinetic analysis software that applied a 1-tissue-compartment model. The K1 rate constant was converted to MBF using previously determined extraction fraction corrections. Correction for patient body motion was applied manually. Results: The average coefficient of variation (COV) in the differences between the 2 MBF measurements was between 28% and 31%. The interobserver COV was between 11% and 15%. Myocardial flow reserve is the ratio of MBF measured at stress and rest, and the COV is correspondingly higher. The COV for the difference in repeated myocardial flow reserve was 33% to 38%, whereas the interobserver COV was 13% to 22%. Conclusions: The COV for the difference in SPECT MBF measurements obtained on separate days is 28% to 31%. The corresponding COV for myocardial flow reserve is 33% to 38%.

Reprojection of 24-frame gated blood-pool SPECT images is an effective means of obtaining LV functional measurements with a dedicated cardiac SPECT camera using standard 2D-planar analysis tools.

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Dynamic SPECT measurement of MBF and MFR in pigs can be performed with 1/4 (Tc99m-tracers) or 1/2 (Tl-201) of the standard injected activity without significantly reducing accuracy and precision.

Rotenone derivatives have shown promise in myocardial perfusion imaging (MPI). CMICE-013 is a novel 123 I-labeled rotenone derivative developed for SPECT MPI. The objective of this study was to assess the image quality of CMICE-013 and compare its uptake with tetrofosmin, sestamibi, and 201 Tl in vivo in a porcine model of stress-induced myocardial ischemia. Methods: Microspheres were injected simultaneously with the radiotracer injections at rest and stress to measure blood flow. Mimicking a 1-d tetrofosmin protocol, stress imaging used 3 times as much activity and occurred 1 h after the rest injection. SPECT images were obtained at both rest and stress. After imaging, the heart was sectioned into 44-50 pieces. In each heart sample, the tracer uptake was measured in a γ counter. The images were aligned, and the decay-corrected ratio of the signals at rest and stress was used to separate the well-counter signal into rest and stress components. The uptake at rest and stress was compared with microsphere flow measurements. Results: The CMICE-013 images showed good contrast between the heart and surrounding organs, with heart-to-liver and heart-to-lung uptake ratios similar to those of the standard tracers. Uptake of CMICE-013 was 1.5% of the injected dose at rest and increased more rapidly with increased blood flow than did the standard SPECT tracers. The percentage injected dose of CMICE-013 taken up by the heart was greater (P , 0.05) than 201 Tl, tetrofosmin, or sestamibi at flows greater than 1.5 mL/min/g. Conclusion: CMICE-013 is a promising new SPECT MPI agent. Repeat ed unexpected shutdowns of several of the major nuclear reactors producing 99 Mo has led to ongoing concern over the stability of the supply of 99m Tc and, consequently, interest in developing alternative tracers. Myocardial perfusion imaging (MPI) remains one of the more common tests performed with 99m Tclabeled agents. For MPI, PET is a potential option using either 82 Rb or 13 N ammonia, because the parent isotope for 82 Rb generators ( 82 Sr) and ammonia are both cyclotron-produced. Interest in PET MPI is growing; however, the number of MPI SPECT scans obtained annually in North America is still orders of magnitude larger and likely to remain so for many years. Thus, a SPECT alternative to 99m Tc MPI tracers remains an important goal.Clinical trials of the 18 F-labeled PET tracer flurpiridaz (1,2) have shown excellent contrast between the heart and surrounding organs and performance superior to standard 99m Tc-based tracers for the identification of disease. This tracer inhibits mitochondrial complex I and derives its specificity for cardiac imaging from the high concentration of mitochondria in the heart. Other compounds that target mitochondrial complex I have been studied previously in SPECT. An iodinated rotenone compound (I-ZIROT) was shown to have excellent uptake in the heart and excellent extraction at higher blood flows (3,4), which is in contrast to the standard SPECT 99m Tc tracers that have a roll-off in their extraction, prod...