Comparison of 99mTc-sestamibi-18F-fluorodeoxyglucose dual isotope simultaneous acquisition and rest-stress 99mTc-sestamibi single photon emission computed tomography for the assessment of myocardial viability

Functional and metabolic improvement after coronary intervention for non-viable myocardium detected by 18F fluorodeoxyglucose positron emission tomography

We report a case of a 64-year-old man suspected of myocardial infarction two months previously. Coronary angiography revealed total occlusion of the left anterior descending (LAD), and left ventriculography (LVG) showed remarkably reduced cardiac function and anterior dyskinesis. Electrocardiogram-gated thallium-201 Single Photon Emission Tomography (TL-SPECT) and ¹⁸F fluorodeoxyglucose positron emission tomography (FDG) were performed separately, and revealed large anterior myocardial infarction with markedly reduced tracer uptake, suggestive of non-viable myocardium. Percutaneous coronary intervention (PCI) was performed and stent was implanted successfully. Six months after PCI, LVG showed remarkable recovery in global function. Significant wall motion improvement and recovered glucose metabolism were observed in the infarcted myocardium despite having previously been diagnosed as lacking viability. <Learning Objectives: In patients with left ventricular dysfunction, revascularized myocardium can contribute to improve cardiac function and prognosis. This evidence was established for old, or chronic status of myocardial infarction which is defined as over one month from onset of acute myocardial infarction. In this case report, we suggest that it can be premature to determine myocardial viability using FDG for the patient with under pre-chronic status after myocardial infarction due to underestimation on myocardial FDG uptake.>.

Dual isotope simultaneous imaging to evaluate the effects of intracoronary bone marrow-derived mesenchymal stem cells on perfusion and metabolism in canines with acute myocardial infarction

Stem cell therapy on acute myocardial infarction (AMI) has been performed for over a decade. In the present study, cardiac perfusion, metabolism and function in dogs with AMI treated by intracoronary injection of bone marrow-derived mesenchymal stem cells (MSCs) were evaluated by dual isotope simultaneous acquisition (DISA) of single positron emission computed tomography (SPECT). Dogs (n=12, 20-30 kg) were randomly assigned to two groups: A graft study (n=6) and control group (n=6). Bone marrow mesenchymal aspirate was collected 3 weeks before surgical procedure. Stem cells were induced by 5-azacytidine for differentiation into myocytes. The dog AMI model was produced by blocking the blood stream at 1/3 of the distinct left anterior descending coronary artery for 90 min. For dogs in the grafting group, MSCs were transplanted by intracoronary injection, and for the control group, 0.9% NaCl was injected instead. At 1 and 10 weeks after MSCs were grafted, respectively, SPECT DISA was performed for each dog in the two groups with ^99mTc-SPECT MIBI (925 MBq) and ¹⁸F-FDG (222 MBq) for evaluation of myocardial perfusion and metabolism. After the dogs were sacrificed, heart tissue was stained by myocyte-specific antibodies for newborn vessels, troponin T and bromodeoxyuridine (BrdU). Following induction by 5-azacytidine, the morphological features with colony formation, microfilament, as well as atrial granules and positive stainings of α-actinin, myosin and troponin I demonstrated strongly that the MSCs differentiated into myocytes. The number of viable myocardial segments was 10 in the grafting group, which was significantly greater compared with the control group. The ejection fraction of the infarcted left ventricle (LVEF,%) increased from 53.80±9.58 to 70.00±7.52 (change, 16.20±2.93) at 1 and 10 weeks after MSCs engraftment, whilst in the control group, LVEF was 50.50±8.02 and 56.50±7.24 (change, 5.50±2.69), respectively. The LVEF difference was statistically significant (P<0.05) between the graft and control groups. Furthermore, immunostaining of all the myocyte-specific antibodies (for newly born vessels, troponin T and BrdU) was positive. In conclusion, direct intracoronary injection of bone marrow MSCs into injured myocardium in the experimental dog AMI model can significantly improve cardiac function with new vessel formation and myocyte-specific biomarker expression, and in particular, the present study further shows that DISA SPECT can be used for the assessment of stem cell transplantation in the heart.

Peptide-based imaging agents targeting phosphatidylserine for the detection of apoptosis

A 14-residue phosphatidylserine (PS)-binding peptide FNFRLKAGQKIRFG (PSBP-0) was scanned with Ala. In addition, a radiometal chelator (SAAC) was introduced at selected sites of the lead peptides. Substitution of the Gln(6) residue in PSBP-0 with Ala resulted in a significant increase in binding affinity to PS as determined by surface plasmon resonance sensorgrams. The binding affinity of the resulting peptide FNFRLKAGAKIRFG (PSBP-6, molecular mass = 1623 Da) to PS (K(d) ∼ 100 nM) increased 10-fold as compared to PSBP-0 (K(d) ∼ 1.38 μM). Introduction of SAAC-Re to the N terminus of PSBP-6 further increased the binding affinity of the resulting peptide SAAC(Re)-PSBP-6 (K(d) ∼ 26 nM). SAAC(Re)-PSBP-6 shows specific binding to apoptotic cells in cell-based assays. Biodistribution studies showed significantly higher uptake of SAAC((99 m)Tc)-PSBP-6 in B16/F10 melanoma treated with poly(L-glutamic acid)-paclitaxel than untreated tumors (4.06 ± 0.55% ID/g vs 1.61 ± 0.33% ID/g, P = 0.00011). SAAC((99 m)Tc)-PSBP-6 is a promising probe for noninvasive imaging of apoptotic cells.

Prediction of functional recovery after revascularization in patients with chronic ischaemic left ventricular dysfunction: head-to-head comparison between 99mTc-sestamibi/18F-FDG DISA SPECT and 13N-ammonia/18F-FDG PET

PURPOSE

(18)F-FDG PET is an important modality for myocardial viability assessment in patients with left ventricular (LV) dysfunction. Dual-isotope simultaneous acquisition (DISA) SPECT may be an alternative to PET. The aim of this study was to compare the diagnostic performance of PET and DISA SPECT for the prediction of improvement in regional and global LV function as well as LV reverse remodelling after revascularization.

METHODS

Patients (n=47) with chronic coronary artery disease and LV dysfunction underwent DISA SPECT (with (99m)Tc-sestamibi and (18)F-FDG) and PET (with (13)N-ammonia and (18)F-FDG) on the same day to assess viability. All patients underwent revascularization and recovery of function was derived from serial magnetic resonance imaging studies.

RESULTS

Of 264 revascularized, dysfunctional segments, 143 (54%) improved in function. For prediction of improvement in regional LV function, PET and DISA SPECT had similar sensitivity (90% versus 89%, NS) and specificity (86% versus 86%, NS). For prediction of improvement in global LV function, sensitivity was 83% for DISA SPECT and 86% for PET (p=NS), whereas both modalities had a specificity of 100%. Finally, sensitivity and specificity for the prediction of LV reverse remodelling were also similar for DISA SPECT and PET.

CONCLUSION

In patients undergoing revascularization, DISA SPECT and PET predict the improvement in regional and global LV function and LV remodelling equally well post revascularization.

Comparison of 99mTc-sestamibi/18FDG DISA SPECT with PET for the detection of viability in patients with coronary artery disease and left ventricular dysfunction

PURPOSE

Dual-isotope simultaneous acquisition (DISA) single-photon emission computed tomography (SPECT) is an attractive technique as it permits assessment of both myocardial glucose metabolism and perfusion within a single session, but few data on its accuracy for the assessment of viability are available as yet. In the present study, DISA SPECT was compared with positron emission tomography (PET) for the detection of myocardial viability in normal and dysfunctional left ventricular (LV) myocardium.

METHODS

Fifty-eight patients with chronic coronary artery disease and LV dysfunction (LV ejection fraction 33+/-12%) were studied. Patients underwent a 1-day dipyridamole stress 99mTc-sestamibi/18F-fluorodeoxyglucose (18FDG) DISA SPECT and 13N-ammonia/18FDG PET protocol. Within 1 week, resting MRI was performed to assess contractile function. Comparison of PET and SPECT data was performed using both visual and quantitative analysis.

RESULTS

The correlation of normalised activities of the flow tracers 99mTc-sestamibi and 13N-ammonia was good (r = 0.82; p < 0.001). The correlation between the two 18FDG studies was also good (r = 0.83; p < 0.001). The agreement for the assessment of viability for all segments between DISA SPECT and PET was 82%, with a kappa-statistic of 0.59 (95% CI 0.53-0.64), without a significant difference; in dysfunctional segments only, the agreement was 82%, with a kappa-statistic of 0.63 (95% CI 0.56-0.70), without a significant difference. When the DISA SPECT data were analysed visually, the agreement between DISA SPECT and PET was 83%, with a kappa-statistic of 0.58 (95% CI 0.52-0.63), without a significant difference. Moreover, there was no significant difference between visual and quantitative DISA SPECT analysis for the detection of viability.

CONCLUSION

This study shows an overall good agreement between 99mTc-sestamibi/18FDG DISA SPECT and PET for the assessment of myocardial viability in patients with severe LV dysfunction. Quantitative or visual analysis of the SPECT data did not influence the agreement with PET, suggesting that visual assessment may be sufficient for clinical purposes.