Usefulness of rapid low-dose/high-dose 1-day 99mTc-sestamibi ECG-gated myocardial perfusion single-photon emission computed tomography

Optimization of 201Tl Dosage in a Simultaneous Acquisition Rest 99mTc/Stress 201Tl Dual-Isotope Myocardial Perfusion Single-Photon Emission Computed Tomography with Semiconductor Gamma Camera

Background: The use of 201Tl in myocardial perfusion single-photon emission computed tomography (SPECT) is predominantly not recommended because of the higher radiation exposure of 201Tl compared to 99mTc agent. However, the advent of new gamma cameras with semiconductor detectors has made it possible to reduce the 201Tl dose and lower radiation exposure. In our hospital, the dose of 201Tl is adjusted according to the patient's body mass index (BMI), with 50 MBq for BMI<25 and 74 MBq for BMI≥25. The dose of 201Tl during simultaneous acquisition dual-isotope myocardial perfusion SPECT (MPS; stress 201Tl and rest 99mTc agent) exceeds 9 mSv/examination when 74 MBq of 201Tl is administered. In order to further reduce the radiation dose, optimization of the 201Tl dose was investigated. Methods: Two hundred and eighty consecutive patients who underwent stress MPS using simultaneous acquisition dual-isotope protocol (SDI protocol) for the estimation of ischemic heart disease were included. Patients with prior myocardial infarction were excluded. Correlations between BMI and acquisition time were determined in patients receiving 50 MBq (n=154) or 74 MBq (n=126) of 201Tl. In addition, linear regression analysis was used to determine the slope and intercept to derive a linear functional equation, and the theoretically optimal 201Tl dose was evaluated. Results: The correlation coefficient between BMI and acquisition time in the 201Tl 50 MBq group was 0.532 (P< 0.00001) and in the 201Tl 74 MBq group was 0.478 (P<0.00001), both showing a positive correlation. Linear regression analysis yielded two equations: y=0.52x-0.32 (201Tl 50 MBq group) and y=0.41x-0.69 (201Tl 74 MBq group). Linear function equation results indicated that patients with BMI between 25 and 30 could be examined within approximately 15 minutes with 50 MBq of 201Tl. Conclusion: Considering examination efficiency, a single acquisition time of less than 15 minutes is ideal. Theoretically, patients with BMI less than 30 could be examined within approximately 15 minutes with 50 MBq of 201Tl.

Incremental Predictive Value of Coronary Calcium Score in Risk Stratification of Coronary Revascularization in Patients With Normal or Mild Ischemia Using Nuclear Myocardial Perfusion Single Photon Emission Computed Tomography

BACKGROUND

The incremental predictive value of the coronary artery calcium score (CACS) for risk stratification of coronary revascularization in patients with normal or mildly abnormal nuclear myocardial perfusion single photon emission computed tomography (MPS) scores is unknown.

METHODS AND RESULTS

We analyzed 528 patients in whom CACS was calculated and who underwent stress MPS within 3 months. Patients with known coronary artery disease, prior coronary revascularization, and those undergoing hemodialysis were excluded. Patients were followed-up with coronary revascularization based on the evidence of physiological ischemia defined by fractional flow reserve or severe coronary stenosis (≥90%). CACS was significantly associated with the summed stress score (SSS) from MPS assessment. Multivariate logistic regression analysis showed that high CACS (≥300; odds ratio [OR] 5.44, 95% confidence interval [CI] 2.28-13.0) and SSS (OR 1.29, 95% CI 1.18-1.40) were significant (P<0.001) predictors of future coronary revascularization. The log-rank test showed that high CACS stratified coronary revascularization in normal SSS (0-3; P<0.001) or mildly abnormal SSS (4-8; P=0.028) groups, whereas high CACS did not significantly stratify coronary revascularization in moderate to severe SSS (≥9; P=0.757).

CONCLUSIONS

Risk stratification using CACS with a cut-off value 300 may have incremental predictive value for revascularization in patients with normal or mildly abnormal MPS.

Diagnostic performance of myocardial perfusion imaging with conventional and CZT single-photon emission computed tomography in detecting coronary artery disease: A meta-analysis

BACKGROUND

We performed a meta-analysis to compare the diagnostic performance of conventional SPECT (C-SPECT) and cadmium-zinc-telluride (CZT)-SPECT systems in detecting angiographically proven coronary artery disease (CAD).

METHODS

Studies published between January 2000 and February 2018 were identified by database search. We included studies assessing C-SPECT or CZT-SPECT as a diagnostic test to evaluate patients for the presence of CAD, defined as at least 50% diameter stenosis on invasive coronary angiography. A study was eligible regardless of whether patients were referred for suspected or known CAD.

RESULTS

We identified 40 eligible articles (25 C-SPECT and 15 CZT-SPECT studies) including 7334 patients (4997 in C-SPECT and 2337 in CZT-SPECT studies). The pooled sensitivity and specificity were 85% and 66% for C-SPECT and 89% and 69% for CZT-SPECT imaging studies. The area under the curve was slightly higher for CZT-SPECT (0.89) compared to C-SPECT (0.83); accordingly, the summary diagnostic OR was 17 for CZT-SPECT and 11 for C-SPECT. The accuracy of the two tests slightly differs between C-SPECT and CZT-SPECT (chi-square 11.28, P < .05). At meta-regression analysis, no significant association between both sensitivity and specificity and demographical and clinical variables considered was found for C-SPECT and CZT-SPECT studies.

CONCLUSIONS

C-SPECT and CZT-SPECT have good diagnostic performance in detecting angiographic proven CAD, with a slightly higher accuracy for CZT-SPECT. This result supports the use of the novel gamma cameras in clinical routine practices also considering the improvements in acquisition time and radiation exposure reduction.

Fast myocardial perfusion imaging with 99mTc in challenging patients using conventional SPECT cameras

BACKGROUND

We attempted to validate the performance of a fast myocardial perfusion imaging (MPI) protocol in diagnostically challenging patients.

METHODS

78 patients with ΒΜΙ > 24.9, LVH or three vessels disease underwent two sequential gated-MPI studies. The first at 15 (Early Imaging, EI) and the second at 45 (Late Imaging, LI) minutes post 99mTc-injection, at both stress and rest. Counts over heart (H), liver (Liv) and subdiaphragmatic space (Sub) and image quality, and myocardial perfusion and function parameters were compared between the two protocols. Coronary angiography was performed within 2 months from MPI, and ROC analysis was used to compare the diagnostic accuracy for the detection of ≥50% diameter luminal stenosis.

RESULTS

Quality was optimal-good in 93% of EI and 98% of LI studies (P = .12), H/Liv and stress H/Sub ratios were similar, but rest H/Sub ratio was lower in EI (P = .009). SSS [10 (0 to 46) vs 9 (0 to 36), P = .006] and SDS [3 (0 to 35) vs 2 (0 to 34), P = .02] were higher in EI protocol. LVEF, motion and thickening scores did not differ between the two protocols. A highly significant (P < .001) linear relationship with clinically negligible mean differences in Bland-Altman analysis was observed for all perfusion and function-related data. Sensitivity (EI 81%, LI 80%) and specificity (65% for both) did not differ (P = .23) between the two protocols.

CONCLUSION

The fast protocol is technically feasible and diagnostically accurate compared to the established protocol in diagnostically challenging patients.

The EXERRT trial: "EXErcise to Regadenoson in Recovery Trial": A phase 3b, open-label, parallel group, randomized, multicenter study to assess regadenoson administration following an inadequate exercise stress test as compared to regadenoson without exercise for myocardial perfusion imaging using a SPECT protocol

BACKGROUND

This study assessed the non-inferiority and safety of regadenoson administration during recovery from inadequate exercise compared with administration without exercise.

METHODS

Patients unable to achieve adequate exercise stress were randomized to regadenoson 0.4 mg either during recovery (Ex-Reg) or 1 hour after inadequate exercise (Regadenoson) (MPI1). All patients also underwent non-exercise regadenoson MPI 1-14 days later (MPI2). The number of segments with reversible perfusion defects (RPDs) detected using single photon emission computerized tomography imaging was categorized. The primary analysis evaluated the majority agreement rate between Ex-Reg and Regadenoson groups.

RESULTS

1,147 patients were randomized. The lower bound of the 95% confidence interval of the difference in agreement rates (-6%) was above the -7.5% non-inferiority margin, demonstrating non-inferiority of Ex-Reg to Regadenoson. Adverse events were numerically less with Ex-Reg (MPI1). In the Ex-Reg group, one patient developed an acute coronary syndrome and another had a myocardial infarction following regadenoson after exercise. Upon review, both had electrocardiographic changes consistent with ischemia prior to regadenoson.

CONCLUSIONS

Administering regadenoson during recovery from inadequate exercise results in comparable categorization of segments with RPDs and with careful monitoring appears to be well tolerated in patients without signs/symptoms of ischemia during exercise and recovery.

Clinical Feasibility of Simultaneous Acquisition Rest (99m)Tc/Stress (201)Tl Dual-Isotope Myocardial Perfusion Single-Photon Emission Computed Tomography With Semiconductor Camera

BACKGROUND

The aim of this study was to evaluate the clinical feasibility of simultaneous acquisition of rest (99m)Tc-tetrofosmin/stress (201)Tl dual-isotope single-photon emission computed tomography with a semiconductor gamma camera.

METHODS AND RESULTS

Ninety-four patients with known or suspected coronary artery disease (CAD) were enrolled in the study. First, patients were injected with (99m)Tc-tetrofosmin (296 MBq) for rest imaging, followed by (201)Tl (74 MBq) injection during 6 min of vasodilator stress test. Immediately after the stress test, the patients underwent the first electrocardiogram (ECG)-gated simultaneous acquisition including rest and stress perfusion scans. Patients were brought back for the second simultaneous acquisition for the comparison of ECG-gated wall motion between stress and rest scan 30 min later. Coronary angiography was performed in all the patients within 3 months of this protocol. Sensitivity, specificity and accuracy on a per patient basis to detect significant coronary artery stenosis (≥75%) were 88.6%, 79.2% and 86.2%, respectively. Per coronary vessel, sensitivity, specificity and accuracy were as follows: 84.9%, 80.5% and 83% in the left anterior descending coronary artery; 75%, 93.1% and 86.2% in the left circumflex coronary artery; and 74.2%, 85.7% and 81.9% in the right coronary artery.

CONCLUSIONS

Simultaneous acquisition of rest (99m)Tc-tetrofosmin/stress (201)Tl dual-isotope protocol had high diagnostic accuracy for significant CAD. (Circ J 2016; 80: 689-695).

Non-invasive assessment and clinical strategy of stable coronary artery disease by magnetic resonance imaging, multislice computed tomography and myocardial perfusion SPECT

Coronary multislice computed tomography (MSCT) angiography and magnetic resonance angiography (MRA) have emerged as new diagnostic techniques that allow direct visualization of the coronary artery. These new modalities have both advantages and disadvantages concerning radiation exposure, the use of contrast medium, ability of visualizing heavily calcified artery lumens, and spatial and temporal resolution. However, these modalities only provide anatomical information of the coronary artery. Functional assessment of the severity of coronary artery disease (CAD) is essential for the management of patients with known or suspected CAD in practical clinical settings. Myocardial perfusion single-photon emission computed tomography is thought to be the most suitable diagnostic procedure for the determination of therapeutic strategy when coronary MSCT and MRA show significant and also insignificant coronary artery lesions. (Circ J 2010; 74: 34 - 40).

New protocol of myocardial SPECT imaging with technetium-99m sestamibi for reducing the time interval between rest and adenosine stress phases

We have developed a new protocol of myocardial perfusion-gated single-photon emission computed tomography (SPECT), by use of technetium-99m sestamibi (MIBI), in which SPECT imaging at rest followed by SPECT imaging after adenosine with low level ergometer stress can be conducted by use of the Monzen position within a shortened total testing time of 1 h or less. The study group consisted of 137 patients who underwent this new imaging protocol. The diagnostic quality of the images was as good as that of images obtained with the conventional method (30-60 min after the injection of MIBI). The SPECT image quality for the 137 patients was evaluated, and the percentages of images rated as excellent, good, fair, and poor were 65.3, 27.4, 5.8, and 1.5% for the rest image, and 68.2, 21.9, 8.4, and 1.5% for the stress image, respectively. The shortened total testing time reduced the physical and mental burden on the patient compared with that of conventional myocardial perfusion imaging. Because this technique allows us to perform rest and stress myocardial imaging within a short period, it is expected to be very useful in the clinical setting.

Incremental prognostic value of cardiac function assessed by ECG-gated myocardial perfusion SPECT for the prediction of future acute coronary syndrome

BACKGROUND

The prognostic value of ECG-gated rest 201Tl/stress 99mTc-tetrofosmin myocardial perfusion single-photon emission computed tomography for the prediction of acute coronary syndrome (ACS: myocardial infarction (MI) and unstable angina (UA)) and the implications of ejection fraction (EF) has not yet been defined in Japanese.

METHODS AND RESULTS

The 1,895 patients were followed up for the occurrence ACS. The mean follow-up interval was 26.9+/-15.5 months. The 142 patients with revascularization within 60 days were censored. Summed stress score (SSS) and summed difference score (SDS) were calculated. The 19 MI and 29 UA occurred (1.1% and 1.6%, respectively). Univariate Cox analysis showed that hypertension (Wald 5.09, p<0.05), poststress EF (Wald 10.9, p<0.01), SSS (Wald 12.4, p<0.001) and SDS (Wald 18.7, p<0.001) were significant predictors of ACS. Multivariate Cox analysis showed that hypertension (Wald 4.27, p<0.05) and SDS (Wald 8.59, p<0.01) were independent predictors. When multiple clinical risk factors (number of coronary risk factors > or =2), significant ischemia (SDS > or =4) and low EF (EF <45%) were applied to multivariate Cox analysis, the combination of significant ischemia and low EF showed the highest predictive value (Wald 11.9; p<0.001) for future ACS.

CONCLUSION

Poststress EF added incremental prognostic value for the prediction of ACS.

Reduction of infracardiac intestinal activity by a small amount of soda water in technetium-99m tetrofosmin myocardial perfusion scintigraphy with adenosine stress

BACKGROUND

In technetium (Tc)-99m myocardial perfusion imaging (MPI), intestinal activity often interferes with the assessment of myocardial perfusion of the inferior wall. We examined whether a small amount of soda water prevents intestinal activity and improves image quality of the inferior wall in Tc-99m tetrofosmin MPI.

METHODS AND RESULTS

Ninety-five patients referred for 1-day rest/stress Tc-99m tetrofosmin MPI were assigned to one of two groups automatically, according to the date when they underwent MPI: the soda water group (n = 63) ingested 100 mL soda water just before image acquisition after adenosine stress, and the control group (n = 32) underwent no intervention. The frequency of intestinal activity was assessed visually on planar images. The inferior myocardial wall and the abdominal activity adjacent to the myocardium were assessed quantitatively on three different planar images during stress, and the mean inferior wall-to-abdomen (I/A) count ratio was calculated. The frequency of intestinal activity was 69.8% in the soda water group, and 90.6% in the control group (P = .038). The I/A count ratio was significantly higher in the soda water group than in the control group (1.98 +/- 0.51 vs 1.50 +/- 0.35, respectively, P < .0001, +/- SD).

CONCLUSIONS

The intake of 100 mL of soda water improves intestinal activity and improves the image quality of the inferior wall.

Prognostic Value of Myocardial Perfusion Single-Photon Emission Computed Tomography for the Prediction of Future Cardiac Events in a Japanese Population A Middle-Term Follow-up Study

BACKGROUND

The prognostic value of rest 201Tl/stress (99m)Tc-tetrofosmin myocardial perfusion single-photon emission computed tomography (SPECT) for the prediction of future hard cardiac events, including acute myocardial infarction (AMI), unstable angina (UAP) and cardiac death, and the implications for risk stratification has not yet been defined in a Japanese population.

METHODS AND RESULTS

The 1,988 patients who underwent rest 201Tl/stress (99m)Tc-tetrofosmin SPECT were identified and followed up for the occurrence of AMI, UAP and cardiac death. The mean follow-up interval was 26.9+/-15.8 months. The 142 patients were revascularized within 60 days after SPECT and they were censored from the prognostic analysis. Summed stress score (SSS), summed rest score and summed difference score (SDS) were calculated using a 5-point scoring (Normal: 0, No uptake: 4) and a 20-segment model; 22 cases of myocardial infarction, 31 of UAP and 22 cardiac deaths occurred (1.2%, 1.7% and 1.2%, respectively). Multivariate Cox regression analysis showed that hypertension (Wald 6.37, p<0.05) and SDS (Wald 8.77, p<0.01) were independent predictors of AMI and UAP. Advanced age (Wald 16.0, p<0.001), SSS (Wald 10.9, p<0.01) and SDS (Wald 4.58, p<0.05) were independent predictors of cardiac death.

CONCLUSION

Myocardial perfusion SPECT yields prognostic information toward the identification of acute coronary syndrome and cardiac death.