Absolute myocardial blood flows derived by dynamic CZT scan vs invasive fractional flow reserve: Correlation and accuracy

Comparison of global and regional myocardial blood flow quantification using dynamic solid-state detector SPECT and Tc-99 m-sestamibi or Tc-99 m-tetrofosmin in a routine clinical setting

Solid-state detector single photon emission computed tomography (SPECT) enables the acquisition of dynamic data for calculation of myocardial blood flow (MBF) and myocardial flow reserve (MFR). Here, we report about our experiences on routine clinical use and robustness using Tc-99 m-sestamibi and Tc-99 m-tetrofosmin. 307 patients underwent dynamic list-mode myocardial perfusion imaging (MPI) and standard static MPI for clinical workup of coronary artery disease on a dedicated cardiac SPECT camera. After exclusion of 33 scans, 274 scans were eligible for MBF and MFR calculation using a 1-tissue-compartment model. Attenuation correction was performed for all patients using an external computed tomogram. Patients underwent stress-only scans, both stress and rest scans or rest-only scans using Tc-99 m-tetrofosmin or Tc-99 m-sestamibi. 30 patients without known cardiovascular comorbidities and without perfusion defect on static scans were compared in a sub analysis. Global stress myocardial blood flow (MBF) was significantly higher than rest MBF (2.3 vs. 1.1 ml/min/g; p < 0.001), and showed a high variability among individuals. Global myocardial flow reserve (MFR) was 2.1 (range 0.5-7.8). An analysis of 30 patients without known cardiovascular comorbidities yielded similar stress MBF measures for Tc-99 m-sestamibi and Tc-99 m-tetrofosmin (3.1 ± 1.2 vs. 2.8 ± 0.9 ml/min/g; p = 0.429). The use of attenuation correction lead to systematically lower MBF measures. Patients who underwent a one-day protocol had notably higher rest MBF (1.2 ± 0.5 vs. 1.0 ± 0.46 ml/min/g; p = 0.009) and consequently a lower MFR. Summed defect scores from standard static scans and presence of cardiovascular comorbidities negatively impacted MBF and MFR. Quantitative SPECT MBF and MFR in a clinical routine setting yields flow measures in range of expectation at an albeit wide range and is comprehensibly linked with results from standard static scan and patients history of cardiovascular diseases. Use of one-day protocols and attenuation correction systematically alters quantitative results. However, SPECT-derived MBF and MFR lack clinical reliability due to less validated reference ranges and high inter-individual variability.

Recent Progress in Myocardial Perfusion Imaging Techniques

Nuclear cardiology, similar to other fields of nuclear medicine, has experience rapid advancements. Myocardial perfusion imaging (MPI), an important component of nuclear cardiology that commenced in the 1970s, plays a crucial role in the non-invasive evaluation and management of coronary artery disease. Over the past decade, MPI has witnessed significant changes and advancements. The introduction of gamma cameras using cadmium zinc telluride (CZT) systems, accompanied by advancements in related software, represents a notable development in this nuclear cardiology. Ongoing research and development effects are actively exploring new radiopharmaceuticals, with a particular focus on their application in positron emission tomography (PET)-MPI. Furthermore, studies have been conducted highlighting the necessity and benefits of hybrid imaging. However, as with other cutting-edge technologies, the practical application of the latest equipment and techniques in nuclear cardiology faces challenges stemming from their high costs of equipment and examinations and limited accessibility, which continue to remain significant barriers in nuclear medicine.

Intraoperative Prediction of Coronary Graft Failure Based on Transit Time Flow Measurement: A PRELIMINARY STUDY

Myocardial revascularization has been known to not affect the prognosis in some patients. Coronary artery bypass graft (CABG) failure may develop one year after CABG surgery. This is accompanied by a high risk of developing myocardial infarction after complete myocardial revascularization in obstructive coronary artery disease (CAD) due to microvascular dysfunction. The study of microvascular dysfunction using intraoperative stress tests with adenosine triphosphate (ATP) allows for the assessment of the coronary bypass flow reserve (CBFR) and the risk of graft failure one year after surgery. The study included 79 CAD patients (238 grafts) who underwent dynamic single-photon emission computed tomography (SPECT) before CABG and dynamic transit time flow measurement (TTFM) during CABG at rest and at stress. The CBFR was calculated by the ratio of the mean graft flow (MGF) at stress to the MGF at rest. A multivariate regression model showed that the MGF at rest (p = 0.043), the MGF at stress (p = 0.026) and the CBFR (p = 0.0001) were significant independent predictors of graft failure. As a result of ROC analysis, the threshold CBFR < 1.67 units correlated with graft failure more closely (sensitivity 82%, specificity 90%) The CBFR is a significant independent predictor of graft failure for up to 16 months.

Myocardial blood flow quantification with SPECT

INTRODUCTION

The addition of absolute myocardial blood flow (MBF) data improves the diagnostic and prognostic accuracy of relative perfusion imaging with nuclear medicine. Cardiac-specific gamma cameras allow measurement of MBF with SPECT.

METHODS

This paper reviews the evidence supporting the use of SPECT to measure myocardial blood flow (MBF). Studies have evaluated SPECT MBF in large animal models and compared it in humans with invasive angiographic measurements and against the clinical standard of PET MBF. The repeatability of SPECT MBF has been determined in both single-site and multi-center trials.

RESULTS

SPECT MBF has excellent correlation with microspheres in an animal model, with the number of stenoses and fractional flow reserve, and with PET-derived MBF. The inter-user coefficient of variability is ∼20% while the COV of test-retest MBF is ∼30%. SPECT MBF improves the sensitivity and specificity of the detection of multi-vessel disease over relative perfusion imaging and provides incremental value in predicting adverse cardiac events.

CONCLUSION

SPECT MBF is a promising technique for providing clinically valuable information in the assessment of coronary artery disease.

The diagnostic role of resting myocardial blood flow in STEMI patients after revascularization

Background

The value of semiquantitative resting myocardial perfusion imaging (MPI) in coronary artery disease (CAD) is limited. At present, quantitative MPI can be performed by a new cadmium zinc tellurium single-photon emission computed tomography (CZT-SPECT) scan. The quantitative index of resting myocardial blood flow (MBF) has received little attention, and its manifestations and clinical value in the presence of unstable coronary blood flow have not been clarified.

Purpose

In patients with ST-segment elevation myocardial infarction (STEMI), whether resting MBF can provide additional value of blood flow than semi-quantitative resting MPI is not sure. We also explored the influencing factors of resting MBF.

Methods

This was a retrospective clinical study. We included 75 patients with STEMI in the subacute phase who underwent resting MPI and dynamic scans after reperfusion therapy. General patient information, STEMI-related data, MPI, gated MPI (G-MPI), and resting MBF data were collected and recorded. According to the clinically provided culprit vessels, the resting MBF was divided into ischemic MBF and non-ischemic MBF. The paired Wilcoxon signed-rank test was used for resting MBF. The receiver operating characteristic (ROC) curves were used to determine the optimal threshold for ischemia, and multiple linear regression analysis was used to analyze the influencing factors of resting MBF.

Results

There was a statistically significant difference between the ischemic MBF and non-ischemic MBF [0.59 (0.47-0.72) vs. 0.76 (0.64-0.93), p < 0.0001]. The ROC curve analysis revealed that resting MBF could identify ischemia to a certain extent, with a cutoff value of 0.5975, area under the curve (AUC) = 0.666, sensitivity = 55.8%, and specificity = 68.7%. Male sex and summed rest score (SRS) were influencing factors for resting MBF.

Conclusion

To a certain extent, resting MBF can suggest residual ischemia after reperfusion therapy in patients with STEMI. There was a negative correlation between male sex, SRS, and ischemic MBF. A lower resting MBF may be associated with more severe myocardial ischemia.

The Influence of Kinetic Models and Attenuation Correction on Cadmium-Zinc-Telluride Single-Photon Emission Computed Tomography (CZT SPECT)-Derived Myocardial Blood Flow and Reserve: Correlation with Invasive Angiography Data

(1) Background: The objective of this study was to determine the optimal post-processing model for dynamic cadmium-zinc-telluride single-photon emission computed tomography (CZT-SPECT). (2) Methods: A total of 235 patients who underwent diagnostic invasive coronary angiography within three months of the SPECT and those who had coronary computed tomography angiography (CCTA) before SPECT (within 3 months) were enrolled in this study. Each SPECT study was processed to obtain global and regional stress myocardial blood flow (sMBF), rest-MBF (rMBF), myocardial flow reserve (MFR) and flow difference (FD) estimates obtained with 1-tissue-compartment (1TCM) and net retention (NR) modes, both with and without attenuation correction. (3) Results: The use of AC led to significantly higher sMBF, rMBF and DF values obtained by 1TCM compared those values derived by 1TCM with NAC; the lowest values of stress MBF and rest MBF were obtained by 1TCM_NAC. The resting flow, MFR and DF were significantly (p < 0.005) higher in the AC model than in NAC. All quantitative variables were significantly (p < 0.05) higher in NR_NAC than in the 1TC_NAC model. Finally, sMBF, rMBF and FD showed significantly (p < 0.05) higher values by using 1TMC_AC compared to NR_AC. (4) Conclusions: We suggested that 1-compartment and net retention models correctly reflect coronary microcirculation and can be used for clinical practice for evaluating quantitative myocardial perfusion by dynamic SPECT. Attenuation correction is an important step in post-processing dynamic SPECT data, which increases the consistency and diagnostic accuracy of models.

SPECT myocardial blood flow quantitation for the detection of angiographic stenoses with cardiac-dedicated CZT SPECT

PURPOSE

CZT SPECT with the enhanced imaging characteristic facilitates SPECT myocardial blood flow (MBF) quantitation moving toward a clinical utility to uncover myocardial ischemia. The purpose of this study was to investigate the diagnostic performance of stress MBF, myocardial flow reserve (MFR) and myocardial flow capacity (MFC) derived from CZT SPECT in the detection of coronary artery disease (CAD).

METHODS

One-hundred and eighty patients underwent two-day rest/adenosine-stress scans for SPECT MBF quantitation. All dynamic SPECT images were reconstructed and corrected with necessary corrections. The one-tissue two-compartment kinetic model was utilized to fit kinetic parameters (K1, k2 and FBV) by numeric optimization and converted to MBF from K1. Rest MBF, stress MBF and MFR in left ventricle and coronary territories were calculated from flow polar maps. MFC was assessed by extents of moderately and severely abnormal flow statuses using an integrated flow diagram. Per-patient and per-vessel analyses were performed to determine cutoff values for the detection of angiographically obstructive and flow-limited CAD.

RESULTS

Using the threshold of ≥ 50% stenosis, 149 patients (82.78%) were classified to have obstructive lesions in 355 vessels (65.74%). Using the threshold of ≥ 70% stenosis, 113 patients (62.78%) were classified to have flow-limited lesions in 282 vessels (52.22%). On per-patient analysis, the optimal cutoff values of stress MBF and MFR to detect ≥ 50% stenosis were (1.44 ml/min/g, 1.96) and (1.34 ml/min/g and 1.75) to detect ≥ 70% stenosis. The optimal cutoff values for severely and combined moderately severely abnormal MFC extents were (2.3-2.5%, 23.1%) and (7.5%, 29.4%), respectively. The overall sensitivity of MFC (0.84-0.86, 0.86-0.90) to detect ≥ 50% and ≥ 70% lesions surpassed those of stress MBF (0.78. 0.78) and MFR (0.80, 0.75) (all p < 0.05) with similar specificity (MFC = 0.84-0.90, 0.87-0.91; stress MBF = 0.87, 0.91; MFR = 0.84, 0.89) (all p≥ 0.05).

CONCLUSION

The non-invasive SPECT MBF quantitation using CZT SPECT is a reliable method to detect angiographically obstructive and flow-limited CAD. Myocardial flow capacity can outperform with higher diagnostic sensitivity than stress MBF or MFR alone.

Quantitative flow ratio derived pullback pressure gradient and CZT-SPECT measured longitudinal flow gradient for hemodynamically significant coronary artery disease

BACKGROUND

Whether physiological coronary diffuseness assessed by quantitative flow reserve (QFR) pullback pressure gradient (PPG) correlates with longitudinal myocardial blood flow (MBF) gradient and improves diagnostic performances for myocardial ischemia remains unknown.

METHODS AND RESULTS

MBF was measured in mL g-1 min-1 with 99mTc-MIBI CZT-SPECT at rest and stress, corresponding myocardial flow reserve (MFR = MBF stress/MBF rest) and relative flow reserve (RFR = MBF stenotic area/MBF reference) were calculated. Longitudinal MBF gradient was defined as apical and basal left ventricle MBF gradient. △longitudinal MBF gradient was calculated by longitudinal MBF gradient at stress and rest. QFR-PPG was acquired from virtual QFR pullback curve. QFR-PPG significantly correlated with hyperemic longitudinal MBF gradient (r = 0.45, P = 0.007) and △longitudinal MBF gradient (stress-rest) (r = 0.41, P = 0.016). Vessels with lower RFR had lower QFR-PPG (0.72 vs. 0.82, P = 0.002), hyperemic longitudinal MBF gradient (1.14 vs. 2.22, P = 0.003) and △longitudinal MBF gradient (0.50 vs. 1.02, P = 0.003). QFR-PPG, hyperemic longitudinal MBF gradient and △longitudinal MBF gradient showed comparable diagnostic performances for predicting decreased RFR (area under curve [AUC]: 0.82 vs. 0.81 vs. 0.75, P = NS) or QFR (AUC: 0.83 vs. 0.72 vs. 0.80, P = NS). In addition, QFR-PPG and QFR in combination showed incremental value compared with QFR for predicting RFR (AUC = 0.83 vs. 0.73, P = 0.046, net reclassification index = 0.508, P = 0.001).

CONCLUSION

QFR-PPG significantly correlated with longitudinal MBF gradient and △longitudinal MBF gradient when used for physiological coronary diffuseness assessment. All three parameters had high accuracy in predicting RFR or QFR. Adding physiological diffuseness assessment increased accuracy for predicting myocardial ischemia.

Measuring myocardial blood flow using dynamic myocardial perfusion SPECT: artifacts and pitfalls

Dynamic acquisition allows absolute quantification of myocardial perfusion and flow reserve, offering an alternative to overcome the potential limits of relative quantification, especially in patients with balanced multivessel coronary artery disease. SPECT myocardial perfusion is widely available, at lower cost than PET. Dynamic cardiac SPECT is now feasible and has the potential to be the next step of comprehensive perfusion imaging. In order to help nuclear cardiologists potentially interested in using dynamic perfusion SPECT, we sought to review the different steps of acquisition, processing, and reporting of dynamic SPECT studies in order to enlighten the potentially critical pitfalls and artifacts. Both patient-related and technical artifacts are discussed. Key parameters of the acquisition include pharmacological stress, radiopharmaceuticals, and injection device. When it comes to image processing, attention must be paid to image-derived input function, patient motion, and extra-cardiac activity. This review also mentions compartment models, cameras, and attenuation correction. Finally, published data enlighten some facets of dynamic cardiac SPECT while several issues remain. Harmonizing acquisition and quality control procedures will likely improve its performance and clinical strength.

Role of nuclear cardiology in diagnosis and risk stratification of coronary microvascular disease

Coronary flow reserve (CFR) with positron emission tomography/computed tomography (PET/CT) has an important role in the diagnosis of coronary microvascular disease (CMD), aids risk stratification and may be useful in monitoring therapy. CMD contributes to symptoms and a worse prognosis in patients with coronary artery disease (CAD), nonischemic cardiomyopathies, and heart failure. CFR measurements may improve our understanding of the role of CMD in symptoms and prognosis in CAD and other cardiovascular diseases. The clinical presentation of CAD has changed. The prevalence of nonobstructive CAD has increased to about 50% of patients with angina undergoing angiography. Ischemia with nonobstructive arteries (INOCA) is recognized as an important cause of symptoms and has an adverse prognosis. Patients with INOCA may have ischemia due to CMD, epicardial vasospasm or diffuse nonobstructive CAD. Reduced CFR in patients with INOCA identifies a high-risk group that may benefit from management strategies specific for CMD. Although measurement of CFR by PET/CT has excellent accuracy and repeatability, use is limited by cost and availability. CFR measurement with single-photon emission tomography (SPECT) is feasible, validated, and would increase availability and use of CFR. Patients with CMD can be identified by reduced CFR and selected for specific therapies.

Prognostic value of myocardial flow reserve derived by quantitative SPECT for patients with intermediate coronary stenoses

BACKGROUND

Functional assessment of myocardial ischemia is critical for patients with intermediate coronary stenosis. As the diagnosis performance of absolute quantification of myocardial blood flow (MBF) and myocardial flow reserve (MFR) by single-photon emission tomography (SPECT) has been proven, its prognostic value in patients with intermediate coronary stenosis remains to be evaluated.

METHODS

Patients with one or more target lesions of ≥ 50% to ≤ 80% diameter stenoses on invasive coronary angiography were prospectively included in this study. All patients were scheduled for clinically indicated SPECT myocardial perfusion imaging (MPI) within 3 months and agreed to provide informed consent to participate in quantitative SPECT acquisitions to obtain MBF and MFR values. The primary endpoint was defined as a composite of the major adverse cardiac events (MACE): Cardiac death, myocardial infarction, late revascularization and heart failure or unstable angina-related rehospitalization.

RESULTS

One hundred and nineteen patients (mean age 57 ± 8 years, 62.2% men) were included in the analysis. The average lumen stenosis of patients was 67.0 ± 10.4%. Over a median follow-up duration of 1408 days (interquartile range 1297-1666 days), 18 patients (15.1%) had MACE. Patients with impaired MFR (MFR < 2) had a significantly higher incidence of events than those with preserved MFR (MFR ≥ 2) in Kaplan-Meier survival analysis (Log-rank = 8.105, P = 0.004), while no significant difference was found between patients with normal relative perfusion and those with relative perfusion abnormalities (log-rank = 0.098, P > 0.05). In a multivariate Cox hazards analysis, the SPECT-derived MFR remained an independent predictor of MACE (HR 0.352, 95% CI 0.145-0.854, P = 0.021).

CONCLUSIONS

In a cohort of patients with angiographic intermediate coronary lesions, SPECT-derived MFR was an independent predictor of prognosis.

Myocardial blood flow evaluation with dynamic cadmium-zinc-telluride single-photon emission computed tomography: Bright and dark sides

Myocardial blood flow (MBF) and myocardial perfusion reserve (MPR) assessment with non-invasive techniques represent an important tool to evaluate both coronary artery disease severity and extent. Currently, cardiac positron emission tomography-computed tomography (PET-CT) is the "gold standard" for the assessment of coronary function and provides accurate estimations of baseline and hyperemic MBF and MFR. Nevertheless, due to the high cost and complexity, PET-CT is not widely used in clinical practice. The introduction of cardiac-dedicated cadmium-zinc-telluride (CZT) cameras has renewed researchers' interest on MBF quantitation by single-photon emission computed tomography (SPECT). Indeed, many studies evaluated MPR and MBF measurements by dynamic CZT-SPECT in different cohorts of patients with suspected or overt coronary artery disease. As well, many others have compared the values obtained by CZT-SPECT to the ones by PET-CT, showing good correlations in detecting significant stenosis, although with different and non-standardized cut-off values. Nevertheless, the lack of standardized protocol for acquisition, reconstruction and elaboration makes more difficult to compare different studies and to further assess the real advantages of MBF quantitation by dynamic CZT-SPECT in clinical routine. Many are the issues involved in the bright and dark sides of dynamic CZT-SPECT. They include different type of CZT cameras, different execution protocols, different tracers with different myocardial extraction fraction and distribution, different software packages with different tools and algorithms, often requiring manual post-processing elaboration. This review article provides a clear summary of the state of the art on MBF and MPR evaluation by dynamic CZT-SPECT and outlines the major issues to solve to optimize this technique.

Prognostic Role of Dynamic CZT Imaging in Heart Failure With Preserved Ejection Fraction

OBJECTIVE

The objective of the study was to evaluate the prognostic role of myocardial flow reserve (MFR) and myocardial blood flow (MBF) estimates obtained with dynamic cadmium-zinc-telluride (CZT) imaging in the development and progression of heart failure with preserved ejection fraction (HFpEF) in patients with nonobstructive coronary artery disease (CAD) during a 12-month follow-up period.

PATIENTS AND METHODS

A total of 112 patients (70 men; median age of 62.5 [57.0; 69.0] years) with nonobstructive coronary artery disease were enrolled in the study. Dynamic CZT-SPECT, echocardiography, and coronary CT angiography studies were performed baseline.

RESULTS

Distribution of patients was performed by adverse events: group 1 comprised patients with adverse outcomes (n = 25), and group 2 comprised those without it (n = 87). Based on receiver operating characteristic analysis, the levels of MFR ≤1.62 (area under the curve [AUС], 0.884; Р < 0.001), stress-MBF ≤1.35 mL/min per gram (AUС, 0.750; Р < 0.001), and NT-proBNP ≥760.5 pg/mL (AUС, 0.764; Р = 0.001) were identified as cutoff values to predict adverse outcomes. Univariate analysis revealed that type 2 diabetes mellitus (P = 0.044), the levels of MFR ≤1.62 (P = 0.014), stress-MBF ≤1.35 mL/min per gram (P = 0.012), NT-proBNP ≥760.5 pg/mL (P = 0.018), and diastolic dysfunction (P = 0.009) were potential risk factors for the development and progression of HFpEF. Multivariate analysis demonstrated that the values of NT-proBNP ≥760.5 pg/mL (odds ratio, 1.87; 95% confidence interval, 1.17-3.62; P = 0.027) and MFR ≤1.62 (odds ratio, 2.801; 95% confidence interval, 1.19-6.55; P = 0.018) were independent predictors of adverse outcomes.

CONCLUSIONS

Our data suggest that reduced MFR ≤1.62 obtained with dynamic CZT imaging and overexpression of NT-proBNP ≥760.5 pg/mL can individuate patients at high risk of development and progression of HFpEF during a 12-month follow-up period, independently of baseline clinical parameters and imaging variables.

Coronary Microvascular Dysfunction: Features and Prognostic Value

(1) Background: The results of the international studies support the assumption that coronary microvascular dysfunction (CMD) occurs significantly more often than previously identified and is associated with adverse outcomes. However, there is a lack of the accurate comprehension of its pathophysiology. The objectives of this study were to evaluate the clinical and instrumental features of CMD and to assess its prognostic value during 12 months of follow-up period. (2) Methods: A total of 118 patients with non-obstructive coronary artery disease (CAD) and preserved LV ejection fraction (62 [59; 64]%) were enrolled in the study. Serum levels of biomarkers were analyzed by enzyme-linked immunoassay. CMD was defined as the reduced myocardial flow reserve (MFR) ≤ 2 obtained by dynamic CZT-SPECT. Two-dimensional transthoracic echocardiography with evaluation of LV diastolic dysfunction was performed baseline. (3) Results: Patients were divided into groups depending on the presence of CMD: CMD+ group (MFR ≤ 2; n = 45), and CMD- group (MFR > 2; n = 73). In CMD+ group, the severity of diastolic dysfunction, the levels of biomarkers of fibrosis and inflammation were higher than in CMD- group. Multivariate regression analysis showed that the presence of diastolic dysfunction (OR 3.27; 95% CI 2.26-5.64; p < 0.001), the hyperexpression of NT-proBNP ≥ 760.5 pg/mL (OR 1.67; 95% CI 1.12-4.15; p = 0.021) and soluble ST2 ≥ 31.4 ng/mL (OR 1.37; 95% 1.08-2.98; p = 0.015) were independent factors associated with CMD. Kaplan-Meier analysis showed that a rate of the adverse outcomes was significantly (p < 0.001) higher in patients with CMD (45.2%, n = 19) than in patients without it (8.6%, n = 6). (4) Conclusions: Our data suggest that the presence of CMD was associated with the severe diastolic dysfunction and hyperexpression of the biomarkers of fibrosis and inflammation. Patients with CMD had higher rate of the adverse outcomes than those without it.

Diagnostic value of quantitative myocardial blood flow assessment by NaI(Tl) SPECT in detecting significant stenosis: a prospective, multi-center study

OBJECTIVES

The aim of this prospective multi-center study was to investigate the diagnostic value of myocardial blood flow (MBF) quantification using NaI(Tl)-based single-photon emission computed tomography (SPECT) for determining coronary artery disease (CAD) defined by quantitative coronary angiography (QCA).

BACKGROUND

Absolute quantitation of MBF and myocardial flow reserve (MFR) using SPECT is clinically feasible; however, whether flow quantification using NaI(Tl) SPECT is superior to commonly performed SPECT myocardial perfusion imaging (MPI) in determining CAD has not been evaluated.

METHODS

Patients with suspected or known CAD underwent pharmacological stress/rest dynamic SPECT imaging and routine SPECT MPI followed by QCA. Obstructive disease was defined as ≥ 50% reduction in luminal diameter on QCA.

RESULTS

One hundred fifty-four patients (462 vessels) were included in the analysis. Obstructive CAD was detected in 76/154 patients (49.4%) and 112/462 vessels (24.2%). Optimal cut-off values were 1.86 mL/min/g for stress MBF and 1.95 for MFR, respectively. Stress MBF and MFR were more sensitive than MPI in both individual patients (stress MBF vs MPI: 81.6% vs 51.3%; MFR vs MPI: 72.4% vs 51.3%) and in coronary vascular regions (stress MBF vs MPI: 78.6% vs 31.3%; MFR vs MPI: 75.9% vs 31.3%; all P < .01). In receiver operating characteristic curve analysis, quantification revealed a significantly greater area under the curve than MPI at the patient (stress MBF vs MPI: 0.761 vs 0.641; MFR vs MPI: 0.770 vs 0.641) and the vessel (stress MBF vs MPI: 0.745 vs 0.613; MFR vs MPI: 0.756 vs 0.613; all P < .05) levels. Integrating quantitative SPECT measures with MPI significantly increased the area under the curve and improved the discriminatory and reclassification capacity.

CONCLUSION

Flow quantification using NaI(Tl) SPECT provides superior sensitivity and discriminatory capacity to MPI in detecting significant stenosis. Clinical trial registration NCT03637725.

A preliminary study of dobutamine myocardial flow reserve on 99mTc-Sestamibi CZT-SPECT

BACKGROUND

With improved resolution and sensitivity, the cadmium zinc telluride (CZT) detector measures myocardial blood flow (MBF) and myocardial flow reserve (MFR) via single photon emission computed tomography (SPECT). Recently, many studies have used vasodilator stress to obtain quantitative indexes. However, dobutamine used as a pharmaceutical stress has been rarely used to quantify myocardial perfusion using CZT-SPECT. Our study retrospectively analyzed the blood flow performance of ^99mTc-Sestamibi (^99mTc -MIBI) CZT-SPECT comparing dobutamine to adenosine.

PURPOSE

The study aims to explore whether dobutamine stress can be used for the myocardial perfusion quantitative analysis via CZT-SPECT as well as compare dobutamine MBF and MFR to adenosine.

METHODS

It was a retrospective study. A total of 68 patients with suspected or known coronary artery disease (CAD) were consecutively enrolled in this study. Thirty-four patients underwent dobutamine stress ^99mTc-MIBI CZT-SPECT. Another thirty-four patients underwent adenosine stress ^99mTc-MIBI CZT-SPECT. Patient characteristics, myocardial perfusion imaging (MPI) results, gated-myocardial perfusion imaging (G-MPI) results and quantitative analysis of MBF and MFR were collected.

RESULTS

In dobutamine stress group, stress MBF was significantly higher than rest MBF (median [interquartile range], 1.63 [1.46-1.94] vs. 0.89 [0.73-1.06], P < 0.001). In adenosine stress group, similar results were observed (median [interquartile range], 2.01 [1.34-2.20] vs. 0.88 [0.75-1.01], P < 0.001). When comparing the dobutamine and adenosine stress group, global MFR showed significant differences (median [interquartile range], the dobutamine group: 1.88 [1.67-2.38] vs. the adenosine group: 2.19 [1.87-2.64], P = 0.037).

CONCLUSION

MBF and MFR can be measured using dobutamine ^99mTc -MIBI CZT-SPECT. In small sample single-center study, there was a difference in MFR produced by adenosine and dobutamine within the suspected or the known CAD population.

The myocardial flow reserve in patients with heart failure with preserved ejection fraction

To evaluate the myocardial flow reserve (MFR) and myocardial blood flow (MBF) parameters in patients with heart failure with preserved ejection fraction (HFpEF) and to assess their relationship with the severity of HF and the levels of soluble ST2 (sST2). A total of 59 consecutive patients (median age of 65.0 (58.0; 69.0) years) with non-obstructive coronary artery disease (CAD) and preserved EF were enrolled. Serum levels biomarkers were measured by enzyme immunoassay. MBF and MFR parameters were evaluated by dynamic CZT-SPECT. All patients were divided into two groups: group 1 comprised patients (n = 41) with HFpEF, and group 2 comprised those (n = 18) without HFpEF. In group 1 global MFR (gMFR) values were lower by 27.8% (p = 0.003) than in group 2. The values of gMFR correlated with NT-proBNP (r = - 0.290) and sST2 (r = -0.331) levels. Based on ROC-analysis, gMFR ≤ 2.27 (AUC = 0.746; p < 0.001) were associated with the presence of HFpEF. In patients with HFpEF (n = 41) the values of gMFR were related to NYHA classes (p < 0.001) and the parameters of diastolic dysfunction (p < 0.001). The values of gMFR ≤ 2.27 may be used for the evaluation of microvascular changes in patients with HFpEF and non-obstructive CAD.

The potential of dynamic 99mTc-sestamibi cadmium zinc telluride-single-photon emission computed tomography camera assessing myocardial flow reserve in patients with heart failure with preserved ejection fraction

Aims

Coronary microvascular dysfunction (CMD) is related to the pathophysiology, mortality, and morbidity of heart failure with preserved ejection fraction (HFpEF). A novel single-photon emission computed tomography (SPECT) camera with cadmium zinc telluride (CZT) detectors allows for the quantification of absolute myocardial blood flow and myocardial flow reserve (MFR) in patients with coronary artery disease. However, the potential of CZT-SPECT assessing for CMD has never been evaluated in patients with HFpEF.

Methods and results

The clinical records of 127 consecutive patients who underwent dynamic CZT-SPECT were retrospectively reviewed. Rest and stress scanning were started simultaneously with 3 and 9 MBq/kg of 99mTc-sestamibi administration, respectively. Dynamic CZT-SPECT imaging data were analysed using a net-retention model with commercially available software. Transthoracic echocardiography was performed in all patients. The MFR value was significantly lower in the HFpEF group (mean ± SEM = 2.00 ± 0.097) than that in the non-HFpEF group (mean ± SEM = 2.74 ± 0.14, P = 0.0004). A receiver operating characteristic analysis indicated that if a cut-off value of 2.525 was applied, MFR could efficiently distinguish HFpEF from non-HFpEF. Heart failure with preserved ejection fraction had a consistently low MFR, regardless of the diastolic dysfunction score. Heart failure with preserved ejection fraction patients with MFR values lower than 2.075 had a significantly higher incidence of heart failure exacerbation.

Conclusion

Myocardial flow reserve assessed by CZT-SPECT was significantly reduced in patients with HFpEF. A lower MFR was associated with a higher hospitalization rate in these patients. Myocardial flow reserve assessed by CZT-SPECT has the potential to predict future adverse events and stratify the severity of disease in patients with HFpEF.

Radionuclide Tracers for Myocardial Perfusion Imaging and Blood Flow Quantification

Myocardial perfusion imaging by nuclear cardiology is widely validated for the diagnosis, risk stratification, and management of patients with suspected or known coronary artery disease. Numerous radiopharmaceuticals are available for single-photon emission computed tomography and PET modalities. Each tracer shows advantages and limitations that should be taken into account in performing an imaging examination. This review aimed to summarize the state-of-the-art radiotracers used for myocardial perfusion imaging and blood flow quantification, highlighting the new technologic advances and promising possible applications.

What Is New in Risk Assessment in Nuclear Cardiology?

Nuclear cardiology techniques allow in-depth evaluation of cardiac patients. A body of literature has established the use of nuclear cardiology. The results obtained with traditional cameras have been reinforced by those obtained with a series of innovations that have revolutionized the field of nuclear cardiology. This article highlights the role of nuclear cardiology in the risk assessment of patients with cardiac disease and sheds light on advancements of nuclear imaging techniques in the cardiovascular field. Patient risk stratification has a key role in modern precision medicine. Nuclear cardiac imaging techniques may quantitatively investigate major disease mechanisms of different cardiac pathologies.

Heart failure with preserved ejection fraction: the role of microvascular dysfunction

Aim. To evaluate the relationship between coronary microvascular dysfunction (CMD), biomarkers of cardiac fibrosis and cardiac remodeling (soluble ST2 (sST2), fibroblast growth factor-23 (FGF-23), matrix metalloproteinase-9 (MMP-9), tissue inhibitor of metalloproteinase-1 (TIMP-1), and NT-proBNP), parameters of diastolic dysfunction (DD), and the presence of heart failure with preserved ejection fraction (HFpEF) in symptomatic patients.

Materials and methods. Study participants were 59 patients with non-obstructive coronary artery disease (CAD) and preserved left ventricular ejection fraction (LVEF) of 62 (56; 67) %. Non-obstructive CAD was verified by coronary computed tomography angiography. Stress-and rest-myocardial blood flow (MBF) and coronary flow reserve (CFR) parameters were evaluated by CZT SPECT. Serum levels of cardiac biomarkers were measured by the enzyme immunoassay. Two-dimensional transthoracic echocardiography was used to assess DD parameters.

Results. Decreased CFR was defined as CFR ≤ 2. Therefore, CMD was defined as the presence of decreased CFR in the absence of flow-limiting CAD. Distribution of patients was performed by CFR values: group 1 included patients with preserved CFR (>2, n = 35), and group 2 encompassed patients with decreased CFR (≤2, n = 24). In 87.5% of cases, patients with CMD were diagnosed with HFpEF, whereas in patients with preserved CFR, heart failure was diagnosed only in 51.4% of cases (p < 0.0001). CFR values were correlated with the left atrial volume (r = –0.527; p = 0.001), E / A ratio (r = –0.321, p = 0.012), and E / e’ (r = –0.307; p = 0.021). Following the ROC analysis, the levels of sST2 ≥ 31.304 ng / ml (AUС = 0.730; р = 0.004) and NT-proBNP ≥ 0.034 pg / ml (AUС = 0.815; р = 0.034) were identified as cut-off values for the presence of CMD in patients with non-obstructive CAD.

Conclusion. The obtained data suggest that CMD may play an essential role in HFpEF. The values of CFR were correlated with DD parameters, and decreased CFR was associated with overexpression of biomarkers of cardiac fibrosis and cardiac remodeling. Serum levels of sST2 and NT-proBNP were identified as cut-off values for the presence of CMD in patients with non-obstructive CAD.

Improved precision of SPECT myocardial blood flow using a net tracer retention model

BACKGROUND

Noninvasive quantification of absolute myocardial blood flow (MBF) and myocardial flow reserve (MFR) provides incremental benefit to relative myocardial perfusion imaging (MPI) to diagnose and manage heart disease. MBF can be measured with single-photon emission computed tomography (SPECT) but the uncertainty in the measured values is high. Standardization and optimization of protocols for SPECT MBF measurements will improve the consistency of this technique. One element of the processing protocol is the choice of kinetic model used to analyze the dynamic image series.

PURPOSE

This study evaluates if a net tracer retention model (RET) will provide a better fit to the acquired data and greater test-retest precision than a one-compartment model (1CM) for SPECT MBF, with (+MC) and without (-MC) manual motion correction.

METHODS

Data from previously acquired rest-stress MBF studies (31 SPECT-PET and 30 SPECT-SPECT) were reprocessed ± MC. Rate constants (K1) were extracted using 1CM and RET, +/-MC, and compared pairwise with standard PET MBF measurements using cross-validation to obtain calibration parameters for converting SPECT rate constants to MBF and to assess the goodness-of-fit of the calibration curves. Precision (coefficient of variation of test re-test relative differences, COV) of flow measurements was computed for 1CM and RET ± MC using data from the repeated SPECT MBF studies.

RESULTS

Both the RET model and MC improved the goodness-of-fit of the SPECT MBF calibration curves to PET. All models produced minimal bias compared with PET (mean bias < 0.6%). The SPECT-SPECT MBF COV significantly improved from 34% (1CM+MC) to 28% (RET+MC, P = 0.008).

CONCLUSION

The RET+MC model provides a better calibration of SPECT to PET and blood flow measurements with better precision than the 1CM, without loss of accuracy.

The current status of CZT SPECT myocardial blood flow and reserve assessment: Tips and tricks

Cardiac PET-derived measurements of myocardial blood flow (MBF) and myocardial flow reserve (MFR) are proven robust indexes of the severity of coronary artery disease (CAD). They facilitate the diagnosis of diffuse epicardial and microvascular disease and are also of prognostic significance. However, low availability and high cost have limited their wide clinical implementation. Over the last 15 years, cadmium zinc telluride (CZT)-based detectors have been implemented into SPECT imaging devices. Myocardial perfusion scintigraphy can be performed faster and with less radiation exposure as compared with standard gamma cameras. Rapid dynamic SPECT studies with higher count rates can be performed. This technological breakthrough has renewed the interest in SPECT MBF assessment in patients with CAD. Currently, two cardiac-centered CZT gamma cameras are available commercially-Discovery NM530c and D-SPECT. They differ in parameters such as collimator design, number of detectors, sensitivity, spatial resolution and image reconstruction. A number of publications have focused on the feasibility of dynamic CZT SPECT and on the correlation with cardiac PET and invasive coronary angiography measurements of fractional flow reserve. Current study reviews the present status of MBF and MFR assessment with CZT SPECT. It also aims to provide an overview of specific issues related to acquisition, processing and interpretation of quantitative studies in patients with CAD.

Reaction of Pertechnetate in Highly Alkaline Solution: Synthesis and Characterization of the Nitridotrioxotechnetate Ba[TcO3 N]

The preparation of novel technetium oxides, their characterization and the general investigation of technetium chemistry are of significant importance, since fundamental research has so far mainly focused on the group homologues. Whereas the structure chemistry of technetium in strongly oxidizing media is dominated by theTc O 4 - ${{\left[{\rm { Tc}}{{\rm { O}}}_{{\rm { 4}}}\right]}^{-}}$ anion, our recent investigation yielded the newTc O 3 N 2 - ${{\left[{\rm { Tc}}{{\rm { O}}}_{{\rm { 3}}}{\rm { N}}\right]}^{{\rm { 2}}-}}$ anion. Brown single crystals of Ba[TcO3 N] were obtained under hydrothermal conditions starting from Ba(OH)2  ⋅ 8H2 O and NH4 [TcO4 ] at 200 °C.Ba [ Tc O 3 N ] ${{\rm { Ba[Tc}}{{\rm { O}}}_{{\rm { 3}}}{\rm { N]}}}$ crystallizes in the monoclinic crystal system with the space group P21 /n (a=7.2159(4) Å, b=7.8536(5) Å, c=7.4931(4) Å and β=104.279(2)°). The crystal structure ofBa [ Tc O 3 N ] ${{\rm { Ba[Tc}}{{\rm { O}}}_{{\rm { 3}}}{\rm { N]}}}$ consists of isolatedTc O 3 N 2 - ${{\left[{\rm { Tc}}{{\rm { O}}}_{{\rm { 3}}}{\rm { N}}\right]}^{{\rm { 2}}-}}$ tetrahedra, which are surrounded by Ba2+ cations. XANES measurements complement the oxidation state +VII for technetium and Raman spectroscopic experiments on Ba[TcO3 N] single crystals exhibit characteristic Tc-O and Tc-N vibrational modes.

Diagnostic accuracy of dynamic CZT-SPECT in coronary artery disease. A systematic review and meta-analysis

BACKGROUND

With the appearance of cadmium-zinc-telluride (CZT) cameras, dynamic myocardial perfusion imaging (MPI) has been introduced, but comparable data to other MPI modalities, such as quantitative coronary angiography (CAG) with fractional flow reserve (FFR) and positron emission tomography (PET), are lacking. This study aimed to evaluate the diagnostic accuracy of dynamic CZT single-photon emission tomography (SPECT) in coronary artery disease compared to quantitative CAG, FFR, and PET as reference.

MATERIALS AND METHODS

Different databases were screened for eligible citations performing dynamic CZT-SPECT against CAG, FFR, or PET. PubMed, OvidSP (Medline), Web of Science, the Cochrane Library, and EMBASE were searched on the 5th of July 2020. Studies had to meet the following pre-established inclusion criteria: randomized controlled trials, retrospective trails or observational studies relevant for the diagnosis of coronary artery disease, and performing CZT-SPECT and within half a year the methodological references. Studies which considered coronary stenosis between 50% and 70% as significant based only on CAG were excluded. Data extracted were sensitivity, specificity, likelihood ratios, and diagnostic odds ratios. Quality was assessed with QUADAS-2 and statistical analysis was performed using a bivariate model.

RESULTS

Based on our criteria, a total of 9 studies containing 421 patients were included. For the assessment of CZT-SPECT, the diagnostic value pooled analysis with a bivariate model was calculated and yielded a sensitivity of 0.79 (% CI 0.73 to 0.85) and a specificity of 0.85 (95% CI 0.74 to 0.92). Diagnostic odds ratio (DOR) was 17.82 (95% CI 8.80 to 36.08, P < 0.001). Positive likelihood ratio (PLR) and negative likelihood ratio (NLR) were 3.86 (95% CI 2.76 to 5.38, P < 0.001) and 0.21 (95% CI 0.13 to 0.33, P < 0.001), respectively.

CONCLUSION

Based on the results of the current systematic review and meta-analysis, dynamic CZT-SPECT MPI demonstrated a good sensitivity and specificity to diagnose CAD as compared to the gold standards. However, due to the heterogeneity of the methodologies between the CZT-SPECT MPI studies and the relatively small number of included studies, it warrants further well-defined study protocols.

Myocardial Blood Flow and Flow Reserve in Patients With Acute Myocardial Infarction and Obstructive and Non-Obstructive Coronary Arteries: CZT SPECT Study

Background

To assess single-photon emission computed tomography cadmium-zinc-telluride (SPECT CZT)-derived myocardial blood flow (MBF) flow reserve (MFR) and flow difference (FD) in patients with acute myocardial infarction (AMI) and to compare this data with serum cardiac troponin and cardiac magnetic resonance (CMR) findings.

Methods

A total of 31 patients with AMI underwent invasive coronary angiography (ICA), serial high-sensitivity serum cardiac troponin I (cTnI) measurement, and CZT SPECT with visual and quantitative (MBF, MFR, and FD) perfusion parameters, and contrast-enhanced CMR. All patients with AMI were divided into two groups: (1) with non-obstructive coronary arteries (MINOCA), n = 10; (2) with obstructive coronary artery disease (MICAD), n = 21.

Results

The values of SSS and SRS were significantly (p < 0.01) higher whereas global stress MBF, MFR significantly lower in patients with MICAD as compared to MINOCA - 5.0 (3.0; 5.0) vs. 9.0 (5.0; 13.0); 2.0 (1.0; 3.0) vs. 6.0 (3.0; 11.0); 2.02 (1.71; 2.37) vs. 0.86 (0.72; 1.02) ml/min/g; and 2.61 (2.23; 3.14) vs. 1.67 (1.1; 1.9), respectively. Stress MBF correlated with cTnI at 24 h and day 4: ρ = -0.39; p = 0.03 and ρ = -0.47; p = 0.007, respectively. FD correlated with cTnI at 24 h and day 4: ρ = -0.39; p = 0.03 and ρ = -0.46; p = 0.009. CMR analysis showed that infarct size, MVO and myocardial edema in patients with MICAD were significantly (< 0.05) higher as compared to MINOCA: 19.4 (10.4; 29.7) vs. 1.8 (0.0; 6.9); 0.1 (0.0; 0.7) vs. 0.0 (0.0; 0.0) and 19.5 (12.0;30.0) vs. 3.0 (0.0; 12.0), respectively. According to vessel-based analysis of CMR data, acute myocardial injury (defined as late gadolinium enhancement and myocardial edema) was observed more frequently in patients with MICAD compared to MINOCA: 34(37%) vs. 5(5%) p = 0.005, respectively. The values of regional stress MBF, MFR and FD were significantly decreased in LV territories characterized by myocardial injury compared to those without: 0.98 (0.73; 1.79) vs. 1.33 (0.94; 2.08) p < 0.01, 1.64 (1.0; 2.36) vs. 2.0 (1.53; 2.89) p < 0.01 and 0.33 (0.05; 0.57) vs. 0.56 (0.36; 1.32) p> 0.01, respectively.

Conclusion

In patients with AMI, SPECT CZT-derived flow measures were associated with the high-sensitivity troponin I as well as the extent of edema, microvascular obstruction, and infarct size detected by CMR. On the regional level, quantitative SPECT CZT measures were significantly lower in vessel territories characterized by myocardial injury.

Low-dose dobutamine stress gated blood pool SPECT assessment of left ventricular contractile reserve in ischemic cardiomyopathy: a feasibility study

PURPOSE

The purpose of the present study was to evaluate the feasibility of gated blood pool single-photon emission computed tomography (GBPS) with low-dose dobutamine (LDD) stress test, performed on a single-photon emission computed tomography (SPECT) camera equipped with cadmium-zinc-telluride (CZT) solid-state detectors, in assessing of left ventricle (LV) contractile reserve in patients with ischemic cardiomyopathy (ICM).

METHODS

A total of 52 patients (age 59 ± 7.2 years, 47 men and 5 women) with ICM and a control group of 10 patients without obstructive coronary artery lesion underwent GBPS and transthoracic echocardiography (TTE) at rest and during LDD stress test (5, 10, 15 µg/kg/min). The duration of each GBPS step was 5 min. Stress-induced changes in LV ejection fraction (ΔLVEF), peak ejection rate, LV volumes, and mechanical dyssynchrony (phase histogram standard deviation, phase histogram bandwidth and entropy) obtained with GBPS were estimated.

RESULTS

All GBPS indices except end-diastolic volume showed significant dynamics during stress test in both groups. The majority of parameters in ICM patients showed significant changes at a dobutamine dose of 10 µg/kg/min as compared to the rest study. Seventeen percent of ICM patients, but none from the control group, showed a decrease in LVEF during stress, accompanied by a significant increase in entropy. The intra- and inter-observer reproducibility was excellent for both rest and stress studies. There was a moderate correlation (r = 0.5, p = 0.01) between GBPS and TTE, with a mean difference value of - 1.7 (95% confidence interval - 9.8; 6.4; p = 0.06) in ΔLVEF.

CONCLUSION

Low-dose dobutamine stress GBPS performed with high-efficiency CZT-SPECT cameras can be performed for evaluating stress-induced changes in LV contractility and dyssynchrony with lower acquisition time. A dobutamine dose of 10 µg/kg/min can potentially suffice to detect stress-induced changes in patients with ICM during GBPS.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT04508608 (August 7, 2020).

The diagnostic value of SPECT CZT quantitative myocardial blood flow in high-risk patients

BACKGROUND

The objective of this study was to evaluate the accuracy of global MBF and MFR quantitation performed by myocardial perfusion scintigraphy (MPS) for the detection of multivessel coronary artery disease (CAD).

METHODS

52 CAD patients underwent CZT MPS, with the evaluation of MBF and MFR, followed by invasive coronary angiography (ICA). According to MPS and ICA results, all patients were divided into three groups: (1) non-obstructive CAD and normal MPS scan (control group) (n = 7), (2) one vessel disease (1VD) (n = 16), (3) multivessel disease (MVD) (n = 29).

RESULTS

Global absolute MBF and MFR were significantly reduced in MVD patients as compared to those with 1VD [0.93 (IQR 0.76; 1.39) vs 1.94 (1.37; 2.21) mL·min-1·g-1, P = .00012] and [1.4 (IQR 1.02; 1.85) vs 2.3 (1.8; 2.67), P = . 0 004], respectively. The Syntax score correlated with global stress MBF (ρ = - 0.64; P < .0001) and MFR (ρ = - 0.53; P = .0003). ROC analysis showed higher sensitivity and specificity for stress MBF and MFR compared with semiquantitative MPS stress evaluation. Multivariate regression analysis showed that only stress MBF [OR (95% CI) 0.59 (0.42-0.82); P < .0003] was an independent predictor of MVD.

CONCLUSIONS

Quantitative myocardial blood flow values assessed with the use of CZT camera may identify high-risk patients, such as those with multivessel disease.

Quantitative Assessment Using the Compartment Model for Detecting Regional Coronary Artery Disease by Dynamic Myocardial Perfusion Single-Photon Emission Computed Tomography

BACKGROUND

This study aimed to quantitatively evaluate myocardial perfusion single-photon emission computed tomography (SPECT) using an original analysis tool in the compartment model for detecting regional significant coronary artery disease (CAD).

METHODS AND RESULTS

This study analyzed 41 patients (median age, 76 years) with suspected or known CAD who underwent both dynamic SPECT using 99 mTc-tetrofosmin and invasive coronary angiography. The quantitative analysis was performed using a single-tissue compartment model to evaluate the diagnostic performance of the myocardial flow reserve (MFR) for regional significant CAD, excluding infarcted territories. In the regional analysis, 114 vessels were assessed, of which 31 were diagnosed as significant coronary lesions (≥70% stenosis and/or fraction flow reserve ≤0.8). The MFR of regional significant CAD was significantly lower than that of non-significant CAD (1.11 [0.97-1.31] vs. 1.74 [1.30-2.27]; P<0.001). In the receiver operating characteristic curve analysis, the MFR displayed an area under the curve (AUC) of 0.81. While analyzing each coronary artery territory, the diagnostic performance of the MFR value in the left anterior descending (LAD) artery territory was found to be significantly higher than that found in qualitative assessment (AUC: 0.84 vs. 0.61).

CONCLUSIONS

A quantitative analysis of dynamic SPECT data facilitated detecting regional CAD. For the LAD artery, the MFR displayed a higher diagnostic performance than the qualitative assessment of conventional myocardial perfusion SPECT.

Regadenoson versus dipyridamole: Evaluation of stress myocardial blood flow response on a CZT-SPECT camera

BACKGROUND

Regadenoson is a selective adenosine receptor agonist. It is currently unclear if the level of hyperemia differs between stress agents. We compared Myocardial Blood Flow (MBF) and Myocardial Flow Reserve (MFR) response on CZT-SPECT Myocardial Perfusion Imaging (MPI) to evaluate if dipyridamole and regadenoson could induce the same level of hyperemia.

METHODS

228 patients with dynamic CZT-SPECT MPI were retrospectively analyzed (66 patients stressed with regadenoson and 162 with dipyridamole) in terms of MBF and MFR. To rule out confounding factors, two groups of 41 patients were matched for clinical characteristics in a sub-analysis, excluding high cardiovascular risk patients.

RESULTS

Overall stress MBF was higher in regadenoson patients (1.71 ± 0.73 vs. 1.44 ± 0.55 mL·min-1·g-1 for regadenoson and dipyridamole, respectively, p < .05). However, when confounding factors were ruled out, stress MBF (1.57 ± 0.56 vs. 1.61 ± 0.62 mL·min-1·g-1 for dipyridamole and regadenoson, respectively, p = .88) and MFR (2.62 ± 0.77 vs. 2.46 ± 0.76 for dipyridamole and regadenoson, respectively, p = .40) were not different between regadenoson and dipyridamole.

CONCLUSIONS

Our results suggest that dipyridamole and regadenoson induce equivalent hyperemia in dynamic SPECT with similar stress MBF and MFR in comparable patients.

Quantification of myocardial perfusion reserve by CZT-SPECT: A head to head comparison with 82Rubidium PET imaging

BACKGROUND

We measured myocardial blood flow (MBF) and perfusion reserve (MPR) by dynamic CZT-SPECT and 82Rb-PET in patients with suspected or known coronary artery disease (CAD) and compared the accuracy of the two methods in predicting obstructive CAD.

METHODS

Twenty-five patients with available coronary angiography data underwent 99mTc-sestamibi CZT-SPECT and 82Rb-PET cardiac imaging. Stress and rest MBF and MPR were calculated by both methods and compared. Diagnostic accuracies of CZT-SPECT and PET were also assessed using a receiver-operator-characteristic curve.

RESULTS

CZT-SPECT yielded similar baseline MBF, but higher hyperemic MBF and MPR values compared to PET. There was a modest correlation between the two methods for MPR (r = 0.56, P < .01). MPR by CZT-SPECT showed a good ability in identify a reduced MPR by PET, with an area under the curve of 0.85. A MPR cut-off of 2.5 was identified by CZT-SPECT for detection of abnormal MPR by PET, with a sensitivity, specificity and accuracy of 86%, 73% and 80%. The area under the curve for the identification of obstructive CAD by regional MPR were 0.83 for CZT-SPECT and 0.84 for PET (P = .90). At CZT-SPECT, a regional MPR of 2.1 provided the best trade-off between sensitivity and specificity for identifying obstructive CAD. Diagnostic accuracy of CZT-SPECT and PET using respective cut-off values was comparable (P = .62).

CONCLUSION

Hyperemic MBF and MPR values obtained by CZT-SPECT are higher than those measured by 82Rb-PET imaging, with a moderate correlation between the two methods. CZT-SPECT shows good diagnostic accuracy for the identification of obstructive CAD. These findings may encourage the use of this new technique to a better risk stratification and patient management.

Capabilities of Modern Semiconductor Gamma Cameras in Radionuclide Diagnosis of Coronary Artery Disease

This paper presents a review of the literature concerning the clinical application of modern semiconductor (CZT) gamma cameras in the radioinuclide diagnosis of coronary artery disease. It contains information on the diagnostic efficacy of myocardial perfusion studies performed with those cameras compared with the widely used scintillation (Anger) cameras, an overview of their effectiveness in comparison with coronary angiography (also fractional flow reserve) and currently available clinical results of a myocardial flow reserve measured with a dynamic SPECT study. Introduction of this imaging modality to the measurement of a myocardial flow reserve aims to facilitate access to this type of study compared to the less available and more expensive PET method used so far.

Comparison between N13NH3-PET and 99mTc-Tetrofosmin-CZT SPECT in the evaluation of absolute myocardial blood flow and flow reserve

BACKGROUND

PET/CT is the standard for quantitative assessments of myocardial blood flow (MBF), but it requires short-lived-tracers, costly, and not widely available. SPECT with Cadmium Zinc Telluride (CZT) detectors allows dynamic acquisition and quantitation of MBF. The study aims were to compare MBF measurements by 99mTc-tetrofosmin-CZT to N13NH3 PET/CT after regadenoson-induced coronary hyperemia and to evaluate the effect of attenuation correction (AC).

METHODS

54 patients were evaluated at rest and during vasodilation by 99mTc-tetrofosmin-CZT and N13NH3 PET/CT within 2 weeks. MBF and MBF reserve (MFR) were measured by CZT with or without AC (NAC).

RESULTS

The global rest MBF was 0.76 ± 0.19 mL/min/gr by PET and 0.76 ± 0.24 by AC-CZT (P = NS) and 1.14 ± 0.4 by NAC-CZT (P < 0.001 vs PET and AC-CZT). Stress MBF was higher when measured by PET than AC-CZT (1.87 ± 0.45 vs 1.62 ± 0.68 mL/min/gr, P < 0.0008), but lower than NAC-CZT (2.36 ± 1.1, P < 0.0003). The MBF reserve ratio (MFR) was higher by PET than AC-CZT (2.52 ± 0.56 vs 2.22 ± 1 (P < 0.009) and NAC-CZT (2.18 ± 1.0, P < 0.004). Linear regression was better between PET (MFR and stress MBF) and AC-CZT than between PET and NAC-CZT. ROC curve analysis showed the significant ability of AC-CZT to predict MFR < 2 and stress MBF < 1.7 (AUC = 0.75 and 0.82 respectively) and to differentiate between normal and CAD patients (AUC = 0.747 and 0.892 for MFR and stress MBF, respectively).

CONCLUSIONS

Our data show a reasonable correlation between MBF and MFR measured by N13NH3-PET and 99mTc-Tetrofosmin-CZT SPECT. NAC-CZT overestimates MBF. AC is recommended when using CZT for measuring MBF.

Research Progress of Imaging Methods for Detection of Microvascular Angina Pectoris in Diabetic Patients

Diabetes is a complex metabolic disease characterized by hyperglycemia. Its complications are various, often involving the heart, brain, kidney, and other essential organs. At present, the number of diabetic patients in the world is growing day by day. The cardiovascular disease caused by diabetes has dramatically affected the quality of life of diabetic patients. It is the leading cause of death of diabetic patients. Diabetic patients often suffer from microvascular angina pectoris without obstructive coronary artery disease. Still, there are typical ECG ischemia and angina pectoris, that is, chest pain and dyspnea under exercise. Unlike obstructive coronary diseases, nitrate does not affect chest pain caused by coronary microvascular angina in most cases. With the increasing emphasis on diabetic microvascular angina, the need for accurate diagnosis of the disease is also increasing. We can use SPECT, PET, CMR, MCE, and other methods to evaluate coronary microvascular function. SPECT is commonly used in clinical practice, and PET is considered the gold standard for non-invasive detection of myocardial blood flow. This article mainly introduces the research progress of these imaging methods in detecting microvascular angina in diabetic patients.

Myocardial Flow Reserve Measurement During CZT-SPECT Perfusion Imaging for Coronary Artery Disease Screening: Correlation With Clinical Findings and Invasive Coronary Angiography-The CFR-OR Study

Purpose: The aim of this study was to assess the results of cadmium zinc telluride (CZT)- single-photon emission computed tomography (SPECT) myocardial flow reserve (MFR) in coronary artery disease (CAD) screening regarding clinical risk and its correlation to invasive coronary angiography (ICA). Methods: A total of 137 patients (61 male and 76 female) referred for CAD screening myocardial perfusion imaging (MPI) between November 2018 and April 2020 were included in the CFR-OR prospective trial. The 10-year risk of cardiovascular death according to the European Society of Cardiology (SCORE) was calculated. SPECT 1-day 99mTc-tetrofosmin protocol was acquired on CZT cardiac-dedicated pinhole cameras. Low-dose thoracic CT was used for coronary calcium score (CCS) evaluation. ICA, when performed within 3 months, was also analyzed. Results: Mean SCORE and mean global MFR were, respectively, 4 ± 3.1% and 2.50 ± 0.74; 34 patients had impaired CFR (using a threshold of 2). There was a significant inverse correlation between MFR and SCORE (p = 0.006), gender (p = 0.019), and number of cardiovascular risk factors (p = 0.01). MFR was significantly reduced in patients with CCS above 1 (p = 0.01). No significant correlation was found between MFR and individual cardiovascular risk factors (dyslipidemia, hypertension, diabetes, or family history of CAD). A total of 23 patients underwent ICA. Global MFR SPECT sensitivity and specificity were 83.3 and 100 %, respectively, with an area under the curve of 0.94. Conclusion: Adding MFR to SPECT MPI for CAD screening on CZT camera may contribute to high-risk patient identification and enhance diagnostic performances. MFR could help physician decision to perform ICA.

Emerging F-18-Labelled PET Myocardial Perfusion Tracers

PURPOSE OF REVIEW

PET myocardial perfusion imaging (MPI) is an established modality for the evaluation of ischemic heart disease and quantitation of myocardial blood flow (MBF). New F-18-labelled radiopharmaceuticals have been recently developed to overcome some of the limitations of currently used tracers such as the need of an on-site cyclotron. The characteristics of the new tracers and the clinical results obtained so far will be reviewed.

RECENT FINDINGS

Most of the interest in the field of ¹⁸F-labelled radiotracers for PET MPI has been concentrated on MC-1 inhibitors, the prototype of which is ¹⁸F-flurpiridaz. It was shown in experimental and clinical reports that these radiotracers allow good quality rest/stress MPI studies and a reliable quantitation of MBF. Recent evidence suggests that PET MPI with ¹⁸F-flurpiridaz may provide a superior diagnostic accuracy for obstructive CAD even if a large comparative clinical trial with SPECT is still ongoing.

A method to measure the extent of myocardial ischemia and steal with SPECT myocardial blood flow quantitation

OBJECTIVE

We introduced a method to measure the extent of myocardial ischemia and steal with SPECT MBF quantitation.

METHODS

Eighty-seven patients who received rest/Dipyridamole-stress ^99mTc-Sestamibi (MIBI) dynamic SPECT scans and coronary angiography were included. Dynamic SPECT images were reconstructed with full physical corrections. The one-tissue kinetic model was utilized to quantify K1 and further converted to MBF with required corrections. Rest MBF, stress MBF and myocardial flow reserve (MFR) were converted to a flow status polar map by a flow diagram. Extents of 7 flow statuses were verified their cutoff points for detecting stenoses. The diagnostic performance (DP) was compared to that of MFR.

RESULTS

Cutoff point of the extent to detect ≥ 50% stenosis was 3.01% for ischemia-steal status and 20.3% for the combined status of ischemia-steal and moderate. Using these criteria, sensitivity, specificity and accuracy to detect ≥ 50% stenosis were (80%, 75%, 79%) and (86%, 68%, 80%) for ≥ 70% stenosis. The DP was superior to that of MFR < 2.0 criterion (≥ 50%: 70%, 63%, 69%; ≥ 70%: 73%, 61%, 69%) (all p < 0.015).

CONCLUSION

SPECT MBF quantitation integrated with the flow diagram can measure the extent of myocardial ischemia and steal which appeared more accurate to detect angiographic stenoses than the single MFR parameter.