Myocardial perfusion imaging with a cadmium zinc telluride-based gamma camera versus invasive fractional flow reserve

The incremental value of coronary artery calcium score in predicting long-term prognosis and defining the warranty period of normal adenosine stress-only myocardial perfusion imaging using CZT SPECT

BACKGROUND

Normal stress-only (SO) myocardial perfusion imaging (MPI) using SPECT reduces imaging time and radiation dose with a good prognosis. However, the long-term prognostic value of combining coronary artery calcium score (CACS) with SO MPI to determine the warranty period remains unknown. Hence, we assessed the incremental prognostic value of CACS and its impact on the warranty period of normal SO MPI using SPECT.

METHODS

We retrospectively included 1375 symptomatic patients without a history of coronary artery disease (CAD) and a normal SO MPI using adenosine who underwent simultaneous CAC scoring. Annual major adverse cardiac events (MACE) rates were calculated for CACS categories: 0, 1-399, 400-999, and ≥1000.

RESULTS

The mean age was 60.0 ± 11.8 years (66.9% female) with a median follow-up of 10.3 [IQR 9.6-10.9] years. The warranty period for annual MACE rate for normal SO SPECT extended the total follow-up time in years. MACE rate categorized by CAC categories demonstrated an increase in MACE rates with increasing CACS; CACS 0 and CACS 1-399 were associated with a 10-year warranty period, CACS 400-999 had a warranty period of 4 years and no warranty period could be given for CACS≥1000 (5.9 % at 1 year).

CONCLUSIONS

CACS as an adjunct to normal pharmacological SO MPI provides additional prognostic information and aids in determining a warranty period.

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.

Diagnostic value of stress thallium-201/rest technetium-99m-sestamibi sequential dual isotope high-speed myocardial perfusion imaging for the detection of haemodynamically relevant coronary artery stenosis

BACKGROUND

The aim of this study was to determine the diagnostic accuracy of stress thallium-201/rest technetium-99m-sestamibi sequential dual-isotope high-speed myocardial perfusion imaging (DI-HS-MPI) against invasively determined fractional flow reserve (FFR).

METHODS

Fifty-four consecutive patients prospectively underwent DI-HS-MPI before invasive coronary angiography. Perfusion was scored visually by summed stress score on a patient and coronary territory basis. Significant coronary artery disease (CAD) was defined by the presence of ≥ 90% stenosis/occlusion or fractional flow reserve ≤ 0.80 for coronary stenosis ≥ 50%.

RESULTS

FFR was measured in 69 of 162 coronary vessels, with 1.28 ± 0.56 vessels assessed/patient. Sensitivity, specificity, and diagnostic accuracy of MPI for the detection of significant CAD were 92.8%, 69.2%, and 81.4%, on a patient basis, and 83.7%, 90.4%, and 88.8% by coronary territory.

CONCLUSIONS

DI-HS-MPI accurately detects functionally significant CAD as defined by using FFR.

Comparison of diagnostic accuracy of stress myocardial perfusion imaging for detecting hemodynamically significant coronary artery disease between cardiac magnetic resonance and nuclear medical imaging: A meta-analysis

AIMS

This study aimed to compare the diagnostic accuracy of stress myocardial perfusion imaging between cardiac magnetic resonance (CMR) and nuclear medical imaging, including single-photon emission computed tomography (SPECT) and positron emission tomography (PET), for the diagnosis of hemodynamically significant coronary artery disease (CAD) with fractional flow reserve (FFR) as the reference standard.

METHODS AND RESULTS

We searched PubMed and Embase for all published studies that evaluated the diagnostic accuracy of stress myocardial perfusion imaging modalities, including CMR, SPECT, and PET, to diagnose hemodynamically significant CAD with FFR as the reference standard. A total of 28 articles met the inclusion criteria and were included in the meta-analysis: 14 CMR, 13 SPECT, and 5 PET articles. The results demonstrated a pooled sensitivity of 0.88 (95% confidence interval [CI]: 0.80-0.93), 0.69 (95% CI: 0.56-0.79), and 0.83 (95% CI: 0.70-0.91), and a pooled specificity of 0.89 (95% CI: 0.85-0.93), 0.85 (95% CI, 0.80-0.89), and 0.89 (95% CI, 0.86-0.91) for CMR, SPECT, and PET, respectively. The area under the curve (AUC) of CMR, PET, and SPECT was 0.94 (95% CI, 0.92-0.96), 0.92 (95% CI, 0.89-0.94), and 0.87 (95% CI, 0.83-0.89), respectively.

CONCLUSIONS

CMR and PET both have high accuracy and SPECT has moderate accuracy to detect hemodynamically significant CAD with FFR as the reference standard. Furthermore, the diagnostic accuracy of CMR at 3.0 T is superior to 1.5 T.

Hybrid anatomo-functional imaging of coronary artery disease: Beneficial irrespective of its core components

Coronary artery disease (CAD) is the most common and important cause of ischemic heart disease, with major implications on global morbidity and mortality. Non-invasive testing is crucial in the diagnostic and prognostic work-up of patients with or at risk of CAD, and also to guide decision making in terms of pharmacologic and revascularization therapy. The traditional paradigm is to view anatomic (i.e., coronary computed tomography) and functional imaging (e.g., myocardial perfusion scintigraphy) tests as opposing alternatives. Such approach is too reductionist and does not capitalize on the strengths of each type of test while risking to overlook the inherent limitations. The combination of anatomic and functional tests in a logic of hybrid imaging holds the promise of overcoming the limitations inherent to anatomic and functional testing, enabling more accurate diagnosis, prognosis, and guidance for revascularization in patients with CAD.

Diagnostic value of cadmium-zinc-telluride myocardial perfusion imaging versus coronary angiography in coronary artery disease: A PRISMA-compliant meta-analysis

BACKGROUND

Rapid progress has been made in research of cadmium-zinc-telluride (CZT) technology in the last few years, which might serve as a new method to diagnose coronary artery disease. However, compared with coronary angiography, the diagnostic value of CZT is still controversial. We aimed to evaluate diagnosis value of coronary angiography versus CZT in coronary artery disease.

METHODS

We searched the database for eligible researches associated with CZT- myocardial perfusion imaging (MPI) and invasive coronary angiography, extracted the relevant data, and rigorously screened it according to the inclusion and exclusion criteria. The accuracy indicators included sensitivity, specificity, accuracy, positive and negative likelihood ratios.

RESULTS

According to the inclusion and exclusion criteria, we finally found 20 studies containing 2350 patients in this search. Pooled results showed that sensitivity of CZT-MPI was 0.84% and 95% confidence interval (95% CI): 0.78 to 0.89, specificity was 0.72, 95% CI (0.62-0.76), the specificity was lower apparently. The positive likelihood ratio was 3.0, 95% CI (2.4-3.8), the negative likelihood ratio was 0.22, 95% CI (0.16-0.31), diagnostic odds ratio was 14, 95% CI (7.84-17.42).

CONCLUSION

This meta-analysis showed that CZT-MPI had satisfactory sensitivity and specificity for diagnosing coronary artery disease. Larger studies are required for further evaluation.

New 99mTc Radiotracers for Myocardial Perfusion Imaging by SPECT

OBJECTIVE

Myocardial Perfusion Imaging (MPI) with radiotracers is an integral component in evaluation of the patients with known or suspected coronary artery diseases (CAD). 99mTc-Sestamibi and 99mTc-Tetrofosmin are commercial radiopharmaceuticals for MPI by single photon-emission computed tomography (SPECT). Despite their widespread clinical applications, they do not meet the requirements of an ideal perfusion imaging agent due to their inability to linearly track the regional myocardial blood flow rate at >2.5 mL/min/g. With tremendous development of CZT-based SPECT cameras over the past several years, the nuclear cardiology community has been calling for better perfusion radiotracers with improved extraction and biodistribution properties.

METHODS

This review will summarize recent research efforts on new cationic and neutral 99mTc radiotracers for SPECT MPI. The goal of these efforts is to develop a 99mTc radiotracer that can be used to detect perfusion defects at rest or under stress, determine the regional myocardial blood flow, and measure the perfusion and left ventricular function.

RESULTS

The advantage of cationic radiotracers (e.g. 99mTc-Sestamibi) is their long myocardial retention because of the positive molecular charge and fast liver clearance kinetics. 99mTc-Teboroxime derivatives have a high initial heart uptake (high first-pass extraction fraction) due to their neutrality. 99mTc- 3SPboroxime is the most promising radiotracer for future clinical translation considering its initial heart uptake, myocardial retention time, liver clearance kinetics, heart/liver ratios and SPECT image quality.

CONCLUSION

99mTc-3SPboroximine is an excellent example of perfusion radiotracers, the heart uptake of which is largely relies on the regional blood flow. It is possible to use 99mTc-3SPboroximine for detection of perfusion defect(s), accurate quantification and determination of regional blood flow rate. Development of such a 99mTc radiotracer is of great clinical benefit for accurate diagnosis of CAD and assessing the risk of future hard events (e.g. heart attack and sudden death) in cardiac patients.

The prognostic value of ultra low-dose thallium myocardial perfusion protocol using CZT SPECT

The purpose of this study was to assess the prognostic value of ultra-low dose thallium myocardial perfusion imaging. Three hundred and sixty-six patients (245 men) underwent ultra-low dose stress-redistribution imaging on CZT SPECT camera GE Discovery NM 530c. The stress test was performed by bicycle ergometry or regadenoson injection. The activity of 0.5 MBq (0.014 mCi) Tl-201 chloride per kilogram of body weight was administered. The stress images were acquired immediately and redistribution images were taken after 3 h. Patient follow-up was focused on combined end-point (death, myocardial infarction, unstable angina, revascularization and hospitalization for heart failure). Data analysis was performed from hospital database, with a mean period 23 months. Patients with revascularization within 1 month after SPECT was excluded as revascularization for diagnosis. Ischaemia on SPECT was found in 72 patients, 294 patients were without ischaemia. In patients with ischaemia there were 21 (29.2%) subjects with cardiac events, and 23 (7.9%) in patients without ischaemia (HR 4.15, 95% CI 2.30-7.51, p < 0.0001). Ultra-low dose thallium perfusion imaging using CZT camera provides very good prognostic results in assessment of myocardial ischaemia.

Impact of data-driven cardiac respiratory motion correction on the extent and severity of myocardial perfusion defects with free-breathing CZT SPECT

BACKGROUND

We previously reported the clinical feasibility and positive impact on image characteristics of a data-driven cardiac respiratory motion (RM) correction method (REGAT) applicable to CZT SPECT myocardial perfusion imaging (MPI). Here, we evaluate its impact on the extent and severity of myocardial perfusion defects (MPD).

METHODS

We included 25 patients having a 1-day 99mTc-Tetrofosmin stress/rest MPI acquired with multi-pinhole CZT SPECT. Acquisitions were processed with REGAT to generate mean RM gated SPECT. These were summed either after (R-SPECT) or without realignment (NR-SPECT). We noted the maximal cardiac RM shift in the 3 axes of the left ventricle (LV). Both visual and semi-quantitative analyses of myocardial tracer uptake were realized. Studies were classified as having an impact on the extent/severity of MPD with REGAT if ≥1 segment presented a severity score changing by ≥1 level between NR-SPECT and R-SPECT. An impact on the extent of MPD was considered present if at least 1 segment shifted from normal (score = 0) to abnormal (score different from 0) or inversely.

RESULTS

Cardiac RM was >10 mm in 55% of studies. With visual and semi-quantitative analyses, an impact on the extent/severity MPD was observed in 14% of all studies (7/49) and 60% of studies with cardiac RM >15 mm. An impact on the extent of MPD was observed in 5 of the 7 upper listed studies. All studies presenting an impact on MPD had RM in the anterior to inferior LV axis >10 mm.

CONCLUSIONS

A substantial number of MPI studies presented significant cardiac RM. Cardiac RM compensation showed a frequent impact on the extent/severity of MPD.

Fractional flow reserve to guide and to assess coronary artery bypass grafting

The aim of this review is to highlight the role of invasive functional evaluation in patients in whom coronary artery bypass graft (CABG) is indicated, and to examine the clinical evidence available in favour of fractional flow reserve (FFR) adoption in these patients, outline appropriate use, as well as point out potential pitfalls. FFR after CABG will also be reviewed, highlighting its correct interpretation and adoption when applied to both native coronary arteries and bypass grafts. Practice European guidelines support the use of FFR to complement coronary angiography with the highest degree of recommendation (Class IA) for the assessment of coronary stenosis before undertaking myocardial revascularization when previous non-invasive functional evaluation is unavailable or not conclusive. As a result, FFR has been adopted in routine clinical practice to guide clinicians decision as to whether or not perform a revascularization. Of note, due to the increasing confidence of the interventional cardiologists, FFR guidance is also being implemented to indicate or guide CABG. This is in anticipation of supportive clear-cut evidence, since recommendations for FFR adoption were based on randomized clinical trials investigating percutaneous coronary intervention (PCI) strategies in which patients with typical indications for CABG were excluded (e.g. left main disease, valvular disease, and coronary anatomy unsuitable for PCI). Based on the critical appraisal of the literature, FFR can play an important role in risk stratification and determining management strategy of patients either before or after CABG.

Value of automatic patient motion detection and correction in myocardial perfusion imaging using a CZT-based SPECT camera

BACKGROUND

Correction of motion has become feasible on cadmium-zinc-telluride (CZT)-based SPECT cameras during myocardial perfusion imaging (MPI). Our aim was to quantify the motion and to determine the value of automatic correction using commercially available software.

METHODS AND RESULTS

We retrospectively included 83 consecutive patients who underwent stress-rest MPI CZT-SPECT and invasive fractional flow reserve (FFR) measurement. Eight-minute stress acquisitions were reformatted into 1.0- and 20-second bins to detect respiratory motion (RM) and patient motion (PM), respectively. RM and PM were quantified and scans were automatically corrected. Total perfusion deficit (TPD) and SPECT interpretation-normal, equivocal, or abnormal-were compared between the noncorrected and corrected scans. Scans with a changed SPECT interpretation were compared with FFR, the reference standard. Average RM was 2.5 ± 0.4 mm and maximal PM was 4.5 ± 1.3 mm. RM correction influenced the diagnostic outcomes in two patients based on TPD changes ≥7% and in nine patients based on changed visual interpretation. In only four of these patients, the changed SPECT interpretation corresponded with FFR measurements. Correction for PM did not influence the diagnostic outcomes.

CONCLUSION

Respiratory motion and patient motion were small. Motion correction did not appear to improve the diagnostic outcome and, hence, the added value seems limited in MPI using CZT-based SPECT cameras.

Novel Approach for 99mTc-Labeling of Red Blood Cells: Evaluation of 99mTc-4SAboroxime as a Blood Pool Imaging Agent

Angiography with radiolabeled red blood cells (RBCs) plays an important role in diagnosis and prognosis in vascular diseases. Both in vitro and in vivo methods have been developed for ^99mTc-labeling of RBCs. However, these methods are complicated and lack reproducibility. Therefore, it is highly desirable to develop an alternative method for routine ^99mTc-labeling of RBCs. In this report, we present a novel approach for ^99mTc-labeling of RBCs. We prepared a new ^99mTc(III) radiotracer [^99mTcCl(CDO)(CDOH)₂B-4AS] (^99mTc-4ASboroxime: 4AS-B(OH)₂ = 4-aminosulfonylphenyl)boronic acid, and CDOH₂ = cyclohexanedione dioxime) in >95% radiochemical purity. Imaging and biodistribution studies were performed in Sprague-Dawley (SD) rats. It was found that the blood radioactivity was ∼6.0%ID/g (∼90% injected dose for 200-225 g SD rats) for ^99mTc-4ASboroxime with low uptake in the myocardium, kidneys, liver, lungs, and muscle, most likely due to lack of leakage of ^99mTc-labeled RBCs from the intravascular space. The blood radioactivity was almost unchanged over the 2 h period, suggesting that the binding of ^99mTc-4ASboroxime to blood components (cells, proteins, and plasma) is stable. The results from γ-counting of the isolated blood components showed that ^99mTc-4ASboroxime had >95% of blood radioactivity binding to RBCs, ∼1% to albumin, and ∼3% remaining free in blood plasma, demonstrating its RBC-specificity. The results from imaging studies in SD rats indicated that ^99mTc-4ASboroxime is predominantly distributed in the blood pool. Main blood vessels were well delineated in the head/neck and abdominal regions. This statement was further substantiated by the results from imaging studies in pigs. ^99mTc-4ASboroxime is an excellent blood pool agent with the potential for diagnosis and prognosis of vascular diseases.

Feasibility of data-driven cardiac respiratory motion correction of myocardial perfusion CZT SPECT: A pilot study

BACKGROUND

We developed a data-driven respiratory motion (RM) correction method (REGAT program) for multiple-pinhole detector CZT SPECT. We verified its clinical feasibility with myocardial perfusion imaging (MPI) and studied its impact on image characteristics.

METHODS

This retrospective study included 18 patients having stress/rest 99mTc-Tetrofosmin MPI SPECT. List mode was acquired on CZT SPECT and processed with REGAT. REGAT generates reconstructed RM-gated volumes that are summed either without realignment (NR-SPECT) or after realignment (R-SPECT). For both stress and rest, we calculated the maximal RM in the 3 axis, and image characteristics of both R-SPECT and NR-SPECT: minimum left ventricular (LV) cavity counts (LV-Min), maximum LV myocardial counts (LV-Max), LV contrast, and FWHM of both anterior (FWHM-ant) and inferior (FWHM-inf) LV myocardial walls.

RESULTS

At both stress and rest, cranio-caudal motion was the dominant axial movement and REGAT had a positive impact on image characteristics as reflected by variations between R-SPECT and NR-SPECT in LV-Min, LV-Max, FWHM-ant, FWHM-inf, and contrast. These latter were well correlated to the amplitude of cranio-caudal motion at both stress and rest.

CONCLUSIONS

Data-driven RM correction of MPI acquired with CZT SPECT is clinically feasible and easily applicable. It presents interesting impact on image characteristics.

Diagnostic Accuracy of Myocardial Perfusion Imaging With CZT Technology: Systemic Review and Meta-Analysis of Comparison With Invasive Coronary Angiography

OBJECTIVES

This study sought to summarize the evidence on stress myocardial perfusion imaging (MPI) using cadmium-zinc-telluride (CZT) technology for the diagnosis of obstructive coronary artery disease (CAD). The CZT cameras are newly introduced, and comparative data with the conventional Anger technology (Anger-MPI) are lacking.

BACKGROUND

The diagnostic accuracy of Anger-MPI for detection of angiographically significant CAD is well established; however, less evidence is available on the diagnostic accuracy of CZT-MPI.

METHODS

Clinical studies comparing CZT-MPI and invasive coronary angiography were systematically searched and abstracted. Calculations of diagnostic accuracy, including sensitivity, specificity, likelihood ratios, and diagnostic odds ratio, were obtained with fixed and random effects, reporting point estimates and 95% confidence intervals.

RESULTS

Based on our search, a total of 16 studies (N = 2,092) were included. The sensitivity of CZT-MPI was 0.84 (95% confidence interval [CI]: 0.78 to 0.89), whereas the specificity of 0.69 (95% CI: 0.62 to 0.76) was significantly reduced. The positive likelihood ratio was 2.73 (95% CI: 2.21 to 3.39), the negative likelihood ratio was 0.24 (95% CI: 0.17 to 0.31), and the diagnostic odds ratio was 11.93 (95% CI: 7.84 to 17.42). At subgroup and meta-regression analyses, the diagnostic accuracy between D-SPECT and Discovery cameras was similar (p = 0.711) and not impacted upon by smaller sample size studies (p = 0.573).

CONCLUSIONS

CZT-MPI has satisfactory sensitivity for angiographically significant CAD, but its suboptimal specificity warrants further development and research.

The value of local normal limits in quantitative Thallium-201 CZT MPI SPECT

BACKGROUND

Considering the distinctive characteristics of CZT detectors, automatic quantification of ischemia using normal limits included with software package may deliver suboptimal results for CAD detection. The present study aims to evaluate the benefits of creating normal limits specific to a local population and laboratory protocol.

METHODS AND RESULTS

Two groups were selected from patients who had undergone a CZT MPI. Normal limits were generated with the QPS application based on the population with low likelihood of CAD. Using the vendor-supplied and the population-specific normal limits i-TPD and vessel-specific SDS results obtained for patients who had subsequently undergone coronary angiography were compared with coronary angiography data. A weak correlation was observed for low i-TPD (stress TPD minus rest TPD) and SDS values. Both databases gave similar values for the area under the ROC curve concerning i-TPD (0.75 to 0.74) and SDS results (0.72 to 0.75 for the LAD, 0.62 to 0.64 for the LCx, and 0.63 to 0.67 for the RCA). Sensitivity (60%), specificity (78%), and predictive positive (84%) and negative (52%) values were also similar with a diagnostic and prognostic threshold value.

CONCLUSION

The use of a population-specific created database did not influence the diagnostic value of thallium-201 MPI QPS results using a CZT camera.

Angiographic underestimation of disease severity in the left anterior descending artery: a fractional flow reserve analysis

OBJECTIVES

This study compared the prevalence of angiographic underestimation of left anterior descending artery (LAD) lesions with non-LAD lesions.

BACKGROUND

Coronary angiography cannot assess the functional severity of a coronary stenosis. Previous studies suggested that lesions of the LAD are more often angiographically underestimated, but evidence is limited.

MATERIALS AND METHODS

Fractional flow reserve (FFR) was performed in 335 coronary lesions (187 LAD lesions and 148 non-LAD lesions). A visually estimated diameter stenosis of at least 70% was considered functionally significant. An FFR value of up to 0.80 was considered significant. Multivariable analyses were carried out.

RESULTS

Angiographically, LAD lesions as well as non-LAD lesions were considered functionally significant in 29% (P=0.94). FFR showed significant stenosis of the LAD in 52% compared with 24% in non-LAD lesions (P<0.001). Underestimation was observed in 30% of LAD lesions compared with 11% in non-LAD lesions (P<0.001). The adjusted odds ratio for underestimation in LAD lesions in comparison with non-LAD lesions was 3.48 (95% confidence interval 1.89-6.41; P<0.001).

CONCLUSION

Underestimation of the functional severity of a coronary stenosis is more common in LAD lesions. FFR should be performed more often for intermediate stenosis of the LAD.

99mTc-3Cboroxime: a novel 99mTc(iii) complex [99mTcCl(CDO)(CDOH)2B-3C] (CDOH2 = cyclohexanedione dioxime; 3C-B(OH)2 = 3-(carbamoylphenyl)boronic acid) with high heart uptake and long myocardial retention

In this study, we found that ^99mTc-3Cboroxime has the myocardial retention longer than that of ^99mTc-Teboroxime, and its heart washout kinetics follows a regressive linear relationship over the 60 min period.

Novel 99mTc(III)-azide complexes [99mTc(N3)(CDO)(CDOH)2B-R] (CDOH2=cyclohexanedione dioxime) as potential radiotracers for heart imaging

INTRODUCTION

In this study, novel ^99mTc(III)-azide complexes [^99mTc(N₃)(CDO)(CDOH)₂B-R] (^99mTc-ISboroxime-N₃: R=IS; ^99mTc-MPboroxime-N₃: R=MP; ^99mTc-PAboroxime-N₃: R=PA; ^99mTc-PYboroxime-N₃: R=PY; and ^99mTc-Uboroxime-N₃: R=5U) were evaluated as heart imaging agents.

METHODS

Complexes [^99mTc(N₃)(CDO)(CDOH)₂B-R] (R=IS, MP, PA, PY and 5U) were prepared by ligand exchange between NaN₃ and [^99mTcCl(CDO)(CDOH)₂B-R]. Biodistribution and imaging studies were carried out in Sprague-Dawley rats. Image quantification was performed to compare their initial heart uptake and myocardial retention.

RESULTS

^99mTc-ISboroxime-N₃, ^99mTc-PYboroxime-N₃ and ^99mTc-Uboroxime-N₃ were prepared with high RCP (93-98%) while the RCP of ^99mTc-MPboroxime-N₃ and ^99mTc-PAboroxime-N₃ was 80-85%. The myocardial retention curves of ^99mTc-ISboroxime-N₃, ^99mTc-PYboroxime-N₃ and ^99mTc-Uboroxime-N₃ were best fitted to the bi-exponential decay function. The half-time of the fast component was 1.6±0.4min for ^99mTc-ISboroxime-N₃, 0.7±0.1min for ^99mTc-PYboroxime-N₃ and 0.9±0.4min for ^99mTc-Uboroxime-N₃. The 2-min heart uptake from biodistribution studies followed the ranking order of ^99mTc-ISboroxime-N₃ (3.60±0.68%ID/g)>^99mTc-PYboroxime-N₃ (2.35±0.37%ID/g)≫^99mTc-Uboroxime-N₃ (1.29±0.06%ID/g). ^99mTc-ISboroxime-N₃ had the highest 2-min heart uptake among ^99mTc radiotracers revaluated in SD rats. High quality SPECT images were obtained with the right and left ventricular walls being clearly delineated. The best image acquisition window was 0-5min for ^99mTc-ISboroxime-N₃.

CONCLUSION

Both azide coligand and boronate caps had significant impact on the heart uptake and myocardial retention of complexes [^99mTc(N₃)(CDO)(CDOH)₂B-R]. Among the radiotracers evaluated in SD rats, ^99mTc-ISboroxime-N₃ has the highest initial heart uptake with the heart retention comparable to that of ^99mTc-Teboroxime. ^99mTc-ISboroxime-N₃ is a promising alternative to ^99mTc-Teboroxime for SPECT MPI.

Performance of cardiac cadmium-zinc-telluride gamma camera imaging in coronary artery disease: a review from the cardiovascular committee of the European Association of Nuclear Medicine (EANM)

The trade-off between resolution and count sensitivity dominates the performance of standard gamma cameras and dictates the need for relatively high doses of radioactivity of the used radiopharmaceuticals in order to limit image acquisition duration. The introduction of cadmium-zinc-telluride (CZT)-based cameras may overcome some of the limitations against conventional gamma cameras. CZT cameras used for the evaluation of myocardial perfusion have been shown to have a higher count sensitivity compared to conventional single photon emission computed tomography (SPECT) techniques. CZT image quality is further improved by the development of a dedicated three-dimensional iterative reconstruction algorithm, based on maximum likelihood expectation maximization (MLEM), which corrects for the loss in spatial resolution due to line response function of the collimator. All these innovations significantly reduce imaging time and result in a lower patient's radiation exposure compared with standard SPECT. To guide current and possible future users of the CZT technique for myocardial perfusion imaging, the Cardiovascular Committee of the European Association of Nuclear Medicine, starting from the experience of its members, has decided to examine the current literature regarding procedures and clinical data on CZT cameras. The committee hereby aims 1) to identify the main acquisitions protocols; 2) to evaluate the diagnostic and prognostic value of CZT derived myocardial perfusion, and finally 3) to determine the impact of CZT on radiation exposure.

New Trends in Radionuclide Myocardial Perfusion Imaging

Radionuclide myocardial perfusion imaging (MPI) with single photon emission computed tomography (SPECT) has been widely used clinically as one of the major functional imaging modalities for patients with coronary artery disease (CAD) for decades. Ample evidence has supported the use of MPI as a useful and important tool in the diagnosis, risk stratification and treatment planning for CAD. Although popular in the United States, MPI has become the most frequently used imaging modality among all nuclear medicine tests in Taiwan. However, it should be acknowledged that MPI SPECT does have its limitations. These include false-positive results due to certain artifacts, false-negative due to balanced ischemia, complexity and adverse reaction arising from current pharmacological stressors, time consuming nature of the imaging procedure, no blood flow quantitation and relatively high radiation exposure. The purpose of this article was to review the recent trends in nuclear cardiology, including the utilization of positron emission tomography (PET) for MPI, new stressor, new SPECT camera with higher resolution and higher sensitivity, dynamic SPECT protocol for blood flow quantitation, new software of phase analysis for evaluation of LV dyssynchrony, and measures utilized for reducing radiation exposure of MPI.

KEY WORDS

Coronary artery disease • Myocardial flow reserve • Myocardial perfusion imaging • Phase analysis • PET • SPECT.