Segmental and global left ventricular function assessment using gated SPECT with a semiconductor Cadmium Zinc Telluride (CZT) camera: phantom study and clinical validation vs cardiac magnetic resonance

4D display of CT LV endocardial and epicardial models morphed from PET Rb-82 perfusion studies accurately quantifies segmental myocardial thickening

BACKGROUND

MPI-derived LV wall thickening assessments for diagnostic purposes has been part of clinical guidelines for two decades. It relies on visual evaluation of tomographic slices or regional quantification displayed in 2D polar maps. 4D displays have not entered clinical usage nor have they been validated on their potential to provide equivalent information. The purpose of this work was to validate a 4D realistic display recently designed to quantitatively represent the thickening information from gated MPI into CT-morphed endocardial and epicardial moving surfaces.

METHODS

Forty patients who underwent 82Rb PET were selected based on LV perfusion quantification. CTA templates of heart anatomy were selected to represent the LV anatomy. Generic CT-derived LV endocardial and epicardial surfaces were modified to represent the end diastolic (ED) phase according to PET-derived ED LV dimensions and wall thickness. These CT myocardial surfaces were then morphed by means of thin plate spline (TPS) techniques, according to the gated PET slices count changes (WThPET) and LV wall motion (WMoPET). A geometric thickening (GeoTh) equivalent to LV WThPET was defined on epicardial and endocardial CT surfaces over the cardiac cycle and the two measures compared. WThPET and GeoTh correlations were performed on a case-by-case basis, by segment and by pooling all 17 segments. Pearson's correlation coefficients (PCC) were calculated to assess the equivalence of the two measures.

RESULTS

Two cohorts of patients (normal and abnormal) were identified based on SSS. R coefficients were as follows: for all pooled segments PCCstress and PCCrest were respectively 0.91 and 0.89 (normal), and 0.9 and 0.91 (abnormal); when individual 17 segments were considered mean PCCstress = 0.92 [0.81-0.98] and mean PCCrest = 0.93 [0.83-0.98] for the abnormal perfusion group; mean PCCstress = 0.89 [0.78-0.97] and mean PCCrest = 0.89 [0.77-0.97] for the normal. When individual studies were considered, R was always > .70 with the exception of five abnormal studies. Inter-user analysis was also conducted.

CONCLUSIONS

Our novel technique for the visualization of LV wall thickening by means of 4D CT endocardial and epicardial surface models accurately replicated 82Rb slice thickening results showing promise for its usage for diagnostic purposes.

Machine Learning for Multi-Vessel Coronary Artery Disease Prediction on Electrocardiogram Gated Single-Photon Emission Computed Tomography

Background: Single-photon emission computed tomography (SPECT) encounters difficulties in diagnosing severe multi-vessel coronary artery disease (svMVD) because of balanced ischemia. We estimated the predictive value of electrocardiogram-gated SPECT for svMVD and improved it using machine learning (ML). Methods and results: We enrolled consecutive 335 patients (median age, 74 years; 255 men) who underwent adenosine stress-gated SPECT (99mTechnesium) and coronary angiography. svMVD was defined as three-vessel disease or left main tract stenosis. Predictive models were constructed using statistical and ML methods. Eighteen cases (5%) showed svMVD, and diabetes, summed stress score (SSS), and the max difference among segmental time of stroke volume per cardiac cycle (MDSV: a parameter of left ventricular [LV] end-systolic dyssynchrony) on adenosine stress were independent significant predictors. The area under the receiver operating characteristic curve (AUC) of SSS and MDSV on stress were 0.759 and 0.763, respectively. Conversely, the extra trees classifier and light gradient boosting machine had improved AUC values of 0.826 and 0.870, respectively, and the MDSV on stress and diabetes showed high feature values in the ML models. Conclusion: ML on SPECT helped to improve the diagnostic performance of svMVD and diabetes, and the parameters of LV dyssynchrony played essential roles in the ML predictive models.

Prognostic value of absent left ventricular ejection fraction reserve with regadenoson SPECT MPI

BACKGROUND

An absent left ventricular ejection fraction (LVEF) reserve with vasodilator stress with PET cardiac imaging has been shown to provide significant independent and incremental value to the perfusion images for prediction of future cardiovascular adverse events. However, the prognostic value of LVEF reserve has not been well characterized with SPECT myocardial perfusion imaging (MPI).

METHODS

We studied 858 consecutive patients with normal and abnormal perfusion pattern with regadenoson SPECT MPI. Change in LVEF was calculated as post-stress LVEF-rest LVEF. Absent LVEF reserve was defined as a drop in LVEF by 5% or more on the post-stress images. The primary outcome was a composite of cardiac death, non-fatal myocardial infarction and late coronary revascularization.

RESULTS

An absent LVEF reserve was more common in patients with abnormal vs normal MPI (31% vs 19%, P = .001). During a median follow-up of 32 months, the primary outcome was experienced by 31% of the study population. An absent LVEF reserve was not associated with an increased risk of the primary outcome in patients with normal (hazard ratio 1.1, 95% CI .4-2.7, P = .8) or abnormal (.75, .56-1.00, P = .05) MPI. There was no significant correlation between extent of ischemia and post-stress change in LVEF (Pearson r = - .072, P = .07).

CONCLUSIONS

In patients undergoing regadenoson SPECT MPI, absent LVEF reserve is not associated with worse cardiac outcomes. Thus, routine reporting of both post-stress and rest LVEF measurements in this setting may not be necessary.

Optimal choice of OSEM and SD reconstruction algorithms in CZT SPECT for hypertrophic cardiomyopathy patients

BACKGROUND

The spectrum dynamics (SD) algorithm is a cardiac reconstruction algorithm of D-SPECT, which improves spatial resolution compared with the ordered-subsets expectation maximization (OSEM) algorithm. We evaluated the wall thickness and left ventricular (LV) volume in patients with hypertrophic cardiomyopathy (HCM) using the SD algorithm.

METHODS

In a phantom study, the myocardial wall was scanned with varying wall thicknesses (10-40 mm). In the clinical study, 30 and 27 normal and HCM patients underwent myocardial perfusion imaging.

RESULTS

In a phantom study, LV volume using the SD algorithm was increased by thickening the wall of the phantom. In the clinical study, the wall thickness and LV volume of OSEM and SD algorithms showed a difference between HCM and normal groups. The wall thickness using OSEM and SD algorithms were 19.4 ± 2.0 and 16.7 ± 1.5 mm in patients with normal, and 27.9 ± 4.9 and 21.8 ± 2.6 mm in patients with HCM.

CONCLUSION

The SD algorithm in cases of HCM may not be able to correctly assess wall thickness and LV volume. Our study suggests that the OSEM is more suitable in cases of HCM than the SD algorithm.

First comparison of performances between the new whole-body cadmium-zinc-telluride SPECT-CT camera and a dedicated cardiac CZT camera for myocardial perfusion imaging: Analysis of phantom and patients

BACKGROUND

Dedicated cardiac Cadmium-zinc-telluride (CZT) cameras show superior performances compared with Anger systems, particularly in terms of spatial resolution and count sensitivity. This study evaluated the performances of a new polyvalent whole body CZT camera (DNM 670CZT) compared with a cardiac dedicated CZT camera (DNM 530c) for myocardial perfusion SPECT.

METHODS

The spatial resolution was evaluated with three linear sources filled with 99mTc. We used a cardiac phantom to evaluate count sensitivity, sharpness index, contrast-to-noise ratio, wall thickness, non-uniformity index, perfusion scores and ventricle volumes for both cameras. The impact of matrix size, and acquisition time was investigated. Concordance between the two cameras was evaluated in patients using QPS/QGS software for quantitative segmental perfusion, motion and thickness scores.

RESULTS

The spatial resolution was identical with the two cameras. Count sensitivity of the DNM 670CZT was twofold lower compared with the DNM 530c, leading to lower sharpness index and contrast-to-noise ratio. The wall thickness and the myocardial volumes were similar. Visual and quantitative assessments of the perfusion patterns have shown a good concordance of the two cameras on phantoms and in patients.

CONCLUSION

This study demonstrated the feasibility of myocardial perfusion SPECT imaging using the new whole-body DNM 670CZT camera.

Current Status of Myocardial Perfusion Imaging With New SPECT/CT Cameras

Myocardial perfusion imaging (MPI) with Single-Photon Emission Computed Tomography (SPECT) has a major role in the management of coronary artery disease. Recent technological advances regarding SPECT detectors with the use of solid-state detectors has allowed for improved imaging quality since a decade with dramatic dose and/or time reduction of imaging protocols due to improved sensitivity and spatial resolution, and is now performed as a routine exam. Interestingly, this new technology has modified our everyday practice, from acquisition protocols (low dose and ultra-fast protocols) to image semiology. Numerous studies have shown how these technical advances have allowed for improved patient management, with similar or improved diagnostic and prognostic information derived from MPI. These improvements have also led to the straightforward implementation of myocardial blood flow measurement. This article reviews the current status of MPI using new SPECT and SPECT/CT cameras.

Gated SPECT myocardial perfusion imaging with cadmium-zinc-telluride detectors allows real-time assessment of dobutamine-stress-induced wall motion abnormalities

BACKGROUND

Left ventricular (LV) ejection fraction (EF) during high dobutamine stress (HD) by real-time gated-SPECT myocardial perfusion imaging (MPI) on a cadmium-zinc-telluride (CZT) gamma camera was validated versus cardiac magnetic resonance imaging (CMR).

METHODS AND RESULTS

After injecting 99mTc-tetrofosmin (320 MBq) in 50 patients (mean age 64 +/- 11 years), EF at rest and post-stress as well as relevant changes in EF at HD (ΔEF ≥ 5%) were assessed. CZT and CMR rest EF values yielded an excellent correlation and agreement (r = 0.96; P < 0.001; Bland-Altman limits of agreement (BA): + 0 to 14.8%). HD EF acquisition was feasible using CZT and correlated better to HD CMR EF than did post-stress CZT EF (r = 0.85 vs 0.76, respectively, all P < 0.001). Agreement in ΔEF detection between HD CMR and immediate post-stress CZT (reflecting standard acquisition using conventional SPECT camera unable to scan during stress) was 45%, while this increased to 85% with real-time HD CZT scan.

CONCLUSION

Real-time ultrafast dobutamine gated-SPECT MPI with a CZT device is feasible and provides accurate measurements of HD LV performance.

Prospective diagnostic performance of semiconductor SPECT myocardial perfusion imaging: wall thickening analysis reduces the need for an additional prone acquisition

PURPOSE

To determine whether the assessment of regional wall thickening (WT) in addition to myocardial perfusion from stress supine acquisitions could compensate for the lack of prone acquisition and the corresponding decrease in the diagnostic performance of SPECT myocardial perfusion imaging (MPI) in patients with known or suspected coronary artery disease (CAD).

METHODS

The study group comprised 41 patients (123 vessels) with known or suspected CAD prospectively recruited for systematic prone and supine ²⁰¹Tl stress SPECT MPI. The diagnostic performance of SPECT MPI was determined for various image sets including nongated supine images (supine NG), nongated combined prone and supine images (prone and supine NG) and gated supine images, allowing WT evaluation from NG images in addition to perfusion (supine NG + WT) using invasive coronary angiography and fractional flow reserve as the gold standards.

RESULTS

The rate of false positives was significantly higher among the supine NG images (20.8%) than among either the prone and supine NG or the supine NG + WT images (3.3% and 2.7%, respectively, P < 0.05 vs. supine NG). Consequently, specificity was higher for the prone and supine NG images than for the supine NG images (96.1% vs. 76.1%, P < 0.01) and was highest for the supine NG + WT images (96.8%, P not significant vs. prone and supine NG), without significant differences in sensitivity (80.0%, 86.6% and 73.3%, respectively, P not significant for all comparisons).

CONCLUSION

The diagnostic performance of supine stress SPECT MPI is improved when WT assessment of ischaemic segments is used as an additional diagnostic criterion to values not significantly different from those with combined prone and supine acquisitions.

Comparison of CZT SPECT and conventional SPECT for assessment of contractile function, mechanical synchrony and myocardial scar in patients with heart failure

AIM

The aim of this study was to compare CZT-SPECT (CZT SPECT) to conventional SPECT (C-SPECT) in the assessment of left ventricular myocardial scar, contractile function, and mechanical synchrony in patients with heart failure (HF).

METHODS

Fifty-nine patients with HF who were referred for myocardial perfusion/metabolism imaging were enrolled. All patients underwent resting 99mTc-MIBI gated myocardial perfusion imaging using a CZT SPECT camera and a C-SPECT camera, respectively, and 18F-FDG PET myocardial metabolism imaging within three days. Summed rest score (SRS) and total perfusion defect (TPD) (as indices of perfusion abnormality), left ventricular (LV), end diastolic volume (EDV), end systolic volume (ESV), and ejection fraction (EF) (as indices of LV systolic function), and histogram band width (BW) and standard deviation (SD) (as indices of mechanical synchrony) were analyzed by automated software while the perfusion/metabolism patterns were analyzed visually.

RESULTS

There was a good correlation between CZT SPECT and C-SPECT for SRS and TPD. CZT SPECT tended to underestimate SRS and TPD compared to C-SPECT. CZT-SPECT and C-SPECT showed excellent agreement in assessing the perfusion/metabolism pattern though a small proportion of normal segments (6.6%) identified by CZT/PET exhibited mismatch pattern on C-SPECT/PET. CZT SPECT also showed excellent correlation with C-SPECT in measuring EDV, ESV, and EF. Finally, BW and SD measured by CZT SPECT correlated well with C-SPECT but CZT SPECT tended to overestimate BW and SD compared to C-SPECT.

CONCLUSION

CZT SPECT provided comparable data to C-SPECT for measuring LV scar, function and synchrony at a considerable reduction in imaging time. CZT SPECT holds a promise for comprehensive evaluation of myocardial performance in patients with HF.

First assessment of simultaneous dual isotope (123I/99mTc) cardiac SPECT on two different CZT cameras: A phantom study

BACKGROUND

We studied the impact of simultaneous dual-isotope acquisition on 123I/99mTc mismatch assessment using two CZT cameras (DNM 530c, GE Healthcare and DSPECT, Biosensors International).

METHODS

We used an anthropomorphic torso phantom (respectively filled with a solution of 123I alone, 99mTc alone, and a mixture of 123I and 99mTc) and its cardiac insert with two defects mimicking two matched and mismatched defects. Mismatch extent and reconstructed image contrast were evaluated.

RESULTS

The acquisition mode (single vs dual) significantly impacted (i) 99mTc (but not 123I) reconstructed segmental activities using both camera (P < .001), and (ii) image contrast (using 123I and DNM 530c, P < .0001; and using both 123I and 99mTc with DSPECT, P < .0001). However, the defect and mismatch size were not impacted by the type of acquisition. With both DNM 530c and DSPECT, Lin's concordance correlation coefficient and Bland-Altman analysis demonstrated an almost perfect concordance and agreement between single- and simultaneous dual-isotope segmental activity (123I and 99mTc).

CONCLUSIONS

This study found no impact of the acquisition mode (single vs dual) or the type of camera (DSPECT vs DNM 530c) on 123I and 99mTc defect size and mismatch, providing a new step toward simultaneous dual-isotope acquisition for combined innervation and perfusion assessment.

Validation of cadmium-zinc-telluride camera for measurement of left ventricular systolic performance

BACKGROUND

There are paucity of data comparing measurements of left ventricular systolic performance using cadmium-zinc-telluride (CZT) semiconductor cameras with other imaging modalities. This study compared the new system with echocardiography (echo) and cardiac magnetic resonance (CMR) imaging.

METHODS

60 Patients presenting with ST-elevated myocardial infarction (MI) were included. Each patient underwent echo, myocardial perfusion imaging using Spectrum Dynamics D-SPECT(r) (CZT-SPECT), and CMR 6 weeks after MI. The primary endpoint was the agreement between CZT-SPECT and CMR for left ventricular ejection fraction (LVEF) measurement.

RESULTS

48 of the 60 patients underwent all 3 studies (echo, CMR, and CZT-SPECT) 40 days after admission. CZT-SPECT and CMR LVEF were well correlated (r = .79, P < .0001), as well as CZT-SPECT vs echo and CMR vs echo (r = .79 and .84, respectively, P < .0001). The segmental LV wall thickening and wall motion also showed good concordance between three techniques.

CONCLUSIONS

CZT-SPECT is reliable for LVEF measurement.

Myocardial perfusion imaging: Lessons learned and work to be done-update

As the second term of our commitment to Journal begins, we, the editors, would like to reflect on a few topics that have relevance today. These include prognostication and paradigm shifts; Serial testing: How to handle data? Is the change in perfusion predictive of outcome and which one? Ischemia-guided therapy: fractional flow reserve vs perfusion vs myocardial blood flow; positron emission tomography (PET) imaging using Rubidium-82 vs N-13 ammonia vs F-18 Flurpiridaz; How to differentiate microvascular disease from 3-vessel disease by PET? The imaging scene outside the United States, what are the differences and similarities? Radiation exposure; Special issues with the new cameras? Is attenuation correction needed? Are there normal databases and are these specific to each camera system? And finally, hybrid imaging with single-photon emission tomography or PET combined with computed tomography angiography or coronary calcium score. We hope these topics are of interest to our readers.

Routine evaluation of left ventricular function using CZT-SPECT, with low injected activities and limited recording times

PURPOSE

Gamma-cameras, with Cadmium-Zinc-Telluride (CZT) detectors, allow to perform myocardial perfusion imaging (MPI) with limited injected activities and recorded times. This study aimed at determining whether the routine assessment of left ventricular (LV) function with such limited counts protocols compares well with reference values from cardiac MRI.

METHODS

The study included patients who have undergone cardiac MRI and an MPI routinely planned on a CZT camera with a low-dose protocol (120 MBq of Sestamibi for stress and 360 MBq at rest for 75 kg body weight), while targeting the recording of only 500 myocardial kcounts in order to limit the recording times (<10 minutes for stress, <4 minutes for rest). SPECT images were reconstructed with a method maintaining rather high spatial (8 mm) and temporal (16 frames/cycle) resolutions.

RESULTS

Seventy-six patients were included, and mean effective dose was 3.5 ± 1.7 mSv for the total MPI protocol. Correlations between CZT-SPECT and MRI were good to excellent for ejection fraction (r 2 = 0.77), end-diastolic (r 2 = 0.88) and end-systolic (r 2 = 0.93) volumes, and the analysis of segmental contractility correlated well between the two techniques (kappa score = 0.72 ± 0.02).

CONCLUSION

LV function, assessed on a CZT camera with low injected activities and limited recording times, correlates well with the reference assessment from cardiac MRI.

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.

Pre-chemotherapy values for left and right ventricular volumes and ejection fraction by gated tomographic radionuclide angiography using a cadmium-zinc-telluride detector gamma camera

BACKGROUND

Estimation of left ventricular ejection fraction (LVEF) using equilibrium radionuclide angiography is an established method for assessment of left ventricular function. The purpose of this study was to establish normative data on left and right ventricular volumes and ejection fraction, using cadmium-zinc-telluride SPECT camera.

METHODS AND RESULTS

From routine assessments of left ventricular function in 1172 patients, we included 463 subjects (194 men and 269 women) without diabetes, previous potentially cardiotoxic chemotherapy, known cardiovascular or pulmonary disease. The lower limits defined as mean value minus two standard deviations for ventricular ejection fraction and end diastolic volume were LVEF (men: 50%, women: 50%), LEDV (men: 45 mL, women: 40 mL), RVEF (men: 29%, women: 28%), and REDV (men: 73 mL, women: 57 mL).There was a significant negative correlation between age and both left and right ventricular volumes in women (r = -0.4, P < .001) but only for right end systolic ventricular volume in men (r = -0.3, P = .001).

CONCLUSION

A set of reference values for cardiac evaluation prior to chemotherapy in cancer patients without other known cardiopulmonary disease is presented. There are age-related changes in cardiac dimensions with age depending on gender, although with only limited influence on LVEF or RVEF.