A new perspective on an old method: gated SPECT imaging for left ventricular contractile function assessment

The ejection fraction (LVEF) is a commonly used marker of left ventricular function. However, because it is strongly influenced by loading conditions, it can be inaccurate in representing cardiac contractility. We therefore evaluated a gated SPECT based tool to simultaneously assess preload, afterload, and contractility. Using gated SPECT-determined ventricular volumes and arterial tension measurements, we calculated ventricular and arterial elastance (Ev and Ea), as well as end-diastolic volumes, which are surrogates for contractility, afterload, and preload, respectively. We applied this protocol to 1462 consecutive patients and assessed the ventricular function in patients with and without myocardial infarction. The median LVEF was 68% (IQR 62-74%). Patients with infarction exhibited decreased contractility (ventricular elastance of 3 mmHg/ml vs. 6 mmHg/ml), compensated by an increase of preload (end-diastolic volume of 100 ml vs. 78 ml) and a decrease in afterload (arterial elastance of 1.8 mmHg/ml vs. 2.2 ml/mmHg). These interactions yielded a preserved ejection fraction in both groups. Gated SPECT-measured volumes were consistent with values reported in the literature. In addition, the combination of nuclear imaging and arterial tension measurement accounted for not only the ejection fraction but also the loading context, providing a more accurate representation of cardiac contractility.

Diagnostic accuracy for CZT gamma camera compared to conventional gamma camera technique with myocardial perfusion single-photon emission computed tomography: Assessment of myocardial infarction and function

BACKGROUND

The solid-state cadmium-zinc-telluride (CZT) gamma camera for myocardial perfusion single-photon emission computed tomography (MPS) has theoretical advantages compared to the conventional gamma camera technique. This includes more sensitive detectors and better energy resolution. We aimed to explore the diagnostic performance of gated MPS with a CZT gamma camera compared to a conventional gamma camera for detection of myocardial infarct (MI) and assessment of left ventricular (LV) volumes and ejection fraction (LVEF), using cardiac magnetic resonance (CMR) as the reference method.

METHODS

Seventy-three patients (26% female) with known or suspected chronic coronary syndrome were examined with gated MPS using both a CZT gamma camera and a conventional gamma camera as well as with CMR. Presence and extent of MI on MPS and late gadolinium enhancement (LGE) CMR was evaluated. For LV volumes, LVEF and LV mass, gated MPS images and cine CMR images were evaluated.

RESULTS

MI was found in 42 patients on CMR. The overall sensitivity, specificity, positive and negative predictive values for the CZT and the conventional gamma camera were the same (67%, 100%, 100% and 69%). For infarct size > 3% on CMR, the sensitivity was 82% for the CZT and 73% for the conventional gamma camera, respectively. LV volumes were significantly underestimated by MPS compared to CMR (P ≤ .002 for all measures). The underestimation was slightly less pronounced for the CZT compared to the conventional gamma camera (2-10 mL, P ≤ .03 for all measures). For LVEF, however, accuracy was high for both gamma cameras.

CONCLUSION

Differences between a CZT and a conventional gamma camera for detection of MI and assessment of LV volumes and LVEF are small and do not appear to be clinically significant.

Effect of left ventricular mechanical dyssynchrony assessed pre-renal transplantation on cardiovascular death post transplantation

BACKGROUND

SPECT myocardial perfusion imaging (MPI) provides an assessment of LV mechanical dyssynchrony (LVMD) which correlates with CVD outcomes in diverse populations including those awaiting renal transplant (RT). The current study examines the association of LVMD on pre-transplant MPI with long-term CVD mortality post RT.

METHODS

We identified consecutive patients who underwent RT at the University of Alabama at Birmingham between 2008 and 2012 from our prospectively collected database. 675 patients in the database underwent MPI and had images amenable for phase analysis. A blinded investigator retrieved the studies and derived LVMD indices including histogram bandwidth (BW), standard deviation (SD), phase peak, phase skewness, and phase kurtosis. The primary outcome was CVD death after RT.

RESULTS

The study cohort had a median age of 54 years, 56% were men, 43% had diabetes, and 7% had prior myocardial infarction. Patients were on dialysis for a median of 3.4 years prior to RT and 34% received living donor transplants. During a median follow-up time after RT of 4.7 years (IQR 3.5 to 6.3 years) 59 patients (9%) succumbed to CVD death. Patients with wider BW, wider SD, lower skewness, and lower kurtosis had an increased risk of CVD death. On multivariate adjustment, BW and skewness remained as independent predictors of CVD deaths.

CONCLUSIONS

LVMD by phase analysis of gated SPECT MPI is associated with increased risk of CVD death after RT. This association is independent of demographics, comorbidities, and traditional findings on MPI and added incremental prognostic information. Assessment of LVMD should be considered for risk stratification in these patients.

Prognostic value of divergent pattern detection by 99mTc-sestamibi gated SPECT in patients with anterior acute myocardial infarction

PURPOSE

In gated myocardial perfusion SPECT, apical remodeling may be identified by the presence of a divergent pattern (DP) of the left ventricle (LV).

METHODS AND RESULTS

We examined 150 anterior ST-elevation myocardial infarction (STEMI) patients, all successfully treated with primary percutaneous coronary interventions (PCI). Perfusion gated-SPECT to measure infarct size, LV end-diastolic (ED) and end-systolic (ES) volumes and ejection fraction (EF) was acquired before hospital discharge and repeated at 6-month follow-up. DP was observed in 26 patients, who had larger infarct size (28 ± 19% vs. 15.7 ± 17%, P < 0.02), and lower EF (33 ± 7% vs. 41 ± 10%, P < 0.001) than patients without DP. At follow-up, DP patients had significantly larger EDV (156 ± 54 vs. 107 ± 44 mL, P < 0.0001), ESV (104 ± 47 vs. 59 ± 36 mL, P < 0.0001) and lower EF (35 ± 12% vs. 48 ± 13%, P < 0.0001). 54% of DP patients developed remodeling at follow-up vs. 12% of those without DP (P < 0.001). During follow up, 7 events in the DP group (27%) and 11 events in patients without DP (9%; P < 0.02) occurred. Kaplan-Meier survival curves showed a worse prognosis for DP patients.

CONCLUSION

In patients with anterior AMI, early DP detection is related to subsequent LV dysfunction, larger infarct size, and worse severity. It is helpful for predicting LV remodeling at short-term follow-up and has prognostic implications.

The assessment of left ventricular mechanical dyssynchrony from gated 99mTc-tetrofosmin SPECT and gated 18F-FDG PET by QGS: a comparative study

BACKGROUND

Due to partly conflicting studies, further research is warranted with the QGS software package, with regard to the performance of gated FDG PET phase analysis as compared to gated MPS as well as the establishment of possible cut-off values for FDG PET to define dyssynchrony.

METHODS

Gated MPS and gated FDG PET datasets of 93 patients were analyzed with the QGS software. BW, Phase SD, and Entropy were calculated and compared between the methods. The performance of gated PET to identify dyssynchrony was measured against SPECT as reference standard. ROC analysis was performed to identify the best discriminator of dyssynchrony and to define cut-off values.

RESULTS

BW and Phase SD differed significantly between the SPECT and PET. There was no significant difference in Entropy with a high linear correlation between methods. There was only moderate agreement between SPECT and PET to identify dyssynchrony. Entropy was the best single PET parameter to predict dyssynchrony with a cut-off point at 62%.

CONCLUSION

Gated MPS and gated FDG PET can assess LVMD. The methods cannot be used interchangeably. Establishing reference ranges and cut-off values is difficult due to the lack of an external gold standard. Further prospective research is necessary.

Reproducibility of global LV function and dyssynchrony parameters derived from phase analysis of gated myocardial perfusion SPECT: A multicenter comparison with core laboratory setting

BACKGROUND

Gated myocardial perfusion scintigraphy (GMPS) phase analysis is an important tool to investigate the physiology of left ventricular (LV) dyssynchrony. We aimed to test the performance of GMPS LV function and phase analysis in different clinical settings and on a diverse population.

METHODS

This is a post hoc analysis of a prospective, non-randomized, multinational, multicenter cohort study. Clinical evaluation and GMPS prior to cardiac resynchronization therapy (CRT)(baseline) and 6-month post CRT (follow-up) were done. LV end-systolic volume (LVESV), LV end-diastolic volume (LVEDV), LV ejection fraction (LVEF), LV phase standard deviation (LVPSD), and percentage of left ventricle non-viable (PLVNV) were obtained by 10 centers and compared to the core lab.

RESULTS

276 GMPS studies had all data available from individual sites and from core lab. There were no statistically significant differences between all variables except for LVPSD. When subjects with no mechanical dyssynchrony were excluded, LVPSD difference became non-significant. LVESV, LVEF, LVPSD and PLVNV had strong correlation in site against core lab comparison. Bland-Altman plots demonstrated good agreement.

CONCLUSIONS

The presented correlation and agreement of LV function and dyssynchrony analysis over different sites with a diverse sample corroborate the strength of GMPS in the management of heart failure in clinical practice.

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.

Sex-specific reference limits of left ventricular ejection fraction and volumes estimated by gated myocardial perfusion imaging for low-risk patients in China: a comparison between three quantitative algorithms

BACKGROUND

Establishing appropriate reference value limits of left ventricular (LV) functional parameters is fundamental for the assessment of cardiac function. At present, there are no reports aimed at establishing reference limits using gated myocardial perfusion imaging (MPI) in mainland China.

METHODS

A total of 175 consecutive patients who were defined as low-risk coronary artery disease patients underwent stress Technetium-99m sestamibi (^99mTc-MIBI)-gated myocardial perfusion single-photon emission computed tomography (SPECT) imaging. The LV ejection fraction (EF), end-diastolic volume (EDV), and end-systolic volume (ESV) were obtained by 3 quantitative algorithms: quantitative-gated SPECT, emory cardiac toolbox, and 4-dimensional model SPECT, respectively. The threshold values were obtained using Gaussian distribution or percentiles. The influence of gender, age, and weight on cardiac functional parameters was analyzed by multiple regressions for linear models.

RESULTS

For males, the lower reference limits of EF were 52%, 63%, and 58%, respectively; and the upper limits of EDV/ESV were 106/45, 152/55, and 135/55 mL, respectively. For females, the lower reference limits of EF were 58%, 66%, and 65%, respectively; and the upper limits of EDV/ESV were 73/27, 105/31, and 88/29 mL, respectively. Compared to females, males had greater cardiac volume values and lower mean EF values. Bland-Altman plots revealed that the cardiac function parameters calculated by the three quantitative algorithms were in high agreement.

CONCLUSIONS

In this study, the reference limits of cardiac parameters calculated by the 3 methods based on single-center data in China were preliminarily established. The threshold values determined by three quantitative algorithms were not interchangeable but were highly correlated.

Head-to-head comparison of a CZT-based all-purpose SPECT camera and a dedicated CZT cardiac device for myocardial perfusion and functional analysis

PURPOSE

To compare the outputs of a novel all-purpose SPECT camera equipped with CZT detectors (Discovery NM/CT 670) with the state-of-the-art represented by a dedicated CZT (Alcyone, Discovery 530c) cardiac camera in patients submitted to myocardial perfusion imaging (MPI).

METHODS

We included 19 patients that underwent sequential low-dose 99mTc-tetrofosmin (148-185 MBq during stress and 296-370 MBq at rest) MPI with Alcyone and Discovery 670 cameras. Quantitative (% tracer's uptake) and semi-quantitative analyses of perfusion data were performed for each scan. Moreover, major left ventricular (LV) functional and structural parameters were derived from each camera and compared.

RESULTS

The two cameras showed excellent correlation for segmental myocardial % uptake at stress (R = 0.90; P < 0.001) and at rest (R = 0.88; P < 0.001) with narrow Bland-Altman limits of agreement. The level of diagnostic agreement of Discovery 670 and Alcyone cameras regarding perfusion analysis was excellent (Cohen's κ 0.85). Similarly, the two cameras showed excellent correlation in the evaluation of LV ejection fraction (R = 0.95), peak filling rate (R = 0.97), and mass (R = 0.98).

CONCLUSIONS

Our preliminary results suggest that MPI with an all-purpose Discovery 670 CZT-SPECT camera is feasible, comparing well with the current state-of-the-art technology.

Safety measures and clinical outcome of Nuclear Cardiology Department during Covid-19 lockdown pandemic: Northern Italy experience

BACKGROUND

The Covid-19 pandemic led to a complete renewal of clinical activities of Italian hospitals. During the lockdown, all hospitals in Italy had to suspend non-urgent clinical activities. The prolonged suspension of elective activities could have caused a series of problems.

METHODS

A new ad hoc protocol was designed. Single-day fast-imaging protocol with regadenoson-stress 99mTc-tetrofosmin imaging was preferred. Patients were contacted by phone 4 days before the test and answered to a questionnaire which will be repeated on the day of the exam. Body temperature <37.5 degrees C and no Covid-19 symptoms were necessary to enter the unit. Patients wore surgical mask and gloves. Social distancing was maintained throughout the examination. Healthcare professionals wore a personal protective equipment.

RESULTS

A total of 46 patients were studied from April 7 to May 15, 2020, before the publication of the recommendations from ASNC and SNMMI. None of the patients experienced complications. Follow-up of patients discharged was carried by phone. No Covid-19 infection symptoms were reported. On May 18, 2020 all the healthcare providers of nuclear cardiology department underwent serological testing IgG and IgM and none were positive.

CONCLUSION

Strict ad hoc hygiene protocol for Covid-19 pandemic avoids diagnostic-therapeutic delay and lengthening of waiting lists. Our experience confirms that pursuing WHO recommendations and recent indication of ASNC and SNMMI is safe for both health providers and patients. Moreover, the incidence of significant inducible ischemia rises when correct stratification of patients is performed.

Left ventricular end-systolic contractile entropy can predict cardiac prognosis in patients with complete left bundle branch block

BACKGROUND

Several patients with complete left bundle branch block (CLBBB) show left ventricular (LV) dyssynchrony and poor cardiac prognosis. However, the prognostic value of LV end-systolic contractile entropy which was measured by single-photon emission computer tomography (SPECT) has not been elucidated in patients with CLBBB.

METHODS AND RESULTS

We recruited consecutive 115 sinus-rhythm patients with CLBBB who underwent ECG-gated 201TlCl-SPECT. After 30 days of observation, finally 102 patients (75.2 ± 9.5 years, 62 male) were enrolled and observed retrospectively for a median of 671 days. Twenty-five patients fell into major cardiac events. Multivariate Cox regression analysis showed estimated glomerular filtration rate (eGFR) ≤ 39.35 mL/min and entropy ≥ 79% were significant and independent predictors for major cardiac events (hazard ratio: 4.256 and 7.587, P value = 0.006 and < 0.001, respectively). Machine learning (Random Forest method) revealed eGFR and entropy had higher feature importance than other predictors (0.140 and 0.138, respectively). Kaplan-Meyer curve analysis demonstrated that the group with entropy ≥ 79% and eGFR ≤ 39.36 mL/min had the worst cardiac prognosis (Logrank: P = 0.002).

CONCLUSIONS

Left ventricular end-systolic contractile entropy predicts poor cardiac prognosis in patients with CLBBB, which may be more valuable than the other parameters of SPECT.

Myocardial perfusion imaging for diabetes: Key points from the evidence and clinical questions to be answered

Diabetes represents a worldwide increasing problem and cardiovascular disease is the most common cause of death in diabetic patients. Pathophysiology that links diabetes to cardiovascular disease is a complex and multifactorial phenomenon evolving over time and involving both large blood vessels (macrovasculature) and small blood vessels (microvasculature). Myocardial perfusion imaging (MPI) imaging by both single-photon emission computer tomography and positron emission tomography with different specific tracers has become an indispensable tool for discriminating normal from diseased myocardial tissues and left ventricular function and monitoring myocardial blood flows, leading to the evaluation of almost overall physiologic consequences of the macro- and microvascular impairment involved in diabetic patients. This review will provide an overview of the role of MPI in the diagnosis and risk assessment of patients with diabetes and suspected or known CAD.

Prognostic significance of post-stress reduction in left ventricular ejection fraction with adenosine stress in Jordanian patients with normal myocardial perfusion

BACKGROUND

The significance of post-stress reduction in left ventricular ejection fraction (LVEF) in patients with normal perfusion on adenosine stress/rest imaging remains controversial.

METHODS

Consecutive patients who underwent 2-day adenosine gated stress/rest 99mTc-sestamibi imaging and had normal perfusion were analyzed. LVEF was quantified at rest and 1 hour post-adenosine. Patients were followed up for hard (cardiac death or nonfatal MI) and soft (coronary revascularization or congestive heart failure) cardiac events for 24.1 ± 11.0 months.

RESULTS

Of 560 patients included in the study, 135 (24.1%) had a post-stress reduction in LVEF of ≥ 5%. Rest LVEF (P < 0.001), known history of CAD (P = 0.01) and transient ischemic dilatation ratio (P = 0.02) were independent predictors of LVEF reduction. Event-free survivals were similar in patients with and without ≥ 5% LVEF reduction (P = 0.8). The unadjusted hazard ratio (95% CI) for cardiac events for ≥ 5% LVEF reduction was 1.09 (0.55-2.15), P = 0.81, while the hazard ratio adjusted for known history of CAD, smoking, post-stress LVEF and peak heart rate was 0.87 (0.44-1.75), P = 0.71.

CONCLUSIONS

Significant post-adenosine reduction in LVEF occurs in about one-fourth of patients with normal perfusion but does not confer adverse prognosis compared with patients without such reduction.

Inter-reader variability of SPECT MPI readings in low- and middle-income countries: Results from the IAEA-MPI Audit Project (I-MAP)

BACKGROUND

Consistency of results between different readers is an important issue in medical imaging, as it affects portability of results between institutions and may affect patient care. The International Atomic Energy Agency (IAEA) in pursuing its mission of fostering peaceful applications of nuclear technologies has supported several training activities in the field of nuclear cardiology (NC) and SPECT myocardial perfusion imaging (MPI) in particular. The aim of this study was to verify the outcome of those activities through an international clinical audit on MPI where participants were requested to report on studies distributed from a core lab.

METHODS

The study was run in two phases: in phase 1, SPECT MPI studies were distributed as raw data and full processing was requested as per local practice. In phase 2, images from studies pre-processed at the core lab were distributed. Data to be reported included summed stress score (SSS); summed rest score (SRS); summed difference score (SDS); left ventricular (LV) ejection fraction (EF) and end- diastolic volume (EDV). Qualitative appraisals included the assessment of perfusion and presence of ischemia, scar or mixed patterns, presence of transient ischemic dilation (TID), and risk for cardiac events (CE). Twenty-four previous trainees from low- and middle-income countries participated (core participants group) and their results were assessed for inter-observer variability in each of the two phases, and for changes between phases. The same evaluations were performed for a group of eleven international experts (experts group). Results were also compared between the groups.

RESULTS

Expert readers showed an excellent level of agreement for all parameters in both phase 1 and 2. For core participants, the concordance of all parameters in phase 1 was rated as good to excellent. Two parameters which were re-evaluated in phase 2, namely SSS and SRS, showed an increased level of concordance, up to excellent in both cases. Reporting of categorical variables by expert readers remained almost unchanged between the two phases, while core participants showed an increase in phase 2. Finally, pooled LVEF values did not show a significant difference between core participants and experts. However, significant differences were found between LVEF values obtained using different software packages for cardiac analysis.

CONCLUSIONS

In this study, inter-observer agreement was moderate-to-good for core group readers and good-to-excellent for expert readers. The quality of reporting is affected by the quality of processing. These results confirm the important role of the IAEA training activities in improving imaging in low- and middle-income countries.

Left ventricular ischemia after arterial switch procedure: Role of myocardial perfusion scintigraphy and cardiac CT

Transposition of the great arteries is a congenital heart defect defined by an abnormal connection between the aorta, pulmonary artery, and the ventricles, resulting in parallel systemic and pulmonary circulations. Long-term follow-up data of patients who underwent correction via an arterial switch operation have recently shown that as a result of re-implantation of the coronary arteries in the neo-aorta, coronary stenosis and occlusion are relatively common complications. In this report, we discuss two cases illustrating the added value of myocardial perfusion imaging (MPI) and cardiac CT for the assessment of these patients. Based on the available literature we conclude that MPI and cardiac CT are excellent non-invasive methods to evaluate coronary anatomy and myocardial function also in this specific group of patients.

The influence of anthropometric and basic circulatory variables on count rate in cadmium-zinc-telluride SPECT gated radionuclide angiography

AIM

To determine the influence of weight, height, gender, age, heart rate, and blood pressure on count rate in cadmium-zinc-telluride single-photon emission computed tomography (CZT SPECT) gated radionuclide angiography.

METHOD

A total of 1,065 eligible patients referred for routine assessment of left ventricular ejection fraction were registered from August 2015 to November 2016. Data were recorded on heart rate, systolic and diastolic blood pressure, age, gender, height, weight, and count rate. All radionuclide angiographies were performed on a dedicated cardiac CZT SPECT camera, GE Discovery 530c. A dose of 550 MBq 99mTc-labeled human serum albumin was administered intravenously to each patient.

RESULTS

Count rate varied from 1.2 to 8.9 counts per second. All test variables were significantly associated with count rate. From the preliminary analysis, weight appeared as the main contributing factor for explaining the variations in count rate with and R2 of 0.68. A model consisting of weight, height, gender, and age explains 75% of the variance in count rate.

CONCLUSION

Patient height, weight, gender, and age have significant impact on count rate when performing CZT radionuclide angiography and may subsequently be used for individualized planning of tracer dosage.

Relationships between electrical and mechanical dyssynchrony in patients with left bundle branch block and healthy controls

BACKGROUND

Abnormal electrical activation may cause dyssynchronous left ventricular (LV) contraction. In this study, we characterized and analyzed electrical and mechanical dyssynchrony in patient with left bundle branch block (LBBB) and healthy controls.

METHODS

Myocardial perfusion imaging (MPI) data from 994 patients were analyzed. Forty-three patient fulfilled criteria for LBBB and 24 for controls. Electrical activation was characterized with vector electrocardiography (VECG) and LV function including mechanical dyssynchrony with ECG-gated MPI phase analysis.

RESULTS

QRS duration (QRSd; r = 0.69, P < .001) and a few other VECG parameters correlated significantly with phase bandwidth (phaseBW) representing mechanical dyssynchrony. End-diastolic volume (EDV; r = 0.59, P < .001), ejection fraction and end-systolic volume correlated also with phaseBW. QRSd (β = 0.47, P < .001) and EDV (β = 0.36, P = .001) were independently associated with phaseBW explaining 55% of its variation. Sixty percent of patients with LBBB had significant mechanical dyssynchrony. Those patients had wider QRSd (159 vs 147 ms, P = .013) and larger EDV (144 vs 94 mL, P = .008) than those with synchronous LV contraction. Cut-off values for mechanical dyssynchrony seen in patients with LBBB were QRSd ≥ 165 ms and EDV ≥ 109 mL.

CONCLUSIONS

Despite obvious conduction abnormality, LBBB is not always accompanied by mechanical dyssynchrony. QRSd and EDV explained 55% of variation seen in phaseBW. These two parameters were statistically different between LBBB cases with and without mechanical dyssynchrony.

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.

Myocardial perfusion and left ventricular quantitative parameters obtained using gated myocardial SPECT: Comparison of three software packages

BACKGROUND

The aim of the present study was to compare Emory Cardiac Toolbox, Myovation, and Quantitative Gated SPECT software regarding the automatic measurements of perfusion and functional left ventricular (LV) quantitative parameters, summed stress score (SSS), perfusion defect score, LV ejection fraction (LVEF), end-diastolic volume, and end-systolic volume (ESV).

METHODS AND RESULTS

99mTc-tetrofosmin gated SPECT studies were performed in 634 consecutive patients based on the one-day stress/rest protocol. Participants were divided into subgroups according to heart size (ESV cut-off value: 25 mL), perfusion (SSS >/≤3), and other patient/protocol-related factors. LVEF was categorized as normal (≥50%), mildly moderately impaired (35-49%), and severely abnormal (<35%). The concordance between the packages was good to excellent, in overall population, ESV ≤25 mL, ESV >25 mL, and SSS >3 subgroups (intraclass correlation coefficients, ICCs 0.73-0.93). In SSS ≤3 subgroup, the correlation was excellent for LV functional parameters, but suboptimal for perfusion variables (ICCs 0.30-0.83). LVEF categorization revealed similar variability (discordance 18.1 and 11.1% for stress/rest LVEF values, respectively). Pair comparisons demonstrated considerable differences concerning all parameters for all patient subgroups. The statistical significance of our findings by ESV and SSS classifications was evaluated.

CONCLUSIONS

Despite the significant concordance between software packages, considerable differences in mean values of myocardial perfusion and LV functional parameters were demonstrated.

Relationship between gated myocardial perfusion SPECT findings and hemodynamic, electrocardiographic, and heart rate changes after Dipyridamole infusion

After dipyridamole infusion, electrocardiographic (ECG), blood pressure and heart rate (HR) changes were seen. We tried to investigate whether there is a relationship between hemodynamic, ECG and HR changes after dipyridamole infusion and gated myocardial perfusion SPECT findings. We studied 206 consecutive patients which underwent a 2-day protocol Dipyridamole Stress/Rest Tc99m-Sestamibi gated myocardial perfusion SPECT. Systolic blood pressure (SBP), diastolic blood pressure (DBP), HR and ECG were recorded. HR was mildly increased while SBP and DBP were mildly decreased after Dipyridamole infusion. There was only statistically significant difference between ECG changes as well as transient ischemic dilation (TID) ratio between normal scans and scans with ischemia (P = 0.02 and P = 0.01 respectively). There was correlation between these variables and summed stress score (SSS) and summed difference score (SDS). Patients with ischemia in their scans, 44.3% had ST depression after Dipyridamole infusion. Also ST depression most frequently was seen in patients with left anterior descending artery disease. From patients with abnormal scan + ST depression after Dipyridamole infusion (33 patient), 27 patient (81.81%) had ischemia. There was an association between TID ratio as well as ECG changes after Dipyridamole infusion and SSS, SDS and coronary artery territory abnormality. Difference between calculated left ventricular ejection fraction using stress and rest images had significant correlation with SSS and SDS. ST depression after Dipyridamole infusion and TID ratio had association with ischemia, SSS and SDS. So in equivocal Gated SPECT findings, they could be very useful for interpretation.

Evaluation of varying physical acquisition parameters in gamma camera gated cardiac SPECT

BACKGROUND

There are various physical factors that limit the quality of the Single Photon Emission Computed Tomography (SPECT) images such as number of frames per projection, number of projections per scan and time per projection in gated myocardial SPECT scan.

OBJECTIVE

The aim of the present work was to evaluate physical acquisition parameters affecting the cardiac imaging to optimize the patient's examination time and image quality that are acquired with the gamma camera and workers radiation protection (through reducing time of radiation exposure) in cardiac SPECT facility. Cardiac functional parameters like ejection fraction (EF), end diastole volume (EDV), end systole volume (ESV) and total perfusion defect (TPD) were evaluated.

METHODS

Thirty patients were divided into three groups as follows: 1- Group (1): contains two sub-groups, one scanned with 8 frames per projection, the other with 16 frames per projection. 2- Group (2): contains two sub-groups, one scanned with 32 projections per scan, the other with 16 projections per scan. 3- Group (3): contains two sub-groups, one scanned at a time per projection of 20 s and the other scanned at 10 s per projection. Parameters such as the Ejection Fraction (EF), End Diastole Volume (EDV), End Systole Volume (ESV) and Total Perfusion Defect (TPD) in SPECT were compared for each group.

RESULTS

There was insignificant difference in the EF, EDV, ESV and TPD between the different groups concerning the number of frames per projection, number of projections per scan and time per projection.

CONCLUSION

The reduction of scan time to half or the number of projections per scan to half or increasing the number of frames per scan from 8 to 16 at the same duration has insignificant effect in the cardiac functional parameters used with gated SPECT scan.

The Diagnostic Value of Tc-99m MIBI Gated Myocardial Perfusion SPECT in Detection of Silent Myocardial Ischemia in Asymptomatic Patients with Type 2 Diabetes Mellitus

OBJECTIVE

In this study, we aimed to evaluate the diagnostic value of Technetium-99m methoxyisobutylisonitrile (Tc-99m MIBI) gated myocardial perfusion SPECT (MPS) in the detection of coronary artery disease (CAD) and silent myocardial ischemia (SMI) in patients with asymptomatic type 2 diabetes mellitus (DM).

MATERIALS AND METHODS

For this purpose, 35 patients with type 2 DM and 15 volunteers with no cardiac symptoms (control group) were included in this study. Exercise tolerance tests (ETT), echocardiography and Tc-99m MIBI gated MPS were performed in patients and volunteers. Computed tomography coronary angiography (CTCA) was performed in patients with coronary ischemia or infarct detected by Tc-99m MIBI gated MPS. The results were analyzed and compared visually and statistically.

RESULTS

The present study revealed a high rate of silent myocardial ischemia (25.71%, N=9) in 35 patients with type 2 DM. Severe CAD in CTCA was detected in four of nine patients with ischemia or infarct by Tc-99m MIBI gated MPS (44.4%). Left ventricular diastolic dysfunction, ischemic pattern and high risk of CAD were detected in the same four patients by echocardiography, ETT and biochemical analysis, respectively. At the end of the statistical evaluation, we found that Tc-99m MIBI gated MPS showed significant correlations with CTCA, echocardiography, ETT, Hba1c level, risk of CAD and diabetic age in diabetic patients with CAD.

CONCLUSION

We propose that Tc-99m MIBI gated MPS is a reliable and non-invasive method that can be used to detect silent myocardial ischemia and CAD in patients with type 2 DM.