Reliability of the 123I-mIBG heart/mediastinum ratio: Results of a multicenter test-retest reproducibility study

Absolute quantitation of sympathetic nerve activity using [123I] metaiodobenzylguanidine SPECT-CT in neurology

BACKGROUND AND PURPOSE

The ability of [123I]metaiodobenzylguanidine (MIBG) sympathetic nerve imaging with three-dimensional (3D) quantitation to clinically diagnose neurological disorders has not been evaluated. This study compared absolute heart counts calculated as mean standardized uptake values (SUVmean) using conventional planar imaging and assessed the contribution of [123I]MIBG single-photon emission computed tomography (SPECT)-CT to the diagnosis of neurological diseases.

METHODS

Seventy-two patients with neurological diseases were consecutively assessed using early and delayed [123I]MIBG SPECT-CT and planar imaging. Left ventricles were manually segmented in early and delayed SPECT-CT images, then the SUVmean and washout rates (WRs) were calculated. Heart-to-mediastinum ratios (HMRs) and WRs on planar images were conventionally computed. We investigated correlations between planar HMRs and SPECT-CT SUVmeans and between WRs obtained from planar and SPECT-CT images. The cutoff for SPECT-CT WRs defined by linear regression and that of normal planar WRs derived from a database were compared with neurological diagnoses of the patients. We assigned the patients to groups according to clinical diagnoses as controls (n = 6), multiple system atrophy (MSA, n = 7), progressive supranuclear palsy (PSP, n = 17), and Parkinson's disease or dementia with Lewy bodies (PD/DLB, n = 19), then compared SPECT-CT and planar image parameters.

RESULTS

We found significant correlations between SPECT-CT SUVmean and planar HMR on early and delayed images (R2 = 0.69 and 0.82, p < 0.0001) and between SPECT-CT and planar WRs (R2 = 0.79, p < 0.0001). A threshold of 31% for SPECT-CT WR based on linear regression resulted in agreement between planar and SPECT-CT WR in 67 (93.1%) of 72 patients. Compared with controls, early and delayed SUVmean in patients with PSP and MSA tended more towards significance than planar HMR. This trend was similar for SPECT-CT WRs in patients with PSP.

CONCLUSIONS

Absolute heart counts and SUVmean determined using [123I]MIBG SPECT-CT correlated with findings of conventional planar images in patients with neurological diseases. Three-dimensional quantitation with [123I]MIBG SPECT-CT imaging might differentiate patients with PSP and MSA from controls.

Cardiovascular Imaging in Women

Multimodality cardiovascular imaging is a cornerstone diagnostic tool in the diagnosis, risk stratification, and management of cardiovascular diseases, whether those involving the coronary tree, myocardial, or pericardial diseases in general and particularly in women. This manuscript aims to shed some light and summarize the very features of cardiovascular disease in women, explore their unique characteristics and discuss the role of cardiovascular imaging in ischemic heart disease and cardiomyopathies. The role of four imaging modalities will be discussed including nuclear medicine, echocardiography, noninvasive coronary angiography, and cardiac magnetic resonance.

Three-Dimensional Heart Segmentation and Absolute Quantitation of Cardiac 123I-metaiodobenzylguanidine Sympathetic Imaging Using SPECT/CT

Background: A three-dimensional (3D) approach to absolute quantitation of 123I-metaiodobenzylguanidine (MIBG) sympathetic nerve imaging using single-photon emission tomography (SPECT) / computed tomography (CT) is not available. Therefore, we calculated absolute cardiac counts and standardized uptake values (SUVs) from images of 72 consecutive patients with cardiac and neurological diseases using 123I-MIBG SPECT/CT and compared them with conventional planar quantitation. We aimed to develop new methods for 3D heart segmentation and the quantitation of these diseases. Methods: We manually segmented early and late SPECT/CT images of the heart in 3D, then calculated mean (SUVmean) and maximum (SUVmax) SUVs. We analyzed correlations between SUVs and planar heart-to-mediastinum ratios (HMRs), and between washout rates (WRs) derived from the SUVs and planar data. We also categorized WRs as normal or abnormal using linear regression lines determined by the relationship between SPECT/CT and planar WRs, and assessed agreement between them. Results: We calculated SUVmean and SUVmax from all early and late 123I-MIBG SPECT/CT images. Planar HMRs correlated with early and late SUVmean (R2=0.59 and 0.73, respectively) and SUVmax (R2=0.46 and 0.60, respectively; both p<0.0001). The SPECT/CT WRs determined based on SUVmean and SUVmax (R2=0.79 and 0.45, p<0.0001) closely correlated with planar WRs. Agreement of high and low WRs between planar WRs and SPECT/CT WRs calculated using SUVmax and SUVmean reached 88.1% and 94.4% respectively. Conclusions: We found that sympathetic nervous activity could be absolutely quantified in 3D from 123I-MIBG SPECT/CT images. Therefore, we propose a new method for quantifying sympathetic innervation on SPECT/CT images.

Stellate Ganglia and Cardiac Sympathetic Overactivation in Heart Failure

Heart failure (HF) is a major public health problem worldwide, especially coronary heart disease (myocardial infarction)-induced HF with reduced ejection fraction (HFrEF), which accounts for over 50% of all HF cases. An estimated 6 million American adults have HF. As a major feature of HF, cardiac sympathetic overactivation triggers arrhythmias and sudden cardiac death, which accounts for nearly 50–60% of mortality in HF patients. Regulation of cardiac sympathetic activation is highly integrated by the regulatory circuitry at multiple levels, including afferent, central, and efferent components of the sympathetic nervous system. Much evidence, from other investigators and us, has confirmed the afferent and central neural mechanisms causing sympathoexcitation in HF. The stellate ganglion is a peripheral sympathetic ganglion formed by the fusion of the 7th cervical and 1st thoracic sympathetic ganglion. As the efferent component of the sympathetic nervous system, cardiac postganglionic sympathetic neurons located in stellate ganglia provide local neural coordination independent of higher brain centers. Structural and functional impairments of cardiac postganglionic sympathetic neurons can be involved in cardiac sympathetic overactivation in HF because normally, many effects of the cardiac sympathetic nervous system on cardiac function are mediated via neurotransmitters (e.g., norepinephrine) released from cardiac postganglionic sympathetic neurons innervating the heart. This review provides an overview of cardiac sympathetic remodeling in stellate ganglia and potential mechanisms and the role of cardiac sympathetic remodeling in cardiac sympathetic overactivation and arrhythmias in HF. Targeting cardiac sympathetic remodeling in stellate ganglia could be a therapeutic strategy against malignant cardiac arrhythmias in HF.

Cardiac 123I-mIBG scintigraphy for prediction of catheter ablation outcome in patients with atrial fibrillation

BACKGROUND

Previous studies show inconsistent results on the role of innervation imaging (with 123I-mIBG) in predicting late atrial fibrillation (AF) recurrence after catheter ablation (CA). These studies included patients with paroxysmal AF and studied prognostic value of post-CA I-123-mIBG parameters. Current study investigated the ability of pre CA 123-I-mIBG imaging to predict late AF recurrence in patients with persistent AF.

METHODS

123I-mIBG cardiac imaging was performed before CA in 82 patients with persistent AF. Patient was followed for 12 months.

RESULTS

Multivariable analysis demonstrated that late heart-to-mediastinum ratio (H/Mlate) and washout rate (WR) were independent predictors of AF recurrence. ROC-curve analysis data showed that H/Mlate <1.6 (sensitivity 73.53%, specificity 81.3%, AUC 0.792, P < .001) and WR > 25.11 (sensitivity 70.6%, specificity 70.8.3%, AUC 0.712, P < .001) indicate high probability of AF relapses during 12 months after CA.

CONCLUSION

Pre-CA parameters of global cardiac sympathetic activity estimated by 123I-mIBG scintigraphy are associated with late AF relapses in persistent AF patients with normal LVEF and absence of significant CAD.

Cardiac 123I-mIBG Imaging in Heart Failure

Cardiac sympathetic upregulation is one of the neurohormonal compensation mechanisms that play an important role in the pathogenesis of chronic heart failure (CHF). In the past decades, cardiac ¹²³I-mIBG scintigraphy has been established as a feasible technique to evaluate the global and regional cardiac sympathetic innervation. Although cardiac ¹²³I-mIBG imaging has been studied in many cardiac and neurological diseases, it has extensively been studied in ischemic and non-ischemic CHF. Therefore, this review will focus on the role of ¹²³I-mIBG imaging in CHF. This non-invasive, widely available technique has been established to evaluate the prognosis in CHF. Standardization, especially among various combinations of gamma camera and collimator, is important for identifying appropriate thresholds for adequate risk stratification. Interestingly, in contrast to the linear relationship between ¹²³I-mIBG-derived parameters and overall prognosis, there seems to be a “bell-shape” curve for ¹²³I-mIBG-derived parameters in relation to ventricular arrhythmia or appropriate implantable cardioverter defibrillator (ICD) therapy in patients with ischemic CHF. In addition, there is a potential clinical role for cardiac ¹²³I-mIBG imaging in optimizing patient selection for implantation of expensive devices such as ICD and cardiac resynchronization therapy (CRT). Based on cardiac ¹²³I-mIBG data risk models and machine learning, models have been developed for appropriate risk assessment in CHF.

Reproducible Quantification of Regional Sympathetic Denervation with [11C]meta-Hydroxyephedrine PET Imaging

BACKGROUND

Regional cardiac sympathetic denervation is predictive of sudden cardiac arrest in patients with ischemic cardiomyopathy. The reproducibility of denervation scores between automated software programs has not been evaluated. This study seeks to (1) compare the inter-rater reliability of regional denervation measurements using two analysis programs: FlowQuant® and Corridor4DM®; (2) evaluate test-retest repeatability of regional denervation scores.

METHODS

N = 190 dynamic [11C]meta-hydroxyephedrine (HED) PET scans were reviewed from the PAREPET trial in ischemic cardiomyopathy patients with reduced left ventricular ejection fraction(LVEF ≤ 35%). N = 12 scans were excluded due to non-diagnostic quality. N = 178 scans were analyzed using FlowQuant and Corridor4DM software, each by two observers. Test-retest scans from N = 20 patients with stable heart failure were utilized for test-retest analysis. Denervation scores were defined as extent × severity of relative uptake defects in LV regions with < 75% of maximal uptake. Results were evaluated using intraclass correlation coefficient (ICC) and Bland-Altman coefficient of repeatability (RPC).

RESULTS

Inter-observer, inter-software, and test-retest ICC values were excellent (ICC = 94% to 99%) and measurement variability was small (RPC < 11%). Mean differences between observers ranged .2% to 1.1% for Corridor4DM (P = .28), FlowQuant (P < .001), and between software programs (P < .001). Kaplan-Meier analysis demonstrated HED scores from both programs were predictive of SCA.

CONCLUSION

Inter-rater reliability for both analysis programs was excellent and test-retest repeatability was consistent. The minimal difference in scores between FlowQuant and Corridor4DM supports their use in future trials.

Convolutional neural network-based automatic heart segmentation and quantitation in 123I-metaiodobenzylguanidine SPECT imaging

Background

Since three-dimensional segmentation of cardiac region in ¹²³I-metaiodobenzylguanidine (MIBG) study has not been established, this study aimed to achieve organ segmentation using a convolutional neural network (CNN) with ¹²³I-MIBG single photon emission computed tomography (SPECT) imaging, to calculate heart counts and washout rates (WR) automatically and to compare with conventional quantitation based on planar imaging.

Methods

We assessed 48 patients (aged 68.4 ± 11.7 years) with heart and neurological diseases, including chronic heart failure, dementia with Lewy bodies, and Parkinson's disease. All patients were assessed by early and late ¹²³I-MIBG planar and SPECT imaging. The CNN was initially trained to individually segment the lungs and liver on early and late SPECT images. The segmentation masks were aligned, and then, the CNN was trained to directly segment the heart, and all models were evaluated using fourfold cross-validation. The CNN-based average heart counts and WR were calculated and compared with those determined using planar parameters. The CNN-based SPECT and conventional planar heart counts were corrected by physical time decay, injected dose of ¹²³I-MIBG, and body weight. We also divided WR into normal and abnormal groups from linear regression lines determined by the relationship between planar WR and CNN-based WR and then analyzed agreement between them.

Results

The CNN segmented the cardiac region in patients with normal and reduced uptake. The CNN-based SPECT heart counts significantly correlated with conventional planar heart counts with and without background correction and a planar heart-to-mediastinum ratio (R² = 0.862, 0.827, and 0.729, p < 0.0001, respectively). The CNN-based and planar WRs also correlated with and without background correction and WR based on heart-to-mediastinum ratios of R² = 0.584, 0.568 and 0.507, respectively (p < 0.0001). Contingency table findings of high and low WR (cutoffs: 34% and 30% for planar and SPECT studies, respectively) showed 87.2% agreement between CNN-based and planar methods.

Conclusions

The CNN could create segmentation from SPECT images, and average heart counts and WR were reliably calculated three-dimensionally, which might be a novel approach to quantifying SPECT images of innervation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13550-021-00847-x.

Quality and utility of [123I]I-metaiodobenzylguanidine cardiac SPECT imaging in nondiabetic postinfarction heart failure patients qualified for implantable cardioverter defibrillator

Objective

Impaired cardiac adrenergic activity has been demonstrated in heart failure (HF) and in diabetes mellitus (DM). [¹²³I]I-metaiodobenzylguanidine (MIBG) enables assessment of the cardiac adrenergic nervous system. Tomographic imaging of the heart is expected to be superior to planar imaging. This study aimed to determine the quality and utility of MIBG SPECT in the assessment of cardiac innervation in postinfarction HF patients without DM, qualified for implantable cardioverter defibrillator (ICD) in primary prevention of sudden cardiac death.

Methods

Consecutive patients receiving an ICD on the basis of contemporary guidelines were prospectively included. Planar MIBG studies were followed by SPECT. The essential analysis was based on visual assessment of the quality of SPECT images (“high”, “low” or “unacceptable”). The variables used in the further analysis were late summed defect score for SPECT images and heart-to-mediastinum rate for planar images. MIBG images were assessed independently by two experienced readers.

Results

Fifty postinfarction nondiabetic HF subjects were enrolled. In 13 patients (26%), the assessment of SPECT studies was impossible. In addition, in 13 of 37 patients who underwent semiquantitative SPECT evaluation, the assessment was equivocal. Altogether, in 26/50 patients (52%, 95% confidence interval 38–65%), the quality of SPECT images was unacceptable or low and was limited by low MIBG cardiac uptake and by comparatively high, interfering MIBG uptake in the neighboring structures (primarily, in the lungs).

Conclusions

The utility of MIBG SPECT imaging, at least with conventional imaging protocols, in the qualification of postinfarction HF patients for ICD, is limited. In approximately half of the postinfarction HF patients, SPECT assessment of cardiac innervation can be impossible or equivocal, even without additional damage from diabetic cardiac neuropathy. The criteria predisposing the patient to good-quality MIBG SPECT are: high values of LVEF from the range characterizing the patients qualified to ICD (i.e., close to 35%) and left lung uptake intensity in planar images comparable to or lower than heart uptake.

Imaging cardiac sympathetic innervation with MIBG: linear conversion of the heart-to-mediastinum ratio between different collimators

BACKGROUND

The heart-to-mediastinum (H/M) ratio is a commonly used parameter to measure cardiac I-123 metaiodobenzylguanidine (MIBG) uptake. Since the H/M ratio is substantially influenced by the collimator type, we investigated whether an empirical linear conversion of H/M ratios between camera systems with low-energy (LE) and medium-energy (ME) collimator is possible.

METHODS

We included 18 patients with parkinsonism who were referred to one of the two participating molecular imaging facilities for the evaluation of cardiac sympathetic innervation by MIBG scintigraphy. Two consecutive planar image datasets were acquired with LE and ME collimators at 4 h after MIBG administration. Linear regression analyses were performed to describe the association between the H/M ratios gained with both collimator settings, and the accuracy of a linear transfer of the H/M ratio between collimators and across centers was assessed using a leave-one-out procedure.

RESULTS

H/M ratios acquired with LE and ME collimators showed a strong linear relationship both within each imaging facility (R² = 0.99, p < 0.001 and R² = 0.90, p < 0.001) and across centers (H/M-LE = 0.41 × H/M-ME + 0.63, R² = 0.97, p < 0.001). A linear conversion of H/M ratios between collimators and across centers was estimated to be very accurate (mean absolute error 0.05 ± 0.04; mean relative absolute error 3.2 ± 2.6%).

CONCLUSIONS

The present study demonstrates that a simple linear conversion of H/M ratios acquired with different collimators is possible with high accuracy. This should greatly facilitate the exchange of normative data between settings and pooling of data from different institutions.

Cardiac sympathetic innervation scintigraphy with 123I-meta-iodobenzylguanidine. Basis, protocols and clinical applications in Cardiology

Imaging of cardiac sympathetic innervation is only possible by nuclear cardiology techniques and its assessment is key in the evaluation of and decision-making for patients with cardiac sympathetic impairment. This review includes the basis of cardiac sympathetic scintigraphy with ¹²³I-meta-iodobenzylguanidine (¹²³I-MIBG), recommended protocols, patient preparation, image acquisition and quantification, reproducibility, dosimetry, etc., and also the clinical indications for cardiac patients, mainly with regard to heart failure, arrhythmia, coronary artery disease, cardiotoxicity, including its contribution to establishing the indication for and monitoring the response to implantable cardiac devices, pharmacological treatment, heart transplantation and other.