Neuronal imaging using SPECT

Cardiac innervations in diabetes mellitus-Anatomical evidence of neuropathy

The extensive innervations of the heart include a complex network of sympathetic, parasympathetic, and sensory nerves connected in loops that serve to regulate cardiac output. Metabolic dysfunction in diabetes affects many different organ systems, including the cardiovascular system; it causes cardiac arrhythmias, silent myocardial ischemia, and sudden cardiac death, among others. These conditions are associated with damage to the nerves that innervate the heart, cardiac autonomic neuropathy (CAN), which is caused by various pathophysiological mechanisms. In this review, the main facts about the anatomy of cardiac innervations and the current knowledge of CAN, its pathophysiological mechanisms, and its diagnostic approach are discussed. In addition, anatomical evidence for CAN from human and animal studies has been summarized.

[123I]Metaiodobenzylguanidine (MIBG) Cardiac Scintigraphy and Automated Classification Techniques in Parkinsonian Disorders

PURPOSE

To provide reliable and reproducible heart/mediastinum (H/M) ratio cut-off values for parkinsonian disorders using two machine learning techniques, Support Vector Machines (SVM) and Random Forest (RF) classifier, applied to [¹²³I]MIBG cardiac scintigraphy.

PROCEDURES

We studied 85 subjects, 50 with idiopathic Parkinson's disease, 26 with atypical Parkinsonian syndromes (P), and 9 with essential tremor (ET). All patients underwent planar early and delayed cardiac scintigraphy after [¹²³I]MIBG (111 MBq) intravenous injection. Images were evaluated both qualitatively and quantitatively; the latter by the early and delayed H/M ratio obtained from regions of interest (ROIt₁ and ROIt₂) drawn on planar images. SVM and RF classifiers were finally used to obtain the correct cut-off value.

RESULTS

SVM and RF produced excellent classification performances: SVM classifier achieved perfect classification and RF also attained very good accuracy. The better cut-off for H/M value was 1.55 since it remains the same for both ROIt₁ and ROIt_2. This value allowed to correctly classify PD from P and ET: patients with H/M ratio less than 1.55 were classified as PD while those with values higher than 1.55 were considered as affected by parkinsonism and/or ET. No difference was found when early or late H/M ratio were considered separately thus suggesting that a single early evaluation could be sufficient to obtain the final diagnosis.

CONCLUSIONS

Our results evidenced that the use of SVM and CT permitted to define the better cut-off value for H/M ratios both in early and in delayed phase thus underlining the role of [¹²³I]MIBG cardiac scintigraphy and the effectiveness of H/M ratio in differentiating PD from other parkinsonism or ET. Moreover, early scans alone could be used for a reliable diagnosis since no difference was found between early and late. Definitely, a larger series of cases is needed to confirm this data.

Lewy body constipation

We systematically reviewed literature regarding “Lewy body constipation”, i.e., constipation due to Lewy body diseases (LBD), with minimal neurologic symptoms. Epidemiology and pathology studies showed that LBD can start with constipation alone, mostly due to neuronal loss and appearance of Lewy bodies in the myenteric plexus. Because LBD significantly increases with age, “Lewy body constipation” may also increase with age. Neuroimaging methods such as metaiodobenzylguanidine (MIBG) scintigraphy and dopamine transporter (DAT) scan provide a way to detect “Lewy body constipation.” Key for “Lewy body constipation” includes minimal non-motor features such as REM sleep behavior disorder (night talking). Add-on therapy may be required to ameliorate constipation in patients. Diagnosis is not always easy; therefore, collaboration of gastroenterologists and neurologists is highly recommended to maximize patients' quality of life. In conclusion, “Lewy body constipation” might become a distinct category among geriatric constipation, regarding patients' follow-up and their management.

Cardiac Sympathetic Activity differentiates Idiopathic and Symptomatic Rapid Eye Movement Sleep Behaviour Disorder

The pathophysiology of rapid eye movement sleep behavior disorder (RBD) associated with narcolepsy type 1 (NT1) is still poorly understood, potentially distinct from idiopathic RBD (iRBD), but may share affected common pathways. We investigated whether MIBG cardiac uptake differs between iRBD and NT1 comorbid with RBD. Thirty-four patients with NT1-RBD and 15 patients with iRBD underwent MIBG cardiac scintigraphy. MIBG uptake was measured by calculating the early and delayed heart to mediastinum (H/M) ratios. A delayed H/M ratio lower than 1.46 was considered abnormal based on a population of 78 subjects without neurological or cardiac diseases. Patients with iRBD were older, had an older RBD onset age and higher REM sleep phasic and tonic muscular activities than NT1-RBD. Lower delayed and early H/M ratios were associated with iRBD, but not with NT1-RBD, in crude and adjusted associations. The delayed H/M ratio differed between iRBD and controls, after adjustment, but not between patients with NT1-RBD and controls. In conclusion, the MIBG cardiac uptake difference between NT1-RBD and iRBD supports the hypothesis of different processes involved in RBD pathogenesis, providing for the first time a cardiac biomarker to differentiate those disorders.

Potential diagnostic value of 131I-MIBG myocardial scintigraphy in discrimination between Alzheimer disease and dementia with Lewy bodies

OBJECTIVES

Clinical difficulty to discriminate between the Alzheimer disease (AD) and dementia with Lewy bodies (DLB) has led researchers to focus on highly sensitive functional imaging modalities. The aim of the present study was to assess ¹³¹I-MIBG cardiac imaging to distinguish between AD and DLB.

PATIENTS AND METHODS

Seventeen patients who were known cases of dementia underwent ¹³¹I-MIBG myocardial scintigraphy to differentiate AD from DLB. Planar and ¹³¹I-MIBG SPECT were obtained 2h after the injection of 1mCi ¹³¹I-MIBG on a dual head gamma camera. The visual assessment of the heart uptake compared with lungs and the quantification based on the heart to mediastinal ratio (HMR) were done. The cardiac receiver operating characteristic (ROC) curve was designed for the optimal HMR cut-off values to predict the diagnoses of the patients. The diagnoses were clinically confirmed during the follow up of 14±8.2 months.

RESULTS

Out of 17 patients (13 males; 76.5%), 10 patients had AD (7 males; 70%) and 7 patients had DLB (6 males; 85%). The pooled HMR was 1.74±0.33 in the study population; with 1.95±0.22 in the AD group and 1.43±0.20 in the DLB group to demonstrate significantly different HMR scores between patients with AD and DLB (p value=0.001). The visual interpretation was positive in 10 patients (accuracy of 88.2%). The shortest distance on the ROC curve to the optimal value corresponding to HMR=1.57 identified 10 patients with a high HMR (positive cardiac uptake) and 7 patients with a low HMR (negative cardiac uptake), the accuracy calculated at 88.2%.

CONCLUSION

¹³¹I-MIBG myocardial scintigraphy is a potential alternative diagnostic modality for discrimination between AD and DLB when ¹²³I is not available.

123I-ioflupane brain SPECT and 123I-MIBG cardiac planar scintigraphy combined use in uncertain parkinsonian disorders

We evaluated the clinical usefulness of the combined use of I-ioflupane brain single photon emission computed tomography (SPECT) and I-metaiodobenzylguanidine (MIBG) cardiac scintigraphy in discriminating uncertain parkinsonism with vascular lesions in striatal nuclei at magnetic resonance imaging (MRI). Forty-three consecutive patients with uncertain parkinsonism and vascular lesions at MRI in striatal nuclei were retrospectively evaluated; the uncertain differential diagnosis was between Parkinson's disease and vascular parkinsonism (PD/VP) in 22 patients, between PD and other neurodegenerative parkinsonism (PD/PS) in 11 patients and between Lewy body dementia and Alzheimer disease (LBD/AD) in the remaining 10 cases. All patients underwent I-ioflupane SPECT with striatal dopaminergic activity determination as binding potentials (BP; cut-off: 3.3). I-MIBG cardiac planar scintigraphy was performed 2 weeks later, in early (15 minutes) and delayed (240 minutes) phases also calculating heart to mediastinum (H/M) ratio (cut-off: 1.56). I-Ioflupane uptake was normal in 9 patients with BP values >3.3, while it was reduced in 34/43 cases with BP values <3.3 at least in one of the striatal nuclei. I-MIBG uptake was normal in 21/43 patients (5 of whom with normal and 16 with I-ioflupane striatal defects) showing the H/M ratio >1.56 in all cases; the uptake was reduced in 22/43 cases, (4 of whom were normal and 18 were with I-ioflupane striatal defects) with the H/M ratio <1.56 in all cases. No statistical differences were found when early and delayed H/M ratios were mutually compared. Combining the 2 radioisotopic procedures, a more reliable diagnosis was achieved in 39/43 cases properly classifying 13 PD, 10 VP, 7 PS, 5 LBD, and 4 AD. However, the diagnosis remained uncertain in four patients with normal I-ioflupane and reduced I-MIBG uptake. The results of the present study confirmed that in uncertain parkinsonian syndromes associated with vascular lesions in striatal nuclei, brain I-ioflupane SPECT alone did not prove able to discriminate between the different forms of disease. Only the association with I-MIBG cardiac scintigraphy, also with the early acquisition alone, allowed the most appropriate diagnosis in 90.7% of our cases. However, patients with normal I-ioflupane and reduced I-I-MIBG uptakes need a close clinical and instrumental follow-up as sympathetic damage could precede striatal disorders in the early stage of PD and LBD.

131I-MIBG myocardial scintigraphy for differentiation of Parkinson's disease from multiple system atrophy or essential tremor in Chinese population

OBJECTIVE

Clinical distinction of Parkinson's disease (PD) from multiple system atrophy (MSA) or essential tremor (ET) is sometimes difficult. The purpose of this study was to assess changes in cardiac sympathetic nerve function in PD, MSA, and ET by ¹³¹I-MIBG myocardial scintigraphy METHODS: Patients with PD (25), MSA (18), or ET (11) and 10 healthy controls (HC) were enrolled. ¹³¹I-MIBG myocardial scintigraphy was performed for each subject, and heart/mediastinum (H/M) ratios were calculated at two sample times (15min and 4h after the injection of ¹³¹I-MIBG), representing the ¹³¹I-MIBG myocardial uptake ratios. The washout ratio (WOR) of MIBG which indicates the activity tone of the presynaptic sympathetic nerves was calculated for each subject.

RESULTS

The H/M ratios at the two sample times (15min and 4h) were 1.65±0.36 and 1.50±0.43 in the PD group, 1.97±0.36 and 2.08±0.57 in the MSA group, 2.34±0.34 and 2.46±0.51 in the ET group, and 2.41±0.26 and 2.66±0.47 in the HC group. The H/M ratios at the two sample times were lower in the PD group than in the MSA, ET, or HC groups, with statistical significance (all P<0.05). The H/M ratios at the two sample times were significantly lower in the MSA group than in the HC group (all P<0.05). There was no significant difference in H/M ratios at either sample time between the ET and HC group (all P>0.05). The washout ratios (WORs) of MIBG were significantly increased in PD group compared with those in MSA, ET and HC groups. In subgroup analysis, The H/M ratios at the two sample times were decreased in early PD group compared with those in early MSA and early ET groups, with statistical significance (all P<0.05).

CONCLUSIONS

Cardiac sympathetic dysfunction can occur in both PD and MSA patients, especially in PD patients, whereas it remains normal in ET patients. ¹³¹I-MIBG myocardial scintigraphy can help distinguish patients with PD from those with MSA or ET with good sensitivity and specificity.

Impact of aging on cardiac sympathetic innervation measured by 123I-mIBG imaging in patients with systolic heart failure

PURPOSE

Sympathetic nervous system (SNS) hyperactivity is a salient characteristic of chronic heart failure (HF) and contributes to the progression of the disease. Iodine-123 meta-iodobenzylguanidine (¹²³I-mIBG) imaging has been successfully used to assess cardiac SNS activity in HF patients and to predict prognosis. Importantly, SNS hyperactivity characterizes also physiological ageing, and there is conflicting evidence on cardiac ¹²³I-mIBG uptake in healthy elderly subjects compared to adults. However, little data are available on the impact of ageing on cardiac sympathetic nerve activity assessed by ¹²³I-mIBG scintigraphy, in patients with HF.

METHODS AND RESULTS

We studied 180 HF patients (age = 66.1 ± 10.5 years [yrs]), left ventricular ejection fraction (LVEF = 30.6 ± 6.3 %) undergoing cardiac ¹²³I-mIBG imaging. Early and late heart to mediastinum (H/M) ratios and washout rate were calculated in all patients. Demographic, clinical, and echocardiographic data were also collected. Our study population consisted of 53 patients aged >75 years (age = 77.7 ± 4.0 year), 67 patients aged 62-72 years (age = 67.9 ± 3.2 years) and 60 patients aged ≤61 year (age = 53.9 ± 5.6 years). In elderly patients, both early and late H/M ratios were significantly lower compared to younger patients (p < 0.05). By multivariate analysis, H/M ratios (both early and late) and washout rate were significantly correlated with LVEF and age.

CONCLUSIONS

Our data indicate that, in a population of HF patients, there is an independent age-related effect on cardiac SNS innervation assessed by ¹²³I-mIBG imaging. This finding suggests that cardiac ¹²³I-mIBG uptake in patients with HF might be affected by patient age.

Introduction to cardiac neuronal imaging: a clinical perspective

Procedures for noninvasive and minimally invasive imaging of cardiac neurons and neuronal function using radiolabeled compounds were developed in the second half of the 20th century. The foundation for these procedures was several centuries of research that identified the structural components of the autonomic nervous system and explored the means by which neurotransmitters such as acetylcholine and norepinephrine contributed to neuronal control of target organ effector cells. This article provides a brief clinical overview of modern approaches to the assessment of cardiac neurons as an introduction to the in-depth articles on the current status of cardiac neuronal imaging presented in this supplement.

123I-MIBG SPECT for Evaluation of Patients with Heart Failure

Heart failure (HF) is characterized by activation of the sympathetic cardiac nerves. The condition of cardiac sympathetic nerves can be evaluated by (123)I-metaiodobenzylguanidine ((123)I-MIBG) imaging. Most cardiac (123)I-MIBG studies have relied on measurements from anterior planar images of the chest. However, it has become progressively more common to include SPECT imaging in clinical and research protocols. This review examines recent trends in (123)I-MIBG SPECT imaging and evidence that provides the basis for the increased use of the procedure in the clinical management of patients with HF. (123)I-MIBG SPECT has been shown to be complementary to planar imaging in patients with HF in studies of coronary artery disease after an acute myocardial infarction. Moreover, (123)I-MIBG SPECT has been used in numerous studies to document regional denervation for arrhythmic event risk assessment. For better quantification of the size and severity of innervation abnormalities in (123)I-MIBG SPECT, programs and protocols specifically for (123)I have been developed. Also, the introduction of new solid-state cameras has created the potential for more rapid SPECT acquisitions or a reduction in radiopharmaceutical activity. Although PET imaging has superior quantitative capabilities, (123)I-MIBG SPECT is, for the foreseeable future, the only widely available nuclear imaging method for assessing regional myocardial sympathetic innervation.

¹²³I-MIBG Imaging for Prediction of Mortality and Potentially Fatal Events in Heart Failure: The ADMIRE-HFX Study

ADMIRE-HF (AdreView Myocardial Imaging for Risk Evaluation in Heart Failure) established the prognostic significance of (123)I-metaiodobenzylguanidine ((123)I-MIBG) imaging in heart failure subjects (median follow-up, 17 mo) using a composite endpoint dominated by heart failure progression. The ADMIRE-HF extension (ADMIRE-HFX) extended follow-up to a median of 24 mo and used mortality as the primary endpoint. The objective of these analyses was to use multiple multivariate risk modeling techniques to determine the independent predictive ability of (123)I-MIBG imaging for mortality outcomes.

METHODS

Data from 964 New York Heart Association class II-III subjects in ADMIRE-HFX were included. All-cause mortality and a composite endpoint of death or death-equivalent events (resuscitated arrest, successful defibrillation for ventricular tachycardia or ventricular fibrillation) were analyzed with multivariate Cox proportional hazards and logistic regression techniques using demographic and clinical variables and the (123)I-MIBG heart-to-mediastinum ratio (H/M). The incremental value of H/M was also examined for the logistic regression models using receiver-operating-characteristic curve methods and for the proportional hazards models using net reclassification improvement.

RESULTS

There were 101 deaths, and 136 subjects had a composite event during follow-up. H/M was significant in all multivariate proportional hazards and logistic regression models for the 2 mortality endpoints, both models developed with only clinical variables and those including left ventricular ejection fraction and b-type natriuretic peptide (BNP). For baseline models including BNP, the addition of H/M did not significantly increase receiver-operating-characteristic curve area. However, there was significant net reclassification improvement with the addition of H/M to a proportional hazards model containing BNP and left ventricular ejection fraction.

CONCLUSION

The multivariate Cox proportional hazards and logistic regression analyses demonstrated consistent significance for H/M when added to the baseline risk models for mortality and mortality-equivalent events.

(123)I-Metaiodobenzylguanidine Myocardial Scintigraphy in Lewy Body-Related Disorders: A Literature Review

Lewy body-related disorders are characterized by the presence of Lewy bodies and Lewy neurites, which have abnormal aggregations of α-synuclein in the nigral and extranigral areas, including in the heart. ¹²³I-metaiodobenzylguanidine (MIBG) scintigraphy is a well-known tool to evaluate cardiac sympathetic denervation in the Lewy body-related disorders. MIBG scintigraphy showed low uptake of MIBG in the Lewy body-related disorders, including Parkinson’s disease, dementia with Lewy bodies, pure autonomic failure and rapid eye movement sleep behavior disorder. This review summarizes previous results on the diagnostic applications of MIBG scintigraphy in Lewy body-related disorders.

Assessment of the efficacy of early phase parameters by (123)I-MIBG dynamic imaging for distinguishing Lewy body-related diseases from Parkinson's syndrome

OBJECTIVE

The aim of this study was to assess the efficacy of early phase washout rate (early WR) and area under the time-activity curve (AUTAC) by (123)I-metaiodobenzylguanidine (MIBG) dynamic chest imaging for distinguishing Lewy body-related diseases (LBRD) from Parkinson's syndrome (PS) and reducing examination time.

METHODS

Sixty-two patients with suspected LBRD who underwent (123)I-MIBG dynamic imaging in early phase were retrospectively selected. The early WR and AUTAC were calculated from (123)I-MIBG dynamic data of the heart. We evaluated the relationships between proposed and conventional parameters by using Spearman's rank correlation coefficient. Differences in parameters between LBRD and PS groups were tested for statistical significance using the Mann-Whitney U test. The diagnostic performance of all parameters for distinguishing LBRD from PS was assessed in terms of receiver operating characteristic (ROC) analysis. Additionally, combination diagnostic performance and concordance rate between early phase parameters and late H/M ratio by kappa statistics were also assessed.

RESULTS

The early WR and AUTAC showed a positive and negative correlation with conventional parameters. Both the early WR and AUTAC of LBRD group were significantly distinguishable from those of the PS group (p < 0.001). Area under the ROC curve of the early WR (0.98) was greater than that of AUTAC (0.91). The diagnostic performance of combination of the early phase parameters was 93 % sensitivity and 100 % specificity. Moreover, the early phase parameters showed excellent agreement with late H/M ratio (k = 0.93).

CONCLUSIONS

The early WR and AUTAC showed high performance for distinguishing LBRD from PS, and the combination diagnosis with early H/M ratio and early WR contribute to improve the diagnostic performance. Thus, these parameters would be useful for reducing the examination time of myocardial (123)I-MIBG scintigraphy to diagnose LBRD.

The role of radionuclide imaging in heart failure

The incidence of heart failure (HF) is increasing and it remains the only area in cardiovascular disease wherein hospitalization rates and mortalities have worsened in the past 25 years. This review is provided to assess the role of radionuclide imaging in HF. The focus is on three aspects: the value of nuclear imaging to distinguish ischemic from non-ischemic etiologies; risk stratification of patients with HF with evaluation of candidates for specific treatment strategies; and the role of cardiac neuronal imaging in patients with HF. Distinguishing ischemic from non-ischemic cardiomyopathy is important because patients with ischemic cardiomyopathy can potentially have dramatic improvement with revascularization. Single photon emission computed tomography (SPECT) has excellent reported sensitivity and negative predictive value in the detection of coronary artery disease in HF patients. SPECT imaging is also useful in establishing treatment strategies in patients with HF, including those with new onset CHF. Cardiac neuronal imaging of mIBG is particularly helpful in risk stratification of patients with HF. The modality can be used to monitor the response to therapy as dysfunctional mIBG uptake may show improvement with pharmacological treatment.

Impact of age on myocardial uptake of ¹²³I-mIBG in older adult subjects without coronary heart disease

BACKGROUND

The purpose of this study was to examine the relationship between myocardial uptake of (123)I-mIBG and age in older normal adult subjects.

METHODS

94 subjects (age 29-82, mean 58.5) without coronary heart disease were studied. All subjects underwent early and delayed planar and 4-hour SPECT (123)I-mIBG imaging. (123)I-mIBG uptake was quantified as heart/mediastinum ratio on planar images (H/M p) and on SPECT images (H/M s) reconstructed by filtered backprojection, ordered subsets-expectation maximization (OSEM), and OSEM with compensation for collimator septal penetration (DSP). Relationships between age and (123)I-mIBG uptake were examined by correlation analysis, t-tests, and analysis of variance.

RESULTS

There was no significant correlation between age and H/M p, reflecting comparable increases in activity in the two regions of interest with age. Results on SPECT analyses were comparable, with no significant correlation between age and H/M s. Using DSP, (123)I-mIBG H/M s was significantly higher in subjects ≥70 of age compared with younger subjects.

CONCLUSIONS

Both cardiac and background uptake of (123)I-mIBG increase with age in older subjects without coronary heart disease, resulting in stability of H/M results (planar and SPECT). This study suggests that prognostic analyses of quantitative (123)I-mIBG uptake in patients with heart disease do not require adjustment for patient age.

Influence of myocardial region of interest definition on quantitative analysis of planar 123I-mIBG images

PURPOSE

In planar (123)I-mIBG myocardial imaging, definition of the heart region of interest (ROI) is a critical step in quantifying uptake. The present study evaluated the impact of changes in heart ROI size on quantitative results in subjects with good and poor uptake.

METHODS

Reference irregular whole-heart and square upper mediastinum ROIs were defined visually on 531 planar (123)I-mIBG images. Based on the reference heart ROI, an automated program created two other ROIs: one larger (+1 pixel) and one smaller (-1 pixel), the stated numbers representing the spacing intervals between each epicardial boundary pixel. Two additional smaller ROIs (-2 and -3 pixels) were drawn for the 100 images (19 %) with a heart/mediastinum (H/M) ratio ≤1.30. The number of pixels, the counts per pixel, and the H/M ratio for each heart ROI were calculated and compared to that in the reference ROI. Washout rate and changes as a function of ROI size were also calculated for 110 subjects who had both early and late images.

RESULTS

The mean changes in heart ROI size ranged from +19.0 % for the +1 pixel to -44.4 % for the -3 pixels ROI. For the +1 and -1 pixel ROIs, mean relative counts per pixel changes were -1.2 % and +0.7 %, respectively, with corresponding ranges of change in the H/M ratio of -0.12 to +0.05 and -0.05 to +0.11. For scans with H/M ratio ≤1.30, mean relative counts per pixel changes were 0, 0, -0.7 %, and -1.4 % for the four ROIs, with range of change in the H/M ratio from -0.13 to +0.05. Mean washout rates were almost identical for the reference ROIs (45.0 %) and the +1 pixel and -1 pixel heart ROIs (44.9 % and 45.1 %, respectively).

CONCLUSION

Significant changes in the size of the best visually defined heart ROI produce minimal, clinically inconsequential changes in the H/M ratio and washout rate, even in subjects with significantly reduced myocardial uptake of (123)I-mIBG.

(123)I-MIBG Scintigraphy as a Powerful Tool to Plan an Implantable Cardioverter Defibrillator and to Assess Cardiac Resynchronization Therapy in Heart Failure Patients

Iodine-123-metaiodobenzylguanidine ((123)I-MIBG) scintigraphy is a nuclear medicine technique which describes the functional status of the cardiac sympathetic nervous system. It is well known that an autonomic dysfunction is present in heart failure setting as a neuronal uptake of norepinephrine is impaired in the failing myocardium. Reduction in sympathetic nervous function in the heart, measured by reduced myocardial uptake of (123)I-MIBG, is an indicator of poor prognosis for heart failure patients. The aim of this paper was to investigate the role of (123)I-MIBG scintigraphy in evaluating the need of implantable cardioverter defibrillator (ICD) and the response to cardiac resynchronization therapy (CRT) in heart failure patients. For this purpose scientific literature data on these topics were reviewed. Based on literature data, (123)I-MIBG scintigraphy seems to be a useful tool to assess which patients may benefit most from an ICD implantation to reduce the risk of ventricular arrhythmia or sudden cardiac death. Furthermore, (123)I-MIBG scintigraphy seems to predict which patients will response to CRT with an improvement in left ventricular function.

Assessment of global cardiac I-123 MIBG uptake and washout using volumetric quantification of SPECT acquisitions

BACKGROUND

Assessment of cardiac innervation using single-photon emission computer tomography (SPECT) is less established than planar imaging, but may be more suitable for quantification. Therefore, a volumetric quantification of I-123 MIBG SPECT acquisitions was performed. Reproducibility, the effects of extra cardiac I-123 MIBG uptake and the relation with conventional planar indices were evaluated.

METHODS

54 patients referred for planar and SPECT I-123 MIBG acquisitions were included. Ellipsoidal or box-shaped volumes of interest were placed on the left ventricle, cardiac lumen, mediastinum, lung and liver. SPECT segmentation was performed twice in all patients. Indices were determined based on the heart-to-mediastinum (HM), myocardial wall-to-mediastinum and myocardial wall-to-lumen regions. HM ratios and washout rates were also determined based on anterior planar images.

RESULTS

Cardiac count densities were highly reproducible (CV 1.5-5.4, ICC 0.96-0.99) and inter-rater variability was low (CV 1.8-6.8, ICC 0.94-0.99). Mediastinal uptake was an important explanatory variable of uptake in the entire heart (early R(2) = 0.36; delayed R(2) =0.43) and myocardial wall (early R(2) = 0.28; delayed R(2) = 0.37). Lung washout was an explanatory variable of organ washout of the heart (heart R(2) = 0.38; myocardial wall R(2) = 0.33). In general, SPECT indices showed moderate-to-good correlations with the planar uptake (PCC 0.497-0.851).

CONCLUSION

By applying a volumetric segmentation method we were able to segment the heart in all patients. SPECT I-123 MIBG quantification was found to be highly reproducible and had a moderate to good correlation with the planar indices.

MIBG scintigraphy in differential diagnosis of Parkinsonism: a meta-analysis

OBJECTIVE

Differential diagnosis between Parkinson's disease (PD) and other Parkinsonism using clinical criteria or imaging methods is often difficult. The purpose of this study is to systematically review and meta-analyze published data about the diagnostic performance of myocardial innervation imaging using (123)I-metaiodobenzylguanidine (MIBG) scintigraphy in differential diagnosis between PD and other Parkinsonism.

METHODS

A comprehensive computer literature search of studies published through March 2011 regarding MIBG scintigraphy in patients with PD and other Parkinsonism was performed in PubMed/MEDLINE and Embase databases. Only studies in which MIBG scintigraphy was performed for differential diagnosis between PD and other Parkinsonism were selected. Pooled sensitivity, pooled specificity and area under the ROC curve were calculated to measure the accuracy of MIBG scintigraphy in differential diagnosis between PD and other Parkinsonism.

RESULTS

Nineteen studies comprising 1,972 patients (1,076 patients with PD, 117 patients with other Lewy body diseases and 779 patients with other diseases) were included in this meta-analysis. The pooled sensitivity of MIBG scintigraphy in detecting PD was 88% (95% CI 86-90%); the pooled specificity of MIBG scintigraphy in discriminating between PD and other Parkinsonism was 85% (95% CI 81-88%). The area under the ROC curve was 0.93.

CONCLUSIONS

In patients with clinically suspected PD, myocardial innervation imaging demonstrated high sensitivity and specificity. MIBG scintigraphy is an accurate test in this setting. Nevertheless, possible causes of false-negative and false-positive results should be kept in mind when interpreting the scintigraphic results.

Pure akinesia with low myocardial metaiodobenzylguanidine uptake

The objective of this study was to delineate the clinical features of patients with pure akinesia and a low heart versus mediastinum ratio below 2.0 in the delayed images of myocardial metaiodobenzylguanidine scintigraphy, a marker for the clinical diagnosis of Lewy body diseases. A total of 13 patients was enrolled. The clinical features of the patients were uniformly elderly (mean age, 73.7 years), a male gender preponderance (10 men and 3 women), relatively mild motor disability (mean Hoehn Yahr grade 2.4) without laterality, festinating gait (77%) and loss of postural reflex (69%), which were the most common; also observed were fair levodopa responses (70%), cognitive dysfunction in some (23%), common autonomic dysfunction (urinary urgency and frequency, 85%; constipation, 77%; and postural hypotension, 38%) and common occipital hypoperfusion (62%). These features may facilitate the clinical differential diagnosis of these patients from patients with pure akinesia due to progressive supranuclear palsy.

Semi-automated algorithm for calculating heart-to-mediastinum ratio in cardiac Iodine-123 MIBG imaging

BACKGROUND

We have developed novel software for semi-automatically measuring heart-to-mediastinum (H/M) ratio in cardiac Iodine-123 (¹²³I)-labeled meta-iodobenzylguanidine (MIBG) imaging. Our aim is to improve the reproducibility of the H/M ratio using the semi-automated method as opposed to the manual method.

METHODS AND RESULTS

The software algorithm automatically determined the mediastinal region of interest (ROI) using information from ¹²³I-MIBG uptake of the heart, lung, liver, and thyroid after a cardiac circular ROI was manually set. A total of 37 patients who underwent both early and delayed ¹²³I-MIBG imaging was retrospectively selected. The heart-to-mediastinum (H/M) ratios were calculated by both semi-automated and manual methods and assessed for the intra- and inter-observer variability. All H/M ratios were classified into three groups: normal, slight abnormality, and severe abnormality. The H/M ratios with the new method were higher than those obtained manually (P < .001). In the test-retest reliability, the intra-class correlation coefficient from the semi-automated method showed excellent reproducibility for early (0.99) and delayed (0.99) imaging. The Bland-Altman plots demonstrated better agreement using the semi-automated method (a range of 95% limits -0.11 to 0.10) than that in the manual method (-0.34 to 0.27). The inter-observer agreement was also good using the semi-automated method (κ = 0.866).

CONCLUSIONS

The H/M ratio using the semi-automated method showed high reproducibility in both early and delayed imaging.

Diagnostic performance of myocardial innervation imaging using MIBG scintigraphy in differential diagnosis between dementia with lewy bodies and other dementias: a systematic review and a meta-analysis

BACKGROUND AND PURPOSE

This study was designed to review the diagnostic performance of myocardial innervation imaging using iodine-123-metaiodobenzylguanidine (MIBG) scintigraphy in differential diagnosis between dementia with Lewy bodies (DLB) and other dementias.

METHODS

A comprehensive computer literature search of studies published through May 2010 regarding MIBG scintigraphy in patients with DLB was performed in PubMed/MEDLINE and Embase databases. Only studies in which MIBG scintigraphy was performed for differential diagnosis between DLB and other dementias were selected. Pooled sensitivity and specificity of MIBG scintigraphy were presented with a 95% confidence interval (CI). The area under the ROC curve was calculated to measure the accuracy of MIBG scintigraphy in differential diagnosis between Lewy body diseases and other dementias.

RESULTS

Ultimately, we identified 8 studies comprising a total of 346 patients with dementia (152 patients with DLB and 194 patients with other dementias). The pooled sensitivity of MIBG scintigraphy in detection of DLB was 98% (95% CI, 94-100%); the pooled specificity of MIBG scintigraphy in differential diagnosis between DLB and other dementias was 94% (95% CI, 90-97%). The area under the ROC curve was .99.

CONCLUSIONS

Myocardial innervation imaging with MIBG scintigraphy demonstrated high pooled sensitivity and specificity in patients with suspected DLB. MIBG scintigraphy is an accurate test for differential diagnosis between DLB and other dementias.

123I-MIBG imaging detects cardiac involvement and predicts cardiac events in Churg-Strauss syndrome

PURPOSE

In Churg-Strauss syndrome (CSS) it is important to detect cardiac involvement, which predicts poor prognosis. This study evaluated whether (123)I-metaiodobenzylguanidine (MIBG) scintigraphy could detect cardiac damage and predict cardiac events in CSS.

METHODS

(123)I-MIBG scintigraphy was performed in 28 patients with CSS, 12 of whom had cardiac involvement. The early and delayed heart to mediastinum ratio (early H/M and delayed H/M) and washout rate were calculated by using (123)I-MIBG scintigraphy and compared with those in control subjects.

RESULTS

Early H/M and delayed H/M were significantly lower and the washout rate was significantly higher in patients with cardiac involvement than in those without and in controls (early H/M, p = 0.0024, p = 0.0001; delayed H/M, p = 0.0002, p = 0.0001; washout rate, p = 0.0012, p = 0.0052 vs those without and vs controls, respectively). Accuracy for detecting cardiac involvement was 86% for delayed H/M and washout rate and 79% for early H/M and B-type natriuretic peptide (BNP). Kaplan-Meier analysis showed significantly lower cardiac event-free rates in patients with early H/M ≤ 2.18 and BNP > 21.8 pg/ml than those with early H/M > 2.18 and BNP ≤ 21.8 pg/ml (log-rank test p = 0.006).

CONCLUSION

Cardiac sympathetic nerve function was damaged in CSS patients with cardiac involvement. (123)I-MIBG scintigraphy was useful in detecting cardiac involvement and in predicting cardiac events.

Mathematical methods to determine quantitative parameters of myocardial 123I-MIBG studies: a review of the literature

(123)I-meta-iodobenzyl-guanidine ((123)I-MIBG) scintigraphy is used to visualize and quantify the sympathetic nerve activity. Although it has been used since 1980 to identify myocardial innervation, it is not yet regarded a routine sympathetic imaging agent in this respect. The lack of large multicentre studies and the presence of variations in the protocols that are used for planar MIBG acquisition confines the comparability of study results and application of normal values. Therefore, the aim of this study was to assess the variations in mathematical methods that are currently used to quantify the heart-to-mediastinum ratio and washout rate (WOR). In addition, normal values were evaluated in concordance with these methods. A systematic literature search yielded 169 unique manuscripts, of which 30 contained a complete description of the acquisition protocol for planar MIBG acquisition, image analysis and quantification of the parameters. The results indicate not only large variations in mathematical methods, but also in various aspects of the protocols that are used during acquisition. In many manuscripts method-specific normal values were used; however, these values were generally generated from small, single-centre studies. This study stresses the need to produce guidelines to achieve a standardized method for MIBG acquisition, image analysis and methods to quantify parameters.

Myocardial iodine-123 meta-iodobenzylguanidine imaging and cardiac events in heart failure. Results of the prospective ADMIRE-HF (AdreView Myocardial Imaging for Risk Evaluation in Heart Failure) study

OBJECTIVES

The ADMIRE-HF (AdreView Myocardial Imaging for Risk Evaluation in Heart Failure) study prospectively evaluated iodine-123 meta-iodobenzylguanidine ((123)I-mIBG) imaging for identifying symptomatic heart failure (HF) patients most likely to experience cardiac events.

BACKGROUND

Single-center studies have demonstrated the poorer prognosis of HF patients with reduced (123)I-mIBG myocardial uptake, but these observations have not been validated in large multicenter trials.

METHODS

A total of 961 subjects with New York Heart Association (NYHA) functional class II/III HF and left ventricular ejection fraction (LVEF) < or =35% were studied. Subjects underwent (123)I-mIBG myocardial imaging (sympathetic neuronal integrity quantified as the heart/mediastinum uptake ratio [H/M] on 4-h delayed planar images) and myocardial perfusion imaging and were then followed up for up to 2 years. Time to first occurrence of NYHA functional class progression, potentially life-threatening arrhythmic event, or cardiac death was compared with H/M (either in relation to estimated lower limit of normal [1.60] or as a continuous variable) using Cox proportional hazards regression. Multivariable analyses using clinical, laboratory, and imaging data were also performed.

RESULTS

A total of 237 subjects (25%) experienced events (median follow-up 17 months). The hazard ratio for H/M > or =1.60 was 0.40 (p < 0.001); the hazard ratio for continuous H/M was 0.22 (p < 0.001). Two-year event rate was 15% for H/M > or =1.60 and 37% for H/M <1.60; hazard ratios for individual event categories were as follows: HF progression, 0.49 (p = 0.002); arrhythmic events, 0.37 (p = 0.02); and cardiac death, 0.14 (p = 0.006). Significant contributors to the multivariable model were H/M, LVEF, B-type natriuretic peptide, and NYHA functional class. (123)I-mIBG imaging also provided additional discrimination in analyses of interactions between B-type natriuretic peptide, LVEF, and H/M.

CONCLUSIONS

ADMIRE-HF provides prospective validation of the independent prognostic value of (123)I-mIBG scintigraphy in assessment of patients with HF. (Meta-Iodobenzylguanidine Scintigraphy Imaging in Patients With Heart Failure and Control Subjects Without Cardiovascular Disease, NCT00126425; Meta-Iodobenzylguanidine [123I-mIBG] Scintigraphy Imaging in Patients With Heart Failure and Control Subjects Without Cardiovascular Disease, NCT00126438).

The significance of cardiac sympathetic nervous system abnormality in the long-term prognosis of patients with a history of ventricular tachyarrhythmia

Severe left ventricular dysfunction or cardiac sympathetic nervous system (SNS) abnormality predicts cardiac death in various heart diseases, including arrhythmogenic disorders. However, it is not clear whether SNS abnormality predicts sudden cardiac death during long-term follow-up in patients with a history of ventricular tachyarrhythmia. We hypothesized that SNS abnormality would be associated with recurrent ventricular arrhythmic events.

METHODS

123I-metaiodobenzylguanidine (MIBG) scintigraphy was performed on 86 patients (mean age+/-SD, 46+/-19 y, 65.1% men) with a history of ventricular tachycardia or fibrillation. 123I-MIBG (111 MBq) was intravenously administered under resting conditions, and planar images were obtained 15 min and 4 h later (anterior view for 6 min; 512x512 matrices; zoom ratio, 1.0). SNS activity was assessed using the heart-to-mediastinum ratio on delayed imaging.

RESULTS

During about 11 y of follow-up (mean+/-SD, 5.2+/-3.7 y), 3 patients (3.5%) had sudden cardiac death and 21 patients (24.4%) had sustained ventricular tachyarrhythmic events. SNS abnormality, defined as a heart-to-mediastinum ratio of less than 2.8, and left ventricular dysfunction, defined as a left ventricular ejection fraction of less than 50%, were associated with sudden cardiac death or recurrent ventricular tachyarrhythmic events (18/40 patients [45%] with SNS abnormality, vs. 6/46 patients [13%] without, P=0.004; 9/15 patients [60%] with left ventricular dysfunction, vs. 15/71 patients [21.1%] without, P=0.008). After adjustment for potential confounding variables such as age, sex, coronary risk factors, medication use, history of structural heart disease, and left ventricular function, SNS abnormality was a powerful predictor of recurrent arrhythmic events, with a hazard ratio of 3.6 [95% confidence interval, 1.4-9.2, P=0.007]). Further, SNS abnormality had incremental and additive prognostic power in combination with left ventricular dysfunction, with an adjusted hazard ratio of 4.4 [95% confidence interval, 1.9-9.9, P<0.0001]).

CONCLUSION

SNS abnormality predicted recurrent ventricular tachyarrhythmic events during long-term follow-up. 123I-MIBG scintigraphic evaluations for SNS abnormality may be an option for screening patients at high risk for sudden cardiac death.

Standardization of the heart-to-mediastinum ratio of 123I-labelled-metaiodobenzylguanidine uptake using the dual energy window method: feasibility of correction with different camera-collimator combinations

BACKGROUND

Although the heart-to-mediastinum (H/M) ratio in a planar image has been used for practical quantification in (123)I-metaiodobenzylguanidine (MIBG) imaging, standardization of the parameter is not yet established. We hypothesized that the value of the H/M ratio could be standardized to the various camera-collimator combinations.

METHODS AND RESULTS

Standard phantoms consisting of the heart and mediastinum were made. A low-energy high-resolution (LEHR) collimator and a medium-energy (ME) collimator were used. We examined multi-window correction methods with (123)I- dual-window (IDW) acquisition, and planar images were obtained with IDW correction and the LEHR collimator. The images were obtained using the following gamma camera systems: GCA 9300A (Toshiba, Tokyo), E.CAM Signature (Toshiba/Siemens, Tokyo) and Varicam (GE, Tokyo). Cardiac phantom studies demonstrated that contamination of the H/M count ratio was greater with the LEHR collimator and least with the ME collimator. The corrected H/M ratio with the LEHR collimator was similar to that with ME collimators. The uncorrected H/M ratio with the ME collimator was linearly related to the H/M ratio with IDW correction with the LEHR collimator. The relationship between the uncorrected H/M ratios determined with the LEHR (E.CAM) and the ME collimators was y = 0.56x + 0.49, where y = H/M ratio with the E.CAM and x = H/M ratio with the ME collimator. The average normal values for the low-energy collimator (n=18) were 2.2+/-0.2 (initial H/M ratio) and 2.42+/-0.2 (delayed H/M ratio), and for the low/medium-energy (LME) collimator (n=14) were 2.63+/-0.25 (initial H/M ratio) and 2.87+/-0.19 (delayed H/M ratio). H/M ratios in previous clinical studies using LEHR collimators are comparable to those with ME collimators.

CONCLUSION

The IDW-corrected H/M ratios determined with the LEHR collimator were similar to those determined with the ME collimator. This finding could make it possible to standardize the H/M ratio in planar imaging among various collimators in the clinical setting.

Evaluation of radioiodinated (2S,alphaS)-2-(alpha-(2-iodophenoxy)benzyl)morpholine as a radioligand for imaging of norepinephrine transporter in the heart

INTRODUCTION

The norepinephrine transporter (NET) is located presynaptically on noradrenergic nerve terminals and plays a critical role in the regulation of the synaptic norepinephrine (NE) concentration via the reuptake of NE. Changes in NET have been recently reported in several cardiac failures. Therefore, a NET-specific radioligand is useful for in vivo assessment of changes in NET density in various cardiac disorders. Recently, we developed a radioiodinated reboxetine analogue, (2S,alphaS)-2-(alpha-(2-iodophenoxy)benzyl)morpholine ((S,S)-IPBM), for NET imaging. In the current study, we assessed the applicability of radioiodinated (S,S)-IPBM to NET imaging in the heart.

METHODS

The NET affinity and selectivity were measured from the ability to displace specific [3H]nisoxetine and (S,S)-[125 I]IPBM binding to rat heart membrane, respectively. To evaluate the distribution of (S,S)-[125 I]IPBM in vivo, biodistribution experiment was performed in rats. With the use of several monoamine transporter binding agents, pharmacological blocking experiments were performed in rats.

RESULTS

In vitro binding assays showed that the affinity of (S,S)-IPBM to NET was similar to those of the well-known NET-specific binding agents, nisoxetine and desipramine. Furthermore, (S,S)-[125 I]IPBM binding was inhibited by nisoxetine and desipramine, but not by dopamine or serotonin transporter binding agents. These data indicated that (S,S)-IPBM had high affinity and selectivity for NET in vitro. Biodistribution studies in rats showed rapid and high uptake of (S,S)-[125 I]IPBM by the heart and rapid clearance from the blood. The heart-to-blood ratio was 31.9 at 180 min after the injection. The administration of nisoxetine and desipramine decreased (S,S)-[125 I]IPBM accumulation in the heart, but injection of fluoxetine and GBR12909 had little influence.

CONCLUSIONS

Radioiodinated (S,S)-IPBM is a potential radioligand for NET imaging in the heart.