Age-related decrease in cardiopulmonary adrenergic neuronal function in children as assessed by I-123 metaiodobenzylguanidine imaging

The Impact of Ageing on 11C-Hydroxyephedrine Uptake in the Rat Heart

We aimed to explore the impact of ageing on 11C-hydroxyephedrine (11C-HED) uptake in the healthy rat heart in a longitudinal setting. To investigate a potential cold mass effect, the influence of specific activity on cardiac 11C-HED uptake was evaluated: 11C-HED was synthesized by N-methylation of (−)-metaraminol as the free base (radiochemical purity >95%) and a wide range of specific activities (0.2–141.9 GBq/μmol) were prepared. ¹¹C-HED (48.7 ± 9.7MBq, ranged 0.2–60.4 μg/kg cold mass) was injected in healthy Wistar Rats. Dynamic 23-frame PET images were obtained over 30 min. Time activity curves were generated for the blood input function and myocardial tissue. Cardiac 11C-HED retention index (%/min) was calculated as myocardial tissue activity at 20–30 min divided by the integral of the blood activity curves. Additionally, the impact of ageing on myocardial 11C-HED uptake was investigated longitudinally by PET studies at different ages of healthy Wistar Rats. A dose-dependent reduction of cardiac 11C-HED uptake was observed: The estimated retention index as a marker of norepinephrine function decreased at a lower specific activity (higher amount of cold mass). This observed high affinity of 11C-HED to the neural norepinephrine transporter triggered a subsequent study: In a longitudinal setting, the 11C-HED retention index decreased with increasing age. An age-related decline of cardiac sympathetic innervation could be demonstrated. The herein observed cold mass effect might increase in succeeding scans and therefore, 11C-HED microPET studies should be planned with extreme caution if one single radiosynthesis is scheduled for multiple animals.

SPECT/CT MIBG Imaging Is Crucial in the Follow-up of the Patients With High-Risk Neuroblastoma

BACKGROUND

Planar whole-body imaging with I-radiolabeled metaiodobenzylguanidine (I-MIBG) is routinely used in the follow-up evaluation of neuroblastoma. In recent years, SPECT with integrated low-dose CT (SPECT/CT) has become more accessible. We investigated how much SPECT/CT can have additional diagnostic value over planar imaging in detection of residual and recurrent neuroblastoma.

METHODS

A total of 170 planar I-MIBG imaging scans with SPECT/CT follow-up scans performed in 147 patients with known high-risk neuroblastoma were retrospectively analyzed. Regions of increased I-MIBG uptake on planar images and the findings on SPECT/CT were compared.

RESULTS

In 61% of the studies, the whole-body planar images and SPECT/CT images yielded the same result. In 39% of the time, however, SPECT/CT images provided additional information.

CONCLUSIONS

In the follow-up of patients with high-risk neuroblastoma, SPECT/CT can significantly improve planar imaging interpretation and impact patient management.

Is 123I-metaiodobenzylguanidine heart-to-mediastinum ratio dependent on age? From Japanese Society of Nuclear Medicine normal database

BACKGROUND

Heart-to-mediastinum ratios (HMRs) of 123I-metaiodobenzylguanidine (MIBG) have usually been applied to prognostic evaluations of heart failure and Lewy body disease. However, whether these ratios depend on patient age has not yet been clarified using normal databases.

METHODS

We analyzed 62 patients (average age 57 ± 19 years, male 45%) derived from a normal database of the Japanese Society of Nuclear Medicine working group. The HMR was calculated from early (15 min) and delayed (3-4 h) anterior planar 123I-MIBG images. All HMRs were standardized to medium-energy general purpose (MEGP) collimator equivalent conditions using conversion coefficients for the collimator types. Washout rates (WR) were also calculated, and we analyzed whether early and late HMR, and WR are associated with age.

RESULTS

Before standardization of HMR to MEGP collimator conditions, HMR and age did not significantly correlate. However, late HMR significantly correlated with age after standardization: late HMR = - 0.0071 × age + 3.69 (r2 = 0.078, p = 0.028), indicating that a 14-year increase in age corresponded to a decrease in HMR of 0.1. Whereas the lower limit (2.5% quantile) of late HMR was 2.3 for all patients, it was 2.5 and 2.0 for those aged ≤ 63 and > 63 years, respectively. Early HMR tended to be lower in subjects with the higher age (p = 0.076), whereas WR was not affected by age.

CONCLUSION

While late HMR was slightly decreased in elderly patients, the lower limit of 2.2-2.3 can still be used to determine both early and late HMR.

Catecholamines influence myocardial 123I MIBG uptake in neuroblastoma patients

Aim: Cardiac 123I metaiodobenzylguanidine (MIBG) imaging can be influenced by several factors. We evaluated the relationship between catecholamine measurements and cardiac 123I MIBG uptake in neuroblastoma patients. Patients, methods: 30 neuroblastoma patients were retrospectively assessed on cardiac 123I MIBG uptake and urinary catecholamine dopamine and metabolites, homovanillic acid (HVA) and vanillylmandelic acid (VMA). Cardiac 123I MIBG uptake was quantified by heart-to-mediastinum (H/M) ratios, which were calculated into standard deviation scores (SDS) using age-specific reference values. Results: In 17 (57%) and 12 patients (40%) H/M ratio measurements were below –1.0 and –2.0 SDS at diagnosis. A significant inverse correlation between the average of urine metabolites HVA and VMA, and H/M ratio SDS was observed (r -.39, p = 0.04). Furthermore, there was a significant correlation between the urinary catecholamine metabolite HVA and H/M ratio SDS (r -.40, p = 0.04). Conclusion: Routine calculation of H/M ratios in 123I MIBG scintigrams of neuroblastoma patients is not helpful because it will not identify cardiac ventricular dysfunction in this patient category. A low H/M ratio on 123I MIBG scintigraphy is explained by increased cathecholamine levels secreted by neuroblastoma tumours.

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.

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.

Proposal for standardization of 123I-metaiodobenzylguanidine (MIBG) cardiac sympathetic imaging by the EANM Cardiovascular Committee and the European Council of Nuclear Cardiology

This proposal for standardization of (123)I-metaiodobenzylguanidine (iobenguane, MIBG) cardiac sympathetic imaging includes recommendations for patient information and preparation, radiopharmaceutical, injected activities and dosimetry, image acquisition, quality control, reconstruction methods, attenuation, scatter and collimator response compensation, data analysis and interpretation, reports, and image display. The recommendations are based on evidence coming from original or scientific studies whenever possible and as far as possible reflect the current state-of-the-art in cardiac MIBG imaging. The recommendations are designed to assist in the practice of performing, interpreting and reporting cardiac sympathetic imaging. The proposed standardization does not include clinical indications, benefits or drawbacks of cardiac sympathetic imaging, and does not address cost benefits or cost effectiveness; however, clinical settings of potential utility are mentioned. Standardization of MIBG cardiac sympathetic imaging should contribute to increasing its clinical applicability and integration into current nuclear cardiology practice.

A series of halogenated heterodimeric inhibitors of prostate specific membrane antigen (PSMA) as radiolabeled probes for targeting prostate cancer

Prostate specific membrane antigen (PSMA) is a validated molecular marker for prostate cancer. A series of glutamate-urea (Glu-urea-X) heterodimeric inhibitors of PSMA were designed and synthesized where X = epsilon-N-(o-I, m-I, p-I, p-Br, o-Cl, m-Cl, p-Cl, p-F, H)-benzyl-Lys and epsilon-(p-I, p-Br, p-Cl, p-F, H)-phenylureido-Lys. The affinities for PSMA were determined by screening in a competitive binding assay. PSMA binding of the benzyllysine series was significantly affected by the nature of the halogen substituent (IC(50) values, Cl < I = Br << F = H) and the ring position of the halogen atom (IC(50) values, p-I < o-I << m-I). The halogen atom had little affect on the binding affinity in the para substituted phenylureido-Lys series. Two lead iodine compounds were radiolabeled with (123)I and (131)I and demonstrated specific PSMA binding on human prostate cancer cells, warranting evaluation as radioligands for the detection, staging, and monitoring of prostate cancer.