Interobserver variability of heart-to-mediastinum ratio in I-123 MIBG sympathetic imaging

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.

Relationship of promising methods in the detection of anthracycline-induced cardiotoxicity in breast cancer patients

Purpose

It remains challenging to identify patients at risk of anthracycline-induced cardiotoxicity. To better understand the different risk-stratifying approaches, we evaluated ¹²³I-metaiodobenzylguanidine (¹²³I-mIBG) scintigraphy and its interrelationship with conventional echocardiography, 2D strain imaging and several biomarkers.

Methods

We performed ¹²³I-mIBG scintigraphy, conventional and strain echocardiography and biomarker (NT-proBNP, TNF-α, galectin-3, IL-6, troponin I, ST-2 and sFlt-1) assessment in 59 breast cancer survivors 1 year after anthracycline treatment. Interobserver and intermethod variability was calculated on planar and SPECT ¹²³I-mIBG scintigraphy, using the heart/mediastinum (H/M) ratio and washout (WO). Pearson’s r and multivariate analyses were performed to identify correlations and independent predictors of ¹²³I-mIBG scintigraphy results.

Results

Delayed planar anterior whole-heart ROI (WH) H/M ratios and WO were the most robust ¹²³I-mIBG parameters. Significant correlations were observed between ¹²³I-mIBG parameters and several conventional echo parameters, global longitudinal and radial strain (GLS and GRS) and galectin-3. The highest Pearson’s r was observed between delayed H/M ratio and GRS (Pearson’s r 0.36, p = 0.01). Multivariate analysis showed that GRS was the only independent predictor of the delayed WH H/M ratio (p = 0.023).

Conclusion

The delayed planar H/M ratio is the most robust ¹²³I-mIBG parameter. It correlates with several conventional echocardiographic parameters, GLS, GRS and galectin-3. Of these, only GRS predicts the H/M ratio.