Nuclear imaging to characterize adrenal tumors: Comparison with MRI

AIM:To describe the role of nuclear imaging modalities using nor-cholesterol,metaiodobenzylguanidine(MIBG)and fluorine-deoxy-glucose(FDG)in adrenal tumors for lesion characterization in comparison with magnetic resonance(MR).METHODS:Population was classified in group 1 consisting of 30 patients with non-hypersecreting unilateral adrenal masses,in group 2 consisting of 34 patients with hypersecreting(n=19)or non-hypersecreting(n=15)adrenal adenomas and in group 3 consisting of 18 patients with chromaffin-tissue tumors(CTT),of which 14 were pheochromocytomas while 4 were paragangliomas(n=4).All patients underwent MR and nuclear studies(nor-cholesterol,MIBG and FDG).Pathology samples(n=63)or follow-up data in adenomas(n=19)were used as standard of reference forimaging studies interpretation.RESULTS:In group 1,MR findings were not highly accurate for lesion characterization,while the results of nuclear scans showed abnormal nor-cholesterol,MIBG and FDG concentration in all cases of adenomas,pheos and malignant tumors,respectively.In group 2,no differences in MR parameters were found between hyperfunctioning and non-hyperfunctioning adenomas,while nor-cholesterol uptake was significantly higher in hyperfunctioning compared to non-hyperfunctioning lesions.In group 3,no differences in MR parameters were found between benign and malignant CCT,while MIBG uptake was significantly higher in malignant compared to benign tumors.CONCLUSION:On the basis of our findings,nuclear imaging modalities using specific target agents are able to better characterize adrenal tumors,compared with MR.In particular,radionuclide techniques are able to identify the nature of adrenal incidentalomas and to differentiate between hypersecreting and non-hypersecreting adenomas as well as between benign and malignant CTT.

Role of nuclear cardiology for guiding device therapy in patients with heart failure

Heart failure is a dynamic condition with high morbidity and mortality and its prognosis should be reassessed frequently, particularly in patients for whom critical treatment decisions may depend on the results of prognostication. In patients with heart failure, nuclear cardiology techniques are useful to establish the etiol-ogy and the severity of the disease, while fewer studies have explored the potential capability of nuclear cardi-ology to guide cardiac resynchronization therapy （CRT） and to select patients for implantable cardioverter defbrillators （ICD）. Left ventricular synchrony may be assessed by radionuclide angiography or gated single-photon emission computed tomography myocardial perfusion scintigraphy. These modalities have shown promise as predictors of CRT outcome using phase analysis. Combined assessment of myocardial viability and left ventricular dyssynchrony is feasible using posi-tron emission tomography and could improve conven-tional response prediction criteria for CRT. Preliminary data also exists on integrated positron emission tomog-raphy/computed tomography approach for assessing myocardial viability, identifying the location of biven-tricular pacemaker leads, and obtaining left ventricular functional data, including contractile phase analysis. Fi-nally, cardiac imaging with autonomic radiotracers may be useful in predicting CRT response and for identifying patients at risk for sudden cardiac death, therefore po-tentially offering a way to select patients for both CRT and ICD therapy. Prospective trials where imaging is combined with image-test driven therapy are needed to better defne the role of nuclear cardiology for guiding device therapy in patients with heart failure.

Comparison of Diagnosing and Staging Accuracy of PET(CT) and MIBG on Patients with Neuroblastoma: Systemic Review and Meta-analysis

To perform a systemic review and meta-analysis of the diagnostic accuracy of PET（CT） and metaiodobenzylguanidine（MIBG） for diagnosing neuroblastoma（NB）, electronic databases were searched as well as relevant references and conference proceedings. The diagnostic accuracy of MIBG and PET（CT） was calculated for NB, primary NB, and relapse/metastasis of NB based on their sensitivity, specificity, and area under the summary receiver operating characteristic curve（AUSROC） in terms of per-lesion and per-patient data. A total of 40 eligible studies comprising 1134 patients with 939 NB lesions were considered for the meta-analysis. For the staging of NB, the per-lesion AUSROC value of MIBG was lower than that of PET（CT） [0.8064±0.0414 vs. 0.9366±0.0166（P〈0.05）]. The per-patient AUSROC value of MIBG and PET（CT） for the diagnosis of NB was 0.8771±0.0230 and 0.6851±0.2111, respectively. The summary sensitivity for MIBG and PET（CT） was 0.79 and 0.89, respectively. The summary specificity for MIBG and PET（CT） was 0.84 and 0.71, respectively. PET（CT） showed higher per-lesion accuracy than MIBG and might be the preferred modality for the staging of NB. On the other hand, MIBG has a comparable diagnosing performance with PET（CT） in per-patient analysis but shows a better specificity.

Clinical use of nuclear cardiology in the assessment of heart failure

A nuclear cardiology test is the most commonly performed non-invasive cardiac imaging test in patients with heart failure, and it plays a pivotal role in their assessment and management. Quantitative gated single positron emission computed tomography (QGS) is used to assess quantitatively cardiac volume, left ventricular ejection fraction (LVEF), stroke volume, and cardiac diastolic function. Resting and stress myocardial perfusion imaging, with exercise or pharmacologic stress, plays a fundamental role in distinguishing ischemic from nonischemic etiology of heart failure, and in demonstrating myocardial viability. Diastolic heart failure also termed as heart failure with a preserved LVEF is readily identified by nuclear cardiology techniques and can accurately be estimated by peak filling rate (PFR) and time to PFR. Movement of the left ventricle can also be readily assessed by QGS, with newer techniques such as threedimensional, wall thickening evaluation aiding its assessment. Myocardial perfusion imaging is also commonly used to identify candidates for implantable cardiac defibrillator and cardiac resynchronization therapies. Neurotransmitter imaging using 123 I-metaiodobenzylguanidine offers prognostic information in patients with heart failure. Metabolism and function in the heart are closely related, and energy substrate metabolism is a potential target of medical therapies to improve cardiac function in patients with heart failure. Cardiac metabolic imaging using 123 I-15-(p-iodophenyl)3-R, S-methylpentadecacoic acid is a commonly used tracer in clinical studies to diagnose metabolic heart failure. Nuclear cardiology tests, including neurotransmitter imaging and metabolic imaging, are now easily preformed with new tracers to refine heart failure diagnosis. Nuclear cardiology studies contribute significantly to guiding management decisions for identifying cardiac risk in patients with heart failure.