Abass Alavi

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

BackgroundRadioiodinated metaiodobenzylguanidine (MIBG) imaging has been used to evaluate adrenergic nerve activity in different organs Cardiac and pulmonary MIBG uptake is important in predicting the prognosis of certain cardiopulmonary diseases. It has been reported that cardiac MIBG uptake decreases with age and is significantly lower in the elderly. However, there has been no systemic study on age-related changes in cardiac and pulmonary MIBG uptake in children. This study was undertaken to determine the changes in MIBG uptake in the developing heart and lung in children and adolescents.Methods and ResultsMIBG scans of 44 children (16 female and 28 male; age range, 2 months to 19 years) without abnormal uptake were selected from a large pool of patients with whole-body MIBG imaging performed for evaluation of neuroblastoma. All of the selected subjects had a normal physiologic distribution of MIBG and no history of heart or lung diseases. The patients were divided into 4 groups by age: group 1, 0 to 24 months; group 2, 25 to 48 months; group 3, 49 to 72 months; and group 4, 73 months or greater. Cardiac and pulmonary MIBG uptake values (expressed as heart-to-mediastinum [H/M] ratio and lung-to-mediastinum [L/M] ratio, respectively) were determined and compared among the 4 groups. H/M and L/M ratios were noted to decrease with age. The mean H/M and L/M ratios were in group 1, 4.13±0.66 and 1.53±0.18, respectively; in group 2, 3.46±0.71 and 1.26±0.18, respectively; in group 3, 3.19±0.94 and 1.13±0.17, respectively; and in group 4, 2.84±0.48 and 1.14±0.14, respectively. There was a significant inverse correlation between H/M ratio and age (r=0.711, P<.001) as well as between L/M ratio and age (r=0.718, P<.001).ConclusionCardiac and pulmonary MIBG uptake is inversely related to age in children.

Modern Quantitative Techniques for PET/CT/MR Hybrid Imaging

The relentless progress that is being made in tomographic imaging modalities is inexorably expanding the application of positron emission tomography (PET) in the clinical field. Some of the most noteworthy advances involve innovations in quantitative techniques for hybrid imaging modalities such as PET/Computed Tomography (CT) and PET/Magnetic Resonance Imaging (MRI), which have greatly improved the ability to segment and analyze functional images produced with radiotracers such as (18F) Fluorodeoxyglucose (FDG). With continued technological progress, quantitative approaches can supplant the more subjective qualitative and semi-quantitative techniques that currently dominate the clinical use of PET.