Seeing more than the Tip of the Iceberg: Approaches to Subthreshold Effects in Functional Magnetic Resonance Imaging of the Brain.

Many functional magnetic resonance imaging (fMRI) studies and presurgical mapping applications rely on mass-univariate inference with subsequent multiple comparison correction. Statistical results are frequently visualized as thresholded statistical maps. This approach has inherent limitations including the risk of drawing overly-selective conclusions based only on selective results passing such thresholds. This article gives an overview of both established and newly emerging scientific approaches to supplement such conventional analyses by incorporating information about subthreshold effects with the aim to improve interpretation of findings or leverage a wider array of information. Topics covered include neuroimaging data visualization, p-value histogram analysis and the related Higher Criticism approach for detecting rare and weak effects. Further examples from multivariate analyses and dedicated Bayesian approaches are provided.

Rare osteoarticular complications on [18F]FDG-PET/CT - following intravesical BCG immunotherapy for bladder cancer.

This case illustrates rare osteoarticular complications of Bacillus Calmette-Guérin (BCG) immunotherapy in a 55-year-old male with high-risk non-muscle-invasive bladder cancer (NMIBC). The patient was referred for 18F-fluorodeoxyglucose ([18F]FDG) positron emission tomography/computed tomography (PET/CT) to rule out bone metastases suspected on prior post-gadolinium magnetic resonance imaging (MRI). Although metastases were excluded, nearly symmetrical uptakes were detected in the costovertebral and costotransverse joints. Medical history revealed that the patient had been receiving intravesical instillations of BCG, the first-line therapy for high-risk NMIBC. The patient was diagnosed with reactive arthritis (ReA), a rare autoimmune complication of BCG, that was successfully treated with a nonsteroidal anti-inflammatory drug (NSAID).

Risk of Upstaging Due to Oncofertility Treatment Mimicking Pelvic Lymphoma on 18F-FDG PET/CT.

ABSTRACT: A 23-year-old woman with primary mediastinal large B-cell lymphoma was referred to 18F-FDG PET/CT for staging. Besides the large mediastinal FDG-avid tumor, another FDG-avid lesion with an SUV higher than expected in corpus luteum cysts was found in the pelvis, raising suspicion for tumor. However, gynecologic ultrasound and review of patient chart revealed history of oncofertility treatment with GNRH analog. This prior treatment was responsible for the intense 18F-FDG uptake within the left ovary, way above the SUV levels commonly associated with menstrual cycle. In this case, the disease was downgraded to stage II, resulting in a less aggressive treatment.

Reshaping the Amyloid Buildup Curve in Alzheimer Disease? Partial-Volume Effect Correction of Longitudinal Amyloid PET Data.

It was hypothesized that the brain ß-amyloid buildup curve plateaus at an early symptomatic stage of Alzheimer disease (AD). Atrophy-related partial-volume effects (PVEs) degrade signal in hot-spot imaging techniques such as amyloid PET. The current study, a longitudinal analysis of amyloid-sensitive PET data, investigated the effect on the shape of the ß-amyloid curve in AD when PVE correction (PVEC) is applied. Methods: We analyzed baseline and 2-y follow-up data for 216 symptomatic individuals on the AD continuum (positive amyloid status) enrolled in the Alzheimer's Disease Neuroimaging Initiative (17 with AD dementia and 199 with mild cognitive impairment), including 18F-florbetapir PET, MRI, and Mini Mental State Examination scores. For PVEC, the modified Müller-Gärtner method was performed. Results: Compared with non-PVE-corrected data, PVE-corrected data yielded significantly higher changes in regional and composite SUV ratio (SUVR) over time (P = 0.0002 for composite SUVRs). Longitudinal SUVR changes in relation to Mini Mental State Examination decreases showed a significantly higher slope for the regression line in the PVE-corrected than in the non-PVE-corrected PET data (F1 = 7.1, P = 0.008). Conclusion: These PVEC results indicate that the ß-amyloid buildup curve does not plateau at an early symptomatic disease stage. A further evaluation of the impact of PVEC on the in vivo characterization of time-dependent AD pathology, including the reliable assessment and comparison of other amyloid tracers, is warranted.

Noradrenaline transporter availability on [11C]MRB PET predicts weight loss success in highly obese adults.

PURPOSE: Although the mechanisms by which the central noradrenaline (NA) system influences appetite and controls energy balance are quite well understood, its relationship to changes in body weight remains largely unknown. The main goal of this study was to further clarify whether the brain NA system is a stable trait or whether it can be altered by dietary intervention. METHODS: We aimed to compare central NA transporter (NAT) availability in ten obese, otherwise healthy individuals with a body mass index (BMI) of 42.4 ± 3.7 kg/m2 (age 34 ± 9 years, four women) and ten matched non-obese, healthy controls (BMI 23.9 ± 2.5 kg/m2, age 33 ± 10 years, four women) who underwent PET with the NAT-selective radiotracer (S,S)-[11C]O-methylreboxetine (MRB) before and 6 months after dietary intervention. RESULTS: MRI-based individual volume-of-interest analyses revealed an increase in binding potential (BPND) in the insula and the hippocampus of obese individuals, which correlated well with changes in BMI (-3.3 ± 5.3%; p = 0.03) following completion of the dietary intervention. Furthermore, voxel-wise regression analyses showed that lower BPND in these regions, but also in the midbrain and the prefrontal cortex, at baseline was associated with higher achieved weight loss (e.g., hippocampal area R2 = 0.80; p < 0.0001). No changes were observed in non-obese controls. CONCLUSION: These first longitudinal interventional data on NAT availability in highly obese individuals indicate that the central NA system is modifiable. Our findings suggest that NAT availability before intervention could help predict the amount and success of weight loss in obese individuals and help adjust treatment options individually by allowing prediction of the benefit of a dietary intervention.