Brain Hemisphere Dissimilarity, a Self-Supervised Learning Approach for alpha-synucleinopathies prediction with FDG PET

Idiopathic Rem sleep Behavior Disorder (iRBD) is a significant biomarker for the development of alpha-synucleinopathies, such as Parkinson's disease (PD) or Dementia with Lewy bodies (DLB). Methods to identify patterns in iRBD patients can help in the prediction of the future conversion to these diseases during the long prodromal phase when symptoms are non-specific. These methods are essential for disease management and clinical trial recruitment. Brain PET scans with 18F-FDG PET radiotracers have recently shown promise, however, the scarcity of longitudinal data and PD/DLB conversion information makes the use of representation learning approaches such as deep convolutional networks not feasible if trained in a supervised manner. In this work, we propose a self-supervised learning strategy to learn features by comparing the brain hemispheres of iRBD non-convertor subjects, which allows for pre-training a convolutional network on a small data regimen. We introduce a loss function called hemisphere dissimilarity loss (HDL), which extends the Barlow Twins loss, that promotes the creation of invariant and non-redundant features for brain hemispheres of the same subject, and the opposite for hemispheres of different subjects. This loss enables the pre-training of a network without any information about the disease, which is then used to generate full brain feature vectors that are fine-tuned to two downstream tasks: follow-up conversion, and the type of conversion (PD or DLB) using baseline 18F-FDG PET. In our results, we find that the HDL outperforms the variational autoencoder with different forms of inputs.

Left atrium hemodynamic in atrial fibrillation and normal subjects

Funding Acknowledgements

Type of funding sources: None.

Background

A computational fluid-dynamics (CFD) model previously developed with the aim of evaluating cardioembolic risk in patient affected by atrial fibrillation (AF) was used for the characterization of the left atrium (LA) hemodynamic in normal subjects (NL), patients affected by paroxysmal atrial fibrillation (PAR-AF) and patients affected by persistent atrial fibrillation (PER-AF). Based on the fluid-dynamics simulations results, we aimed at enhancing differences in blood flow in AF patients and NL and at better understanding the relationship between AF progression and stroke risk on a patient-specific basis.

Methods

3D patient-specific anatomical and motion models were derived from ECG-gated coronary artery CT acquired with retrospective protocol. These models represented the computational domain for CFD simulations in which inflow initial conditions were derived from PW Doppler at the mitral valve and at the pulmonary veins. Velocity field and vortex structures both within the LA and left atrial appendage (LAA) were assessed in 10 NL, 5 PAR-AF and 4 PER-AF. Blood stasis was evaluated by populating the LAA with 500 particles and counting the number of particles still present after five cardiac cycles.

Results

Velocities inside the LA and in the LAA presented different amplitude and distribution in the 3 groups (peak velocity – NL: 50÷60 cm/s, PAR-AF: 40÷50 cm/s, PER-AF: 15÷25 cm/s). The mean velocity resulted lower in the PER-AF compared with PAR-AF (mean velocity – PAR-AF: 25÷35 cm/s, PER-AF: 8÷20 cm/s) at the LAA ostium and inside the LAA, in which the wash-out effect was strongly reduced (Figure 1). On the other hand, the mean velocity in the NL was higher with respect of AF patients (mean velocity – NL: 40÷45 cm/s). A higher number of vortex structures was observed in NL compared with AF patients, thus favouring the hypothesis of a more efficient wash-out of the LA and of the LAA. Blood stasis in terms of number of particles in the LAA after five cardiac cycles confirmed these results (NL: 5±2, PAR-AF: 18±3, PER-AF: 41±10).

Conclusions

The developed approach quantifies differences in LA hemodynamic between AF and NL patients, also allowing a stratification of the atrial disease progression in terms of variations in the blood velocity, organization of blood flow and quantification of blood stasis.

Cortical metabolic changes and clinical outcome in normal pressure hydrocephalus after ventriculoperitoneal shunt: Our preliminary results

INTRODUCTION

Our objective was to evaluate the cortical metabolic changes and clinical outcome in patients affected by idiopathic normal pressure hydrocephalus (iNPH) after a placement of ventriculoperitoneal (VP) shunt.

MATERIALS AND METHODS

10 patients affected by suspected iNPH underwent a CSF hydrodynamics evaluation based on a lumbar infusion test (LIT). The main selection criterion for surgery was based on intracranial elasticity (IE)>0.30. All subjects with an IE>0.30 underwent a PET scan with 18 fluorodeoxiglucose (¹⁸F-FDG) at baseline (PET1) and 1 month after surgery (PET2). Furthermore, the same patients were submitted to clinical evaluation before and 1 month after surgery through neuropsychological tests and gait analysis.

RESULTS

An overall number of 20 18F-FDG PET scans were performed in all the enrolled patients. As compared to PET1, PET2 showed an increase in glucose consumption in the left frontal and left parietal lobe in PET2 as compared to PET1 (P<.001). All the enrolled patients presented a significant increase in neuropsychological scores (i.e Frontal Assessment Battery and Montreal Cognitive Assessment) and have clinically improved at gait analysis. A significant correlation was found between the increase of cortical glucose consumption in the left parietal area and the cognitive improvement as detectable by neuropsychological assessment.

CONCLUSIONS

Improvement in 18F FDG PET glucose metabolism could be considered a useful imaging marker for the assessment of iNPH response to VP shunting.

Hearing and cognitive impairment: a functional evaluation of associative brain areas in patients affected by Alzheimer's disease

Auditory dysfunction observed in patients with cognitive diseases is probably due to the alteration of some brain areas involved in sound stimulus processing. The present study aimed to investigate differences in such processing and in connectivity of the primary auditory cortex in patients affected by Alzheimer's disease (AD) and in normal subjects. We examined 131 diagnosed AD patients and a control group (CG) of 36 normal subjects. After a complete clinical investigation, focused on hearing function, all subjects underwent a brain FDG PET/CT. AD subjects vs CG showed reduced glucose consumption in BA 6,7,8,39, whereas we did not find differences in the primary auditory cortex. In AD, connectivity analyses showed a positive correlation of the primary auditory cortex with BA 6,8,21,31,39,40,42 and a negative correlation with BA 19, cerebellum and basal ganglia. Our findings suggest that neurological evaluation of patients with hearing loss might allow earlier (preclinical) identification of those affected by cognitive impairment.

Laser treatment of medical skin disease in women

Laser treatment is a relatively new and increasingly popular modality for the treatment of many dermatologic conditions. A number of conditions that predominantly occur in women and that have a paucity of effective treatments include rosacea, connective tissue disease, melasma, nevus of Ota, lichen sclerosus (LS), notalgia paresthetica and macular amyloidosis, and syringomas. Laser therapy is an important option for the treatment of patients with these conditions. This article will review the body of literature that exists for the laser treatment of women with these medical conditions.

Aspects of cerebral plasticity related to clinical features in acute vestibular neuritis: a "starting point" review from neuroimaging studies

Vestibular neuritis (VN) is one of the most common causes of vertigo and is characterised by a sudden unilateral vestibular failure (UVF). Many neuroimaging studies in the last 10 years have focused on brain changes related to sudden vestibular deafferentation as in VN. However, most of these studies, also due to different possibilities across diverse centres, were based on different times of first acquisition from the onset of VN symptoms, neuroimaging techniques, statistical analysis and correlation with otoneurological and psychological findings. In the present review, the authors aim to merge together the similarities and discrepancies across various investigations that have employed neuroimaging techniques and group analysis with the purpose of better understanding about how the brain changes and what characteristic clinical features may relate to each other in the acute phase of VN. Six studies that strictly met inclusion criteria were analysed to assess cortical-subcortical correlates of acute clinical features related to VN. The present review clearly reveals that sudden UVF may induce a wide variety of cortical and subcortical responses - with changes in different sensory modules - as a result of acute plasticity in the central nervous system.

Reverse perfusion pattern in myocardial spect with 99mTc-sestaMIBI

RATIONALE

The aim of our study was to investigate the myocardial perfusion deficit in rest images as compared to stress images in myocardial scintigraphy (MS).

OBJECTIVES

The aim of this study is to investigate the reverse perfusion (RP) pattern in MS.

METHODS AND RESULTS

263 patients were enrolled in the study (72 females and 191 males; mean age 65.7 ± 9.5 years old). Mean body mass index (BMI) was of 27.6 ± 3.8 Kg/m2. 115 patients were positive for a previous history of myocardial infarction (MI). 142 patients reported a revascularization treatment (percutaneous transluminal coronary angioplasty, PTCA, cardiac stent placement, coronary artery bypass grafting, CABG). All the patients underwent MS following standard single day Stress/Rest protocol. In our series, 27 patients presented a RP pattern. We did not find statistically significant differences when considering age (p = 0.7988), sex (p = 0.0657), BMI (p = 0.8611), diabetes (p = 0.8259), dyslipidemia (p = 0.1464) or smoking status (p = 0.6829) in RP patients vs. non-RP patients. A history of MI is related to a RP pattern (p < 0.0001). A history of previous revascularization was not related with RP (p = 0.6868).

DISCUSSION

The result of our study suggested that RP is probably related to artifacts of various origins. Further studies are necessary especially in microvascular dysfunction or a long history of disease.

Endovascular management of acute stroke

Ischemic stroke is the third leading cause of death and most common cause of permanent disability in industrialized nations. Eighty-five percent of strokes are ischemic in nature, with an associated mortality between 53% and 92%. The focus of treatment for acute stroke starts with prompt and accurate diagnosis of ischemic brain tissue at risk, followed by time sensitive delivery of therapy that effectively and safely restores flow to that vascular territory. Time-dependent reperfusion therapy is the only proven treatment for Acute Ischemic Stroke. In this paper, we review the clinical and imaging factors that are relevant to guide endovascular treatment decisions; the different approaches of stroke therapy and the devices used with the goal of obtaining the most rapid and complete recanalization possible, while minimizing vascular damage and hemorrhagic complications. It is paid particular attention to indications and outcomes of the different endovascular stroke therapy devices use, as defined in major clinical trials or current clinical practice. Anterior circulation strokes represent the primary focus of this review.

Different patterns of cardiac sympathetic denervation in tremor-type compared to akinetic-rigid-type Parkinson's disease: molecular imaging with ¹²³I-MIBG

The aim of this study was to evaluate the correlation between the clinical motor phenotypes of Parkinson's disease (PD) and ¹²³I-MIBG myocardial uptake. In total, 53 patients with PD [31 males and 22 females, mean age 62±10 years; 19 Hoehn & Yahr (H&Y) stage 1, 9 stage 1.5, 15 stage 2 and 10 at stage 3] were examined and subdivided into different clinical forms on the basis of dominance of resting tremor (n=19, TDT) and bradykinesia plus rigidity (n=34, ART). This status was correlated with the semi-quantitative analysis of ¹²³I-MIBG myocardial uptake. An age-matched control group of 18 patients was recruited (8 males and 10 females, mean age 62.4±16.3 years). ¹²³I-MIBG myocardial uptake significantly correlated with disease duration in early (r²=0.1894; P=0.0028) and delayed images (r²=0.1795; P=0.0037) in PD patients, while no correlation was found when considering age at examination, UPDRS III motor examination section score and H&Y score. PD patients showed a reduced ¹²³I-MIBG myocardial uptake compared to the control group in early (P=0.0026) and delayed images (P=0.0040), and ¹²³I-MIBG myocardial uptake was significantly lower in delayed images in TDT patients compared with ART patients (P=0.0167). A decrease was detected in the heart-to-mediastinum (H/M) ratio in delayed images compared to that of the early images in TDT patients (P=0.0040) and in the whole PD population (P=0.0012), while no differences were found in ART patients (P=0.1043). The results of the present study revealed that the cardiac sympathetic system is more severely impaired in TDT than in ART patients and ¹²³I-MIBG molecular imaging has the potential help in improving therapeutic planning in these patients.

Coronaric stent-graft deployment in the treatment of carotid blowout

"Carotid blowout syndrome" is defined as a hemorrhage caused by rupture of the carotid artery and its branches, and may be a severe complication of rhinopharyngeal carcinoma. This study aimed to highlight the usefulness and versatility of endovascular stent-graft placement as a rescue treatment in life-threatening carotid blowout syndrome. We describe the unconventional use of a 6 × 5 mm balloon-expandable coronaric covered stent in a patient with a diagnosis of spinocellular rhinopharyngeal carcinoma, followed by carotid blowout syndrome. Although long-term follow-up is needed to assess the eventuality of bleeding recurrence, the immediate clinical results were satisfactory.

Different patterns of nigrostriatal degeneration in tremor type versus the akinetic-rigid and mixed types of Parkinson's disease at the early stages: molecular imaging with 123I-FP-CIT SPECT

The various associations of motor and non-motor symptoms, the onset of motor complications, the cognitive disorder's appearance and other factors make Parkinson's disease (PD) a heterogeneous syndrome with multiple phenotypes. The necessity of discriminating between different forms of PD could have a role in understanding the pathophysiology of extrapyramidal signs with clinical implications. The aim of this study was to evaluate if there is a relationship between the clinical motor phenotypes of PD and the scintigraphic pattern of 123I-FP-CIT single photon emission computed tomography (SPECT). We examined 47 patients with early idiopathic PD (25 males; 22 females; mean age 58±2 years) and subdivided them in different clinical forms on the basis of dominance of resting tremor (n=20), bradykinesia plus rigidity (n=20) and the presence of both clinical signs [mixed type (MT, n=7)]. We correlated this status with the semi-quantitative analysis of SPECT with 123I-FP-CIT. Tremor type patients showed a lower reduction of 123I-FP-CIT uptake compared to akinetic-rigid type patients in contralateral caudate (P=0.0139) and putamen (P=0.0028) nuclei. 123I-FP-CIT uptake was higher in the ipsilateral caudate (P=0.0050) and putamen (P=0.0012) of tremor type patients compared to akinetic-rigid type patients. Comparisons of the striatal uptake in the tremor type and akinetic-rigid type patients with the MT patients revealed significant differences only in the ipsilateral and contralateral caudate. Our data indicate that in akinetic-rigid patients the dopaminergic system is more involved compared to that in the tremor type patients and that this difference is present from the initial stage of the disease. Moreover, our results suggest that PD phenotypes could be related not only to the dopaminergic involvement but also to other systems.