MRI signatures associated with active ischemia and disease severity in cerebral small vessel disease.

Objective: Cerebral small vessel disease, a leading cause of stroke and cognitive impairment, manifests on neuroimaging with white matter hyperintensities (WMH) and disrupted microstructure in normal-appearing white matter. WMH, by definition have high T2 FLAIR signal; however, both T2 FLAIR and T1 signal in WMH are highly variable. We hypothesized that signal intensity parameters would differ in cerebral small vessel disease compared to healthy controls and that signal heterogeneity would be associated with more severe ischemia.

Development and in silico imaging trial evaluation of a deep-learning-based transmission-less attenuation compensation method for DaT SPECT.

Background: Quantitative measures of dopamine transporter (DaT) uptake in the caudate, putamen, and globus pallidus (GP) derived from DaT-single-photon emission computed tomography (SPECT) images are being investigated as biomarkers to diagnose, assess disease status, and track the progression of Parkinsonism. Reliable quantification from DaT-SPECT images requires performing attenuation compensation (AC), typically with a separate x-ray CT scan. Such CT-based AC (CTAC) has multiple challenges, a key one being the non-availability of x-ray CT components on many clinical SPECT systems.

Harmonization of cerebral blood flow measurements by multi-delay 3D gradient and spin echo, and single-delay 2D echo planar imaging.

Purpose: Cerebral blood flow (CBF) is commonly measured by pseudo-continuous arterial spin labeling (PCASL) in human research, but recent advancements in methodology have limited data reuse. The object of this work is to harmonize two distinct PCASL techniques within a cohort with a wide range of CBF values.

Methods: Participants had two PCASL sequences collected within a single session: a single post-label delay sequence with a 2D echo-planar imaging (EPI) readout, " ", and a five post-label delay sequence with gradient and spin echo (GRASE) 3D readout, " ".

Brain Age Modeling and Cognitive Outcomes in Young Adults With and Without Sickle Cell Anemia.

Importance: Both sickle cell anemia (SCA) and socioeconomic status have been associated with altered brain structure and cognitive disability, yet precise mechanisms underlying these associations are unclear.

Objective: To determine whether brains of individuals with and without SCA appear older than chronological age and if brain age modeling using brain age gap (BAG) can estimate cognitive outcomes and mediate the association of socioeconomic status and disease with these outcomes.

Design, Setting, And Participants: In this cross-sectional study of 230 adults with and without SCA, individuals underwent brain magnetic resonance imaging (MRI) and cognitive assessment.

Increased White Matter Aerobic Glycolysis in Multiple Sclerosis.

Objective: Despite treatments which reduce relapses in multiple sclerosis (MS), many patients continue to experience progressive disability accumulation. MS is associated with metabolic disruptions and cerebral metabolic stress predisposes to tissue injury and possibly impaired remyelination. Additionally, myelin homeostasis is metabolically expensive and reliant on glycolysis.

Cerebral Oxygen Metabolic Stress in Children and Adults With Large Vessel Vasculopathy Due to Sickle Cell Disease.

Background And Objectives: Large vessel vasculopathy (LVV), or moyamoya syndrome, increases the risk of stroke in patients with sickle cell disease (SCD), yet effective treatments are lacking. In atherosclerotic carotid disease, previous studies demonstrated elevated oxygen extraction fraction (OEF) as a predictor of ipsilateral stroke. In a SCD cohort, we examined hemispheric hemodynamic and oxygen metabolic dysfunction as tissue-based biomarkers of cerebral ischemic risk in patients with LVV.

Accuracy and Longitudinal Consistency of PET/MR Attenuation Correction in Amyloid PET Imaging amid Software and Hardware Upgrades.

Background And Purpose: Integrated PET/MR allows the simultaneous acquisition of PET biomarkers and structural and functional MRI to study Alzheimer disease (AD). Attenuation correction (AC), crucial for PET quantification, can be performed by using a deep learning approach, DL-Dixon, based on standard Dixon images. Longitudinal amyloid PET imaging, which provides important information about disease progression or treatment responses in AD, is usually acquired over several years.

Intracranial aneurysms in sickle cell disease are associated with hemodynamic stress and anemia.

Although hemodynamic stress plays a key role in aneurysm formation outside of sickle cell disease (SCD), its role is understudied in patients with SCD. We hypothesized that tissue-based markers of hemodynamic stress are associated with aneurysm presence in a prospective SCD cohort. Children and adults with SCD, with and without aneurysms, underwent longitudinal brain magnetic resonance imaging/magnetic resonance angiography (MRA) to assess cerebral blood flow (CBF) and oxygen extraction fraction (OEF).

SPICER: Self-supervised learning for MRI with automatic coil sensitivity estimation and reconstruction.

Purpose: To introduce a novel deep model-based architecture (DMBA), SPICER, that uses pairs of noisy and undersampled k-space measurements of the same object to jointly train a model for MRI reconstruction and automatic coil sensitivity estimation.

Methods: SPICER consists of two modules to simultaneously reconstructs accurate MR images and estimates high-quality coil sensitivity maps (CSMs). The first module, CSM estimation module, uses a convolutional neural network (CNN) to estimate CSMs from the raw measurements.

Comparison of cerebral oxygen extraction fraction using ASE and TRUST methods in patients with sickle cell disease and healthy controls.

Abnormal oxygen extraction fraction (OEF), a putative biomarker of cerebral metabolic stress, may indicate compromised oxygen delivery and ischemic vulnerability in patients with sickle cell disease (SCD). Elevated OEF was observed at the tissue level across the brain using an asymmetric spin echo (ASE) MR method, while variable global OEFs were found from the superior sagittal sinus (SSS) using a T2-relaxation-under-spin-tagging (TRUST) MRI method with different calibration models. In this study, we aimed to compare the average ASE-OEF in the SSS drainage territory and TRUST-OEF in the SSS from the same SCD patients and healthy controls.

Increased theta-low gamma phase-amplitude coupling in resting electroencephalography after intermittent theta burst stimulation.

Objective: Intermittent theta burst stimulation (iTBS) is based on the phase-amplitude coupling (PAC) pattern. We aimed to investigate the effect of iTBS on PAC in resting electroencephalography (EEG), which may provide insight into the underlying mechanism.

Methods: Twenty-one healthy volunteers were recruited and received both active and sham neuroimaging-guided iTBS on two separate days, which was precisely delivered to the right superior temporal gyrus.

Effects of a brief HIIT intervention on cognitive performance in older women.

Cardiorespiratory fitness (CRF) mitigates age-related decline in cognition and brain volume. Little is known, however, about the effects of high-intensity interval training (HIIT) on cognitive aging and the relationship between HIIT, cognition, hippocampal subfield volumes, and cerebral oxygen extraction fraction (OEF). Older sedentary women participated in an 8-week HIIT intervention.

An automatic pipeline for PET/MRI attenuation correction validation in the brain.

Purpose: PET/MRI quantitative accuracy for neurological applications is challenging due to accuracy of the PET attenuation correction. In this work, we proposed and evaluated an automatic pipeline for assessing the quantitative accuracy of four different MRI = based attenuation correction (PET MRAC) approaches.

Methods: The proposed pipeline consists of a synthetic lesion insertion tool and the FreeSurfer neuroimaging analysis framework.

Neuroinflammation and amyloid deposition in the progression of mixed Alzheimer and vascular dementia.

Background: Alzheimer's disease (AD) and vascular contributions to cognitive impairment and dementia (VCID) pathologies coexist in patients with cognitive impairment. Abnormal amyloid beta (Aβ) deposition is the hallmark pathologic biomarker for AD. Neuroinflammation may be a pathophysiological mechanism in both AD and VCID.

Vascular space occupancy asymmetric spin echo (VASO-ASE) for non-invasive quantification of cerebral oxygen extraction fraction.

Purpose: Asymmetric spin echo (ASE) MRI is a method for measuring regional oxygen extraction fraction (OEF); however, extravascular tissue models have been shown to under-estimate OEF. The hypothesis investigated here is that the addition of a vascular-space-occupancy (VASO) pre-pulse will more fully suppress blood water signal and provide global OEF values more consistent with physiological expectation and O positron emission tomography (PET)-validated T -relaxation-under-spin-tagging (TRUST) OEF measures.

Methods: Healthy adults (n = 14; age = 27.

Silent Infarcts, White Matter Integrity, and Oxygen Metabolic Stress in Young Adults With and Without Sickle Cell Trait.

Background: Individuals with sickle cell anemia have heightened risk of stroke and cognitive dysfunction. Given its high prevalence globally, whether sickle cell trait (SCT) is a risk factor for neurological injury has been of interest; however, data have been limited. We hypothesized that young, healthy adults with SCT would show normal cerebrovascular structure and hemodynamic function.

Oxygen Metabolic Stress and White Matter Injury in Patients With Cerebral Small Vessel Disease.

Background: Chronic hypoxia-ischemia is a putative mechanism underlying the development of white matter hyperintensities (WMH) and microstructural disruption in cerebral small vessel disease. WMH fall primarily within deep white matter (WM) watershed regions. We hypothesized that elevated oxygen extraction fraction (OEF), a signature of hypoxia-ischemia, would be detected in the watershed where WMH density is highest.

A Path to Qualification of PET/MRI Scanners for Multicenter Brain Imaging Studies: Evaluation of MRI-Based Attenuation Correction Methods Using a Patient Phantom.

PET/MRI scanners cannot be qualified in the manner adopted for hybrid PET/CT devices. The main hurdle with qualification in PET/MRI is that attenuation correction (AC) cannot be adequately measured in conventional PET phantoms because of the difficulty in converting the MR images of the physical structures (e.g.

The lateralization and reliability of spatial mismatch negativity elicited by auditory deviants with virtual spatial location.

Mismatch negativity (MMN) is an intensively studied event-related potential component that reflects pre-attentive auditory processing. Existing spatial MMN (sMMN) studies usually use loud-speakers in different locations or deliver sound with binaural localization cues through earphones to elicit MMN, which either was practically complicated or sounded unnatural to the subjects. In the present study, we generated head related transfer function (HRTF)-based spatial sounds and verified that the HRTF-based sounds retained the left and the right spatial localization cues.

Deep learning-based T1-enhanced selection of linear attenuation coefficients (DL-TESLA) for PET/MR attenuation correction in dementia neuroimaging.

Purpose: The accuracy of existing PET/MR attenuation correction (AC) has been limited by a lack of correlation between MR signal and tissue electron density. Based on our finding that longitudinal relaxation rate, or R , is associated with CT Hounsfield unit in bone and soft tissues in the brain, we propose a deep learning T -enhanced selection of linear attenuation coefficients (DL-TESLA) method to incorporate quantitative R for PET/MR AC and evaluate its accuracy and longitudinal test-retest repeatability in brain PET/MR imaging.

Methods: DL-TESLA uses a 3D residual UNet (ResUNet) for pseudo-CT (pCT) estimation.

Precise theta burst transcranial magnetic stimulation selectively reduced duration-related mismatch negativity.

Background: Mismatch negativity (MMN) is a typical event-related potential component reflecting pre-attentive processing. MMN impairment, especially reduced duration-related MMN (dMMN), has been suggested as a potential predictive biomarker for the onset of schizophrenia.

Objective: This study attempts to manipulate specific MMN activities using advanced neuroimaging-guided intermittent theta-burst stimulations (iTBS), which will be helpful to uncover the sources of MMN generation and contribute to the development of new clinical treatments.