VICTR: Venous transit time imaging by changes in T1 relaxation

PURPOSE

Abnormalities in cerebral veins are a common finding in many neurological diseases, yet there is a scarcity of MRI techniques to assess venous hemodynamic function. The present study aims to develop a noncontrast technique to measure a novel blood flow circulatory measure, venous transit time (VTT), which denotes the time it takes for water to travel from capillary to major veins.

METHODS

The proposed sequence, venous transit time imaging by changes in T1 relaxation (VICTR), is based on the notion that as water molecules transition from the tissue into the veins, they undergo a change in T1 relaxation time. The validity of the measured VTT was tested by studying the VTT along the anatomically known flow trajectory of venous vessels as well as using a physiological vasoconstrictive challenge of caffeine ingestion. Finally, we compared the VTT measured with VICTR MRI to a bolus-tracking method using gadolinium-based contrast agent.

RESULTS

VTT was measured to be 3116.3 ± 326.0 ms in the posterior superior sagittal sinus (SSS), which was significantly longer than 2865.0 ± 390.8 ms at the anterior superior sagittal sinus (p = 0.004). The test-retest assessment showed an interclass correlation coefficient of 0.964. VTT was significantly increased by 513.8 ± 239.3 ms after caffeine ingestion (p < 0.001). VTT measured with VICTR MRI revealed a strong correlation (R = 0.84, p = 0.002) with that measured with the contrast-based approach. VTT was found inversely correlated to cerebral blood flow and venous oxygenation across individuals.

CONCLUSION

A noncontrast MRI technique, VICTR MRI, was developed to measure the VTT of the brain.

Efficient optimization of an accelerator neutron source for neutron capture therapy using genetic algorithms

BACKGROUND

In recent years, genetic algorithms have been applied in the field of nuclear technology design, producing superior optimization results compared to traditional methods. They can be employed in the design and optimization of beam shaping assemblies (BSA) BSA to obtain the desired neutron beams. But it should be noted that the direct combination of Monte Carlo methods with genetic algorithms requires a significant amount of computational resources and time.

PURPOSE

Design and optimize BSA more efficiently to achieve neutron beams that meet specified recommendations.

METHODS

We propose an approach of NSGA II with crucial variables which are identified by multivariate statistical techniques. This approach significantly reduces the problem sizes, thus reducing the time required for optimization. We illustrate this methodology using the example of BSA design for AB-BNCT.

RESULTS

The computational efficiency has tripled with crucial variables. By using NSGA II, we obtained optimized models conforming to both the new and old version IAEA BNCT guidelines through a single optimization process and subjected them to phantom analysis. The results demonstrate that models obtained through this method can meet the IAEA recommendations with deep advantage depth (AD) and high absorbed ratio (AR).

CONCLUSION

The genetic algorithm with crucial variables displays tremendous potential in addressing BSA optimization challenges.

In vivo mapping of hippocampal venous vasculature and oxygenation using susceptibility imaging at 7T

Mapping the small venous vasculature of the hippocampus in vivo is crucial for understanding how functional changes of hippocampus evolve with age. Oxygen utilization in the hippocampus could serve as a sensitive biomarker for early degenerative changes, surpassing hippocampal tissue atrophy as the main source of information regarding tissue degeneration. Using an ultrahigh field (7T) susceptibility-weighted imaging (SWI) sequence, it is possible to capture oxygen-level dependent contrast of submillimeter-sized vessels. Moreover, the quantitative susceptibility mapping (QSM) results derived from SWI data allow for the simultaneous estimation of venous oxygenation levels, thereby enhancing the understanding of hippocampal function. In this study, we proposed two potential imaging markers in a cohort of 19 healthy volunteers aged between 20 and 74 years. These markers were: 1) hippocampal venous density on SWI images and 2) venous susceptibility (Δχvein) in the hippocampus-associated draining veins (the inferior ventricular veins (IVV) and the basal veins of Rosenthal (BVR) using QSM images). They were chosen specifically to help characterize the oxygen utilization of the human hippocampus and medial temporal lobe (MTL). As part of the analysis, we demonstrated the feasibility of measuring hippocampal venous density and Δχvein in the IVV and BVR at 7T with high spatial resolution (0.25 × 0.25 × 1 mm3). Our results demonstrated the in vivo reconstruction of the hippocampal venous system, providing initial evidence regarding the presence of the venous arch structure within the hippocampus. Furthermore, we evaluated the age effect of the two quantitative estimates and observed a significant increase in Δχvein for the IVV with age (p=0.006, r2 = 0.369). This may suggest the potential application of Δχvein in IVV as a marker for assessing changes in atrophy-related hippocampal oxygen utilization in normal aging and neurodegenerative diseases such as AD and dementia.

Vascular Aging in the Choroid Plexus: A 7T Ultrasmall Superparamagnetic Iron Oxide (USPIO)-MRI Study

BACKGROUND

The choroid plexus (ChP), a densely vascularized structure, has drawn increasing attention for its involvement in brain homeostasis and waste clearance. While the volumetric changes have been explored in many imaging studies, few studies have investigated the vascular degeneration associated with aging in the ChP.

PURPOSE

To investigate the sub-structural characteristics of the ChP, particularly the vascular compartment using high-resolution 7T imaging enhanced with Ferumoxytol, an ultrasmall super-paramagnetic iron oxide, which greatly increase the susceptibility contrast for vessels.

STUDY TYPE

Prospective.

SUBJECTS

Forty-nine subjects without neurological disorders (age: 21-80 years; 42 ± 17 years; 20 females).

FIELD STRENGTH/SEQUENCE

7-T with 2D and 3D T2* GRE, 3D MPRAGE T1, 2D TSE T2, and 2D FLAIR.

ASSESSMENT

The vascular and stromal compartments of the ChP were segmented using K-means clustering on post-contrast 2D GRE images. Visual and qualitative assessment of ChP vascular characteristics were conducted independently by three observers. Vascular density (Volvessel/VolChP ratio) and susceptibility change (Δχ) induced by Ferumoxytol were analyzed on 3D GRE-derived susceptibility-weighted imaging and quantitative susceptibility mapping, respectively.

STATISTICAL TESTS

Independent t-test, Mann-Whitney U test, and Chi-square test were utilized for group comparisons. The relationship between age and ChP's vascular alterations was examined using Pearson's correlation. Intra-class coefficient was calculated for inter-observer agreement. A P value <0.05 was considered statistically significant.

RESULTS

2D GRE images demonstrated superior contrast and accurate delineation of ChP substructures (ICC = 0.86). Older subjects exhibited a significantly smaller vascular density (16.5 ± 4.34%) and lower Δχ (22.10 ± 12.82 ppb) compared to younger subjects (24.85 ± 6.84% and 34.64 ± 12.69 ppb). Vascular density and mean Δχ within the ChP negatively correlated with age (r = -0.48, and r = -0.45).

DATA CONCLUSION

Ferumoxytol-enhanced 7T images can demonstrate ChP alterations in elderly with decreased vascular density and expansion of nonvascular compartment.

EVIDENCE LEVEL

1 TECHNICAL EFFICACY: Stage 2.

Simultaneous perfusion, diffusion, T2 *, and T1 mapping with MR fingerprinting

PURPOSE

Quantitative mapping of brain perfusion, diffusion, T2 *, and T1 has important applications in cerebrovascular diseases. At present, these sequences are performed separately. This study aims to develop a novel MRI technique to simultaneously estimate these parameters.

METHODS

This sequence to measure perfusion, diffusion, T2 *, and T1 mapping with magnetic resonance fingerprinting (MRF) was based on a previously reported MRF-arterial spin labeling (ASL) sequence, but the acquisition module was modified to include different TEs and presence/absence of bipolar diffusion-weighting gradients. We compared parameters derived from the proposed method to those derived from reference methods (i.e., separate sequences of MRF-ASL, conventional spin-echo DWI, and T2 * mapping). Test-retest repeatability and initial clinical application in two patients with stroke were evaluated.

RESULTS

The scan time of our proposed method was 24% shorter than the sum of the reference methods. Parametric maps obtained from the proposed method revealed excellent image quality. Their quantitative values were strongly correlated with those from reference methods and were generally in agreement with values reported in the literature. Repeatability assessment revealed that ADC, T2 *, T1 , and B1 + estimation was highly reliable, with voxelwise coefficient of variation (CoV) <5%. The CoV for arterial transit time and cerebral blood flow was 16% ± 3% and 25% ± 9%, respectively. The results from the two patients with stroke demonstrated that parametric maps derived from the proposed method can detect both ischemic and hemorrhagic stroke.

CONCLUSION

The proposed method is a promising technique for multi-parametric mapping and has potential use in patients with stroke.

Burden of lung cancer attributed to particulate matter pollution in China: an epidemiological study from 1990 to 2019

OBJECTIVES

The aim of this study was to examine the disease burden of lung cancer attributable to particulate matter (PM2.5) pollution in China from 1990 to 2019.

STUDY DESIGN

Data from the Global Burden of Disease Study 2019 were used to estimate the disease burden of tracheal, bronchus and lung cancer attributed to PM2.5 over time in China.

METHODS

Joinpoint regression models were applied to disability-adjusted life years (DALYs) to assess the time trends and estimate the impact of PM2.5 on the overall disease burden of lung cancer. Furthermore, age-period-cohort models were conducted to assess the relationships between lung cancer DALYs attributed to PM2.5 exposure and age, calendar period and birth cohort trends in China from 1990 to 2019.

RESULTS

Lung cancer DALYs attributable to household air pollution from solid fuels decreased with an average annual percent change (AAPC) of 2.9 % per 100,000 population, while those attributable to ambient particular matter pollution (APE) increased (AAPC: -4.7 % per 100,000 population) over the past 30 years. The burden of lung cancer in terms of DALYs in males was higher than in females, and it demonstrated an age-dependent increase. The period and cohort effects also had significant impacts on the DALYs rates of lung cancer attributable to APE, indicating an overall increase in lung cancer DALYs for all age groups in each year.

CONCLUSIONS

This study highlights the need for effective strategies to reduce PM2.5 exposure in China, particularly from outdoor sources. Gender differences and age, period and cohort effects observed in the study provide valuable insights into long-term trends of lung cancer burden attributed to PM2.5.

Reduced Oxygen Extraction Fraction in Deep Cerebral Veins Associated with Cognitive Impairment in Multiple Sclerosis

Studying the relationship between cerebral oxygen utilization and cognitive impairment is essential to understanding neuronal functional changes in the disease progression of multiple sclerosis (MS). This study explores the potential of using venous susceptibility in internal cerebral veins (ICVs) as an imaging biomarker for cognitive impairment in relapsing-remitting MS (RRMS) patients. Quantitative susceptibility mapping derived from fully flow-compensated MRI phase data was employed to directly measure venous blood oxygen saturation levels (SvO2) in the ICVs. Results revealed a significant reduction in the susceptibility of ICVs (212.4 ± 30.8 ppb vs 239.4 ± 25.9 ppb) and a significant increase of SvO2 (74.5 ± 1.89 % vs 72.4 ± 2.23 %) in patients with RRMS compared with age- and sex-matched healthy controls. Both the susceptibility of ICVs (r = 0.646, p = 0.004) and the SvO2 (r = -0.603, p = 0.008) exhibited a strong correlation with cognitive decline in these patients assessed by the Paced Auditory Serial Addition Test, while no significant correlation was observed with clinical disability measured by the Expanded Disability Status Scale. The findings suggest that venous susceptibility in ICVs has the potential to serve as a specific indicator of oxygen metabolism and cognitive function in RRMS.

In Vivo Detection of Age-Related Tortuous Cerebral Small Vessels using Ferumoxytol-enhanced 7T MRI

Histopathological studies suggest that cerebral small vessel tortuosity is crucial in age-related blood flow reduction and cellular degeneration. However, in vivo evidence is lacking. Here, we used Ferumoxytol-enhanced 7T MRI to directly visualize cerebral small vessels (>300 µm), enabling the identification of vascular tortuosity and exploration of its links to age, tissue atrophy, and vascular risk factors. High-resolution 2D/3D gradient echo MRI at 7T enhanced with Ferumoxytol, an ultrasmall superparamagnetic iron oxide (USPIO), was obtained and analyzed for cerebral small medullary artery tortuosity from 37 healthy participants (21-70 years; mean/SD: 38±14 years; 19 females). Tortuous artery count and tortuosity indices were compared between young and old groups. Age effects on vascular tortuosity were examined through partial correlations and multiple linear regression, adjusting for sex, body mass index (BMI), blood pressure (BP), and other vascular risk factors. Associations between tortuous medullary arteries and tissue atrophy, perivascular spaces (PVS), and white matter (WM) hyperintensities were explored. Age and BMI, rather than BP, showed positive correlations with both tortuous artery count and tortuosity indices. A significant correlation existed between the number of tortuous arteries and WM atrophy. WM lesions were found in proximity to or at the distal ends of tortuous medullary arteries, especially within the deep WM. Moreover, the elderly population displayed a higher prevalence of PVS, including those containing enclosed tortuous arteries. Leveraging the blooming effect of Ferumoxytol, 7T MRI excels in directly detecting cerebral small arterial tortuosity in vivo, unveiling its associations with age, BMI, tissue atrophy, WMH and PVS.

[Pay attention to the infectious complications in the clinical application of biological agents]

Biological agents have been widely used in the treatment of many clinical diseases by targeting specific immune cells or cytokines. In the course of clinical use, biological agents can lead to secondary immune deficiency, which increases the risk of infection. At present, there are no evidence-based guidelines or management opinions on the differences of infections caused by various biological agents, how to identify infectious complications in the course of treatment with different biological agents at an early stage, and how to take effective and targeted prevention. This paper summarizes the infection complications and their characteristics that need to be paid attention to in the clinical introduction of biological agents, aiming to help clinicians make reasonable decisions for infection complications in the process of using biological agents, reduce the incidence of infection, and improve the success rate of diagnosis and treatment.

Improving measurement of blood-brain barrier permeability with reduced scan time using deep-learning-derived capillary input function

PURPOSE

In Dynamic contrast-enhanced MRI (DCE-MRI), Arterial Input Function (AIF) has been shown to be a significant contributor to uncertainty in the estimation of kinetic parameters. This study is to assess the feasibility of using a deep learning network to estimate local Capillary Input Function (CIF) to estimate blood-brain barrier (BBB) permeability, while reducing the required scan time.

MATERIALS AND METHOD

A total of 13 healthy subjects (younger (<40 y/o): 8, older (> 67 y/o): 5) were recruited and underwent 25-min DCE-MRI scans. The 25 min data were retrospectively truncated to 10 min to simulate a reduced scan time of 10 min. A deep learning network was trained to predict the CIF using simulated tissue contrast dynamics with two vascular transport models. The BBB permeability (PS) was measured using 3 methods: (i) Ca-25min, using DCE-MRI data of 25 min with individually sampled AIF (Ca); (ii) Ca-10min, using truncated 10min data with AIF (Ca); and (iii) Cp-10min, using truncated 10 min data with CIF (Cp). The PS estimates from the Ca-25min method were used as reference standard values to assess the accuracy of the Ca-10min and Cp-10min methods in estimating the PS values.

RESULTS

When compared to the reference method(Ca-25min), the Ca-10min and Cp-10min methods resulted in an overestimation of PS by 217 ± 241 % and 48.0 ± 30.2 %, respectively. The Bland Altman analysis showed that the mean difference from the reference was 8.85 ± 1.78 (x10-4 min-1) with the Ca-10min, while it was reduced to 1.63 ± 2.25 (x10-4 min-1) with the Cp-10min, resulting in an average reduction of 81%. The limits of agreement also reduced by up to 39.2% with the Cp-10min. We found a 75% increase of BBB permeability in the gray matter and a 35% increase in the white matter, when comparing the older group to the younger group.

CONCLUSIONS

We demonstrated the feasibility of estimating the capillary-level input functions using a deep learning network. We also showed that this method can be used to estimate subtle age-related changes in BBB permeability with reduced scan time, without compromising accuracy. Moreover, the trained deep learning network can automatically select CIF, reducing the potential uncertainty resulting from manual user-intervention.

[Doublecortin-like kinase 1 activates Hippo pathway to promote migration, invasion and proliferation of pancreatic cancer cells]

Objective: To explore the mechanism of Doublecortin-like kinase 1 (DCLK1) in promoting cell migration, invasion and proliferation in pancreatic cancer. Methods: The correlation between DCLK1 and Hippo pathway was analyzed using TCGA and GTEx databases and confirmed by fluorescence staining of pancreatic cancer tissue microarrays. At the cellular level, immunofluorescence staining of cell crawls and western blot assays were performed to clarify whether DCLK1 regulates yes associated protein1 (YAP1), a downstream effector of the Hippo pathway. Reverse transcription-quantitative real-time polymerase chain reaction (RT-qPCR) was used to analyze the expressions of YAP1 binding transcription factor TEA-DNA binding proteins (TEAD) and downstream malignant behavior-promoting molecules CYR61, EDN1, AREG, and CTGF. Transwell test of the DCLK1-overexpressing cells treated with the Hippo pathway inhibitor Verteporfin was used to examine whether the malignant behavior-promoting ability was blocked. Analysis of changes in the proliferation index of experimental cells used real-time label-free cells. Results: TCGA combined with GTEx data analysis showed that the expressions of DCLK1 and YAP1 molecules in pancreatic cancer tissues were significantly higher than those in adjacent tissues (P<0.05). Moreover, DCLK1was positively correlated with the expressions of many effectors in the Hippo pathway, including LATS1 (r=0.53, P<0.001), LATS2 (r=0.34, P<0.001), MOB1B (r=0.40, P<0.001). In addition, the tissue microarray of pancreatic cancer patients was stained with multicolor fluorescence, indicated that the high expression of DCLK1 in pancreatic cancer patients was accompanied by the up-regulated expression of YAP1. The expression of DCLK1 in pancreatic cancer cell lines was analyzed by the CCLE database. The results showed that the expression of DCLK1 in AsPC-1 and PANC-1 cells was low. Thus, we overexpressed DCLK1 in AsPC-1 and PANC-1 cell lines and found that DCLK1 overexpression in pancreatic cancer cell lines promoted YAP1 expression and accessible to the nucleus. In addition, DCLK1 up-regulated the expression of YAP1 binding transcription factor TEAD and increased the mRNA expression levels of downstream malignant behavior-promoting molecules. Finally, Verteporfin, an inhibitor of the Hippo pathway, could antagonize the cell's malignant behavior-promoting ability mediated by high expression of DCLK1. We found that the number of migrated cells with DCLK1 overexpressing AsPC-1 group was 68.33±7.09, which was significantly higher than 22.00±4.58 of DCLK1 overexpressing cells treated with Verteporfin (P<0.05). Similarly, the migration number of PANC-1 cells overexpressing DCLK1 was 65.66±8.73, which was significantly higher than 37.00±6.00 of the control group and 32.33±9.61 of Hippo pathway inhibitor-treated group (P<0.05). Meanwhile, the number of invasive cells in the DCLK1-overexpressed group was significantly higher than that in the DCLK1 wild-type group cells, while the Verteporfin-treated DCLK1-overexpressed cells showed a significant decrease. In addition, we monitored the cell proliferation index using the real-time cellular analysis (RTCA) assay, and the proliferation index of DCLK1-overexpressed AsPC-1 cells was 0.66±0.04, which was significantly higher than 0.38±0.01 of DCLK1 wild-type AsPC-1 cells (P<0.05) as well as 0.05±0.03 of DCLK1-overexpressed AsPC1 cells treated with Verteporfin (P<0.05). PANC-1 cells showed the same pattern, with a proliferation index of 0.77±0.04 for DCLK1-overexpressed PANC-1 cells, significantly higher than DCLK1-overexpressed PANC1 cells after Verteporfin treatment (0.14±0.05, P<0.05). Conclusion: The expression of DCLK1 is remarkably associated with the Hippo pathway, it promotes the migration, invasion, and proliferation of pancreatic cancer cells by activating the Hippo pathway.

Prospective Longitudinal Perfusion in Probable Alzheimer's Disease Correlated with Atrophy in Temporal Lobe

Reduced cerebral blood flow (CBF) in the temporoparietal region and gray matter volumes (GMVs) in the temporal lobe were previously reported in patients with mild cognitive impairment (MCI) and Alzheimer's disease (AD). However, the temporal relationship between reductions in CBF and GMVs requires further investigation. This study sought to determine if reduced CBF is associated with reduced GMVs, or vice versa. Data came from 148 volunteers of the Cardiovascular Health Study Cognition Study (CHS-CS), including 58 normal controls (NC), 50 MCI, and 40 AD who had perfusion and structural MRIs during 2002-2003 (Time 2). Sixty-three of the 148 volunteers had follow-up perfusion and structural MRIs (Time 3). Forty out of the 63 volunteers received prior structural MRIs during 1997-1999 (Time 1). The relationships between GMVs and subsequent CBF changes, and between CBF and subsequent GMV changes were investigated. At Time 2, we observed smaller GMVs (p<0.05) in the temporal pole region in AD compared to NC and MCI. We also found associations between: (1) temporal pole GMVs at Time 2 and subsequent declines in CBF in this region (p=0.0014) and in the temporoparietal region (p=0.0032); (2) hippocampal GMVs at Time 2 and subsequent declines in CBF in the temporoparietal region (p=0.012); and (3) temporal pole CBF at Time 2 and subsequent changes in GMV in this region (p = 0.011). Therefore, hypoperfusion in the temporal pole may be an early event driving its atrophy. Perfusion declines in the temporoparietal and temporal pole follow atrophy in this temporal pole region.

Measuring water exchange on a preclinical MRI system using filter exchange and diffusion time dependent kurtosis imaging

PURPOSE

Filter exchange imaging (FEXI) and diffusion time (t)-dependent diffusion kurtosis imaging (DKI(t)) are both sensitive to water exchange between tissue compartments. The restrictive effects of tissue microstructure, however, introduce bias to the exchange rate obtained by these two methods, as their interpretation conventionally rely on the Kärger model of barrier limited exchange between Gaussian compartments. Here, we investigated whether FEXI and DKI(t) can provide comparable exchange rates in ex vivo mouse brains.

THEORY AND METHODS

FEXI and DKI(t) data were acquired from ex vivo mouse brains on a preclinical MRI system. Phase cycling and negative slice prewinder gradients were used to minimize the interferences from imaging gradients.

RESULTS

In the corpus callosum, apparent exchange rate (AXR) from FEXI correlated with the exchange rate (the inverse of exchange time, 1/τex ) from DKI(t) along the radial direction. In comparison, discrepancies between FEXI and DKI(t) were found in the cortex due to low filter efficiency and confounding effects from tissue microstructure.

CONCLUSION

The results suggest that FEXI and DKI(t) are sensitive to the same exchange processes in white matter when separated from restrictive effects of microstructure. The complex microstructure in gray matter, with potential exchange among multiple compartments and confounding effects of microstructure, still pose a challenge for FEXI and DKI(t).

Three-dimensional multi-parameter brain mapping using MR fingerprinting

The purpose of this study was to develop and test a 3D multi-parameter MR fingerprinting (MRF) method for brain imaging applications. The subject cohort included 5 healthy volunteers, repeatability tests done on 2 healthy volunteers and tested on two multiple sclerosis (MS) patients. A 3D-MRF imaging technique capable of quantifying T1, T2 and T1ρ was used. The imaging sequence was tested in standardized phantoms and 3D-MRF brain imaging with multiple shots (1, 2 and 4) in healthy human volunteers and MS patients. Quantitative parametric maps for T1, T2, T1ρ, were generated. Mean gray matter (GM) and white matter (WM) ROIs were compared for each mapping technique, Bland-Altman plots and intra-class correlation coefficient (ICC) were used to assess repeatability and Student T-tests were used to compare results in MS patients. Standardized phantom studies demonstrated excellent agreement with reference T1/T2/T1ρ mapping techniques. This study demonstrates that the 3D-MRF technique is able to simultaneously quantify T1, T2 and T1ρ for tissue property characterization in a clinically feasible scan time. This multi-parametric approach offers increased potential to detect and differentiate brain lesions and to better test imaging biomarker hypotheses for several neurological diseases, including MS.

[Efficacy and safety of daptomycin in the treatment of gram-positive infective endocarditis: a meta-analysis]

Objective: To assess the efficacy and safety of daptomycin in the treatment of gram-positive infective endocarditis (IE) systematically. Methods: China Biology Medicine Database (CBM), China National Knowledge Internet (CNKI), Wanfang Data, VIP Database, PubMed, Embase, the Cochrane Library, and Web of Science were searched from the time of establishing databases to April 2022 to obtain relevant controlled and uncontrolled studies of daptomycin for gram-positive infective endocarditis, using key search terms ("daptomycin","gram-positive bacterial infections","endocarditis"). We performed literature screening according to inclusion/exclusion criteria, data extraction, and quality assessment, and performed random-effects meta-analyses for pooled results data using R software. Results: A total of 11 studies (including 13 articles) were included. The findings in the three controlled studies showed that in the treatment of staphylococcus aureus endocarditis, there was no statistically significant differences in in-hospital death risk (RR=0.66, 95%CI: 0.24-1.84, P=0.427) and 6-month death risk (RR=1.27, 95%CI: 0.75-2.14, P=0.374) for daptomycin versus anti-staphylococcal penicillin or vancomycin; in the treatment of enterococcal endocarditis, there was no statistically significant difference in death risk (both P>0.05) for daptomycin versus ampicillin combined with ceftriaxone (RR=0.39, 95%CI: 0.06-2.49) and ampicillin or vancomycin plus or minus gentamicin (RR=0.42, 95%CI: 0.05-3.36); and for daptomycin versus ampicillin or vancomycin combined with an aminoglycoside antibiotic, the differences in in-hospital death risk (RR=0.80, 95%CI: 0.11-5.83) and 6-month death risk (RR=0.47, 95%CI: 0.07-3.21) were not statistically significant(both P>0.05). In a cost-effectiveness study, daptomycin as first-line treatment could save the medical cost of 4 037 pounds per patient compared with vancomycin over a longer period of patient treatment. The results of the meta-analysis of uncontrolled studies showed that the mean clinical success rate of daptomycin for left-side endocarditis was 77% (95%CI: 70% to 83%; I²=28%), for MSSA-infective right-side endocarditis was 87% (95%CI: 73%-95%), and for MRSA-infective right-side endocarditis was 78% (95%CI: 38%-95%; I²=49%); while the mortality rate [mean mortality rate for left-side endocarditis was 13% (95%CI: 11%-17%; I²=0); the mortality rate for right-side endocarditis was reported in only 2 studies, 3% and 27%, respectively] or the rate of daptomycin-related adverse events (4%) was within the acceptable ranges for clinical practice. Conclusions: The death risk in the treatment of infective endocarditis with dattomycin is comparable to that of other antibiotics, and the clinical success rate is higher. Some efficacy may be achieved with daptomycin while other treatments are not effective in treating IE.

Seeing is believing: ultra-high field magnetic resonance imaging in vascular and neurodegeneration research

Ultra-high field (UHF) magnetic resonance (MR) refers to a main operating field strength of 7 teslas (T) or higher. UHF MR offers unique opportunities for revealing new insights into the microstructures and functions of the brain that are not available on conventional field strength MR. Recently, the U.S. Food and Drug Administration (FDA) has cleared the 7 T magnetic resonance imaging (MRI) device for clinical use, which has doubled the 7 T systems installed in the US. Central to this powerful evolution is the concomitant increase of signal-to-noise ratio (SNR) and susceptibility contrast at UHF MRI. Compared to 3 T, 7 T offers a 2 to 3-fold increase in image SNR, which will allow us to image high resolution with voxel volume of less than 0.1 mm3, while the largely increased susceptibility or T2* contrast at ultra-high field MRI will be the key benefit for brain imaging. Sequences sensitive to magnetic susceptibility include susceptibility-weighted imaging (SWI) and quantitative susceptibility mapping (QSM). Thanks to the susceptibility-induced blooming effect, small veins at a micro level (e.g. <50 µm) can be seen on 220 x 220 µm matrix size SWI.1 With the strengths being provided on UHF MR, several key clinical benefits are discussed. The perivenous lesion development or central vein sign in multiple sclerosis (MS) has been revealed in vivo for the first time,2 which has proved useful for a differential diagnosis of MS.3 Seven teslas MRI showed improved detection of cortical MS lesions that are consistent with histopathological patterns of cortical demyelinating lesions regarding their cortical layer involvement that are not seen on 3 T MRI.4 The visibility of small venous architecture, including small cortical and medullary veins, has an important implication for tissue oxygen utilization and neuronal degeneration.5 By introducing an ultrasmall-superparamagnetic-iron-oxide (USPIO) contrast agent (e.g., ferumoxytol), the small arterioles can also be seen on 7 T SWI, which allows the detection of small arterial tortuosity in the elderly, likely the major cause of small vessel disease. Seven teslas markedly increased the sensitivity in detecting iron deposition and microbleeds associated with brain structures and lesions, and this provides critical insights on brain pathology, in particular in age-related neurodegenerative diseases. Seven teslas MRI improves the characterization of age-related choroid plexus degeneration, including both volume and signal changes, which may have an impact on waste clearance and cerebrospinal fluid (CSF) production. Figure 1 demonstrates a few representative examples of the potential of 7 T. In summary, seeing the unseen on 7 T provides opportunities not only for an early diagnosis, but also for clinical research of disease mechanisms and treatment strategy development.

The influence of body position on cerebrospinal fluid circulation

Background. Cerebrospinal fluid (CSF) circulation consists of two components, a net flow and a pulsatile flow. CSF is generally believed to be produced through the ventricular choroid plexuses and absorbed in sites such as the subarachnoid granulations and nerve roots, contributing to the net flow. The pulsatile driving forces include cardiac vascular pulsation, respiration and muscular contraction.1 Measuring CSF flow in the upright posture is important because we spend most of our lifetime upright. Methods. Thirty asymptomatic volunteers (age: 22-72; 9 males, 21 females) were scanned in the upright seated and supine position on a 0.6 T multi-position MRI scanner (Fonar, New York, USA). CSF flow and spinal cord pulsation were imaged and quantified at the axial mid-C2 level with cine phase-contrast MRI. Results. In the upright posture, heart rate increased by 10%, and peak CSF diastolic flow decreased by 43% compared to the supine posture.2 In addition, the oscillatory volume of CSF exchanged between the spine and cranium decreased by 37% when going from supine to upright posture, consistent with a previous study.3 This could mean that the amount of time spent in different postures as we age may affect the efficiency of glymphatic brain waste clearance and development of neurodegenerative diseases. A less studied but diagnostically important aspect of CSF flow is the concomitant pulsation of spinal cord and central nervous system (CNS) tissue. For example, it is found that in Alzheimer’s Disease patients, the spinal cord at mid-C2 is pulsating much more in the mid to high frequency range (4 to 8 Hz) compared to normal older people in the supine posture. In the normal population, the mid-C2 spinal cord pulsates much less in the upright posture, with a 40% reduction of peak systolic velocity compared to the supine posture. Other postural differences include the more prominent appearance of nerve roots in the supine posture, shift of venous outflow from jugular veins to epidural/smaller veins, and the slimming of the neck when upright. It is also found that CSF flow is much more sensitive to aging in the upright than in the supine position. More specifically, as we age, heart rate change between postures diminishes and the upright peak systolic/peak-to-peak pressure gradient decreases. Since studies have shown that meditation can slow down brain aging, it would be beneficial to study its effect on CSF flow and the process of brain waste production and clearance. Conclusions. Besides delineating the many significant postural differences in CSF circulation, multi-position CSF imaging is also valuable in diagnosing various diseases such as Chiari malformation,4 Ehlers-Danlos syndrome and tethered cord syndrome in the lumbar spine. Often pathology that is not evident in the traditional supine imaging position can be visualized in other patient positions. Finally, a seminal study5 in rodents found that glymphatic transport is most efficient in the lateral recumbent position compared to supine or prone position, which concluded that posture must be considered in future diagnostic imaging procedures to assess CSF – interstitial fluid (ISF) transport in humans.

<I>In vivo</I> vascular mapping of the human hippocampus using MICRO imaging

BACKGROUND: There is an urgent need for better detection and understanding of vascular abnormalities at the micro-level, where critical vascular nourishment and cellular metabolic changes occur. This is especially the case for structures such as the midbrain and hippocampus, where both the feeding and draining vessels are quite small. The hippocampus is a complex grey matter structure that plays an important role in spatial and episodic memory. It can be affected by a wide range of pathologies including vascular abnormalities. Being able to monitor vascular changes in normal aging in various hippocampal subfields will allow us to better understand vascular vulnerability across the hippocampus. METHODS: We recently introduced the concept of microvascular in-vivo contrast revealed origins (MICRO) protocol to image micro-cerebral vessels.1-3 MICRO uses ferumoxytol, an ultra-small superparamagnetic iron oxides (USPIO) agent, to induce susceptibility in the arteries and veins; and by imaging with high resolution (0.22×0.44×1 mm3) susceptibility weighted imaging sequence (SWI) at 3 T. Although the increased vascular susceptibility enhances the visibility of small sub-voxel vessels, the accompanying strong signal loss of the large vessels deteriorates the local tissue contrast. Hence, data are collected at different time points during a gradual administration (final concentration = 4 mg/kg) of ferumoxytol. Dynamically acquired SWI data were co-registered and combined (phase gradient-based adaptive combination or SWIPGAC) to reduce the blooming artifacts from large vessels, preserving the small-vessel contrast. RESULTS: The presence of ferumoxytol helped to enhance the microvasculature, something that has previously only been demonstrated in cadaver brain studies. Figure 1 shows the difference between the pre-contrast SWI and SWIPGAC data in visualizing the micro-vasculature across four healthy subjects. The intra-hippocampal and superficial major arteries (obtained through a non-linear subtraction method) and veins (obtained by averaging the T1-shortening map, pre-contrast quantitative susceptibility mapping (QSM) and pre-contrast R2* maps) are used as an overlay in the third column to better visualize the major vessels penetrating and draining the hippocampus. The hippocampal fissure, along with the fimbria, granular cell layer of the dentate gyrus and cornu ammonis layers (except for CA1), showed higher micro-vascular density than the other parts of hippocampus. The CA1 region exhibited a significant correlation with age (R=−0.37, p<0.05, n=37). demonstrating an overall loss of hippocampal vascularity in the normal aging process. Moreover, the vascular density reduction was more prominent than the age correlation with the volume reduction (R=−0.1, p>0.05, n=37) of the CA1 subfield. CONCLUSIONS: With this USPIO-induced increase in susceptibility comes the potential to study the cerebral micro-vasculature using high-resolution SWI. There was a strong negative correlation between hippocampal functional vessel density (FVD) (especially in CA1) and age. This FVD reduction was more prominent than volume reduction vs age, suggesting that vascular atrophy may precede reductions in tissue volume. Mapping the hippocampal vasculature has immediate implications for understanding the effects of normal aging and the etiology of many neurovascular diseases. MICRO imaging brings us into the decade of imaging the microvasculature of the entire human body.

<I>In vivo</I> mapping of hippocampal venous vasculature and oxygen saturation using dual-echo SWI/QSM at 7 T: a potential marker for neurodegeneration

Background: The current understanding of the venous system in the hippocampus is mostly based on histological and autopsy studies.1 However, the main disadvantage is that it only reveals the anatomy of the vascular system at the post-mortem stage and lacks physiological aspects associated with neuronal metabolism. In vivo characterization of the venous system using susceptibility weighted imaging (SWI) at 7 T could provide valuable information on both venous anatomy and blood oxygen saturation, through high-resolution SWI venography2 and quantitative susceptibility mapping (QSM).3 In this study, we aim to elucidate the hierarchical network of the hippocampal venous system and then test the feasibility of using venous susceptibility to characterize venous oxygenation level changes related to neurodegeneration. Methods: Seven healthy volunteers were recruited for this study. We used high in-plane resolution of flow-compensated dual-echo gradient echo sequence (TE1/TE2/TR=7.5/15/22 ms, voxel size: 0.25*0.25*1 mm). SWI and QSM were then reconstructed using the iterative SWI and mapping (iterative SWIM) algorithm,3 as shown in Figure 1. Hippocampus masks were extracted from the T1-MPRAGE image, which was transformed to SWI space afterwards. To reduce the partial volume effect from the tissue-vessel boundary, we extract the venous susceptibility value from each voxel along the centerline of the vessels. Results: High-resolution in vivo mapping of hippocampal venous vasculature exhibits a high analogy to Duvernoy’s reference4 for hippocampal vascularization. As shown in Figure 1, there is a shape of venous arch near the fimbria of the hippocampus, and small veins extending through the arch are possibly the intrahippocampal veins. The intrahippocampal veins will eventually reach the inferior ventricular vein (IVV) (anteriorly) and medial atrial vein (MAV) (posteriorly), before joining the basal vein of Rosenthal (BVR). For venous susceptibility quantification, Figure 1 shows the representative color-coded QSM for centerline extraction on BVR. Conclusions: Our results showed improved visualization of the micro venous system in the hippocampus using high-resolution 7 T SWI data without the contrast agent.5 In summary, the characterization of venous QSM in major tributaries related to the hippocampus offers a novel perspective on oxygen utilization in the hippocampus, which may be useful for studying age-related dementia. We delineated the hierarchical network of the hippocampus venous system using SWI/QSM at 7 T and extract the venous density and venous susceptibility value in hippocampus-related small veins and major venous tributaries, as an overall measure for venous oxygenation level related to the hippocampus, which may be used as an early marker for hippocampal atrophy in Alzheimer’s disease.

Relationship of grey matter and white matter changes the visibility of perivascular space across normative lifespan

Background: Perivascular space (PVS), also known as Virchow-Robin space, has been recently recognized as one of the most important components in the glymphatic system of the brain,1 which is closely related to waste and toxins clearance in the brain. On T1- and T2-weighted images, PVS has similar signal intensities to cerebrospinal fluid (CSF), which are frequently observed in the centrum semiovale (CSO) and basal ganglia (BG) regions. A previous study2 has shown that PVS increases with age and enlarged PVS was deemed associated with neurodegenerative and vascular abnormalities in the elderly.3 Although the exact mechanism is still elusive, more evidence showed visible PVS in younger adults or even at the adolescent stage. In this study, we use the human connectome project (HCP) lifespan pilot cohort to characterize the relationship of neuronal tissue to PVS visibility across the normative lifespan. Methods: T1-weighted (0.8mm isotropic, TE/TR=2.12/2400 ms), T2-weighted (0.8mm isotropic, TE/TR=563/3200 ms), and diffusion magnetic resonance imaging (MRI) (1.5 mm isotropic, dir80) data were used from HCP lifespan pilot project (N=27, F/M: 12/15, age 8-75 years). PVS segmentation in white matter (WM) and BG was performed using the same method described in Sepehrband et al.4 (Figure 1). WM PVS volume fraction was calculated by dividing the total PVS volume by WM volume. Pearson correlation and one-way ANOVA were used for statistical analysis. Results: The grey matter (GM) volume fraction is negatively correlated with WM PVS volume (p<0.001, R2=0.374). In addition, we have observed an increase in PVS volume fraction in WM across the lifespan, but there is no significant difference in PVS volume fraction before the age of 55. From an age group range of 8-35 years old, the visible PVS is mostly located in CSO, less PVS is observed in the BG region. However, on the other hand, in the elderly group (age >65 years), high-visibility of PVS is observed both in WM and BG regions. Conclusions: Across the normative lifespan, PVS appearance is negatively correlated with the GM atrophy index, indicating the potential usage of PVS as a marker of neurodegeneration. In WM, we reported that increased PVS is associated with advancing age, which is consistent with previous reports.2 Interestingly, we found that in adolescent populations, the PVS occurs mostly in CSO but not in the BG region. In CSO, as shown from fiber orientation distribution analysis, the PVS is mainly located in crossing fiber regions with lower fiber density. However, In BG regions, the PVS occurs in deep GM nuclei (caudate, putamen) and major fiber tracts such as internal capsules or cortical spinal tracts, which are more densely packed compared to crossing-fibers in CSO. Previous studies have reported that the WM blood flow is inversely correlated with FA,5 the tightly structured fibers tend to show lower blood flow if compared to loosened ones. The high visibility of PVS in CSO may also be due to more loosened fiber structures, which lead to more axonal spaces for PVS fluid movement.

Improving the estimation of subtle blood-brain barrier permeability changes in aging using a deep learning approach

Background: Increasing evidence suggests detecting the subtle changes in blood-brain barrier (BBB) permeability in normal aging and in Alzheimer’s disease by using dynamic contrast-enhanced MRI (DCE-MRI) (Figure 1).1,2 However, measuring these subtle changes poses a great challenge for accurate measurement, resulting in inconsistent results among previous studies.1,2 Two major challenges are long scan times, as suggested by other studies, and the selection of the arterial input function (AIF). In this study, we aim to estimate the capillary level input function (CIF) using a deep learning network to overcome these two challenges. Methods: Healthy volunteers (n=12, age 21-78) were recruited for DCE-MRI scan for 28 min. Golden-angle radial sampling parallel (GRASP) sequence was used to obtain the dynamic images at ~5s/frame. Individual AIF was sampled from the superior sagittal sinus of the brain. FSL3 was used to segment the gray and white matter. Each voxel was fitted using the graphical Patlak model4 to assess the vascular permeability-surface area product (PS) for both 28-min data and 10-min truncated data. We used a 3x3 kernel sliding through the images, and feed each voxel’s dynamic as the input to our vision-transformer.5 Training data were generated using individual AIFs with a mathematical model and used to simulate dynamic patches using the extended Patlak model.4 Results: The conventional approach with AIF results in the majority of voxels exhibiting negative PS, regardless of scan time. This is not physiologically valid, as this indicates the contrast agent extravasates into the vessel. However, the proposed approach with the network-predicted CIF results in most voxels in positive PS, even with a scan-time of 10 min. The estimated PS levels are in good accordance with the previous studies.1 Due to the limited sample size, we could not find the difference in BBB permeability between young and old groups. Conclusions: Our approach showed promising quantification of subtle permeability. The results in this study suggest that our proposed CIF-based approach provides an appropriate input function for DCE analysis, allowing assessment of subtle permeability changes in the BBB even with a reduced scan time of 10 min. Future studies will include larger cohorts to investigate the BBB permeability changes in normal aging.

Blood-brain barrier permeability in response to caffeine challenge

PURPOSE

Caffeine is known to alter brain perfusion by acting as an adenosine antagonist, but its effect on blood-brain barrier (BBB) permeability is not fully elucidated. This study aimed to dynamically monitor BBB permeability to water after a single dose of caffeine tablet using a non-contrast MRI technique.

METHODS

Ten young healthy volunteers who were not regular coffee drinkers were studied. The experiment began with a pre-caffeine measurement, followed by four measurements at the post-caffeine stage. Water-extraction-with-phase-contrast-arterial-spin-tagging (WEPCAST) MRI was used to assess the time dependence of BBB permeability to water following the ingestion of 200 mg caffeine. Other cerebral physiological parameters including cerebral blood flow (CBF), venous oxygenation (Yv ), and cerebral metabolic rate of oxygen (CMRO2 ) were also examined. The relationships between cerebral physiological parameters and time were studied with mixed-effect models.

RESULTS

It was found that, after caffeine ingestion, CBF and Yv showed a time-dependent decrease (p < 0.001), while CMRO2 did not change significantly. The fraction of arterial water crossing the BBB (E) showed a significant increase (p < 0.001). In contrast, the permeability-surface-area product (PS), i.e., BBB permeability to water, remained constant (p = 0.94). Additionally, it was observed that changes in physiological parameters were non-linear with regard to time and occurred at as early as 9 min after caffeine tablet ingestion.

CONCLUSION

These results suggest an unchanged BBB permeability despite alterations in perfusion during a vasoconstrictive caffeine challenge.

Cerebral metabolic rate of oxygen (CMRO2) changes measured with simultaneous tDCS-MRI in healthy adults

BACKGROUND

Transcranial direct current stimulation (tDCS) is a safe and well-tolerated noninvasive technique used for cortical excitability modulation. tDCS has been extensively investigated for its clinical applications; however further understanding of its underlying in-vivo physiological mechanisms remains a fundamental focus of current research.

OBJECTIVES

We investigated the simultaneous effects of tDCS on cerebral blood flow (CBF), venous blood oxygenation (Yv) and cerebral metabolic rate of oxygen (CMRO₂) using simultaneous MRI in healthy adults to provide a reference frame for its neurobiological mechanisms.

METHODS

Twenty-three healthy participants (age = 35.6 ± 15.0 years old, 10 males) completed a simultaneous tDCS-MRI session in a 3 T scanner fitted with a 64-channels head coil. A MR-compatible tDCS device was used to acquire CBF, Yv and CMRO₂ at three time points: pre-, during- and post- 15 minutes of 2.0 mA tDCS on left anodal dorsolateral prefrontal cortex.

RESULTS

During tDCS, CBF significantly increased (57.10 ± 8.33 mL/100g/min) from baseline (53.67 ± 7.75 mL/100g/min; p < 0.0001) and remained elevated in post-tDCS (56.79 ± 8.70 mL/100g/min). Venous blood oxygenation levels measured in pre-tDCS (60.71 ± 4.12 %) did not significantly change across the three timepoints. The resulting CMRO₂ significantly increased by 5.9 % during-tDCS (175.68 ± 30.78 µmol/100g/min) compared to pre-tDCS (165.84 ± 25.32 µmol/100g/min; p = 0.0015), maintaining increased levels in post-tDCS (176.86 ± 28.58 µmol/100g/min).

CONCLUSIONS

tDCS has immediate effects on neuronal excitability, as measured by increased cerebral blood supply and oxygen consumption supporting increased neuronal firing. These findings provide a standard range of CBF and CMRO₂ changes due to tDCS in healthy adults that may be incorporated in clinical studies to evaluate its therapeutic potential.

Reduced white matter venous density on MRI is associated with neurodegeneration and cognitive impairment in the elderly

High-resolution susceptibility weighted imaging (SWI) provides unique contrast to small venous vasculature. The conspicuity of these mesoscopic veins, such as deep medullary veins in white matter, is subject to change from SWI venography when venous oxygenation in these veins is altered due to oxygenated blood susceptibility changes. The changes of visualization in small veins shows potential to depict regional changes of oxygen utilization and/or vascular density changes in the aging brain. The goal of this study was to use WM venous density to quantify small vein visibility in WM and investigate its relationship with neurodegenerative features, white matter hyperintensities (WMHs), and cognitive/functional status in elderly subjects (N = 137). WM venous density was significantly associated with neurodegeneration characterized by brain atrophy (β = 0.046± 0.01, p < 0.001), but no significant association was found between WM venous density and WMHs lesion load (p = 0.3963). Further analysis of clinical features revealed a negative trend of WM venous density with the sum-of-boxes of Clinical Dementia Rating and a significant association with category fluency (1-min animal naming). These results suggest that WM venous density on SWI can be used as a sensitive marker to characterize cerebral oxygen metabolism and different stages of cognitive and functional status in neurodegenerative diseases.

The role of booster vaccination and ongoing viral evolution in seasonal circulation of SARS-CoV-2

Periodic resurgences of COVID-19 in the coming years can be expected, while public health interventions may be able to reduce their intensity. We used a transmission model to assess how the use of booster doses and non-pharmaceutical interventions (NPIs) amid ongoing pathogen evolution might influence future transmission waves. We find that incidence is likely to increase as NPIs relax, with a second seasonally driven surge expected in autumn 2022. However, booster doses can greatly reduce the intensity of both waves and reduce cumulative deaths by 20% between 7 January 2022 and 7 January 2023. Reintroducing NPIs during the autumn as incidence begins to increase again could also be impactful. Combining boosters and NPIs results in a 30% decrease in cumulative deaths, with potential for greater impacts if variant-adapted boosters are used. Reintroducing these NPIs in autumn 2022 as transmission rates increase provides similar benefits to sustaining NPIs indefinitely (307 000 deaths with indefinite NPIs and boosters compared with 304 000 deaths with transient NPIs and boosters). If novel variants with increased transmissibility or immune escape emerge, deaths will be higher, but vaccination and NPIs are expected to remain effective tools to decrease both cumulative and peak health system burden, providing proportionally similar relative impacts.

Comparison of serum neurodegenerative biomarkers among hospitalized COVID-19 patients versus non-COVID subjects with normal cognition, mild cognitive impairment, or Alzheimer's dementia

INTRODUCTION

Neurological complications among hospitalized COVID-19 patients may be associated with elevated neurodegenerative biomarkers.

METHODS

Among hospitalized COVID-19 patients without a history of dementia (N = 251), we compared serum total tau (t-tau), phosphorylated tau-181 (p-tau181), glial fibrillary acidic protein (GFAP), neurofilament light chain (NfL), ubiquitin carboxy-terminal hydrolase L1 (UCHL1), and amyloid beta (Aβ40,42) between patients with or without encephalopathy, in-hospital death versus survival, and discharge home versus other dispositions. COVID-19 patient biomarker levels were also compared to non-COVID cognitively normal, mild cognitive impairment (MCI), and Alzheimer's disease (AD) dementia controls (N = 161).

RESULTS

Admission t-tau, p-tau181, GFAP, and NfL were significantly elevated in patients with encephalopathy and in those who died in-hospital, while t-tau, GFAP, and NfL were significantly lower in those discharged home. These markers correlated with severity of COVID illness. NfL, GFAP, and UCHL1 were higher in COVID patients than in non-COVID controls with MCI or AD.

DISCUSSION

Neurodegenerative biomarkers were elevated to levels observed in AD dementia and associated with encephalopathy and worse outcomes among hospitalized COVID-19 patients.

Age-Related Tortuosity of Carotid and Vertebral Arteries: Quantitative Evaluation With MR Angiography

Background and Purpose

The vascular tortuosity (VT) of the internal carotid artery (ICA), and vertebral artery (VA) can impact blood flow and neuronal function. However, few studies involved quantitative investigation of VT based on magnetic resonance imaging (MRI). The main purpose of our study was to evaluate the age and gender effects on ICA and VA regarding the tortuosity and flow changes by applying automatic vessel segmentation, centerline tracking, and phase mapping on MR angiography.

Methods

A total of 247 subjects (86 males and 161 females) without neurological diseases participated in this study. All subjects obtained T1-weighted MRI, 3D time-of-flight MR angiography, and 2D phase-contrast (PC) MRI scans. To generate quantitative tortuosity metrics from TOF images, the vessel segmentation and centerline tracking were implemented based on Otsu thresholding and fast marching algorithms, respectively. Blood flow and velocity were measured using PC MRI. Among the 247 subjects, 144 subjects (≤ 60 years, 49 males/95 females) were categorized as the young group; 103 subjects (>60 years, 37 males/66 females) were categorized as the old group.

Results

Independent t-test showed that older subjects had higher tortuosity metrics, whereas lower blood flow and velocity than young subjects (p < 0.0025, Bonferroni-corrected). Cerebral blood flow calculated using the sum flux of four target arteries normalized by the brain mass also showed significantly lower values in older subjects (p < 0.001). The age was observed to be positively correlated with the VT metrics. Compared to the males, the females demonstrated higher geometric indices within VAs as well as faster age-related vascular profile changes. After adjusting age and gender as covariates, maximum blood velocity is negatively correlated with geometric measurements. No association was observed between blood flux and geometric measures.

Conclusions

Vascular auto-segmentation, centerline tracking, and phase mapping provide promising quantitative assessments of tortuosity and its effects on blood flow. The neck arteries demonstrate quantifiable and significant age-related morphological and hemodynamic alterations. Moreover, females showed more distinct vascular changes with age. Our work is built upon a comprehensive quantitative investigation of a large cohort of populations covering adult lifespan using MRI, the results can serve as reference ranges of each decade in the general population.

727 BOOSTING BONE HEALTH: IMPROVING JUNIOR DOCTORS’ CONFIDENCE IN ASSESSING AND MANAGING FRAGILITY FRACTURES

Introduction

Fragility fractures are a major disease burden in the UK. With an ageing population and number of fragility fractures predicted to double in 50 years, prevention in this high-risk population needs to be addressed. This audit aimed to examine the assessment of fracture risk in patients presenting with fragility fractures and improve awareness amongst trainee doctors through education.

Methods

A retrospective study was conducted on patients over 65 years admitted with fragility fractures, excluding neck of femur, from January to March 2021 (n = 51). Data was collected on Fracture Risk Assessment Tool (FRAX) scores, dual energy X-ray absorptiometry (DEXA) scans, and risk factors including body mass index (BMI), previous fragility fracture, smoking, alcohol intake, and serum calcium and vitamin D. A teaching seminar for junior doctors was delivered to increase confidence in assessing and managing fragility fractures.

Results

The mean age of patients was 79, with most common presentations being proximal humerus, distal femur and ankle fractures. 46% of patients had a previous fragility fracture. Smoking and alcohol history were documented in 72% and 60% of patients respectively, and 29% had BMIs calculated. 68% had calcium and 45% had vitamin D checked. DEXA scans occurred in 12%, all of whom had osteopenia or osteoporosis. Over half of patients were already on bone protection and 28% were subsequently started on bisphosphonates. A teaching session was delivered to junior doctors (n = 10), leading to improved confidence in assessing fracture risk by 30%, and improved confidence in managing fragility fractures by 35%. Knowledge of FRAX score increased from 62% to 100%.

Conclusion

A significant proportion of the over-65 population are likely to present with fragility fractures. Improving awareness and confidence amongst junior doctors can lead to identification of risk factors and help better prevent and manage fragility fractures in this high-risk population.

Virtual mouse brain histology from multi-contrast MRI via deep learning

¹H MRI maps brain structure and function non-invasively through versatile contrasts that exploit inhomogeneity in tissue micro-environments. Inferring histopathological information from magnetic resonance imaging (MRI) findings, however, remains challenging due to absence of direct links between MRI signals and cellular structures. Here, we show that deep convolutional neural networks, developed using co-registered multi-contrast MRI and histological data of the mouse brain, can estimate histological staining intensity directly from MRI signals at each voxel. The results provide three-dimensional maps of axons and myelin with tissue contrasts that closely mimic target histology and enhanced sensitivity and specificity compared to conventional MRI markers. Furthermore, the relative contribution of each MRI contrast within the networks can be used to optimize multi-contrast MRI acquisition. We anticipate our method to be a starting point for translation of MRI results into easy-to-understand virtual histology for neurobiologists and provide resources for validating novel MRI techniques.

Prediction and verification of survival in patients with non-small-cell lung cancer based on an integrated radiomics nomogram

AIM

To develop and validate a nomogram to predict 1-, 2-, and 5-year survival in patients with non-small-cell lung cancer (NSCLC) by combining optimised radiomics features, clinicopathological factors, and conventional image features extracted from three-dimensional (3D) computed tomography (CT) images.

MATERIALS AND METHODS

A total of 172 patients with NSCLC were selected to construct the model, and 74 and 72 patients were selected for internal validation and external testing, respectively. A total of 828 radiomics features were extracted from each patient's 3D CT images. Univariable Cox regression and least absolute shrinkage and selection operator (LASSO) regression were used to select features and generate a radiomics signature (radscore). The performance of the nomogram was evaluated by calibration curves, clinical practicability, and the c-index. Kaplan-Meier (KM) analysis was used to compare the overall survival (OS) between the two subgroups.

RESULT

The radiomics features of the NSCLC patients correlated significantly with survival time. The c-indexes of the nomogram in the training cohort, internal validation cohort, and external test cohort were 0.670, 0.658, and 0.660, respectively. The calibration curves showed that the predicted survival time was close to the actual survival time. Decision curve analysis shows that the nomogram could be useful in the clinic. According to KM analysis, the 1-, 2- and 5-year survival rates of the low-risk group were higher than those of the high-risk group.

CONCLUSION

The nomogram, combining the radscore, clinicopathological factors, and conventional CT parameters, can improve the accuracy of survival prediction in patients with NSCLC.

Upright versus supine MRI: effects of body position on craniocervical CSF flow

Background

Cerebrospinal fluid (CSF) circulation between the brain and spinal canal, as part of the glymphatic system, provides homeostatic support to brain functions and waste clearance. Recently, it has been observed that CSF flow is strongly driven by cardiovascular brain pulsation, and affected by body orientation. The advancement of MRI has allowed for non-invasive examination of the CSF hydrodynamic properties. However, very few studies have addressed their relationship with body position (e.g., upright versus supine). It is important to understand how CSF hydrodynamics are altered by body position change in a single cardiac phase and how cumulative long hours staying in either upright or supine position can affect craniocervical CSF flow.

Methods

In this study, we investigate the changes in CSF flow at the craniocervical region with flow-sensitive MRI when subjects are moved from upright to supine position. 30 healthy volunteers were imaged in upright and supine positions using an upright MRI. The cranio-caudal and caudo-cranial CSF flow, velocity and stroke volume were measured at the C2 spinal level over one cardiac cycle using phase contrast MRI. Statistical analysis was performed to identify differences in CSF flow properties between the two positions.

Results

CSF stroke volume per cardiac cycle, representing CSF volume oscillating in and out of the cranium, was ~ 57.6% greater in supine (p < 0.0001), due to a ~ 83.8% increase in caudo-cranial CSF peak velocity during diastole (p < 0.0001) and extended systolic phase duration when moving from upright (0.25 ± 0.05 s) to supine (0.34 ± 0.08 s; p < 0.0001). Extrapolation to a 24 h timeframe showed significantly larger total CSF volume exchanged at C2 with 10 h spent supine versus only 5 h (p < 0.0001).

Conclusions

In summary, body position has significant effects on CSF flow in and out of the cranium, with more CSF oscillating in supine compared to upright position. Such difference was driven by an increased caudo-cranial diastolic CSF velocity and an increased systolic phase duration when moving from upright to supine position. Extrapolation to a 24 h timeframe suggests that more time spent in supine position increases total amount of CSF exchange, which may play a beneficial role in waste clearance in the brain.

Clinical outcomes of keratinized mucosa augmentation in jaws reconstructed with fibula or iliac bone flaps

This prospective study was undertaken to evaluate the treatment outcomes of keratinized mucosa augmentation (KMA) on the buccal and palatal/lingual sides of implants in jaws reconstructed after oncological surgery. Forty-two implants in 12 patients whose jaws had been reconstructed with a fibula or iliac bone flap were included. KMA was performed at 3 months after implant placement; this included an apically displaced partial-thickness flap and a free gingival graft (FGG) around the implants to increase the keratinized mucosa width (KMW). Patients were followed up for at least 6 months post-surgery. KMW, shrinkage, and patient pain and discomfort measured on a visual analogue scale were analysed. A histological analysis was performed of tissue epithelium from two patients. The results showed that KMW was >2 mm on both the buccal and palatal/lingual sides during follow-up. Before surgery, histological analysis showed epithelium with no epithelial spikes; normal keratinized epithelial spikes were observed at 8 weeks after KMA. Greater KMW was observed around implants in reconstructed maxillae than around those in reconstructed mandibles (P < 0.001). Patients felt more pain at the donor site than at the recipient site during the first 3 days post-surgery. KMA with FGG was predictable in reconstructed jaws and may help maintain the long-term stability of implants.

Bilateral Distance Partition of Periventricular and Deep White Matter Hyperintensities: Performance of the Method in the Aging Brain

RATIONALE AND OBJECTIVES

Periventricular and deep white matter hyperintensities (WMHs) in the elderly have been reported with distinctive roles in the progression of cognitive decline and dementia. However, the definition of these two subregions of WMHs is arbitrary and varies across studies. Here, we evaluate three partition methods for WMH subregions, including two widely used conventional methods (CV & D10) and one novel method based on bilateral distance (BD).

MATERIALS AND METHODS

The three partition methods were assessed on the MRI scans of 60 subjects, with 20 normal control, 20 mild cognitive impairment, and 20 Alzheimer's disease (AD). Resulting WMH subregional volumes were (1) compared among different partition methods and subject groups, and (2) tested for clinical associations with cognition and dementia. Inter-rater, intrarater, and interscan reproducibility of WMHs volumes were tested on 12 randomly selected subjects from the 60.

RESULTS

For all three partition methods, increased periventricular WMHs were found for AD subjects over normal control. For BD and D10, but not CV method, increased Periventricular WMHs were found for AD subjects over mild cognitive impairment. Significant correlations were found between PVWMHs and Mini-Mental State Examination, Montreal Cognitive Assessment, and Clinical Dementia Rating scores. Furthermore, PVWMHs under BD partition showed higher correlations than D10 and CV. High intrarater and interscan reproducibility (ICCA = 0.998 and 0.992 correspondingly) and substantial inter-rater reproducibility (ICCA = 0.886) were detected.

CONCLUSION

Different WMH partition methods showed comparable diagnostic abilities. The proposed BD method showed advantages in quantifying PVWMH over conventional CV and D10 methods, in terms of higher consistency, larger contrast, and higher diagnosis accuracy. Furthermore, the PVWMH under BD partition showed stronger clinical correlations than conventional methods.

Transcript expression profiling of fibromelanosis-related genes in black-bone chickens

1. The aim of the present study was to identify differentially expressed genes (DEGs) and metabolic pathways involved in this phenotype. Fibromelanosis is the most striking feature of black-bone chickens, such as the Silkie and Dongxiang indigenous breeds. Due to the accumulation of eumelanin in connective tissues, fibromelanosis manifests as black colouration of the skin, muscles, gut, and periosteum. Studies on fibromelanosis can provide useful information pertaining to human diseases and offer commercial value to the poultry industry. However, the genetic basis of fibromelanosis remains unclear.2. Digital gene expression analysis was performed on black and white skin samples collected from the HW1 black-bone chicken line to detect differences in genome-wide expression patterns. A total of >30 billion bp were sequenced, and 2,707,926,466 bp and 2,948,782,964 bp of clean data obtained for creation of libraries for black and white skin, respectively. In total, 252 DEGs from 15,508 mapped genes were identified with 83 up-regulated in white skin and 169 up-regulated in black skin.3. Gene ontology analysis highlighted that genes from the extracellular region and associated components were abundant among the DEGs. Pathway analysis revealed that many DEGs were linked to amino acid metabolism and the immune system. qRT-PCR validation using 14 genes showed good conformity with the sequence analysis of fibromelanosis-related genes.4. The results showed that L-dopachrometautomerase precursor (DCT), tyrosine aminotransferase (TAT), 4-hydroxyphenylpyruvate dioxygenase (HPD) from the tyrosine metabolism pathway, coagulation factor II (F2), fibrinogen beta chain (FGB), plasminogen (PLG) and complement component 7 (C7) from the complement and coagulation cascades were important genes in the fibromelanosis process in black-bone chickens. These candidate genes require further correlation analysis and functional verification.