High resolution and contrast 7 tesla MR brain imaging of the neonate

Introduction

Ultra-high field MR imaging offers marked gains in signal-to-noise ratio, spatial resolution, and contrast which translate to improved pathological and anatomical sensitivity. These benefits are particularly relevant for the neonatal brain which is rapidly developing and sensitive to injury. However, experience of imaging neonates at 7T has been limited due to regulatory, safety, and practical considerations. We aimed to establish a program for safely acquiring high resolution and contrast brain images from neonates on a 7T system.

Methods

Images were acquired from 35 neonates on 44 occasions (median age 39 + 6 postmenstrual weeks, range 33 + 4 to 52 + 6; median body weight 2.93 kg, range 1.57 to 5.3 kg) over a median time of 49 mins 30 s. Peripheral body temperature and physiological measures were recorded throughout scanning. Acquired sequences included T2 weighted (TSE), Actual Flip angle Imaging (AFI), functional MRI (BOLD EPI), susceptibility weighted imaging (SWI), and MR spectroscopy (STEAM).

Results

There was no significant difference between temperature before and after scanning (p = 0.76) and image quality assessment compared favorably to state-of-the-art 3T acquisitions. Anatomical imaging demonstrated excellent sensitivity to structures which are typically hard to visualize at lower field strengths including the hippocampus, cerebellum, and vasculature. Images were also acquired with contrast mechanisms which are enhanced at ultra-high field including susceptibility weighted imaging, functional MRI, and MR spectroscopy.

Discussion

We demonstrate safety and feasibility of imaging vulnerable neonates at ultra-high field and highlight the untapped potential for providing important new insights into brain development and pathological processes during this critical phase of early life.

Data‐driven motion‐corrected brain MRI incorporating pose‐dependent B 0 fields

Purpose

To develop a fully data‐driven retrospective intrascan motion‐correction framework for volumetric brain MRI at ultrahigh field (7 Tesla) that includes modeling of pose‐dependent changes in polarizing magnetic (B₀) fields.

Theory and Methods

Tissue susceptibility induces spatially varying B₀ distributions in the head, which change with pose. A physics‐inspired B₀ model has been deployed to model the B₀ variations in the head and was validated in vivo. This model is integrated into a forward parallel imaging model for imaging in the presence of motion. Our proposal minimizes the number of added parameters, enabling the developed framework to estimate dynamic B₀ variations from appropriately acquired data without requiring navigators. The effect on data‐driven motion correction is validated in simulations and in vivo.

Results

The applicability of the physics‐inspired B₀ model was confirmed in vivo. Simulations show the need to include the pose‐dependent B₀ fields in the reconstruction to improve motion‐correction performance and the feasibility of estimating B₀ evolution from the acquired data. The proposed motion and B₀ correction showed improved image quality for strongly corrupted data at 7 Tesla in simulations and in vivo.

Conclusion

We have developed a motion‐correction framework that accounts for and estimates pose‐dependent B₀ fields. The method improves current state‐of‐the‐art data‐driven motion‐correction techniques when B₀ dependencies cannot be neglected. The use of a compact physics‐inspired B₀ model together with leveraging the parallel imaging encoding redundancy and previously proposed optimized sampling patterns enables a purely data‐driven approach.

Polybrominated diphenyl ethers and perfluorinated alkyl substances in blood serum of New Zealand adults, 2011-2013

A national survey was conducted in 2011-2013 to assess serum concentrations of brominated flame retardants (BFRs) and perfluorinated alkyl substances (PFASs) in adult New Zealanders. Participants were randomly selected from the 2010 Electoral Roll within 64 demographic strata according to 4 age groups, 4 geographic regions, 2 ethnic groups (Māori/non-Māori) and sex. Eligible participants (n = 734; response rate of contacted individuals = 37%) donated up to 30 mL of blood, after which serum was pooled (49 pools for BFRs, 63 pools for PFASs) according to demographic strata. BFRs were analysed by GC-HRMS and PFASs by LC-MS/MS. Associations between serum BFRs and PFASs and demographic variables (age, region, ethnicity, sex) were assessed using regression analysis. The weighted geometric mean (GM) serum concentrations of BDE47, BDE99, BDE100, and BDE153 were 2.0, 0.66, 0.43, and 1.2 ng/g lipid, respectively. The weighted geometric mean (GM) serum concentrations of PFOS, PFOA, PFHxS, and PFNA were 3.4, 2.4, 1.0, and 0.66 ng/mL, respectively. The majority of BFRs showed higher serum concentrations in younger age groups. Conversely, the four PFASs showed higher serum concentrations in older age groups. Concentrations of BFRs and PFASs were generally lower in females compared to males. In New Zealand, both age and sex are important determinants of BFR and PFAS serum concentrations.

Chlorinated persistent organic pollutants in serum of New Zealand adults, 2011-2013

A national survey was conducted in 2011-2013 to assess serum concentrations of persistent organic pollutants (POPs) in adult New Zealanders. Participants were randomly selected from the 2010 Electoral Roll within 64 demographic strata according to 4 age groups, 4 regions, 2 ethnic groups (Māori/non-Māori) and gender. Eligible subjects (n=734) donated up to 30ml of blood, after which serum was pooled (n=49) according to demographic strata prior to analysis by GC-HRMS. Associations between demographic variables (age, region, ethnicity, gender) and serum POPs were assessed using linear regression. The weighted geometric mean (GM) of PCDD/Fs was 5.3pg/g lipid toxic equivalents using the WHO 2005 toxic equivalence factors (TEQ₀₅), which increased by age (3.2, 4.4, 4.8, and 8.1pg/g lipid for the 19-24, 25-34, 35-49, and 50-64year age groups, respectively). The weighted GM of dioxin-like PCBs was 1.4pg TEQ₀₅/g lipid which also increased by age (0.82, 0.86, 1.4, and 2.3pg/g lipid for the same age groups, respectively). Of the detected OCPs, the highest concentration was observed for p,p'-DDE (weighted GM, 220ng/g lipid) followed by hexachlorobenzene (HCB; 7.3ng/g lipid), beta-HCH (7.0ng/g lipid), and dieldrin (4.7ng/g lipid). For most Cl-POPs, concentrations were lowest in the youngest age group, and were similar for men and women and Māori and non-Māori. Serum Cl-POPs were, on average, 50% lower than those measured 15years earlier in 1997. This survey provides evidence of declining serum concentrations of chlorinated POPs in the New Zealand adult population. Age was the most important determinant of POPs concentrations. Body burdens of PCDD/Fs and PCBs in New Zealand are relatively low by international comparison, while for OCPs they are similar or lower compared to those reported for other developed countries.

Hospitals, geriatric medicine, and the long-term care of elderly people 1946-1976

This article investigates the development and interaction of the views of medical professionals and health officials on elderly care between 1946 and the early 1970s. It examines how the cultural and political context in which new ideas on the treatment of elderly people emerged in the early post-war period affected policy development in this area. The article argues that, in combination, the political and financial imperatives of health officials and the cultural prejudices of many in the medical profession created a situation in which progressive ideas about geriatric medicine and home care were used, not to improve the overall standard of care for elderly people, but to restrict their access to long-term medical and nursing care. The most important development in this respect, it will be argued, were efforts made by government from the mid-1950s to restrict the amount of provision for older people in hospitals, through the introduction of a geriatric bed norm. What lay at the heart of this question, the article concludes, was the reluctance of policy-makers to confront directly issues relating to the continuing care of old people with complex health problems. The reasons for this reluctance will be examined.