Quantitative T1 and T2 MRI signal characteristics in the human brain: different patterns of MR contrasts in normal ageing

OBJECTIVE: The objective of this study was to examine age-dependent changes in both T(1)-weighted and T(2)-weighted image contrasts and spin-echo T(2) relaxation time in the human brain during healthy ageing. METHODS: A total of 37 participants between the ages of 49 and 87 years old were scanned with a 3 Tesla system, using T(1)-weighted, T(2) weighted and quantitative spin-echo T(2) imaging. Contrast between image intensities and T(2) values was calculated for various regions, including between individual hippocampal subfields. RESULTS: The T(1) contrast-to-noise (CNR) and gray:white signal intensity ratio (GWR) did not change in the hippocampus, but it declined in the cingulate cortex with age. In contrast, T(2) CNR and GWR declined in both brain regions. T(2) relaxation time was almost constant in gray matter and most (but not all) hippocampal subfields, but increased substantially in white matter, pointing to an age effect on water relaxation in white matter. CONCLUSIONS: Changes in T(1) and T(2) MR characteristics influence the appearance of brain images in later life and should be considered in image analyses of aged subjects. It is speculated that alterations at the cell biology level, with concomitant alterations to the local magnetic environment, reduce dephasing and subsequently prolong spin-echo T(2) through reduced diffusion effects in later life. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s10334-016-0573-0) contains supplementary material, which is available to authorized users

Magnetic Resonance Imaging to Detect Early Molecular and Cellular Changes in Alzheimer’s Disease

Recent pharmaceutical trials have demonstrated that slowing or reversing pathology in Alzheimer's disease is likely to be possible only in the earliest stages of disease, perhaps even before significant symptoms develop. Pathology in Alzheimer's disease accumulates for well over a decade before symptoms are detected giving a large potential window of opportunity for intervention. It is therefore important that imaging techniques detect subtle changes in brain tissue before significant macroscopic brain atrophy. Current diagnostic techniques often do not permit early diagnosis or are too expensive for routine clinical use. Magnetic Resonance Imaging (MRI) is the most versatile, affordable, and powerful imaging modality currently available, being able to deliver detailed analyses of anatomy, tissue volumes, and tissue state. In this mini-review, we consider how MRI might detect patients at risk of future dementia in the early stages of pathological change when symptoms are mild. We consider the contributions made by the various modalities of MRI (structural, diffusion, perfusion, relaxometry) in identifying not just atrophy (a late-stage AD symptom) but more subtle changes reflective of early dementia pathology. The sensitivity of MRI not just to gross anatomy but to the underlying “health” at the cellular (and even molecular) scales, makes it very well suited to this task

Quantitative T2 mapping of white matter:applications for ageing and cognitive decline

In MRI, the coherence lifetime T2 is sensitive to the magnetic environment imposed by tissue microstructure and biochemistry in vivo. Here we explore the possibility that the use of T2 relaxometry may provide information complementary to that provided by diffusion tensor imaging (DTI) in ageing of healthy controls (HC), Alzheimer’s disease (AD) and mild cognitive impairment (MCI). T2 and diffusion MRI metrics were quantified in HC and patients with MCI and mild AD using multi-echo MRI and DTI. We used tract-based spatial statistics (TBSS) to evaluate quantitative MRI parameters in white matter (WM). A prolonged T2 in WM was associated with AD, and able to distinguish AD from MCI, and AD from HC. Shorter WM T2 was associated with better cognition and younger age in general. In no case was a reduction in T2 associated with poorer cognition. We also applied principal component analysis, showing that WM volume changes independently of  T2, MRI diffusion indices and cognitive performance indices. Our data add to the evidence that age-related and AD-related decline in cognition is in part attributable to WM tissue state, and much less to WM quantity. These observations suggest that WM is involved in AD pathology, and that T2 relaxometry is a potential imaging modality for detecting and characterising WM in cognitive decline and dementia

Final 192-week efficacy and safety results of the ADVANCE trial, comparing 3 first-line antiretroviral regimens

BACKGROUND: ADVANCE compared 3 World Health Organization-recommended first-line regimens in participants with HIV who were antiretroviral naive. METHODS: This randomized, open-label, noninferiority trial enrolled participants living with HIV with no antiretroviral exposure in the previous 6 months to 1 of the following arms: tenofovir alafenamide (TAF) / emtricitabine (FTC) + dolutegravir (DTG) (2 tablets), tenofovir disoproxil fumarate (TDF) / FTC + DTG (2 tablets), or a fixed-dose combination of TDF / FTC / efavirenz (EFV) (1 tablet). We report the final safety and efficacy data up to 192 weeks. RESULTS: Repeat consent from the original 351 participants randomized to each arm was obtained from 230 participants (66%) in the TAF/FTC + DTG arm, 209 (60%) in the TDF/FTC + DTG arm, and 183 (52%) in the TDF/FTC/EFV arm. At 192 weeks, 213 (61%) of the original 351 participants in the TAF/FTC + DTG arm, 195 (56%) in the TDF/FTC + DTG arm, and 172 (49%) in the TDF/FTC/EFV arm had confirmed RNA <50 copies/mL, with low virologic failure in all groups and no significant integrase inhibitor mutations in any arm. Mean weight gain was 8.9 kg (SD, 7.1) in the TAF/FTC + DTG arm, 5.9 kg (SD, 7.1) in the TDF/FTC + DTG arm, and 3.2 kg (SD, 8.1) in the TDF/FTC/EFV arm at 192 weeks from baseline and was greatest among women, those taking TAF, and those with lower baseline CD4 counts. The weight trajectory slowed after week 96. There were few clinical events and minor laboratory changes and differences among arms after 96 weeks. There were no significant differences in treatment-emergent hypertension or pregnancy outcomes by arm. CONCLUSIONS: High viral suppression was seen across arms, with no resistance to DTG. Weight gain continued but slowed after 96 weeks, with few clinical events or laboratory changes

Risks of metabolic syndrome in the ADVANCE and NAMSAL trials

IntroductionThe ADVANCE and NAMSAL trials evaluating antiretroviral drugs have both reported substantial levels of clinical obesity in participants. As one of the main risk factors for metabolic syndrome, growing rates of obesity may drive metabolic syndrome development. This study aims to evaluate the risk of metabolic syndrome in the ADVANCE and NAMSAL trials.MethodsThe number of participants with metabolic syndrome was calculated at baseline and week 192 as central obesity and any of the following two factors: raised triglycerides, reduced HDL-cholesterol, raised blood pressure and raised fasting glucose. Differences between the treatment arms were calculated using the χ2 test.ResultsAcross all visits to week 192, treatment-emergent metabolic syndrome was 15% (TAF/FTC + DTG), 10% (TDF/FTC + DTG) and 7% (TDF/FTC/EFV) in ADVANCE. The results were significantly higher in the TAF/FTC + DTG arm compared to the TDF/FTC/EFV arm (p &lt; 0.001), and the TDF/FTC + DTG vs. the TDF/FTC/EFV arms (p &lt; 0.05) in all patients, and in females. In NAMSAL, the incidence of treatment-emergent metabolic syndrome at any time point was 14% (TDF/3TC + DTG) and 5% (TDF/3TC + EFV) (p &lt; 0.001). This incidence was significantly greater in the TDF/3TC/DTG arm compared to the TDF/3TC/EFV arm in all patients (p &lt; 0.001), and in males (p &lt; 0.001)ConclusionIn this analysis, we highlight treatment-emergent metabolic syndrome associated with dolutegravir, likely driven by obesity. Clinicians initiating or monitoring patients on INSTI-based ART must counsel for lifestyle optimisation to prevent these effects

JoVE article Matlab software

The Matlab scripts will compute parametric maps from Bruker MR images as described in the JoVE paper published in 201

Dolutegravir plus Two Different Prodrugs of Tenofovir to Treat HIV

BACKGROUND: Two drugs under consideration for inclusion in antiretroviral therapy (ART) regimens for human immunodeficiency virus (HIV) infection are dolutegravir (DTG) and tenofovir alafenamide fumarate (TAF). There are limited data on their use in low- and middle-income countries. METHODS: We conducted a 96-week, phase 3, investigator-led, open-label, randomized trial in South Africa, in which we compared a triple-therapy combination of emtricitabine (FTC) and DTG plus either of two tenofovir prodrugs - TAF (TAF-based group) or tenofovir disoproxil fumarate (TDF) (TDF-based group) - against the local standard-of-care regimen of TDF-FTC-efavirenz (standard-care group). Inclusion criteria included an age of 12 years or older, no receipt of ART in the previous 6 months, a creatinine clearance of more than 60 ml per minute (>80 ml per minute in patients younger than 19 years of age), and an HIV type 1 (HIV-1) RNA level of 500 copies or more per milliliter. The primary end point was the percentage of patients with a 48-week HIV-1 RNA level of less than 50 copies per milliliter (as determined with the Snapshot algorithm from the Food and Drug Administration; noninferiority margin, -10 percentage points). We report the primary (48-week) efficacy and safety data. RESULTS: A total of 1053 patients underwent randomization from February 2017 through May 2018. More than 99% of the patients were black, and 59% were female. The mean age was 32 years, and the mean CD4 count was 337 cells per cubic millimeter. At week 48, the percentage of patients with an HIV-1 RNA level of less than 50 copies per milliliter was 84% in the TAF-based group, 85% in the TDF-based group, and 79% in the standard-care group, findings that indicate that the DTG-containing regimens were noninferior to the standard-care regimen. The number of patients who discontinued the trial regimen was higher in the standard-care group than in the other two groups. In the per-protocol population, the standard-care regimen had equivalent potency to the other two regimens. The TAF-based regimen had less effect on bone density and renal function than the other regimens. Weight increase (both lean and fat mass) was greatest in the TAF-based group and among female patients (mean increase, 6.4 kg in the TAF-based group, 3.2 kg in the TDF-based group, and 1.7 kg in the standard-care group). No resistance to integrase inhibitors was identified in patients receiving the DTG-containing regimens. CONCLUSIONS: Treatment with DTG combined with either of two tenofovir prodrugs (TAF and TDF) showed noninferior efficacy to treatment with the standard-care regimen. There was significantly more weight gain with the DTG-containing regimens, especially in combination with TAF, than with the standard-care regimen. (ADVANCE ClinicalTrials.gov number, NCT03122262.)