Combining navigator and optical prospective motion correction for high-quality 500 µm resolution quantitative multi-parameter mapping at 7T.

PURPOSE: High-resolution quantitative multi-parameter mapping shows promise for non-invasively characterizing human brain microstructure but is limited by physiological artifacts. We implemented corrections for rigid head movement and respiration-related B0-fluctuations and evaluated them in healthy volunteers and dementia patients. METHODS: Camera-based optical prospective motion correction (PMC) and FID navigator correction were implemented in a gradient and RF-spoiled multi-echo 3D gradient echo sequence for mapping proton density (PD), longitudinal relaxation rate (R1) and effective transverse relaxation rate (R2*). We studied their effectiveness separately and in concert in young volunteers and then evaluated the navigator correction (NAVcor) with PMC in a group of elderly volunteers and dementia patients. We used spatial homogeneity within white matter (WM) and gray matter (GM) and scan-rescan measures as quality metrics. RESULTS: NAVcor and PMC reduced artifacts and improved the homogeneity and reproducibility of parameter maps. In elderly participants, NAVcor improved scan-rescan reproducibility of parameter maps (coefficient of variation decreased by 14.7% and 11.9% within WM and GM respectively). Spurious inhomogeneities within WM were reduced more in the elderly than in the young cohort (by 9% vs. 2%). PMC increased regional GM/WM contrast and was especially important in the elderly cohort, which moved twice as much as the young cohort. We did not find a significant interaction between the two corrections. CONCLUSION: Navigator correction and PMC significantly improved the quality of PD, R1, and R2* maps, particularly in less compliant elderly volunteers and dementia patients.

Loss and dispersion of superficial white matter in Alzheimer's disease: a diffusion MRI study.

Pathological cerebral white matter changes in Alzheimer's disease have been shown using diffusion tensor imaging. Superficial white matter changes are relatively understudied despite their importance in cortico-cortical connections. Measuring superficial white matter degeneration using diffusion tensor imaging is challenging due to its complex organizational structure and proximity to the cortex. To overcome this, we investigated diffusion MRI changes in young-onset Alzheimer's disease using standard diffusion tensor imaging and Neurite Orientation Dispersion and Density Imaging to distinguish between disease-related changes that are degenerative (e.g. loss of myelinated fibres) and organizational (e.g. increased fibre dispersion). Twenty-nine young-onset Alzheimer's disease patients and 22 healthy controls had both single-shell and multi-shell diffusion MRI. We calculated fractional anisotropy, mean diffusivity, neurite density index, orientation dispersion index and tissue fraction (1-free water fraction). Diffusion metrics were sampled in 15 a priori regions of interest at four points along the cortical profile: cortical grey matter, grey/white boundary, superficial white matter (1 mm below grey/white boundary) and superficial/deeper white matter (2 mm below grey/white boundary). To estimate cross-sectional group differences, we used average marginal effects from linear mixed effect models of participants' diffusion metrics along the cortical profile. The superficial white matter of young-onset Alzheimer's disease individuals had lower neurite density index compared to controls in five regions (superior and inferior parietal, precuneus, entorhinal and parahippocampus) (all P < 0.05), and higher orientation dispersion index in three regions (fusiform, entorhinal and parahippocampus) (all P < 0.05). Young-onset Alzheimer's disease individuals had lower fractional anisotropy in the entorhinal and parahippocampus regions (both P < 0.05) and higher fractional anisotropy within the postcentral region (P < 0.05). Mean diffusivity was higher in the young-onset Alzheimer's disease group in the parahippocampal region (P < 0.05) and lower in the postcentral, precentral and superior temporal regions (all P < 0.05). In the overlying grey matter, disease-related changes were largely consistent with superficial white matter findings when using neurite density index and fractional anisotropy, but appeared at odds with orientation dispersion and mean diffusivity. Tissue fraction was significantly lower across all grey matter regions in young-onset Alzheimer's disease individuals (all P < 0.001) but group differences reduced in magnitude and coverage when moving towards the superficial white matter. These results show that microstructural changes occur within superficial white matter and along the cortical profile in individuals with young-onset Alzheimer's disease. Lower neurite density and higher orientation dispersion suggests underlying fibres undergo neurodegeneration and organizational changes, two effects previously indiscernible using standard diffusion tensor metrics in superficial white matter.

Utility of perfusion PET measures to assess neuronal injury in Alzheimer's disease.

INTRODUCTION: 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) is commonly used to estimate neuronal injury in Alzheimer's disease (AD). Here, we evaluate the utility of dynamic PET measures of perfusion using 11C-Pittsburgh compound B (PiB) to estimate neuronal injury in comparison to FDG PET. METHODS: FDG, early frames of PiB images, and relative PiB delivery rate constants (PiB-R1) were obtained from 110 participants from the Dominantly Inherited Alzheimer Network. Voxelwise, regional cross-sectional, and longitudinal analyses were done to evaluate the correlation between images and estimate the relationship of the imaging biomarkers with estimated time to disease progression based on family history. RESULTS: Metabolism and perfusion images were spatially correlated. Regional PiB-R1 values and FDG, but not early frames of PiB images, significantly decreased in the mutation carriers with estimated year to onset and with increasing dementia severity. DISCUSSION: Hypometabolism estimated by PiB-R1 may provide a measure of brain perfusion without increasing radiation exposure.

PERFORMANCE OF OVID MEDLINE SEARCH FILTERS TO IDENTIFY HEALTH STATE UTILITY STUDIES.

OBJECTIVES: This study was designed to assess the sensitivity of three Ovid MEDLINE search filters developed to identify studies reporting health state utility values (HSUVs), to improve the performance of the best performing filter, and to validate resulting search filters. METHODS: Three quasi-gold standard sets (QGS1, QGS2, QGS3) of relevant studies were harvested from reviews of studies reporting HSUVs. The performance of three initial filters was assessed by measuring their relative recall of studies in QGS1. The best performing filter was then developed further using QGS2. This resulted in three final search filters (FSF1, FSF2, and FSF3), which were validated using QGS3. RESULTS: FSF1 (sensitivity maximizing) retrieved 132/139 records (sensitivity: 95 percent) in the QGS3 validation set. FSF1 had a number needed to read (NNR) of 842. FSF2 (balancing sensitivity and precision) retrieved 128/139 records (sensitivity: 92 percent) with a NNR of 502. FSF3 (precision maximizing) retrieved 123/139 records (sensitivity: 88 percent) with a NNR of 383. CONCLUSIONS: We have developed and validated a search filter (FSF1) to identify studies reporting HSUVs with high sensitivity (95 percent) and two other search filters (FSF2 and FSF3) with reasonably high sensitivity (92 percent and 88 percent) but greater precision, resulting in a lower NNR. These seem to be the first validated filters available for HSUVs. The availability of filters with a range of sensitivity and precision options enables researchers to choose the filter which is most appropriate to the resources available for their specific research.

Can service integration work for universal health coverage? Evidence from around the globe.

Universal health coverage (UHC) is at the heart of the new 2030 Agenda for Sustainable Development. Health service integration is seen by World Health Organization as an essential requirement to achieve UHC. However, to date the debate on service integration has focused on perceived benefits rather than empirical impact. We conducted a global review in a systematic manner searching for empirical outcomes of service integration experiments in UHC countries and those on the path to UHC. Sixty-seven articles and reports were found. We grouped results into a unique integration typology with six categories - medical staff from different disciplines; patients and medical staff; care package for one medical condition; care package for two or more medical conditions; specialist stand-alone services with GP services; community locations. We showed that it is possible to integrate services in different human development contexts delivering positive outcomes for patients and clinicians without incurring additional costs. However, the improved outcomes shown were incremental rather than radical and suggest that integration is likely to enhance already well established systems rather than fundamentally changing the outcomes of care.

Systematic Review of Retraction Devices for Laparoscopic Surgery.

BACKGROUND: Retraction plays a vital role in optimizing the field of vision in minimal-access surgery. As such, a number of devices have been marketed to aid the surgeon in laparoscopic retraction. This systematic review explores the advantages and disadvantages of the different instruments in order to aid surgeons and their institutions in selecting the appropriate device. Primary outcome measures include operation time, length of stay, use of staff, patient morbidity, ease of use, conversion rates to open surgery, and cost. METHODS: Systematic literature searches were performed in MEDLINE, EMBASE, The Cochrane Library, Current Controlled Trials, and ClinicalTrials.gov. The search strategy focused on studies testing a retraction device. The selection process was based on a predefined set of inclusion and exclusion criteria. Data were then extracted and analyzed. RESULTS: Out of 1360 papers initially retrieved, 12 articles were selected for data extraction and analysis. A total of 10 instruments or techniques were tested. Devices included the Nathanson's liver retractor, liver suspension tape, the V-List technique, a silicone disk with or without a snake retractor, the Endoloop, the Endograb, a magnetic retractor, the VaroLift, a laparoscope holder, and a retraction sponge. None of the instruments reported were associated with increased morbidity. No studies found increased rates of conversion to open surgery. All articles reported that the tested instruments might spare the use of an assistant during the procedure. It was not possible to determine the impact on length of stay or operation time. CONCLUSIONS: Each analyzed device facilitates retraction, providing a good field of view while allowing reduced staff numbers and minimal patient morbidity. Due to economic and environmental advantages, reusable devices may be preferable to disposable instruments, although the choice must be primarily based on clinical judgement.