MRI-based cerebrovascular reactivity using transfer function analysis reveals temporal group differences between patients with sickle cell disease and healthy controls

AbstractObjectivesCerebrovascular reactivity (CVR) measures the ability of cerebral blood vessels to change their diameter and, hence, their capacity to regulate regional blood flow in the brain. High resolution quantitative maps of CVR can be produced using blood-oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) in combination with a carbon dioxide stimulus, and these maps have become a useful tool in the clinical evaluation of cerebrovascular disorders. However, conventional CVR analysis does not fully characterize the BOLD response to a stimulus as certain regions of the brain are slower to react to the stimulus than others, especially in disease. Transfer function analysis (TFA) is an alternative technique that can account for dynamic temporal relations between signals and has recently been adapted for CVR computation. We investigated the application of TFA in data on children with sickle cell disease (SCD) and healthy controls, and compared them to results derived from conventional CVR analysis.Materials and methodsData from 62 pediatric patients with SCD and 34 age-matched healthy controls were processed using conventional CVR analysis and TFA. BOLD data were acquired on a 3Tesla MRI scanner while a carbon dioxide stimulus was quantified by sampling the end-tidal partial pressures of each exhaled breath. In addition, T1 weighted structural imaging was performed to identify grey and white matter regions for analysis. The TFA method generated maps representing both the relative magnitude change of the BOLD signal in response to the stimulus (Gain), as well as the BOLD signal speed of response (Phase) for each subject. These were compared to CVR maps calculated from conventional analysis. The effect of applying TFA on data from SCD patients versus controls was also examined.ResultsThe Gain measures derived from TFA were significantly higher than CVR values based on conventional analysis in both SCD patients and healthy controls, but the difference was greater in the SCD data. Moreover, while these differences were uniform across the grey and white matter regions of controls, they were greater in white matter than grey matter in the SCD group. Phase was also shown to be significantly correlated with the amount that TFA increases CVR estimates in both the grey and white matter.ConclusionsWe demonstrated that conventional CVR analysis underestimates vessel reactivity and this effect is more prominent in patients with SCD. By using TFA, the resulting Gain and Phase measures more accurately characterize the BOLD response as it accounts for the temporal dynamics responsible for the CVR underestimation. We suggest that the additional information offered through TFA can provide insight into the mechanisms underlying CVR compromise in cerebrovascular diseases

Association Between p.Leu54Met Polymorphism at the Paraoxonase-1 Gene and Plantar Fascia Thickness in Young Subjects With Type 1 Diabetes

OBJECTIVE— In type 1 diabetes, plantar fascia, a collagen-rich tissue, is susceptible to glycation and oxidation. Paraoxonase-1 (PON1) is an HDL-bound antioxidant enzyme. PON1 polymorphisms have been associated with susceptibility to macro- and microvascular complications. We investigated the relationship between plantar fascia thickness (PFT) and PON1 gene variants, p.Leu54Met, p.Gln192Arg, and c.-107C>T, in type 1 diabetes

PACT: An initiative to introduce computational thinking to second-level education in Ireland

PACT (Programming ∧ Algorithms ⇒ Computational Thinking) is a partnership between researchers in the Department of Computer Science at Maynooth University and teachers at selected post-primary schools around Ireland. Starting in September 2013, seven Irish secondary schools took part in a pilot study, delivering material prepared by the PACT team to Transition Year students. Three areas of Computer Science were identified as being key to delivering a successful course in computational thinking, namely, programming, algorithms and computability. An overview of the PACT module is provided, as well as analysis of the feedback obtained from students and teachers involved in delivering the initial pilot

The regular matroids with no 5-wheel minor

For r in {3, 4}, the class of binary matroids with no minor isomorphic to M(Wr), the rank-r wheel, has an easily described structure. This paper determines all graphs with no W5-minor and uses this to show that the class of regular matroids with no M(W5)-minor also has a relatively simple structure. © 1989

Transfer function analysis assesses resting cerebral perfusion metrics using hypoxia-induced deoxyhemoglobin as a contrast agent

Introduction: Use of contrast in determining hemodynamic measures requires the deconvolution of an arterial input function (AIF) selected over a voxel in the middle cerebral artery to calculate voxel wise perfusion metrics. Transfer function analysis (TFA) offers an alternative analytic approach that does not require identifying an AIF. We hypothesised that TFA metrics Gain, Lag, and their ratio, Gain/Lag, correspond to conventional AIF resting perfusion metrics relative cerebral blood volume (rCBV), mean transit time (MTT) and relative cerebral blood flow (rCBF), respectively.Methods: 24 healthy participants (17 M) and 1 patient with steno-occlusive disease were recruited. We used non-invasive transient hypoxia-induced deoxyhemoglobin as an MRI contrast. TFA and conventional AIF analyses were used to calculate averages of whole brain and smaller regions of interest.Results: Maps of these average metrics had colour scales adjusted to enhance contrast and identify areas of high congruence. Regional gray matter/white matter (GM/WM) ratios for MTT and Lag, rCBF and Gain/Lag, and rCBV and Gain were compared. The GM/WM ratios were greater for TFA metrics compared to those from AIF analysis indicating an improved regional discrimination.Discussion: Resting perfusion measures generated by The BOLD analysis resulting from a transient hypoxia induced variations in deoxyhemoglobin analyzed by TFA are congruent with those analyzed by conventional AIF analysis

Heterogeneous motor BOLD-fMRI responses in brain areas exhibiting negative BOLD cerebrovascular reactivity indicate that steal phenomenon does not always result from exhausted cerebrovascular reserve capacity

Introduction: Brain areas exhibiting negative blood oxygenation-level dependent cerebrovascular reactivity (BOLD-CVR) responses to carbon dioxide (CO2) are thought to suffer from a completely exhausted autoregulatory cerebrovascular reserve capacity and exhibit vascular steal phenomenon. If this assumption is correct, the presence of vascular steal phenomenon should subsequently result in an equal negative fMRI signal response during a motor-task based BOLD-fMRI study (increase in metabolism without an increase in cerebral blood flow due to exhausted reserve capacity) in otherwise functional brain tissue. To investigate this premise, the aim of this study was to further investigate motor-task based BOLD-fMRI signal responses in brain areas exhibiting negative BOLD-CVR. Material and methods: Seventy-one datasets of patients with cerebrovascular steno-occlusive disease without motor defects, who underwent a CO2-calibrated motor task-based BOLD-fMRI study with a fingertapping paradigm and a subsequent BOLD-CVR study with a precisely controlled CO2-challenge during the same MRI examination, were included. We compared BOLD-fMRI signal responses in the bilateral pre- and postcentral gyri - i.e. Region of Interest (ROI) with the corresponding BOLD-CVR in this ROI. The ROI was determined using a second level group analysis of the BOLD-fMRI task study of 42 healthy individuals undergoing the same study protocol. Results: An overall decrease in BOLD-CVR was associated with a decrease in BOLD-fMRI signal response within the ROI. For patients exhibiting negative BOLD-CVR, we found both positive and negative motor-task based BOLD-fMRI signal responses. Conclusion: We show that the presence of negative BOLD-CVR responses to CO2 is associated with heterogeneous motor task-based BOLD-fMRI signal responses, where some patients show -more presumed- negative BOLD-fMRI signal responses, while other patient showed positive BOLD-fMRI signal responses. This finding may indicate that the autoregulatory vasodilatory reserve capacity does not always need to be completely exhausted for vascular steal phenomenon to occur

Treatment of Psoriasis in Patients With Psoriatic Arthritis: An Updated Literature Review Informing the 2021 GRAPPA Treatment Recommendations

Objective. Our aim was to summarize and evaluate the current quality of evidence regarding the efficacy of therapies for cutaneous psoriasis (PsO) in patients with psoriatic arthritis (PsA).Methods. A literature search of MEDLINE, Embase, Cochrane Library databases, and conference abstracts was conducted to identify interventional randomized controlled trials in patients with PsA between February 2013 and December 2021. Studies were included if PsO outcomes included achieving at least 75% improvement in the Psoriasis Area and Severity Index and the blinded comparison period was >= 10 weeks. The Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) methodology was employed to assess quality of the evidence to inform and update the 2021 Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA) treatment recommendations.Results. A total of 116 studies and 36 abstracts identified in the initial search were screened. A total of 37 studies (40 treatment arms) met the criteria for final inclusion. Phosphodiesterase 4 inhibitors, Janus kinase inhibitors, and tyrosine kinase 2 inhibitors, interleukin 17 inhibitors (IL-17i), IL-12/23i, IL-23i, and tumor necrosis factor inhibitors (TNFi) had high-quality data broadly supporting the efficacy of each class for plaque PsO over placebo. Head-to-head studies with high-quality data supported both IL-17i and IL-23i over TNFi.Conclusion. Several pharmacologic therapeutic classes have high-quality evidence demonstrating efficacy for cutaneous PsO in the PsA population. The findings will be integrated into the 2021 GRAPPA treatment recommendations, intended to guide selection of a therapeutic class where efficacy in 1 or more cutaneous or musculoskeletal domains is required