Effects of Thresholding on Voxel-Wise Correspondence of Breath-Hold and Resting-State Maps of Cerebrovascular Reactivity

Functional magnetic resonance imaging for presurgical brain mapping enables neurosurgeons to identify viable tissue near a site of operable pathology which might be at risk of surgery-induced damage. However, focal brain pathology (e.g., tumors) may selectively disrupt neurovascular coupling while leaving the underlying neurons functionally intact. Such neurovascular uncoupling can result in false negatives on brain activation maps thereby compromising their use for surgical planning. One way to detect potential neurovascular uncoupling is to map cerebrovascular reactivity using either an active breath-hold challenge or a passive resting-state scan. The equivalence of these two methods has yet to be fully established, especially at a voxel level of resolution. To quantitatively compare breath-hold and resting-state maps of cerebrovascular reactivity, we first identified threshold settings that optimized coverage of gray matter while minimizing false responses in white matter. When so optimized, the resting-state metric had moderately better gray matter coverage and specificity. We then assessed the spatial correspondence between the two metrics within cortical gray matter, again, across a wide range of thresholds. Optimal spatial correspondence was strongly dependent on threshold settings which if improperly set tended to produce statistically biased maps. When optimized, the two CVR maps did have moderately good correspondence with each other (mean accuracy of 73.6%). Our results show that while the breath-hold and resting-state maps may appear qualitatively similar they are not quantitatively identical at a voxel level of resolution.

Download Full-text

Hemodynamic evaluation of patients with Moyamoya Angiopathy: comparison of resting-state fMRI to breath-hold fMRI and [15O]water PET

Neuroradiology ◽

10.1007/s00234-021-02814-8 ◽

2021 ◽

Author(s):

Leonie Zerweck ◽

Constantin Roder ◽

Till-Karsten Hauser ◽

Johannes Thurow ◽

Annerose Mengel ◽

...

Keyword(s):

Resting State ◽

Resting State Fmri ◽

Cerebrovascular Reactivity ◽

Breath Hold ◽

Data Sets ◽

Moyamoya Angiopathy ◽

Perfusion Reserve ◽

Hemodynamic Evaluation ◽

Patient Cooperation ◽

High Level

Abstract Purpose Patients with Moyamoya Angiopathy (MMA) require hemodynamic evaluation to assess the risk of stroke. Assessment of cerebral blood flow with [15O]water PET and acetazolamide challenge is the diagnostic standard for the evaluation of the cerebral perfusion reserve (CPR). Estimation of the cerebrovascular reactivity (CVR) by use of breath-hold-triggered fMRI (bh-fMRI) as an index of CPR has been proposed as a reliable and more readily available approach. Recent findings suggest the use of resting-state fMRI (rs-fMRI) which requires minimum patient compliance. The aim of this study was to compare rs-fMRI to bh-fMRI and [15O]water PET in patients with MMA. Methods Patients with MMA underwent rs-fMRI and bh-fMRI in the same MRI session. Maps of the CVR gained by both modalities were compared retrospectively by calculating the correlation between the mean CVR of 12 volumes of interest. Additionally, the rs-maps of a subgroup of patients were compared to CPR-maps gained by [15O]water PET. Results The comparison of the rs-maps and the bh-maps of 24 patients revealed a good correlation (Pearson’s r = 0.71 ± 0.13; preoperative patients: Pearson’s r = 0.71 ± 0.17; postoperative patients: Pearson’s r = 0.71 ± 0.11). The comparison of 7 rs-fMRI data sets to the corresponding [15O]water PET data sets also revealed a high level of agreement (Pearson’s r = 0.80 ± 0.19). Conclusion The present analysis indicates that rs-fMRI might be a promising non-invasive method with almost no patient cooperation needed to evaluate the CVR. Further prospective studies are required.

Download Full-text

Resting-state functional magnetic resonance imaging for surgical planning in pediatric patients: a preliminary experience

Journal of Neurosurgery Pediatrics ◽

10.3171/2017.6.peds1711 ◽

2017 ◽

Vol 20 (6) ◽

pp. 583-590 ◽

Cited By ~ 18

Author(s):

Jarod L. Roland ◽

Natalie Griffin ◽

Carl D. Hacker ◽

Ananth K. Vellimana ◽

S. Hassan Akbari ◽

...

Keyword(s):

Clinical Practice ◽

Resting State ◽

Surgical Planning ◽

Pediatric Patients ◽

Clinical Decision Making ◽

Case Series ◽

Individual Basis ◽

Wide Range ◽

Neurosurgical Patients ◽

State Analysis

OBJECTIVECerebral mapping for surgical planning and operative guidance is a challenging task in neurosurgery. Pediatric patients are often poor candidates for many modern mapping techniques because of inability to cooperate due to their immature age, cognitive deficits, or other factors. Resting-state functional MRI (rs-fMRI) is uniquely suited to benefit pediatric patients because it is inherently noninvasive and does not require task performance or significant cooperation. Recent advances in the field have made mapping cerebral networks possible on an individual basis for use in clinical decision making. The authors present their initial experience translating rs-fMRI into clinical practice for surgical planning in pediatric patients.METHODSThe authors retrospectively reviewed cases in which the rs-fMRI analysis technique was used prior to craniotomy in pediatric patients undergoing surgery in their institution. Resting-state analysis was performed using a previously trained machine-learning algorithm for identification of resting-state networks on an individual basis. Network maps were uploaded to the clinical imaging and surgical navigation systems. Patient demographic and clinical characteristics, including need for sedation during imaging and use of task-based fMRI, were also recorded.RESULTSTwenty patients underwent rs-fMRI prior to craniotomy between December 2013 and June 2016. Their ages ranged from 1.9 to 18.4 years, and 12 were male. Five of the 20 patients also underwent task-based fMRI and one underwent awake craniotomy. Six patients required sedation to tolerate MRI acquisition, including resting-state sequences. Exemplar cases are presented including anatomical and resting-state functional imaging.CONCLUSIONSResting-state fMRI is a rapidly advancing field of study allowing for whole brain analysis by a noninvasive modality. It is applicable to a wide range of patients and effective even under general anesthesia. The nature of resting-state analysis precludes any need for task cooperation. These features make rs-fMRI an ideal technology for cerebral mapping in pediatric neurosurgical patients. This review of the use of rs-fMRI mapping in an initial pediatric case series demonstrates the feasibility of utilizing this technique in pediatric neurosurgical patients. The preliminary experience presented here is a first step in translating this technique to a broader clinical practice.

Download Full-text

A practical modification to a resting state fMRI protocol for improved characterization of cerebrovascular function

10.1101/2021.02.15.431289 ◽

2021 ◽

Author(s):

Rachael C. Stickland ◽

Kristina M. Zvolanek ◽

Stefano Moia ◽

Apoorva Ayyagari ◽

César Caballero-Gaudes ◽

...

Keyword(s):

Resting State ◽

Incidental Finding ◽

Pressure Change ◽

Resting State Fmri ◽

Blood Oxygenation ◽

Cerebrovascular Reactivity ◽

Breath Hold ◽

Bold Fmri ◽

Cerebrovascular Function

ABSTRACTCerebrovascular reactivity (CVR), defined here as the Blood Oxygenation Level Dependent (BOLD) response to a CO2 pressure change, is a useful metric of cerebrovascular function. Both the amplitude and the timing (hemodynamic lag) of the CVR response can bring insight into the nature of a cerebrovascular pathology and aid in understanding noise confounds when using functional Magnetic Resonance Imaging (fMRI) to study neural activity. This research assessed a practical modification to a typical resting-state fMRI protocol, to improve the characterization of cerebrovascular function. In 9 healthy subjects, we modelled CVR and lag in three resting-state data segments, and in data segments which added a 2–3 minute breathing task to the start of a resting-state segment. Two different breathing tasks were used to induce fluctuations in arterial CO2 pressure: a breath-hold task to induce hypercapnia (CO2 increase) and a cued deep breathing task to induce hypocapnia (CO2 decrease). Our analysis produced voxel-wise estimates of the amplitude (CVR) and timing (lag) of the BOLD-fMRI response to CO2 by systematically shifting the CO2 regressor in time to optimize the model fit. This optimization inherently increases grey matter CVR values and fit statistics. The inclusion of a simple breathing task, compared to a resting-state scan only, increases the number of voxels in the brain that have a significant relationship between CO2 and BOLD-fMRI signals, and improves our confidence in the plausibility of voxel-wise CVR and hemodynamic lag estimates. We demonstrate the clinical utility and feasibility of this protocol in an incidental finding of Moyamoya disease, and explore the possibilities and challenges of using this protocol in younger populations. This hybrid protocol has direct applications for CVR mapping in both research and clinical settings and wider applications for fMRI denoising and interpretation.

Download Full-text

Supplemental Material for Cortical Gray Matter Atrophy in Healthy Aging Cannot Be Explained by Undetected Incipient Cognitive Disorders: A Comment on Burgmans et al. (2009)

Neuropsychology ◽

10.1037/a0018827.supp ◽

2010 ◽

Keyword(s):

Gray Matter ◽

Healthy Aging ◽

Cognitive Disorders ◽

Gray Matter Atrophy ◽

Cortical Gray Matter

Download Full-text

Slowing of Cortical Gray Matter Atrophy with Teriflunomide is Associated with Delayed Conversion to Clinically Definite MS

SSRN Electronic Journal ◽

10.2139/ssrn.3288899 ◽

2018 ◽

Author(s):

Robert Zivadinov ◽

Michael G. Dwyer ◽

Ellen Carl ◽

Elizabeth M. Poole ◽

Steve Cavalier ◽

...

Keyword(s):

Gray Matter ◽

Gray Matter Atrophy ◽

Cortical Gray Matter

Download Full-text

Interruptions: Affective futures and uncanny presences at Giemaš, Finnmark

Polar Record ◽

10.1017/s0032247420000443 ◽

2021 ◽

Vol 57 ◽

Author(s):

Marianne Elisabeth Lien

Keyword(s):

Open Pit ◽

Open Pit Mining ◽

Mining Company ◽

Mining Site ◽

Wide Range ◽

Migratory Movement ◽

A Site ◽

Affective Relations ◽

North Norway

Abstract This paper concerns affective relations and unexpected interruptions as the planned expansion of an extractive open-pit mining site gathers momentum. The site is a mountain in Varanger, North Norway, criss-crossed by a sand-coloured meshwork of roads that are part of the current infrastructure of a quartzite quarry. Recently purchased by Chinese investors, the mining company Elkem plans a massive expansion of the operations, which will interrupt a wide range of practices and projects, including the migratory movement of reindeer, as well as their grazing patterns. Known as Giemaš amongst Sámi speakers, the mountain is also alluded to as a site of other powers, manifesting as unexpected accidents. In this article, I explore how the planned expansion evokes this contested site as more than a singular mountain, and how divergent epistemic formations interrupt the making of extractive resources in multiple ways.

Download Full-text

MR-Based Correction of Brain PET Measurements for Heterogeneous Gray Matter Radioactivity Distribution

Journal of Cerebral Blood Flow & Metabolism ◽

10.1097/00004647-199607000-00016 ◽

1996 ◽

Vol 16 (4) ◽

pp. 650-658 ◽

Cited By ~ 96

Author(s):

Carolyn Cidis Meltzer ◽

Jon Kar Zubieta ◽

Jonathan M. Links ◽

Paul Brakeman ◽

Martin J. Stumpf ◽

...

Keyword(s):

Gray Matter ◽

Accurate Determination ◽

Brain Structures ◽

Volume Averaging ◽

Partial Volume Correction ◽

Sampling Errors ◽

Partial Volume ◽

Volume Correction ◽

Healthy Elderly ◽

Wide Range

Partial volume and mixed tissue sampling errors can cause significant inaccuracy in quantitative positron emission tomographic (PET) measurements. We previously described a method of correcting PET data for the effects of partial volume averaging on gray matter (GM) quantitation; however, this method may incompletely correct GM structures when local tissue concentrations are highly heterogeneous. We have extended this three-compartment algorithm to include a fourth compartment: a GM volume of interest (VOI) that can be delineated on magnetic resonance (MR) imaging. Computer simulations of PET images created from human MR data demonstrated errors of up to 120% in assigned activity values in small brain structures in uncorrected data. Four-compartment correction achieved full recovery of a wide range of coded activity in GM VOIs such as the amygdala, caudate, and thalamus. Further validation was performed in an agarose brain phantom in actual PET acquisitions. Implementation of this partial volume correction approach in [18F]fluorodeoxyglucose and [11C]-carfentanil PET data acquired in a healthy elderly human subject was also performed. This newly developed MR-based partial volume correction algorithm permits the accurate determination of the true radioactivity concentration in specific structures that can be defined by MR by accounting for the influence of heterogeneity of GM radioactivity.

Download Full-text

Haemorheological Effects on Thrombocyte Adhesion and Aggregation Found Under Controlled Flow Conditions

10.1055/s-0039-1687333 ◽

1979 ◽

Author(s):

P.D. Richardson

Keyword(s):

Rate Of Change ◽

Continuous Observation ◽

Flow Conditions ◽

Wide Range ◽

Stream Migration ◽

Local Shear ◽

Videotape Recording ◽

Controlled Flow ◽

A Site

Thrombocyte adhesion and aggregation in a vessel or on a chamber wall can be measured most readily if the flow is controlled and steady, and continuous observation is used. Videotape recording is very helpful for subsequent quantification of the dynamics. The adhesion of each thrombocyte can occur for a finite time interval:this interval has been observed to have a wide range. Platelets which escape often leave open a site which attracts other platelets preferentially. The rate of change of adhesion density (platelets/mm2) is affected by the local shear rate and the shear history upstream. Aggregation is affected similarly, and also proceeds with some platelet turnover. The role of erythrocytes in facilitating cross-stream migration of thrombocytes (which can enhance the growth rate of large thrombi) appears due in part to convective flow fields induced by the motion of erythrocytes in a shear flow, which can be demonstrated theoretically and experimentally. Observations of the phenomenlogy of adhesion and aggregation under controlled flow conditions and comparison with fLu id-dynamically based theory allows representation in terras of a small number of parameters with prospects of prediction of behaviour over a wide range of haemodynamic conditions; biochemical changes lead to changes in values of the parameters, so that activating agents and inhibiting agents modify values in different directions.

Download Full-text

A Study on Estimation of Internal Pressure Creep Life Using Small Punch Creep (SPC) Tests for Boiler Pipes

Volume 6: Materials and Fabrication, Parts A and B ◽

10.1115/pvp2009-77336 ◽

2009 ◽

Author(s):

Toshimi Kobayashi ◽

Toru Izaki ◽

Junichi Kusumoto ◽

Akihiro Kanaya

Keyword(s):

Internal Pressure ◽

Residual Life ◽

Test Results ◽

Creep Life ◽

Creep Tests ◽

Good Correspondence ◽

Small Punch ◽

Uniaxial Creep ◽

Wide Range ◽

The Relationship

The small punch creep (SPC) test is possible to predict residual creep life at a high accuracy. But, the results of SPC tests cannot be compared with uniaxial creep or internal pressure creep results directly. In this report, the relationship between SPC test results and uniaxial creep test results in ASME A335 P11 (1.25Cr-0.5Mo Steel) was studied. The obtained relationship between SPC load and equivalent uniaxial creep stress formed a simple linear equation under the wide range of test temperature and test period. Then, the SPC results can be compared with uniaxial results by converting SPC loads to the equivalent uniaxial creep stresses. The relationship between SPC test results and internal pressure creep tests results was also studied. The internal creep life of as-received P11 pipe was almost same as SPC result when the hoop stress was converted to the SPC load. The creep lives of internal pressure creep influenced materials also showed good correspondence with SPC results. Therefore SPC can estimate the residual life of internal pressure creep influenced materials.

Download Full-text