Dataset Information

A method to correct background phase offset for phase-contrast MRI in the presence of steady flow and spatial wrap-around artifact.

ABSTRACT: PURPOSE:Background phase offsets in phase-contrast MRI are often corrected using polynomial regression; however, correction performance degrades when temporally invariant outliers such as steady flow or spatial wrap-around artifact are present. We describe and validate an iterative method called automatic rejection of temporally invariant outliers (ARTO), which excludes these outliers from the fitting process. METHODS:The ARTO method iteratively removes pixels with large polynomial regression errors analyzed by a Gaussian mixture model fitting of the residual distribution. A total of 150 trials of a simulated phantom (75 with wrap-around artifact) and 125 phase-contrast MRI cines from 22 healthy subjects (48 with wrap-around artifact) were used for validation. Background phase offsets were corrected using second-order weighted regularized least squares (WRLS) with and without ARTO. Flow volumes after WRLS and WRLS+ARTO corrections were compared with the known truth (phantom) and stationary phantom reference (in vivo) using Bland-Altman analysis. The ratio between the pulmonary flow and the systemic flow was also computed in a subset of 6 subjects. RESULTS:In the simulated phantom, compared with WRLS and no correction, correction with WRLS+ARTO produced superior agreement in volumetric flow quantification with the known truth. In vivo, WRLS+ARTO also produced superior agreement with stationary phantom-corrected volumetric flow compared with WRLS and no correction. In data sets with wrap-around artifact, WRLS produced significantly larger variance in the pulmonary flow and systemic flow ratio than stationary phantom correction (P = .0008). CONCLUSION:The proposed method provides automatic exclusion of temporally invariant outliers and produces flow quantification results comparable to stationary phantom correction.

SUBMITTER: Pruitt AA

PROVIDER: S-EPMC6372316 | biostudies-literature | 2019 Apr

REPOSITORIES: biostudies-literature

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A method to correct background phase offset for phase-contrast MRI in the presence of steady flow and spatial wrap-around artifact.

Pruitt Aaron A AA Jin Ning N Liu Yingmin Y Simonetti Orlando P OP Ahmad Rizwan R

Magnetic resonance in medicine 20181115 4

<h4>Purpose</h4>Background phase offsets in phase-contrast MRI are often corrected using polynomial regression; however, correction performance degrades when temporally invariant outliers such as steady flow or spatial wrap-around artifact are present. We describe and validate an iterative method called automatic rejection of temporally invariant outliers (ARTO), which excludes these outliers from the fitting process.<h4>Methods</h4>The ARTO method iteratively removes pixels with large polynomia ...[more]

PMID: 30431176

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Project description:BACKGROUND:The aim of this study is to understand the determinants of adherence to wrap-around care (WAC) by professional care providers working in child and family services. WAC is a care coordination method targeting families with complex needs. The core components of WAC involve activating family members and the social network, integrating the care provider network, and assessing, planning and evaluating the care process. WAC was introduced in the Netherlands using two approaches: the network approach (NA) and the team approach (TA). METHODS:A cross-sectional study was conducted using a digital questionnaire targeted at care providers. After imputation of missing data, univariate and multilevel regression analyses were conducted to study the associations between adherence to the core components of WAC, the determinants of adherence and background characteristics. RESULTS:In total 145 out of 275 care providers (52.7%) responded to the questionnaire. Multilevel regression analysis showed that self-efficacy of the care providers and the way WAC is organised (NA versus TA region) were significantly associated with adherence to core components of WAC. Self-efficacy was significantly associated with all WAC core components (activating family members and the social network: ? (95% confidence interval, CI)?=?.27(.04-.50), integrating the network of care providers: ? (95% CI)?=?.27(.05-.50) and assessing, planning and evaluating the care process: ? (95% CI)?=?.30(.08-.52)). The way WAC is organised was significantly associated to two core components (activating family members and the social network: ? (95% CI)?=?.18(0.1-.37) and integrating the network of care providers: ? (95% CI)?=?.25(.09-.42)). CONCLUSION:The way WAC is organised and the self-efficacy of care providers who use WAC are factors that are relevant for the redesign of the strategy for introducing WAC. Longitudinal research into the predictive value of determinants of adherence to WAC is advised.

Project description:BackgroundCardiovascular magnetic resonance (CMR) phase contrast (PC) flow measurements suffer from phase offset errors. Background subtraction based on stationary phantom measurements can most reliably be used to overcome this inaccuracy. Stationary tissue correction is an alternative and does not require additional phantom scanning. The aim of this study was 1) to compare measurements with and without stationary tissue correction to phantom corrected measurements on different GE Healthcare CMR scanners using different software packages and 2) to evaluate the clinical implications of these methods.MethodsCMR PC imaging of both the aortic and pulmonary artery flow was performed in patients on three different 1.5 T CMR scanners (GE Healthcare) using identical scan parameters. Uncorrected, first, second and third order stationary tissue corrected flow measurement were compared to phantom corrected flow measurements, our reference method, using Medis QFlow, Circle cvi42 and MASS software. The optimal (optimized) stationary tissue order was determined per scanner and software program. Velocity offsets, net flow, clinically significant difference (deviation > 10% net flow), and regurgitation severity were assessed.ResultsData from 175 patients (28 (17-38) years) were included, of which 84% had congenital heart disease. First, second and third order and optimized stationary tissue correction did not improve the velocity offsets and net flow measurements. Uncorrected measurements resulted in the least clinically significant differences in net flow compared to phantom corrected data. Optimized stationary tissue correction per scanner and software program resulted in net flow differences (> 10%) in 19% (MASS) and 30% (Circle cvi42) of all measurements compared to 18% (MASS) and 23% (Circle cvi42) with no correction. Compared to phantom correction, regurgitation reclassification was the least common using uncorrected data. One CMR scanner performed worse and significant net flow differences of > 10% were present both with and without stationary tissue correction in more than 30% of all measurements.ConclusionPhase offset errors had a significant impact on net flow quantification, regurgitation assessment and varied greatly between CMR scanners. Background phase correction using stationary tissue correction worsened accuracy compared to no correction on three GE Healthcare CMR scanners. Therefore, careful assessment of phase offset errors at each individual scanner is essential to determine whether routine use of phantom correction is necessary.Trial registrationObservational Study.

Dataset Information

A method to correct background phase offset for phase-contrast MRI in the presence of steady flow and spatial wrap-around artifact.

Publications

A method to correct background phase offset for phase-contrast MRI in the presence of steady flow and spatial wrap-around artifact.

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