Dataset Information

Frequency-Domain Approach To Determine Magnetic Address-Sensor Separation Distance Using the Harmonic Ratio Method.

ABSTRACT: In this work, we describe an approach to determine the distance separating a magnetic address from a scanning magnetoresistive sensor, a critical adjustable parameter for certain bioassay analyses where magnetic nanoparticles are used as labels. Our approach is leveraged from the harmonic ratio method (HRM), a method used in the hard drive industry to control the distance separating a magnetoresistive read head from its data platter with nanometer resolution. At the heart of the HRM is an amplitude comparison of a signal's fundamental frequency to that of its harmonics. When the signal is derived from the magnetic field pattern of a periodic array of magnetic addresses, the harmonic ratio contains the information necessary to determine the separation between the address array and the read head. The elegance of the HRM is that there is no need of additional components to the detection platform to determine a separation distance; the streaming "bit signal" contains all the information needed. In this work, we demonstrate that the tenets governing HRM used in the hard drive industry can be applied to the bioanalytical arena where submicrometer to 100 ?m separations are required.

SUBMITTER: Young CC

PROVIDER: S-EPMC4758469 | biostudies-other | 2016 Feb

REPOSITORIES: biostudies-other

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Frequency-Domain Approach To Determine Magnetic Address-Sensor Separation Distance Using the Harmonic Ratio Method.

Young Colin C CC Blackley Benjamin W BW Porter Marc D MD Granger Michael C MC

Analytical chemistry 20160126 4

In this work, we describe an approach to determine the distance separating a magnetic address from a scanning magnetoresistive sensor, a critical adjustable parameter for certain bioassay analyses where magnetic nanoparticles are used as labels. Our approach is leveraged from the harmonic ratio method (HRM), a method used in the hard drive industry to control the distance separating a magnetoresistive read head from its data platter with nanometer resolution. At the heart of the HRM is an amplit ...[more]

PMID: 26879366

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Project description:PurposeSpatial position accuracy in magnetic resonance imaging (MRI) is an important concern for a variety of applications, including radiation therapy planning, surgical planning, and longitudinal studies of morphologic changes to study neurodegenerative diseases. Spatial accuracy is strongly influenced by gradient linearity. This work presents a method for characterizing the gradient non-linearity fields on a per-system basis, and using this information to provide improved and higher-order (9th vs. 5th) spherical harmonic coefficients for better spatial accuracy in MRI.MethodsA large fiducial phantom containing 5229 water-filled spheres in a grid pattern is scanned with the MR system, and the positions all the fiducials are measured and compared to the corresponding ground truth fiducial positions as reported from a computed tomography (CT) scan of the object. Systematic errors from off-resonance (i.e., B0) effects are minimized with the use of increased receiver bandwidth (±125kHz) and two acquisitions with reversed readout gradient polarity. The spherical harmonic coefficients are estimated using an iterative process, and can be subsequently used to correct for gradient non-linearity. Test-retest stability was assessed with five repeated measurements on a single scanner, and cross-scanner variation on four different, identically-configured 3T wide-bore systems.ResultsA decrease in the root-mean-square error (RMSE) over a 50cm diameter spherical volume from 1.80mm to 0.77mm is reported here in the case of replacing the vendor's standard 5th order spherical harmonic coefficients with custom fitted 9th order coefficients, and from 1.5mm to 1mm by extending custom fitted 5th order correction to the 9th order. Minimum RMSE varied between scanners, but was stable with repeated measurements in the same scanner.ConclusionsThe results suggest that the proposed methods may be used on a per-system basis to more accurately calibrate MR gradient non-linearity coefficients when compared to vendor standard corrections.

Dataset Information

Frequency-Domain Approach To Determine Magnetic Address-Sensor Separation Distance Using the Harmonic Ratio Method.

Publications

Frequency-Domain Approach To Determine Magnetic Address-Sensor Separation Distance Using the Harmonic Ratio Method.

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