Fluke 76-903 User Manual

Nuclear Associates 76-903

MRI Multi-Purpose Phantom

Users Manual

Fluke Biomedical

Radiation Management Services

6045 Cochran Road Cleveland, Ohio 44139

440.498.2564

www.flukebiomedical.com/rms

Table of Contents

Section 1: Introduction................................................................................................ 1-1

1.1 Introduction .................................................................................................. 1-1

1.2 Orientation – Imaging Method...................................................................... 1-1

1.3 Choosing Echo Time.................................................................................... 1-1

1.4 NMR Solution............................................................................................... 1-2

Section 2: Specifications ............................................................................................ 2-1

2.1 Phantom Design .......................................................................................... 2-1

Section 3: Theory of Operation................................................................................... 3-1

3.1 Omni Directional Application........................................................................ 3-1

3.2 Concentric Conical Rings Section................................................................ 3-1

3.2.1 Slice Thickness Uniformity ........................................................................ 3-1

3.2.2 Aspect Ratio.............................................................................................. 3-1

3.2.3 Magnetic Field Homogeneity..................................................................... 3-2

3.3 Flood Section............................................................................................... 3-2

3.3.1 RF Uniformity ............................................................................................ 3-3

3.3.2 T

3.4 Insert Section............................................................................................... 3-3

3.4.1 Folded Step Ramps................................................................................ 3-4

3.4.2 Fold Step Ramp Analysis ....................................................................... 3-4

3.4.3 Measurement Method............................................................................. 3-4

3.4.4 Slice Contiguity (Gap)............................................................................. 3-5

3.4.5 Resolution Pattern.................................................................................. 3-5

3.4.6 Star Pattern ............................................................................................ 3-6

and T2 Values ....................................................................................... 3-3

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Introduction

Section 1

Introduction

1.1 Introduction

This phantom is designed for comprehensive evaluation of critical imaging parameters of magnetic resonance imaging (MRI) in a time efficient manner. Particular attention was paid to obtaining all the necessary image quality information with a minimum number of imaging sequences. It is designed to study parameters unique to multi-slice two-dimensional and three-dimensional Fourier imaging.

The overall dimensions of the phantom adjust so that it can be positioned in each of the three major imaging planes: axial, coronal and sagittal.

The phantom can be used for the measurement of absolute values for calibration purposes. However, its design is optimized for time efficient daily quality assurance.

The performance parameters that can be evaluated using the phantom include: slice orientation, slice thickness, interslice distance, aspect ratio, magnetic field uniformity, radio-frequency signal uniformity, spatial resolution, T evaluate such parameters as resonant frequency, radio frequency power setting, radio frequency quadrature setting, magnetic field gradient calibration, slice off-set parameters, image off-set, and other image artifacts peculiar to MRI.

and T

values, and modulation transfer function. The phantom can also be used to

1.2 Orientation Imaging Method

In a two-dimensional Fourier transform (2DFT) imaging of MRI, the data is collected in two orthogonal directions, i.e., encoding and readout.

In some imaging sequences, the spatial resolution may be different in the two directions. The star pattern is designed to study such asymmetric resolution as well as qualitative modulation transfer function (MTF) in MR images. For this reason, it is important to properly orient the star pattern. Note four lines or dots on the wall of the phantom.

Place the phantom in the imaging system readout direction.

SO that one is in either the phase encoding or frequency

1.3 Choosing Echo Time

Any clinical multi-slice imaging sequence can be used. Often, however, the imaging sequences with the shortest echo time (TE), largest number of slices possible within the pulse repetition time (TR), and single excitation (no averaging) will demonstrate the performance of an imaging system under one of the most demanding situations. For a daily QA program, it is important to record all the important imaging parameters. An example of such a table of imaging parameters can be found in Table 1-1.

1-1

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