Fluke 76-908, 76-907 User Manual

Nuclear Associates

76-907 and 76-908

AAPM MRI Phantoms

March 2005
Manual No. 38616 Rev. 3
©2003, 2005 Fluke Corporation, All rights reserved. Printed in U.S.A.
All product names are trademarks of their respective companies

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: General Information................................................................................... 1-1

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

1.2 Phantom Description.................................................................................... 1-1

1.2.1 3D Resolution and Slice (3DRAS) Phantom (Model 76-908) ................. 1-2

1.2.2 Uniformity and Linearity (UAL) Phantom (76-907).................................. 1-4

Section 2: Operations .................................................................................................. 2-1

2.1 Phantom Preparation................................................................................... 2-1

2.1.1 Signal Producing Solution ...................................................................... 2-1

2.1.2 Filling the Phantom................................................................................. 2-1

2.2 Preparation for Scanning ............................................................................. 2-2

2.2.1 Positioning the Phantom......................................................................... 2-2

2.2.2 Scanning Parameters............................................................................. 2-2

2.3 Tests with 3D Resolution and Slice (3DRAS) Phantom............................... 2-2

2.3.1 Resonance Frequency ........................................................................... 2-2

2.3.2 Signal-To-Noise Ratio ............................................................................ 2-3

2.3.3 High-Contrast Spatial Resolution ........................................................... 2-3

2.3.4 Slice Thickness ...................................................................................... 2-4

2.3.5 Slice Position and Separation................................................................. 2-4

2.3.6 Example Images..................................................................................... 2-5

2.4 Tests with Uniformity and Linearity (UAL) Phantom .................................. 2-10

2.4.1 Image Uniformity .................................................................................. 2-10

2.4.2 Spatial Linearity (Distortion) ................................................................. 2-10

2.4.3 Image Artifacts ..................................................................................... 2-11

2.4.4 Action Criteria....................................................................................... 2-12

2.4.5 Example Images................................................................................... 2-12

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General Information

Introduction

Section 1

General Information

1.1 Introduction

This user's manual describes a set of MRI phantoms that were manufactured based on the AAPM
recommendations and their use in measuring the MRI system performance. These phantoms were
designed to measure them conveniently and quickly. The AAPM recommended image parameters
described in this document are:

• Image uniformity

• Resonance frequency

• Slice position/separation

• Spatial linearity

• Phase related image artifacts

• Signal-to-noise

• Slice thickness

• Spatial resolution

This set of parameters is measured for monitoring the sensitivity and geometric characteristics of MR
imaging clinical systems as specified in the AAPM document.

1

Two phantoms were designed to meet the AAPM specifications. This manual describes a set of test
procedures associated with the phantoms that can be used to evaluate the performance of clinical
magnetic resonance imaging systems. These procedures and tests, which are described in the AAPM
document, can be used to establish absolute performance standards as well as routine quality assurance
programs.

The manual does not include procedures to measure any T1, T2, or proton density, because at the
present time there are no commonly accepted standard methods for determining T1, T2, and proton
density from image data and because the assessment of these parameters is not currently a part of
clinical practice.

1.2 Phantom Description

AAPM specifications provide a framework of requirements for MRI phantoms and their use, but it defines
neither how phantoms should be constructed nor how inserts are to be organized. The AAPM MR
Phantoms take into consideration a number of factors that maximize convenience and time efficiency for
the user. The phantoms were designed to provide maximum amount of information in a reproducible
manner with the shortest data acquisition time.

The set consists of two phantoms: a three dimensional resolution and slice (3DRAS) phantom and an
uniformity and linearity (UAL) phantom

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Nuclear Associates 76-908 & 76-907

Operators Manual

1.2.1 3D Resolution and Slice (3DRAS) Phantom (Model 76-908)

The 3DRAS phantom has outer dimensions of 6" x 6" x 5" (Figure 1-1). Six resolution inserts and slice
thickness 4 ramp sets were placed inside of the rectangular box to allow image acquisition in any one of
the three directions (sagital, coronal, and transaxial) without repositioning the phantom.

Outer Shape 6" X 6" X 5" Cubical Box

Figure 1-1. 3DRAS Phantom

The resolution section (Figure 1-2) has square holes of 0.5 mm, 0.75 mm, 1.0 mm and 2.0 mm side
dimensions. The spacing between the holes is equal to their side dimensions. The holes are precisely
parallel to each other and are ¾” long. Square holes are used rather than drilled cylindrical holes because
square holes can be manufactured more precisely than cylindrical holes.

Resolution Block Detail - 2 Required

A set of two resolution sections are positioned perpendicular to each other (Figure 1-3) in three imaging
planes (sagital, coronal, and transaxial). Two sections are used per imaging plane since the spatial
resolution of MR images can be asymmetric between the encoding and frequency (read-out) direction.

0.5 x 0.5 mm

0.75 x 0.75 mm

Figure 1-2. Resolution Block Detail

1.0 x 1.0 mm 2.0 x 2.0 mm

1”

2 ¼ “

”

Not to scale

1-2

General Information

p

Phantom Description

#1

1

#4

1 mm Gap

Box Dimension of the Box 6: x 6:
Walls are Made with ¼” Material

2 mm Gap

1 mm Ga

#3

Filling Hole ( ¼”)

Resolution Block

Resolution Blocks

#2

2 mm Gap

Resolution Blocks
w/Vertical Holes

Slice Thickness
Block Groups (4)

Figure 1-3. Resolution Sections in Three Imaging Planes

The slice-thickness phantom consists of two crossed thin ramps (Figure 1-4).

Figure 1-4. Slice Thickness Phantom

Triangular blocks make 4" x 4" square with diagonal gaps of 1 or 2 mm. Four triangular blocks are glued
with 1 mm or 2 mm gap.

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Nuclear Associates 76-908 & 76-907

Operators Manual

A ramp-crossing angle of 90° yields an angle of 45° between the ramp and the imaging slice plane. Each
slice thickness section consists of four triangular blocks arranged to form (signal producing) hot ramps
filling the gaps of 1 mm or 2 mm (Figure 1-5).

Slice Thickness Measurement Gaps

Gaps are 1 mm or 2 mm Throughout

Figure 1-5. Slice Thickness Sections

The ramps of the 1 mm gaps (forming diagonal lines) are glued at the opposite side inner wall of the
3DRAS phantom. Two sets of ramp sections are included in the phantom in order to allow the slice
thickness measurements in all three dimensions.

In a single multi-slice scan, the user can obtain images for signal-to-noise ratio, resolution in two
directions, slice thickness, and slice-to-slice gap.

1.2.2 Uniformity and Linearity (UAL) Phantom (76-907)

The UAL phantom has outer dimensions of 13" x 13" x 4" (Figure 1-6) with a small bubble (Figure 1-7)
filled with a solution attached on the surface of the phantom. A rectangular shape was adopted for ease
of reproducible positioning. Two parts of the phantom, flood and grid, are incorporated into one.

1-4