Benutzeranleitung / Produktwartung 76-907 des Produzenten Fluke
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Nuclear Associates 76-907 and 76-908 AAPM MRI Phantoms Users Manual March 2005 Manual No. 38616 Rev. 3 © 2003, 2005 Fluke Corporat i on, All rights reserved .
Fluke Biomedical Radiation Management Services 6045 Cochran Road Cleveland, Ohio 44139 440.498.2564 www.flukebiomedical.com/rms.
i Table of Contents Section 1: General Info rmation ................................................................................... 1-1 1.1 Introduc tion .............................................................................................
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General Information Introduction 1 1-1 Section 1 General Information 1.1 Introduction This user's manual descr ibes a set of MRI phantoms that we re manufactured ba sed on the AAPM recommendations and thei r use in measuring t he MRI system performan ce.
Nuclear Associates 76-908 & 76-907 Operators Manual 1-2 1.2.1 3D Resolution and Slice (3DRAS) Phantom (Model 76-908) The 3DRAS phantom has outer dim ensions of 6" x 6" x 5" (Figure 1-1).
General Information Phantom Description 1 1-3 Figure 1-3. Resolution Sections in Three Imaging Pl anes The slice-thickness phanto m consists of two crossed thin ramps (Figure 1-4 ). Figure 1-4. Slice Thickness Phantom Triangular blocks make 4" x 4" sq uare with diagonal gaps of 1 or 2 mm.
Nuclear Associates 76-908 & 76-907 Operators Manual 1-4 A ramp-crossing angle of 90° yields an a ngle of 45° between the ramp and the imaging slice plane. Ea ch slice thickness section con sists of four triangular blocks arrang ed to form (signal producing) h ot ramps filling the gaps of 1 mm or 2 mm (Figure 1-5).
General Information Phantom Description 1 1-5 MR Phantom for Spatial Linearity, Signal-To-Noise, and Image Artifact Figure 1-6. UAL Phantom MRI Phantom for Spatial Linearity, Signal-To-Noise, and Image Artifact Figure 1- 7.
Nuclear Associates 76-908 & 76-907 Operators Manual 1-6 The flood phantom has a uniform solution, the image of which can be used to measure the uniformity in signal intensity in the images. The grid section con s ists of grids that can be used to assess geometri c linearity.
Operation Phantom Preparation 2 2-1 Section 2 Operation 2.1 Phantom Preparation The phantoms can be shipped filled with solutions or solutions can be shipped separately.
Nuclear Associates 76-908 & 76-907 Operators Manual 2-2 2.2 Preparation for Scanning 2.2.1 Positioning the Phantom The 3DRAS phantom can be pla ced in a head coil or a body coil. The center of the phantom should coincide approximately with the center of the RF coil.
Operation Tests with 3D Resolution and Slice (3DRAS) Phantom 2 2-3 resonance frequency adju stment and some may be completely automated. Resonance frequency shoul d be recorded daily for trend analysis. Values of resonance frequency should gene rally not deviate by more tha n 50 ppm between successive daily measurements.
Nuclear Associates 76-908 & 76-907 Operators Manual 2-4 • The high contrast resolution should rem ain constant for repeated measurements und er the same scan conditions and should be equ al to the pixel size. For example, for a 25.6 cm field of view with a 256 x 256 acquisitions m atrix, the resolution should be 1 mm.
Operation Tests with 3D Resolution and Slice (3DRAS) Phantom 2 2-5 direction) is measured and relate d to the slice posi tion. For a 45° ramp, the distance from a centered reference pin to the slice profile midpoint will be equ al to the point of the ramps located at the isocenter.
Nuclear Associates 76-908 & 76-907 Operators Manual 2-6 Figures 2-2 and 2-3 represent two adja cent sagital vi ews of the phantom. The resolution hole s are well resolved in vertical and ho rizontal direction and the two slices are 6 mm apart (SP = 14.
Operation Tests with 3D Resolution and Slice (3DRAS) Phantom 2 2-7 Figures 2-4 and 2-5 show two adj acent coronal view s of the phantom. The slice thickne ss lines of 1 mm ramps on the right and bottom of the images are too faint to be seen . Figure 2-5 Figure 2-4.
Nuclear Associates 76-908 & 76-907 Operators Manual 2-8 Figure 2-6 shows a resolution hole imag e against a background le ss opaque than in previou s images, indicating that the position of the resolution blo ck is su ch that it is partially covered by the slice.
Operation Tests with 3D Resolution and Slice (3DRAS) Phantom 2 2-9 Figures 2-7 and 2-8 show an exampl e of the slice thickness measureme nt analysis. A signal intensity profile is drawn vertically through a set of slice thi c kness ramp Images. The profile is the sli ce thickness profile.
Nuclear Associates 76-908 & 76-907 Operators Manual 2-10 2.4 Tests With Uniformity and Linearity (UAL) Phantom 2.4.1 Image Uniformity Image uniformity refers to the ability of the MR imag ing syste m to produce a constant signal re sponse throughout the scanned volume when th e object bei ng imaged has homogeneou s MR characteristics.
Operation Tests with Uniformity and Linea rity (UAL) Phantom 2 2-11 (2) Non-linear m agnetic field gradients Variability is best observed over the largest field-of-view. The phantom should occupy at least 60% of the largest field-of-view. Figu re 1-1 provides an illustration of a patte rn that is used to evaluate spatial linearity.
Nuclear Associates 76-908 & 76-907 Operators Manual 2-12 DC-Offset Errors DC-offset errors typically appear a s a single bright pixel (sometimes a s a dark pixel if overflow or processing has occurred) at the center of the image matrix. The existence of this error is a ssessed visually.
Operation Tests with Uniformity and Linea rity (UAL) Phantom 2 2-13 Figure 2-9.
Nuclear Associates 76-908 & 76-907 Operators Manual 2-14 Figure 2-10 is a flood image showing the uniformity o f si gnal intensity. Field non-uniformit y is also shown on the outer edges. Figure 2-10 Figure 2-11 shows a horizont al inten sity profile with a narrow window setting.
Operation Tests with Uniformity and Linea rity (UAL) Phantom 2 2-15 Figure 2-12 is an image of the signal bubble for quadr ature e rror. If there were any quadrature phase error, another ghost circle woul d be visible in the lo wer right-hand corne r of the image.
Fluke Corporation Radiation Management Services 6045 Cochran Road Cleveland, Ohio 44139 440.498.2564 www.flukebiomedical.com/rms.
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