Fluke 76-908 manuale d’uso

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 . Printed in U .S.A. All product names are trademar ks of their respective companies[...]

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i Table of Contents Section 1: General Info rmation ................................................................................... 1-1 1.1 Introduc tion .................................................................................................. 1-1 1.2 Phantom De scription ................................................................[...]

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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. These phantoms were designed to measure them conv eniently and quickly. The AAPM recommend[...]

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). Six re solution inserts and slice thickness 4 ramp sets were placed inside of the recta ngular box to allow image acquisition in a ny one of the[...]

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. Four triangular blocks are glued with 1 mm 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). Figure 1-5. Slice Thickness [...]

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. UAL Phantom with Side View 4” 13” Glue Glue Glue Glue Flood Section Two Grids Stacked Glue Glue Glue 3/16” Wall ¼” Wa[...]

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. A small pancake shaped containe r holding producing so lutio n is atta[...]

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. Each use r can also prepare a solution. 2.1.1 Signal Producing Solution At each operating field st rength, AAPM recommends that the chos en NMR material should exhibit the followin[...]

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. The UAL phantom can be use d only with a body coil. 2.2.2 Scanning Parameters F[...]

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. 2.3.2 Signal-To-Noise Ratio[...]

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. 2.3.4 Slice Thickness Sl[...]

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. All measurements should be made al ong the line made up of the mag[...]

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 = 14.5 and 20.5). The slice thickness images of short vertical lines on top and bottom of the phant[...]

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. For resolution measure, it is advised to use a slice that co vers the central port[...]

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. One can also obtain the slice thickness by me asu ring full [...]

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. Factors A[...]

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. Consideration sh[...]

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. Receive Quadrature Errors Receive quadrature gho sts will [...]

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. Such information ca n be used as baseline data. Figure 2-11[...]

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. Quadrature error has become less common in most of the recent MRI syste ms. Figure 2-[...]

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