Artifacts

6,510 views

Published on

1 Comment
9 Likes
Statistics
Notes
  • VERY USEFUL THANK U
       Reply 
    Are you sure you want to  Yes  No
    Your message goes here
No Downloads
Views
Total views
6,510
On SlideShare
0
From Embeds
0
Number of Embeds
3
Actions
Shares
0
Downloads
348
Comments
1
Likes
9
Embeds 0
No embeds

No notes for slide
  • <number>
  • <number>
  • <number>
  • <number>
  • Artifacts

    1. 1. M R I Physics CourseM R I Physics Course Jerry Allison Ph.D.Jerry Allison Ph.D. Chris Wright B.S.Chris Wright B.S. Tom Lavin M.S.M.P.Tom Lavin M.S.M.P. Department of RadiologyDepartment of Radiology Medical College of GeorgiaMedical College of Georgia
    2. 2. Artifacts and Suppression TechniquesArtifacts and Suppression Techniques Artifacts / Undesirable ContrastArtifacts / Undesirable Contrast Chemical Shift artifactChemical Shift artifact Truncation (Gibbs) ArtifactTruncation (Gibbs) Artifact Errors in dataErrors in data Aliasing (wrap around)Aliasing (wrap around) Zippers / Stars (Zero line artifact)Zippers / Stars (Zero line artifact) Flow artifactFlow artifact Metallic artifact (magnetic field perturbations)Metallic artifact (magnetic field perturbations) M R I Physics CourseM R I Physics Course chapter 12chapter 12
    3. 3. Artifacts and Suppression TechniquesArtifacts and Suppression Techniques MotionMotion Magnetic Susceptibility artifactMagnetic Susceptibility artifact Surface Coil artifactSurface Coil artifact N/2 Ghosts in EPIN/2 Ghosts in EPI M R I Physics CourseM R I Physics Course chapter 12chapter 12
    4. 4. Artifacts and Suppression TechniquesArtifacts and Suppression Techniques Chemical shift artifactsChemical shift artifacts --At 1.5T the Larmor frequency of fat is approximately 220At 1.5T the Larmor frequency of fat is approximately 220 Hz lower than water. MRI images can be considered to beHz lower than water. MRI images can be considered to be images of free water with a superimposed spatiallyimages of free water with a superimposed spatially misregistered fat image.misregistered fat image. -Chemical shift artifacts produce high intensity and low-Chemical shift artifacts produce high intensity and low intensity bands near fat/water interfaces, primarily in theintensity bands near fat/water interfaces, primarily in the frequency encode direction.frequency encode direction. --Dark boundaries between regions are sometimes calledDark boundaries between regions are sometimes called “contour artifacts”.“contour artifacts”. 4
    5. 5. 5 Kidney example: from theKidney example: from the http://www.mritutor.orghttp://www.mritutor.org websitewebsite ((© 1994-2003 by© 1994-2003 by Ray BallingerRay Ballinger))
    6. 6. Copyright ©Radiological Society of North America, 1999 Williams, R. L. et al. Radiology 1999;212:151-154
    7. 7. Chemical shift at 7T: oil and waterChemical shift at 7T: oil and water
    8. 8. Artifacts and Suppression TechniquesArtifacts and Suppression Techniques (continued)(continued) Truncation (Gibbs) artifactTruncation (Gibbs) artifact --Truncation artifact or Gibbs phenomena appear as a periodicTruncation artifact or Gibbs phenomena appear as a periodic “ringing” at high contrast interfaces.“ringing” at high contrast interfaces. -Truncation artifact is caused by underestimation or-Truncation artifact is caused by underestimation or overestimation of the signal at high contrast boundaries.overestimation of the signal at high contrast boundaries. 8
    9. 9. Artifacts and Suppression TechniquesArtifacts and Suppression Techniques (continued)(continued) Truncation (Gibbs) artifactTruncation (Gibbs) artifact -The step function resulting from a high contrast-The step function resulting from a high contrast interface cannot be accurately depicted by the finiteinterface cannot be accurately depicted by the finite number of sine and cosine waves prescribed by anumber of sine and cosine waves prescribed by a typical MR image acquisition matrix.typical MR image acquisition matrix. -Truncation artifacts can be diminished by a decrease-Truncation artifacts can be diminished by a decrease in pixel size or raw data filtering. It is important toin pixel size or raw data filtering. It is important to remember that raw data filtering affects all imageremember that raw data filtering affects all image data not just the artifactual portions.data not just the artifactual portions. -Pixel size can be decreased by increasing the-Pixel size can be decreased by increasing the imaging matrix or decreasing the field of view.imaging matrix or decreasing the field of view. 9
    10. 10. Artifacts and Suppression TechniquesArtifacts and Suppression Techniques (continued)(continued) Partial Volume ArtifactsPartial Volume Artifacts -Caused by an imaging voxel containing two-Caused by an imaging voxel containing two different tissues and therefore possessing a signaldifferent tissues and therefore possessing a signal average of both tissues.average of both tissues. 10
    11. 11. Artifacts and Suppression TechniquesArtifacts and Suppression Techniques (continued)(continued) 11
    12. 12. Artifacts and Suppression TechniquesArtifacts and Suppression Techniques (continued)(continued) Errors in dataErrors in data -Errors in data can cause striped images, washed out-Errors in data can cause striped images, washed out images and zipper artifacts.images and zipper artifacts. -Failure of the array processor can produce a variety-Failure of the array processor can produce a variety of stripes and patterns (i.e. corduroy artifacts) onof stripes and patterns (i.e. corduroy artifacts) on reconstructed images.reconstructed images. 12
    13. 13. Artifacts and Suppression TechniquesArtifacts and Suppression Techniques (continued)(continued) -Leaking RF shield:-Leaking RF shield: The exam room is RF shielded to attenuate RF energyThe exam room is RF shielded to attenuate RF energy from radio, television, etc. Failure of the shield canfrom radio, television, etc. Failure of the shield can produce zipper artifacts. To demonstrate a leakingproduce zipper artifacts. To demonstrate a leaking RF shield, scan with the door open. A simple test ofRF shield, scan with the door open. A simple test of the RF shield is to see if a transistor radio receivesthe RF shield is to see if a transistor radio receives signal in the exam room with the door closed.signal in the exam room with the door closed. 13
    14. 14. Artifacts and Suppression TechniquesArtifacts and Suppression Techniques (continued)(continued) RF receiver gainRF receiver gain -If the RF receiver gain is set such that the voltage-If the RF receiver gain is set such that the voltage level of the amplified signal exceeds the voltagelevel of the amplified signal exceeds the voltage range of the ADC, washed out images result.range of the ADC, washed out images result. -The RF receiver gain settings are generally adjusted-The RF receiver gain settings are generally adjusted by auto prescan to avoid this artifact.by auto prescan to avoid this artifact. 14
    15. 15. Artifacts and Suppression TechniquesArtifacts and Suppression Techniques (continued)(continued) Aliasing (wrap-around)Aliasing (wrap-around) -Aliasing or wrap-around artifacts can occur when-Aliasing or wrap-around artifacts can occur when the anatomy exceeds the field of view. Aliasing canthe anatomy exceeds the field of view. Aliasing can occur in the frequency encode direction or the phaseoccur in the frequency encode direction or the phase encode direction.encode direction. 15
    16. 16. 16
    17. 17. Artifacts and Suppression TechniquesArtifacts and Suppression Techniques (continued)(continued) Aliasing (wrap-around)Aliasing (wrap-around) -Solution 1: Sampling faster may reduce or eliminate-Solution 1: Sampling faster may reduce or eliminate aliasing but results in an increased receiveraliasing but results in an increased receiver bandwidth with decreased SNR.bandwidth with decreased SNR. 17
    18. 18. Artifacts and Suppression TechniquesArtifacts and Suppression Techniques (continued)(continued) Aliasing (wrap-around)Aliasing (wrap-around) Solution 2:-Use of a larger FOV than actuallySolution 2:-Use of a larger FOV than actually desired and display of the central “non-aliased”desired and display of the central “non-aliased” portion of the image. This is the essence of “Noportion of the image. This is the essence of “No Phase Wrap”, “No Frequency Wrap” andPhase Wrap”, “No Frequency Wrap” and “Oversampling”. Aliasing in the frequency encode“Oversampling”. Aliasing in the frequency encode direction is generally prevented on modern MRIdirection is generally prevented on modern MRI systems by oversampling.systems by oversampling. 18
    19. 19. 19
    20. 20. Artifacts and Suppression TechniquesArtifacts and Suppression Techniques (continued)(continued) Aliasing (wrap-around)Aliasing (wrap-around) -Siemens: Oversampling in the frequency encode-Siemens: Oversampling in the frequency encode direction doubles the number of points sampled.direction doubles the number of points sampled. -GE: Oversampling in the frequency encode direction is-GE: Oversampling in the frequency encode direction is always utilized.always utilized. -Oversampling in the frequency encode direction does-Oversampling in the frequency encode direction does not change image acquisition time (or number of slices ornot change image acquisition time (or number of slices or echo time).echo time). 20
    21. 21. Artifacts and Suppression TechniquesArtifacts and Suppression Techniques (continued)(continued) Aliasing (wrap-around)Aliasing (wrap-around) -Aliasing also occurs in the phase encode direction. This-Aliasing also occurs in the phase encode direction. This can be cured by use of “No Phase Wrap:GE” orcan be cured by use of “No Phase Wrap:GE” or “Oversampling:Siemens”.“Oversampling:Siemens”. -Siemens: Oversampling in the phase encode-Siemens: Oversampling in the phase encode direction increases the number of phase encodes by adirection increases the number of phase encodes by a user selectable percentage.user selectable percentage. -GE: “No Phase Wrap” doubles the number of phase-GE: “No Phase Wrap” doubles the number of phase encode samples (and halves the number ofencode samples (and halves the number of excitations).excitations). 21
    22. 22. 22
    23. 23. Artifacts and Suppression TechniquesArtifacts and Suppression Techniques (continued)(continued) Aliasing (wrap-around)Aliasing (wrap-around) -Removal of phase encode aliasing can require-Removal of phase encode aliasing can require additional scan time.additional scan time. -In gradient recalled echo imaging, aliasing may-In gradient recalled echo imaging, aliasing may produce a pronounced zebra stripe artifact. Thisproduce a pronounced zebra stripe artifact. This artifact can be eliminated by oversampling (“Noartifact can be eliminated by oversampling (“No Phase Wrap”) or increasing the FOV.Phase Wrap”) or increasing the FOV. 23
    24. 24. Artifacts and Suppression TechniquesArtifacts and Suppression Techniques (continued)(continued) Aliasing (wrap-around)Aliasing (wrap-around) -Aliasing can occur in the slice encoding direction in-Aliasing can occur in the slice encoding direction in a 3D data set. GE routinely discards the foura 3D data set. GE routinely discards the four outermost slices in a 3D data set (acquire 128 slices;outermost slices in a 3D data set (acquire 128 slices; displays 124 slices: acquire 64 slices; display 60displays 124 slices: acquire 64 slices; display 60 slices: acquire 32 slices; display 28 slices). Aliasingslices: acquire 32 slices; display 28 slices). Aliasing or wrap-around in the slice encoding direction isor wrap-around in the slice encoding direction is often still visible in the outermost slices.often still visible in the outermost slices. -The phase encode axis is usually chosen as the-The phase encode axis is usually chosen as the narrower aspect of anatomy in order to minimizenarrower aspect of anatomy in order to minimize phase encoding aliasing.phase encoding aliasing. 24
    25. 25. Artifacts and Suppression TechniquesArtifacts and Suppression Techniques (continued)(continued) Aliasing (wrap-around)Aliasing (wrap-around) -Solution 3: ”SAT”uration bands can be applied-Solution 3: ”SAT”uration bands can be applied outside the FOV to reduce aliasing artifacts.outside the FOV to reduce aliasing artifacts. 25
    26. 26. Artifacts and Suppression TechniquesArtifacts and Suppression Techniques (continued)(continued) Zippers/Stars (Zero line artifact)Zippers/Stars (Zero line artifact) -Bands having a dashed appearance through the-Bands having a dashed appearance through the center of image.center of image. -Stars consist of a bright dot in the center of the image-Stars consist of a bright dot in the center of the image with dashed line tails along the frequency and phasewith dashed line tails along the frequency and phase encode directions.encode directions. -The signal for each point in an MRI image is actually-The signal for each point in an MRI image is actually a sinc function ([sin x] / x) in both the frequencya sinc function ([sin x] / x) in both the frequency encode and the phase encode direction.encode and the phase encode direction. 26
    27. 27. Artifacts and Suppression TechniquesArtifacts and Suppression Techniques (continued)(continued) -The sinc function signal actually contributes to several-The sinc function signal actually contributes to several pixels in an image but ordinarily the signal side lobes ispixels in an image but ordinarily the signal side lobes is small and is not recognized in an image.small and is not recognized in an image. 27 Zippers/Stars (Zero line artifact)Zippers/Stars (Zero line artifact)
    28. 28. Artifacts and Suppression TechniquesArtifacts and Suppression Techniques (continued)(continued) Zippers/Stars (Zero line artifact)Zippers/Stars (Zero line artifact) -A large noise signal can cause zipper or star-A large noise signal can cause zipper or star artifacts. If the noise signal has large amplitudeartifacts. If the noise signal has large amplitude the signal from side lobes is large enough tothe signal from side lobes is large enough to show up as a dashed pattern in the reconstructedshow up as a dashed pattern in the reconstructed image.image. 28
    29. 29. Artifacts and Suppression TechniquesArtifacts and Suppression Techniques (continued)(continued) Flow artifactsFlow artifacts -Flow artifacts occur due to in-flow/out-flow time of-Flow artifacts occur due to in-flow/out-flow time of flight phenomena and due to phase accumulation in aflight phenomena and due to phase accumulation in a gradient magnetic field.gradient magnetic field. 29
    30. 30. Artifacts and Suppression TechniquesArtifacts and Suppression Techniques (continued)(continued) Flow artifactsFlow artifacts -Flow compensation (gradient motion rephasing) can-Flow compensation (gradient motion rephasing) can recover some phase dispersion attributable to flow.recover some phase dispersion attributable to flow. 1st order gradient moment nulling: compensation1st order gradient moment nulling: compensation for constant velocityfor constant velocity 30
    31. 31. Artifacts and Suppression TechniquesArtifacts and Suppression Techniques (continued)(continued) Flow artifactsFlow artifacts -Depends on-Depends on -Flow velocity-Flow velocity -Flow direction-Flow direction -Slice thickness-Slice thickness -TR / TE-TR / TE -Direction of artifacts can be reversed by swapping-Direction of artifacts can be reversed by swapping the phase and frequency encode directions.the phase and frequency encode directions. 31
    32. 32. Artifacts and Suppression TechniquesArtifacts and Suppression Techniques (continued)(continued) Metallic artifacts (magnetic field perturbations)Metallic artifacts (magnetic field perturbations) -Metals can cause distortions in the static magnetic-Metals can cause distortions in the static magnetic field.field. -Ferromagnetic metals can dramatically distort the-Ferromagnetic metals can dramatically distort the static field due to the alignment of many magneticstatic field due to the alignment of many magnetic “domains”.“domains”. -Non-ferromagnetic metals can distort the static-Non-ferromagnetic metals can distort the static magnetic field due to smaller magnetic susceptibilitymagnetic field due to smaller magnetic susceptibility effects.effects. -Metal artifacts are generally worse with gradient-Metal artifacts are generally worse with gradient recalled echo sequences than with spin echorecalled echo sequences than with spin echo sequences.sequences. 32
    33. 33. Artifacts and Suppression TechniquesArtifacts and Suppression Techniques (continued)(continued) Metallic artifactsMetallic artifacts -During imaging, eddy currents may be induced in-During imaging, eddy currents may be induced in some metal objects resulting in induced magnetism.some metal objects resulting in induced magnetism. -The effect of metallic objects is signal loss and-The effect of metallic objects is signal loss and image distortion:image distortion: -Ferromagnetic metal -Cosmetics (Fe, Co)-Ferromagnetic metal -Cosmetics (Fe, Co) -Dental amalgams -Implants-Dental amalgams -Implants -Non-ferromagnetic metal -Shrapnel-Non-ferromagnetic metal -Shrapnel 33
    34. 34. Signal voids near metalSignal voids near metal implants (e.g., fillings, as inimplants (e.g., fillings, as in this gradient-echo picture) arethis gradient-echo picture) are due to magnetic susceptibilitydue to magnetic susceptibility differences.differences. 34 MRI artifact website, Vancouver, BC © Copyright 1996, Wayne Patola and Bruce Coulter http://wwwrad.pulmonary.ubc.ca/stpaulsstuff/MRart/gre.html Artifacts and SuppressionArtifacts and Suppression Techniques (continued)Techniques (continued)
    35. 35. Artifacts and Suppression TechniquesArtifacts and Suppression Techniques (continued)(continued) MotionMotion -Patient motion produces ghost images; primarily in-Patient motion produces ghost images; primarily in the phase encode direction.the phase encode direction. -In the frequency encode direction, motion produces-In the frequency encode direction, motion produces little displacement in the 4-8 msec interval when datalittle displacement in the 4-8 msec interval when data are collected.are collected. 35
    36. 36. Artifacts and Suppression TechniquesArtifacts and Suppression Techniques (continued)(continued) MotionMotion -In the phase encode direction, motion can produce-In the phase encode direction, motion can produce large displacements (and associated large phaselarge displacements (and associated large phase errors) since it can be as much as a few secondserrors) since it can be as much as a few seconds between collection of adjacent lines of k-space.between collection of adjacent lines of k-space. -Solutions for motion artifacts include:-Solutions for motion artifacts include: -Restraints-Restraints -Physiological triggering to capture anatomy in the same-Physiological triggering to capture anatomy in the same aspect of the respiratory or cardiac cycle for each line ofaspect of the respiratory or cardiac cycle for each line of k-space.k-space. -Cardiac triggering is used frequently.-Cardiac triggering is used frequently. -Peripheral gating is available.-Peripheral gating is available. -Respiratory triggering is available but impractical.-Respiratory triggering is available but impractical. 36
    37. 37. Artifacts and Suppression TechniquesArtifacts and Suppression Techniques (continued)(continued) Solutions for motion artifacts include:Solutions for motion artifacts include: -Respiratory-Ordered Phase Encoding (ROPE) also-Respiratory-Ordered Phase Encoding (ROPE) also known as respiratory compensation or retrospectiveknown as respiratory compensation or retrospective cardiac gating. Each acquisition is assigned to k-spacecardiac gating. Each acquisition is assigned to k-space based upon the respiratory phase or cardiac phasebased upon the respiratory phase or cardiac phase when it was acquired. Retrospective cardiac gating iswhen it was acquired. Retrospective cardiac gating is similar to a first pass MUGA scan in Nuclearsimilar to a first pass MUGA scan in Nuclear Medicine.Medicine. -Fat suppression to eliminate bright ghosting from-Fat suppression to eliminate bright ghosting from moving fat.moving fat. -ChemSAT-ChemSAT -STIR-STIR -SAT bands-SAT bands 37
    38. 38. Artifacts and Suppression TechniquesArtifacts and Suppression Techniques (continued)(continued) Magnetic susceptibility artifactsMagnetic susceptibility artifacts -The magnetic susceptibility of material present in an-The magnetic susceptibility of material present in an MRI image varies. Various soft tissues have variousMRI image varies. Various soft tissues have various magnetic susceptibilities. Air has a very lowmagnetic susceptibilities. Air has a very low magnetic susceptibility. Iron deposits frommagnetic susceptibility. Iron deposits from hemorrhage, liver iron overload, etc. have very highhemorrhage, liver iron overload, etc. have very high magnetic susceptibility.magnetic susceptibility. 38
    39. 39. Artifacts and Suppression TechniquesArtifacts and Suppression Techniques (continued)(continued) Magnetic susceptibility artifactsMagnetic susceptibility artifacts -Perturbations in the static magnetic field due to magnetic-Perturbations in the static magnetic field due to magnetic susceptibility can cause geometric distortion and changes insusceptibility can cause geometric distortion and changes in signal intensity. Geometric distortions occur primarily in thesignal intensity. Geometric distortions occur primarily in the frequency encode direction. Signal intensity can be increasedfrequency encode direction. Signal intensity can be increased or decreased by magnetic susceptibility. The artifacts causedor decreased by magnetic susceptibility. The artifacts caused by magnetic susceptibility can sometimes be observed inby magnetic susceptibility can sometimes be observed in slices adjacent to the inhomogeneity. These artifacts may beslices adjacent to the inhomogeneity. These artifacts may be more prominent on gradient recalled echo images or long TEmore prominent on gradient recalled echo images or long TE spin echo images. Magnetic susceptibility may be usefulspin echo images. Magnetic susceptibility may be useful contrast for imaging of calcification and hemorrhage.contrast for imaging of calcification and hemorrhage. 39
    40. 40. Phantom SusceptibilityPhantom Susceptibility in a T2* Weighted Sequencein a T2* Weighted Sequence
    41. 41. Susceptibility Artifact inSusceptibility Artifact in Orthogonal T2* (EPI) imagesOrthogonal T2* (EPI) images
    42. 42. Artifacts and Suppression TechniquesArtifacts and Suppression Techniques (continued)(continued) Surface coil artifactSurface coil artifact -The sensitivity of surface coils falls off dramatically-The sensitivity of surface coils falls off dramatically with distance from the coil. Tissues close to thewith distance from the coil. Tissues close to the surface coil will have higher intensity than tissuessurface coil will have higher intensity than tissues farther from the coil. This artifact is very apparent infarther from the coil. This artifact is very apparent in TT11 weighted imaging of the spine where subcutaneousweighted imaging of the spine where subcutaneous fat produces very intense signal due to it’s short Tfat produces very intense signal due to it’s short T11 value and proximity to the coil.value and proximity to the coil. -GE Signa has an option “Image Intensity-GE Signa has an option “Image Intensity Correction” that is designed to reduce surface coilCorrection” that is designed to reduce surface coil artifacts (not used).artifacts (not used). 42
    43. 43. Surface Coil ArtifactSurface Coil Artifact -Notice how the SNR varies across the FOV for an 8-Notice how the SNR varies across the FOV for an 8 channel (parallel) brain coil.channel (parallel) brain coil. 43 Artifacts and Suppression TechniquesArtifacts and Suppression Techniques (continued)(continued)
    44. 44. Artifacts and Suppression TechniquesArtifacts and Suppression Techniques (continued)(continued) N / 2 Ghosts in EPIN / 2 Ghosts in EPI -EPI is very sensitive to ghosting artifacts. Because-EPI is very sensitive to ghosting artifacts. Because the MRI signal is sampled under alternatingthe MRI signal is sampled under alternating gradients, it is necessary to reverse (invert) everygradients, it is necessary to reverse (invert) every other line. Any imperfection in the entire MRIother line. Any imperfection in the entire MRI imaging chain can modulate the MRI signal at halfimaging chain can modulate the MRI signal at half the Nyquist frequency. The result can be an “N / 2”the Nyquist frequency. The result can be an “N / 2” ghost in the phase encode direction.ghost in the phase encode direction. - N / 2 ghosts can be minimized by:- N / 2 ghosts can be minimized by: -calibration scans (with no phase encodes)-calibration scans (with no phase encodes) -image filtering-image filtering 44
    45. 45. GHOSTS!GHOSTS! 45
    46. 46. Challenge: DielectricChallenge: Dielectric ResonanceResonance • Larmor frequency increases for stronger magnetsLarmor frequency increases for stronger magnets • RF wavelength approaches body dimensions and FOVRF wavelength approaches body dimensions and FOV dimensionsdimensions –– λλairair = 4.7m at 1.5T= 4.7m at 1.5T –– λλairair = 2.35m at 3T= 2.35m at 3T –– λλtissuetissue = 0.3m at 3T !!!!!!!! (high dielectric constant)= 0.3m at 3T !!!!!!!! (high dielectric constant) • Can produce dielectric resonances which may reduce RFCan produce dielectric resonances which may reduce RF penetrationpenetration – Standing wavesStanding waves – Image shadingImage shading – Worse in body imaging than headWorse in body imaging than head – Worse in large patients (obese)Worse in large patients (obese) • Dielectric resonance effects occur at all field strengths butDielectric resonance effects occur at all field strengths but become apparent at 3Tbecome apparent at 3T 46
    47. 47. Challenge: Dielectric ResonanceChallenge: Dielectric Resonance UGA (Torso Array)UGA (Torso Array) 47
    48. 48. Challenge: Dielectric ResonanceChallenge: Dielectric Resonance MCG (Torso Array)MCG (Torso Array) 48 T2 T2 STIR
    49. 49. © 2006 GE Healthcare© 2006 GE Healthcare
    50. 50. © 2006 GE Healthcare© 2006 GE Healthcare
    51. 51. © 2006 GE Healthcare© 2006 GE Healthcare
    52. 52. © 2006 GE Healthcare© 2006 GE Healthcare

    ×