Advances in Imaging: Echo, CT, CMR Justin D Pearlman MD ME PhD Director, Dartmouth Advanced Imaging...
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Transcript of Advances in Imaging: Echo, CT, CMR Justin D Pearlman MD ME PhD Director, Dartmouth Advanced Imaging...
Advances in Imaging:Advances in Imaging:
Echo, CT, CMREcho, CT, CMR
Justin D Pearlman MD ME PhDJustin D Pearlman MD ME PhD
Director, Dartmouth Advanced Imaging CenterDirector, Dartmouth Advanced Imaging Center
DisclosuresDisclosures
• Consultant for:Consultant for:–General ElectricGeneral Electric–Picker/Marconi/PhillipsPicker/Marconi/Phillips–ChironChiron–Boehringer-IngelheimBoehringer-Ingelheim–MagnaLabMagnaLab–Perfusion=off-label use of contrastPerfusion=off-label use of contrast
Dartmouth Advanced Imaging Dartmouth Advanced Imaging Center - AimsCenter - Aims
•1. Realtime 1. Realtime CMRCMR
•2. 4D Cardiac 2. 4D Cardiac CTCT
•3. 3D Echo, PET3. 3D Echo, PET
High-end imaging capabilities; Bench->BedsideHigh-end imaging capabilities; Bench->Bedside
•ViabilityViability
•MyopathyMyopathy
•MicrocirculatiMicrocirculationon
•DxDx
•RxRx
EquipmentEquipment
MREcho
CT
Images: CMR vs. EchoImages: CMR vs. Echo
Echo short axisEcho short axisCMR short axisCMR short axis
Cost: $400-800Cost: $500-$1500
SimilaritiesSimilaritiesEchoEcho
• Inject packets of energy Inject packets of energy waves, pulsed,waves, pulsed,
Receive echoesReceive echoes• Scan to collect data to Scan to collect data to
convert to imageconvert to image• TomographicTomographic• DynamicDynamic• Flow signal from phase Flow signal from phase
shiftshift
CMRCMR• Insert packets of energy Insert packets of energy
waves, pulsed,waves, pulsed,Receive echoesReceive echoes
• Scan to collect data to Scan to collect data to convert to imageconvert to image
• TomographicTomographic• DynamicDynamic• Flow signal from phase Flow signal from phase
shiftshift
DifferencesDifferences• Sound SpeedSound Speed
– 1540 m/s1540 m/s• Echo=A-mode (amp-time)Echo=A-mode (amp-time)• Stopped byStopped by
– MetalMetal– BoneBone– Air-tissueAir-tissue
• Views limited by rib window, Views limited by rib window, contact, anglecontact, angle
• Resolution depends on Resolution depends on frequency, beamwidthfrequency, beamwidth
• Bright blood requires contrastBright blood requires contrast
• Radiowave SpeedRadiowave Speed– 299,792,258 m/s299,792,258 m/s
• Echo=K-mode (amp-spatial freq)Echo=K-mode (amp-spatial freq)• Distorted byDistorted by
– MetalMetal– (No problems with bone, (No problems with bone,
air/tissue)air/tissue)• Any viewAny view• Resolution is adjustable down to Resolution is adjustable down to
10 microns, limited by noise and 10 microns, limited by noise and acquisition timeacquisition time
• Bright blood many waysBright blood many ways
Echo CMR
Basis for MRIBasis for MRI
B0 B1 Mz Mxy+ + Gx,y,z
+
MagnetismMagnetism
MagnetismMagnetism
Change in MagnetizationChange in Magnetization
0
0.2
0.4
0.6
0.8
1
-1 0 1 2 3 4 5
Time (seconds)L
on
git
ud
inal
Mag
neti
zati
on
0
0.5
1
-5 5 15 25 35 45
Time (milliseconds)
Tra
ns
ve
rse
Ma
gn
eti
za
tio
n
-1
-0.5
0
0.5
1
-1 0 1 2 3 4 5
Time (seconds)Lo
ng
itu
din
al
Mag
neti
zati
on
T1/TR
T1/TI
T2/TE
1-e(-TR/T1)
1-2e(-TI/T1)
e(-TE/T2)
K-SpaceK-Space
+ =
0.5 (3,2) + (2,5)
2,5
K-space sumsK-space sums
(3,2) + (2,5) (3,2) + 0.5 (2,5)
3,2 Sum
Fourier TransformFourier Transform
Pulse SequencePulse SequenceGradient Echo (FLASH)Gradient Echo (FLASH)
Pulse SequencePulse SequenceInversion Recovery (STIR)Inversion Recovery (STIR)
MethodsMethods
• Magnetization PreparationMagnetization Preparation
• ExcitationExcitation
• Spatial Encoding, EchoesSpatial Encoding, Echoes
• Image ReconstructionImage Reconstruction
Bright Blood TurboGradient Echo, Dark Blood FSEDIR, Fat-suppresive TIR, … (100’s)
Corresponding notionsCorresponding notions
• Echo IntenseEcho Intense • Short T1 (if T1-Short T1 (if T1-weighted image)weighted image)
• Short T2 (if T2-Short T2 (if T2-weighted image)weighted image)
• Water (if fat Water (if fat suppressed)suppressed)
• Fat (if not fat Fat (if not fat suppressed)suppressed)
Fat vs. Fat Suppression: RVDFat vs. Fat Suppression: RVD
RV RV
JDP 2/02
FatFat++ vs. Fat- vs. Fat-
SMART functionSMART function
0%
10%
20%
30%
40%
Motion Thickening
SMART
Fixed
0%
10%
20%
30%
40%
Motion Thickening
bFGF-2
Saline
Pearlman JD et al Serial motion assessment by reference tracking (SMART): application to detection of local functional impact of chronic myocardial ischemia. J Comput Assist Tomogr, 2001. 25(4): p. 558-62
Self-Triggered MRASelf-Triggered MRA
Coronary ImagingCoronary Imaging
Coronary ImagingCoronary Imaging
Calcium ScoringCalcium ScoringClaims:•Negative score may indicate non-cardiac sources of chest pain•Scores over 1,000 predict coronary event within the next 2-3 years•Positive scores referred for catheterization or stress test•BUT significant disease may have negative score•Positive score may be stable plaque
Current Use: Current Use: Aberrant Coronary OriginsAberrant Coronary Origins
Dynamic CTDynamic CT
Elastic Match of CoronariesElastic Match of Coronaries
• Fast CT of mom
• Elastic match contrast
• Simulated holography as background, for context
Coronary Sinus RxCoronary Sinus Rx
4D CMR4D CMR
Perfusion-Sensitive ImagingPerfusion-Sensitive Imaging
Resting delayed blood arrival predicts ischemiaResting delayed blood arrival predicts ischemia
Rest Delayed Blood ArrivalRest Delayed Blood ArrivalDark Late Zone Arrived
Space-Time MapSpace-Time Map
We introduced Space-
Time Maps to see delay
in blood arrival in a
single derived image
Perfusion EquitimePerfusion Equitime
Rest MRI vs. Rest MRI vs. rest Thallium / stress MIBIrest Thallium / stress MIBI
Blood Distribution Defects
2.97 3.13
2.10
0
1
2
3
4
MRI Stress Rest
# S
eg
me
nts
(o
f 8
)
P<0.001P=0.35
Coverage of Defects
75 81
61
83
62
99
0
20
40
60
80
100
mri/str str/mri res/mri mri/res res/str str/res
Target/Reference
Co
ve
rag
e (
%)
P=0.43P<0.001
P=0.01
Total number
Disease vessel 105 38 97 2.69 0.10
CABG 42 10 26 1.08 0.13
Angioplasty 36 22 56 0.92 0.14
Table 1: Clinical Characteristics of Study Population
Patients
N % Prevalence SE
Stent 15 11 28 0.38 0.11
3
17
32
17
3 2
10
30
3 2
9
42
33
8
33
1212
20
25
10
4 5
23
0
5
10
15
20
25
30
35
1 2 3 4 5 6 7 8
Location
Nu
mb
er
of
De
fec
ts
MRI
stress
rest
Agreement between Rest MRI and Rest / Stress Nuclear
ViabilityViability
Delayed EnhancementDelayed Enhancement62 year old patient with 3-vessel CAD c/o angina at rest.Hx MI 1992, PTCA LAD 1992, CABG 1995.Scintigraphy, MRI : lateral + anteroseptal wall defects
LV
RV
RA
LAlateral
septum
MV
TV
LVOT
Scar
Delayed Enhancement vs. Delayed Enhancement vs. Delayed ArrivalDelayed Arrival
Molecular ImagingMolecular ImagingbFGF2
Microvascular MRIMicrovascular MRI
• Tissue bright• Major vessels visible• Dynamic physiology
• Small vessels hidden
Angiogenesis-Sensitive MRIAngiogenesis-Sensitive MRI
No contrast Dark Flash 3D CT Validation
r=.95
Acad Rad 4:680 ’97 Nat Med 1:1085 ‘95Radiology 214:801 ‘00
Dark Flare Dark Flare PredictsPredicts ImprovedImproved Blood Blood Arrival From AngiogenesisArrival From Angiogenesis
Baseline 1 Month 2 Months
Dark Flare/Delayed Arrival CombinedDark Flare/Delayed Arrival Combined
First Dose-Response for Angiogenesis RxDA=Demand, CX=Response
Angiogenesis imaging may also Angiogenesis imaging may also help diagnose and treat cancerhelp diagnose and treat cancer
34 y.o. woman with apalpable breast mass.
Ultrasound negativeMammography negative
Collateral Sensitive MRI: fat black, collateral neovascular development flashes; cancer found.
MRI Microscopy in Large TargetMRI Microscopy in Large Target
Fold-over problem Limit signal to 1 cm2
Avoid fold-over
RME =
Response-
Modulated
ExcitationFold-over No fold-over
Look at bowl of kiwi40 micron resolution
Intravascular ImagingIntravascular Imaging
What to knowWhat to know• VocabularyVocabulary
–BB00, B, B11, M, Mzz, M, Mxyxy, T, T11, T, T22, T, T22*,*,, , , , , , –TI, TR, TE, TI, TR, TE, , Matrix, FOV, , Matrix, FOV, , TD, TW, TD, TW
–GE, SE, FISP, HASTE, …GE, SE, FISP, HASTE, …
• Tilted Tomographic AnatomyTilted Tomographic Anatomy
• Pathophysiology, Clinical DecisionsPathophysiology, Clinical Decisions
• Physics, Image ProcessingPhysics, Image Processing
Echo vs. CMREcho vs. CMR
CMR
Echo
“Both are watching out for the CAT skinner”
Clinical ExampleClinical Example 42 y.o. man with large 42 y.o. man with large
cell lymphomacell lymphoma Radiation to chestRadiation to chest Paroxysmal atrial Paroxysmal atrial
fibrillationfibrillation CT: Mediastinal CT: Mediastinal
mass ? LA mass ? LA compressioncompression
Long Axis 4 Chamber ViewLong Axis 4 Chamber View
Echo MRI: mass, effusion
Long Axis 2 Chamber ViewLong Axis 2 Chamber View
Echo: ? NL fxn MRI:effusion,mass
Long Axis 3 Chamber ViewLong Axis 3 Chamber ViewEcho MRI
Long Axis 5 Chamber ViewLong Axis 5 Chamber ViewEcho: WNL MRI: Effusion,Mass
Short Axis Cine (Stack) ViewShort Axis Cine (Stack) ViewMRI: Effusion, MassEcho: WNL
Short Axis Stack Short Axis Stack CineCine
Clinical ExampleClinical Example
• 63 y.o. 63 y.o. WomanWoman
• Paroxysmal Paroxysmal Atrial FibAtrial Fib
Long Axis 2 Chamber ViewLong Axis 2 Chamber ViewEcho: LVH MRI: LVH
Long Axis 3 Chamber ViewLong Axis 3 Chamber ViewEcho: ASH MRI:LVH+RVH
Long Axis 4 Chamber ViewLong Axis 4 Chamber ViewEcho: ASH; lung/RV MRI: LVH+RVH
Long Axis 5 Chamber ViewLong Axis 5 Chamber ViewEcho: “ASH” MRI: LVH+RVH
Cine Stacks: RPA stenosisCine Stacks: RPA stenosis
Short Grid Base Cine ViewShort Grid Base Cine ViewEcho: hyperkinetic MRI: Rt septum hypo, order
Clinical ExampleClinical Example
• 61 y.o. woman61 y.o. woman• Tamoxiphen Tamoxiphen
RxRx• Idiopathic Idiopathic
CHFCHF
Long Axis 2 Chamber ViewLong Axis 2 Chamber View
Echo MRI
Long Axis 4 Chamber ViewLong Axis 4 Chamber ViewEcho MRI
Long Axis 5 Chamber ViewLong Axis 5 Chamber ViewEcho: ?Good EF MRI: EF 11%
Long Axis Rotating ViewsLong Axis Rotating ViewsMRI: DCM, CS, IVC
Short Axis ( Grid Tag Stack) ViewShort Axis ( Grid Tag Stack) ViewEcho: Low EF ?Constriction MRI:DCM, No constriction
Clinical ExampleClinical Example
• 60 y.o. Woman 60 y.o. Woman s/p L s/p L Mastectomy, XRTMastectomy, XRT
• CO=1.0CO=1.0• TR=4+TR=4+
4L Chamber View4L Chamber ViewEcho MRI
Grid Cine vs. DobutamineGrid Cine vs. Dobutamine
10ug/kg0 ug/kg 20 ug/kg
RV Strain vs Dobutamine RxRV Strain vs Dobutamine Rx
6.00
7.00
8.00
9.00
10.00
11.00
12.00
13.00
14.00
0.09 0.17 0.26 0.34 0.43 0.52 0.60 0.69 0.77 0.10
Seconds
Str
ain
0 ug/kg10 ug/kg20 ug/kg
Apical RV Strain vs. RxApical RV Strain vs. Rx
6.00
7.00
8.00
9.00
10.00
11.00
12.00
13.00
14.00
0.09 0.17 0.26 0.34 0.43 0.52 0.60 0.69 0.77 0.10
Seconds
Str
ain
0 ug/kg10 ug/kg20 ug/kg
AV ProsthesisAV Prosthesis
Suture DehiscenceSuture Dehiscence
Aortic Cusp AneurysmAortic Cusp Aneurysm
MR ArtifactsMR Artifacts• Chemical Shift ArtifactsChemical Shift Artifacts : Fat, water yield sum of two shifted images 3.5 PPM : Fat, water yield sum of two shifted images 3.5 PPM• AliasingAliasing : : Field of view divides all of space – sine wave is infinite pattern, so copies sumField of view divides all of space – sine wave is infinite pattern, so copies sum• Black Boundary ArtifactsBlack Boundary Artifacts : : At 1.5 T, 3.5 PPM water - fat shift cancels at 4.5 ms multiples from 2.3 At 1.5 T, 3.5 PPM water - fat shift cancels at 4.5 ms multiples from 2.3
ms, eg 6.8, 11.3, and 15.9 ms. Avoid with TE's close to 4.5, 9, 13.6,....ms, eg 6.8, 11.3, and 15.9 ms. Avoid with TE's close to 4.5, 9, 13.6,....
• Gibbs or Truncation ArtifactsGibbs or Truncation Artifacts : Ringing : Ringing• Zipper ArtifactsZipper Artifacts : Door open : Door open• Phase-encoded Motion ArtifactsPhase-encoded Motion Artifacts : Ghosts : Ghosts• Entry Slice PhenomenonEntry Slice Phenomenon : Artery/Vein dark or bright by slice order; false “clot” : Artery/Vein dark or bright by slice order; false “clot”• Slice-overlap ArtifactsSlice-overlap Artifacts : Faded : Faded• Magic Angle EffectsMagic Angle Effects : Tendon gets T2 increased 100x at 55 angulation : Tendon gets T2 increased 100x at 55 angulation• MoireMoire Fringes Fringes : Aliasing + Phase differences R/L : Aliasing + Phase differences R/L• RF Overflow Artifacts : Washed outRF Overflow Artifacts : Washed out• Central Point Artifact : SpikeCentral Point Artifact : Spike• Susceptibility Artifacts : Microscopic gradients -> Bright/Dark spotsSusceptibility Artifacts : Microscopic gradients -> Bright/Dark spots• Zero-fill Artifact : DC offset -> Gibbs ringing -> Zebra stripesZero-fill Artifact : DC offset -> Gibbs ringing -> Zebra stripes
!
Thank you for your Thank you for your attentionattention
Key TermsKey Terms• Resonance = Specific matching frequencyResonance = Specific matching frequency• Excitation = Sending in a pulsed radiowaveExcitation = Sending in a pulsed radiowave• K-space trajectory = Data collection patternK-space trajectory = Data collection pattern• Magnetic Field Gradients = Magnetic Field Gradients =
– Spatial encoding toolSpatial encoding tool• MR Echo is not from tissue interface – it is externally produced from all locations in slice byMR Echo is not from tissue interface – it is externally produced from all locations in slice by
– Refocusing Radiowave PulseRefocusing Radiowave Pulse– and/or Gradient Reversaland/or Gradient Reversal
• Image is produced by “Fourier Transform”Image is produced by “Fourier Transform”– Converts “K-space” data to “X-space” imageConverts “K-space” data to “X-space” image
• Pulse Sequence = Sequence of pulses, gradients Pulse Sequence = Sequence of pulses, gradients and steps to get an image or series of imagesand steps to get an image or series of images
Key TermsKey Terms• T1 = Time to develop magnetizationT1 = Time to develop magnetization• Gradient = Magnetic Field Slope low-high in X, Y, or ZGradient = Magnetic Field Slope low-high in X, Y, or Z• Gradient-echo = echo caused by reversing X gradientGradient-echo = echo caused by reversing X gradient• Spin-echo = echo caused by addition of a radiowave refocusing pulseSpin-echo = echo caused by addition of a radiowave refocusing pulse• T2 = Time constant for loss in transverse magnetization with spin-echoT2 = Time constant for loss in transverse magnetization with spin-echo• T2*= Time constant for loss in transverse magnetization with gradient-echo; T2*= Time constant for loss in transverse magnetization with gradient-echo;
susceptibilitysusceptibility• TR = “Repetition time” = T1 contrast weightTR = “Repetition time” = T1 contrast weight• TE = “Echo time” = T2 or T2* contrast weightTE = “Echo time” = T2 or T2* contrast weight• T1 Weighted = method emphasizing T1 differencesT1 Weighted = method emphasizing T1 differences• T2 Weighted = method emphasizing T2 differencesT2 Weighted = method emphasizing T2 differences