SlideShare a Scribd company logo
Diffusion MRI
2011. 9. 29.
KAIST 바이오및뇌공학과
이정원
1
What is diffusion?
• Fick’s Law (1855, Adolf Fick)
J : diffusion flux (mol/m2s)
D : diffusion coefficient or diffusivity (m2/s)
Φ : Concentration in dimensions (mol/m3)
x : the position (m)
t : time (s)
2
What is diffusion?
• Brownian motion (Robert Brown, 1827)
– the presumably random drifting of particles suspended in a fluid
The characteristic bell-shaped curves of
the diffusion of Brownian particles.
3
What is diffusion?
• Einstein recognized that Brownian motion was associated with diffusion
– No macroscopic concentration gradient is needed.
– Self-diffusion arising from local concentration fluctuations
• Einstein derived the self-diffusion coefficient of the Brownian particle
– Einstein expressed the energy change as the total work done by the particles contained within
the volume
– Diffusion coefficient
• Einstein rewrote Fick’s laws for the diffusion
– in terms of diffusion under probability gradients
𝐷 =
𝑘 𝐵 𝑇
6𝜋𝜂𝑅
: Sutherland-Einstein relation (1905)
𝑘 𝐵 ∶ 𝐵𝑜𝑙𝑡𝑧𝑚𝑎𝑛𝑛′
𝑠 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡
𝜂 ∶ viscosity
T ∶ absolute temperature
R ∶ radius of the spherical particle
𝐾𝑛
𝜁
− 𝐷
𝛿𝑛
𝛿𝑥
= 0
𝐾 ∶ 𝑛𝑒𝑡 𝑓𝑜𝑟𝑐𝑒
𝑛 ∶ the number of Brownian particles per unit volume
𝜁 ∶ friction
D ∶ diffusion coefficient
X ∶ position
𝑃 𝑟 𝑟′
, 𝑡 : 𝑐𝑜𝑛𝑑𝑖𝑡𝑖𝑜𝑛𝑎𝑙 𝑝𝑟𝑜𝑏𝑎𝑏𝑙𝑖𝑡𝑦 𝑡ℎ𝑎𝑡 𝑎 𝑝𝑎𝑟𝑡𝑖𝑐𝑙𝑒 𝑠𝑡𝑎𝑟𝑡𝑖𝑛𝑔 𝑎𝑡 𝑟 𝑎𝑡 𝑡𝑖𝑚𝑒 𝑧𝑒𝑟𝑜 𝑤𝑖𝑙𝑙 𝑚𝑜𝑣𝑒 𝑡𝑜 𝑟′
𝑎𝑓𝑡𝑒𝑟 𝑎 𝑡𝑖𝑚𝑒 𝑡
: Einstein equation for diffusion
4
Why diffusion?
• Tissue cellularity • Connectivity
5
DW-MRI DTI
How to measure the diffusion in MRI
• A review of MR imaging sequences
Gradient Echo
sequence
Spin Echo
sequence
6
How to measure the diffusion in MRI
7
Allen W. Song, Brain Imaging and Analysis Center, Duke University,
“Principles of MRI Physics and Engineering”
Gradient Echo DW-MRI Spin Echo DW-MRI
• Almost any MR imaging sequence can be designed to be sensitive to diffusion
– By adding magnetic field gradients
• To magnetically label spins carried by diffusing molecules
• Only parallel component has an effect
How to measure the diffusion in MRI
Stationary
water
Mobile
water
Stationary
water
Mobile
water
8
How to measure the diffusion in MRI
• The first gradient pulse
– Alters the phase shift of each proton
– By an amount dependent on the water molecule’s spatial location relative to the gradient
• The second gradient pulse
– if the water molecule does not move between the application of the first and second
gradient pulses
• Reverse this phase shift
– If there is movement of the water molecule between application of the first and second
gradient pulses
• Complete rephasing cannot happen, causing signal loss from this spatial location
• The amount of signal loss is directly proportional to the degree of water motion (the protons’
mean diffusional path length)
• Two components measured
– Magnitude: the extent to which protons are free to diffuse
• Signal loss ∝ degree of water motion (the protons’ mean diffusional path length)
– Direction: preferential diffusion direction
• Signal loss is proportional to the motion component in the same direction as the diffusion
gradient. No signal loss would occur if the motion was perpendicular to the gradient direction.
9
How to measure the diffusion in MRI
Gradient and spin
90
RF
Dephasing
Rephasing
10
Imperfect refocusing
=Signal loss!
How to measure the diffusion in MRI
If spin moves
90
RF
Dephasing
Rephasing
G
11
Equation of diffusion attenuation, and b-value
• There is a particular problem
– The combination of the imaging and the diffusion gradient pulses produce attenuation
effects
• So, b-value is suggested
– To summarize all gradient effects (diffusion and imaging pulses)
– The diffusion sensitivity of the sequence
– Without additional gradients, SE imaging sequences has very low b-values (around 1 s/mm2)
𝐴 𝑇𝐸 : ln
𝑆
𝑆𝑜
= −𝛾2 𝐺2 𝛿2 ∆ −
𝛿
3
𝑫 = −𝑏𝑫
b-value
SignalIntensity
D
12
Various sequences of diffusion-weighted MRI
• Pulsed field gradient spin echo (PFGSE)
• Double pulsed gradient spin echo
– Two gradient pulse pairs on the same spin magnetization
– To compensate flow
• Stimulated echo
• Gradient echo
𝐴 𝑇𝐸 = exp(−𝛾2 𝐺2 𝛿2 ∆ −
𝛿
3
𝐷)
𝐴 𝑇𝐸 = exp(−𝛾2 𝐺2 𝛿2 ∆ −
𝛿
3
+
𝜀3
30
−
𝛿𝜀3
6
𝐷)
13
We can get diffusion-weighted MR images
• Among various MRI images
– T1-weighted MRI
– T2-weighted MRI
– FLAIR (Fluid attenuated inversion recovery)
– Proton Density weighted MRI
– Diffusion-weighted MRI
– Diffusion Tensor Imaging
– Susceptibility Weighted Imaging (SWI)
– Dynamic Susceptibility Contrast (DSC) MRI
– Magnetic Resonance Spectroscopy (MRS)
– Functional MRI
CT T1
weighted
T2-
weighted
Diffusion
weighted
ADC map
14
Diffusion-weighted image vs. Diffusion map
• Diffusion-weighted image
– Darkness: high diffusion
– Brightness: low diffusion
– Intensity is affected by many other parameters than diffusion
• Diffusion map (ADC map)
– To obtain pure maps of the diffusion coefficient
– By acquiring two images with different b-values, b and b0
– Darkness: low, slow diffusion
– Brightness: high, fast diffusion
𝐴 = [1 − exp −
TR
𝑇1
]exp −
𝑇𝐸
𝑇2
exp(−𝑏𝑫)
𝑫 𝑥,𝑦,𝑧 = −ln[
𝐴 𝑥,𝑦,𝑧 𝑏
𝐴 𝑥,𝑦,𝑧 𝑏0
]/(𝑏 − 𝑏0)
Diffusion-weighted image ADC map
15
Diffusion map
• Two b-value acquisitions
– Best precision: b-b0 = 1/D (in the brain b-b0 = 1000 to 1500 s/mm2)
• More than two b-value acquisitions
– Better accuracy
– To get further information on tissue microstructure and dynamics
16b-value
SignalIntensity
D
IVIM
• IVIM (intravoxel incoherent motion)
– Pseudo-diffusion process from movement of the blood in the microvasculature
– A means to cover all molecular displacements to which “diffusion” MRI could be sensitive
– Diffusion measurements with MRI may include perfusion effects and not just true diffusion
• Perfusion effects at very low b-values (<200 s/mm2)
– Only two b-values (0 and 1000 s/mm2) could include perfusion effect
• Overestimation of the true diffusion coefficient D
17
ADC (apparent diffusion coefficient)
• ADC map
– Describes microscopic water diffusibility in the presence of factors that restrict diffusion
within tissues.
– ADC is measured by combining two diffusion-weighted images
• typically with (Sb) and without (So) diffusion weighting
• or using two b-values
– Multiple b-values are needed
• To differentiate between perfusion and diffusion
– The area of high diffusion is represented as a bright area; a high ADC value
18
ADC (apparent diffusion coefficient)
• To take into account diffusion and pseudo-diffusion processes
• By replacing the microscopic diffusion coefficient D with a global parameter, ADC
• In the brain, as larger b-values can generally be used and f is very small (2~4%)
ADC ≡ −ln[
𝐴(𝑏)
𝐴(𝑏0)
]/(𝑏 − 𝑏0)
𝐴𝐷𝐶 ≈ 𝐷 + 𝑓/𝑏 f : perfusion fraction
Diffusion-weighted image ADC map
19
Fast and slow diffusion pool
• The biexponential model
𝐴 = 𝑓𝑠𝑙𝑜𝑤 exp −𝑏𝐷𝑠𝑙𝑜𝑤 + 𝑓𝑓𝑎𝑠𝑡exp(−𝑏𝐷𝑓𝑎𝑠𝑡)
f: the volume fraction (fslow + ffast = 1)
D: the diffusion coefficient
20
Clinical applications of DW-MRI
• Clinical applications
– Tissue characterization (differentiating benign from malignant lesions)
– Tumor staging
– Predicting treatment outcomes (before and soon after starting therapy)
– Monitoring treatment response after chemotherapy or radiation
– Differentiating post-therapeutic changes from residual active tumor
– Detecting recurrent cancer
– Detecting lymph node involvement by cancer
21
Biological processes
involved in therapy induced changes in tumor ADC
22
식세포 활동
Primary brain tumor in DW-MRI
23
Charles-Edwards, E.M. and deSouza, N.M. (2006). “Diffusion-weighted magnetic
resonance imaging and its application to cancer.” Cancer imaging : the official
publication of the International Cancer Imaging Society, 6, pp. 135-43.
B-value = 0 B-value = 500 B-value = 1000 ADC map
Edema
Tumor
Treatment response prediction
• Functional diffusion map (fDM) as a biomarker
24
Summary
• Fick’s law of diffusion → Einstein equation
• Why diffusion?
– Tissue cellularity : DW-MRI
– Connectivity : DTI
• How to measure diffusion in MRI
– By adding a pair of magnetic field gradients (diffusion gradient)
– Diffusivity → signal attenuation
• High signal : low diffusion
• Low signal : high diffusion
• The b-value
– the diffusion sensitivity of the sequence (correlated with G, ∆, 𝛿)
• ADC map: tissue cellularity
– From (more than) two DW-MRI with different b-value → ADC map
– High intensity : high diffusion
– Low intensity : low diffusion
• IVIM
– Blood flow effect analysis
• Biexponential model
– Slow and fast diffusion pool
– Intra-cellular and extra-cellular compartment
• Clinical application
– Tissue characterization
– Tumor staging
– prediction and monitoring of treatment response
25
𝐴 = 𝑓𝑠𝑙𝑜𝑤 exp −𝑏𝐷𝑠𝑙𝑜𝑤 + 𝑓𝑓 𝑎𝑠𝑡exp(−𝑏𝐷𝑓𝑎𝑠𝑡)
References
26

More Related Content

What's hot

Perfusion MRI (DSC and DCE perfusion techniques) for radiology residents
Perfusion MRI (DSC and DCE perfusion techniques) for radiology residentsPerfusion MRI (DSC and DCE perfusion techniques) for radiology residents
Perfusion MRI (DSC and DCE perfusion techniques) for radiology residents
Riham Dessouky
 
Diffusion Tensor Imaging (2011-10-04 이정원)
Diffusion Tensor Imaging (2011-10-04 이정원)Diffusion Tensor Imaging (2011-10-04 이정원)
Diffusion Tensor Imaging (2011-10-04 이정원)
이정원 JeongwonLee
 
Diffusion weighted imaging
Diffusion  weighted imagingDiffusion  weighted imaging
Diffusion weighted imaging
Sharath Raj
 
Diffusion tensor imaging in Neurology
Diffusion tensor imaging in NeurologyDiffusion tensor imaging in Neurology
Diffusion tensor imaging in Neurology
Osama Ragab
 
Presentation1.pptx, perfusiona and specroscopy imaging in brain tumour.
Presentation1.pptx, perfusiona and specroscopy imaging in brain tumour.Presentation1.pptx, perfusiona and specroscopy imaging in brain tumour.
Presentation1.pptx, perfusiona and specroscopy imaging in brain tumour.Abdellah Nazeer
 
Presentation1, radiological application of diffusion weighted imges in neuror...
Presentation1, radiological application of diffusion weighted imges in neuror...Presentation1, radiological application of diffusion weighted imges in neuror...
Presentation1, radiological application of diffusion weighted imges in neuror...
Abdellah Nazeer
 
MR Spectroscopy
MR SpectroscopyMR Spectroscopy
MR Spectroscopy
NeurologyKota
 
MRI BREAST PPT
MRI BREAST PPTMRI BREAST PPT
MRI BREAST PPT
Naba Kumar Barman
 
MR Spectroscopy
MR SpectroscopyMR Spectroscopy
MR Spectroscopy
SusmitaShrestha9
 
Diagnostic Imaging of Brain Tumors
Diagnostic Imaging of Brain TumorsDiagnostic Imaging of Brain Tumors
Diagnostic Imaging of Brain Tumors
Mohamed M.A. Zaitoun
 
MR spectroscopy
MR spectroscopyMR spectroscopy
MR spectroscopy
Dr. Shahnawaz Alam
 
Imaging of white matter diseases
Imaging of white matter diseasesImaging of white matter diseases
Imaging of white matter diseases
Navni Garg
 
Phase Contrast and ECG-Gated MRA
Phase Contrast and ECG-Gated MRA Phase Contrast and ECG-Gated MRA
Phase Contrast and ECG-Gated MRA
Rahman Ud Din
 
Basic physics and normal interpretation of MRS
Basic physics and normal interpretation of MRSBasic physics and normal interpretation of MRS
Basic physics and normal interpretation of MRS
tanzilur rahman
 
Magnetic Resonance Angiography and Venography
Magnetic Resonance Angiography and VenographyMagnetic Resonance Angiography and Venography
Magnetic Resonance Angiography and Venography
Anjan Dangal
 
MR imaging of liver
MR imaging of liverMR imaging of liver
MR imaging of liver
Parvathy Nair
 
CT perfusion physics and its application in Neuroimaging
CT perfusion physics and its application in NeuroimagingCT perfusion physics and its application in Neuroimaging
CT perfusion physics and its application in Neuroimaging
Dr.Suhas Basavaiah
 
Quantitative CT and MR Imaging of Liver
Quantitative CT and MR Imaging of Liver Quantitative CT and MR Imaging of Liver
Quantitative CT and MR Imaging of Liver
Dr. Manoj Krishnan Sarojam
 
Diffusion-weighted and Perfusion MR Imaging for Brain Tumor Characterization ...
Diffusion-weighted and Perfusion MR Imaging for Brain Tumor Characterization ...Diffusion-weighted and Perfusion MR Imaging for Brain Tumor Characterization ...
Diffusion-weighted and Perfusion MR Imaging for Brain Tumor Characterization ...
Arif S
 

What's hot (20)

Perfusion MRI (DSC and DCE perfusion techniques) for radiology residents
Perfusion MRI (DSC and DCE perfusion techniques) for radiology residentsPerfusion MRI (DSC and DCE perfusion techniques) for radiology residents
Perfusion MRI (DSC and DCE perfusion techniques) for radiology residents
 
Diffusion Tensor Imaging (2011-10-04 이정원)
Diffusion Tensor Imaging (2011-10-04 이정원)Diffusion Tensor Imaging (2011-10-04 이정원)
Diffusion Tensor Imaging (2011-10-04 이정원)
 
Diffusion weighted imaging
Diffusion  weighted imagingDiffusion  weighted imaging
Diffusion weighted imaging
 
Diffusion tensor imaging in Neurology
Diffusion tensor imaging in NeurologyDiffusion tensor imaging in Neurology
Diffusion tensor imaging in Neurology
 
Mri prostate
Mri prostateMri prostate
Mri prostate
 
Presentation1.pptx, perfusiona and specroscopy imaging in brain tumour.
Presentation1.pptx, perfusiona and specroscopy imaging in brain tumour.Presentation1.pptx, perfusiona and specroscopy imaging in brain tumour.
Presentation1.pptx, perfusiona and specroscopy imaging in brain tumour.
 
Presentation1, radiological application of diffusion weighted imges in neuror...
Presentation1, radiological application of diffusion weighted imges in neuror...Presentation1, radiological application of diffusion weighted imges in neuror...
Presentation1, radiological application of diffusion weighted imges in neuror...
 
MR Spectroscopy
MR SpectroscopyMR Spectroscopy
MR Spectroscopy
 
MRI BREAST PPT
MRI BREAST PPTMRI BREAST PPT
MRI BREAST PPT
 
MR Spectroscopy
MR SpectroscopyMR Spectroscopy
MR Spectroscopy
 
Diagnostic Imaging of Brain Tumors
Diagnostic Imaging of Brain TumorsDiagnostic Imaging of Brain Tumors
Diagnostic Imaging of Brain Tumors
 
MR spectroscopy
MR spectroscopyMR spectroscopy
MR spectroscopy
 
Imaging of white matter diseases
Imaging of white matter diseasesImaging of white matter diseases
Imaging of white matter diseases
 
Phase Contrast and ECG-Gated MRA
Phase Contrast and ECG-Gated MRA Phase Contrast and ECG-Gated MRA
Phase Contrast and ECG-Gated MRA
 
Basic physics and normal interpretation of MRS
Basic physics and normal interpretation of MRSBasic physics and normal interpretation of MRS
Basic physics and normal interpretation of MRS
 
Magnetic Resonance Angiography and Venography
Magnetic Resonance Angiography and VenographyMagnetic Resonance Angiography and Venography
Magnetic Resonance Angiography and Venography
 
MR imaging of liver
MR imaging of liverMR imaging of liver
MR imaging of liver
 
CT perfusion physics and its application in Neuroimaging
CT perfusion physics and its application in NeuroimagingCT perfusion physics and its application in Neuroimaging
CT perfusion physics and its application in Neuroimaging
 
Quantitative CT and MR Imaging of Liver
Quantitative CT and MR Imaging of Liver Quantitative CT and MR Imaging of Liver
Quantitative CT and MR Imaging of Liver
 
Diffusion-weighted and Perfusion MR Imaging for Brain Tumor Characterization ...
Diffusion-weighted and Perfusion MR Imaging for Brain Tumor Characterization ...Diffusion-weighted and Perfusion MR Imaging for Brain Tumor Characterization ...
Diffusion-weighted and Perfusion MR Imaging for Brain Tumor Characterization ...
 

Similar to Diffusion Weighted MRI (2011-09-29 이정원)

DWI/ ADC -MRI principles in veterinary medicine
DWI/ ADC -MRI  principles in veterinary medicineDWI/ ADC -MRI  principles in veterinary medicine
DWI/ ADC -MRI principles in veterinary medicine
Robert Cruz
 
DWI/ ADC MRI principles/ applications in veterinary medicine
DWI/ ADC MRI principles/ applications  in veterinary medicineDWI/ ADC MRI principles/ applications  in veterinary medicine
DWI/ ADC MRI principles/ applications in veterinary medicine
Robert Cruz
 
Recent Advances In MRI
Recent Advances In MRIRecent Advances In MRI
Recent Advances In MRI
Upakar Paudel
 
Wave properties
Wave propertiesWave properties
Wave properties
www.fixURscore.com
 
DIFFUSION TENSOR IMAGING_MFD .pptx
DIFFUSION TENSOR IMAGING_MFD       .pptxDIFFUSION TENSOR IMAGING_MFD       .pptx
DIFFUSION TENSOR IMAGING_MFD .pptx
keerthikrishna41
 
IR Spectroscopy - Sudheerkumar Kamarapu, M. Pharmacy Lecture pdf
IR Spectroscopy - Sudheerkumar Kamarapu, M. Pharmacy Lecture pdfIR Spectroscopy - Sudheerkumar Kamarapu, M. Pharmacy Lecture pdf
IR Spectroscopy - Sudheerkumar Kamarapu, M. Pharmacy Lecture pdf
Dr. Sudheer Kumar Kamarapu
 
Usg physics
Usg physicsUsg physics
Usg physics
LALIT KARKI
 
6. IR Spectroscopy 2022.pptx
6. IR Spectroscopy 2022.pptx6. IR Spectroscopy 2022.pptx
6. IR Spectroscopy 2022.pptx
Williamkambi
 
Infrared spectroscopy
Infrared spectroscopy Infrared spectroscopy
Infrared spectroscopy
Suvarta Maru
 
Ec 2401 wireless communication unit 2
Ec 2401 wireless communication   unit 2Ec 2401 wireless communication   unit 2
Ec 2401 wireless communication unit 2
JAIGANESH SEKAR
 
DIFFUSION & PERFUSION r MRI.ppt
DIFFUSION  &   PERFUSION  r MRI.pptDIFFUSION  &   PERFUSION  r MRI.ppt
DIFFUSION & PERFUSION r MRI.ppt
ranjitharadhakrishna3
 
Underwater channel modelling
Underwater channel modellingUnderwater channel modelling
Underwater channel modellingSupriya Ankushe
 
Underwater channel modelling
Underwater channel modellingUnderwater channel modelling
Underwater channel modellingSupriya Ankushe
 
Underwater channel modelling
Underwater channel modellingUnderwater channel modelling
Underwater channel modellingSupriya Ankushe
 
2. Introduction to Spectroscopy 2022.pptx
2. Introduction to Spectroscopy 2022.pptx2. Introduction to Spectroscopy 2022.pptx
2. Introduction to Spectroscopy 2022.pptx
Williamkambi
 
6_2018_05_05!06_59_31_PM.ppt
6_2018_05_05!06_59_31_PM.ppt6_2018_05_05!06_59_31_PM.ppt
6_2018_05_05!06_59_31_PM.ppt
BhupendraShilpi
 
Propagation mechanisms
Propagation mechanismsPropagation mechanisms
Propagation mechanisms
METHODIST COLLEGE OF ENGG & TECH
 
Wave properties
Wave propertiesWave properties
Wave properties
SaifullahSiddiqui7
 

Similar to Diffusion Weighted MRI (2011-09-29 이정원) (20)

DWI/ ADC -MRI principles in veterinary medicine
DWI/ ADC -MRI  principles in veterinary medicineDWI/ ADC -MRI  principles in veterinary medicine
DWI/ ADC -MRI principles in veterinary medicine
 
DWI/ ADC MRI principles/ applications in veterinary medicine
DWI/ ADC MRI principles/ applications  in veterinary medicineDWI/ ADC MRI principles/ applications  in veterinary medicine
DWI/ ADC MRI principles/ applications in veterinary medicine
 
Recent Advances In MRI
Recent Advances In MRIRecent Advances In MRI
Recent Advances In MRI
 
Wave properties
Wave propertiesWave properties
Wave properties
 
DIFFUSION TENSOR IMAGING_MFD .pptx
DIFFUSION TENSOR IMAGING_MFD       .pptxDIFFUSION TENSOR IMAGING_MFD       .pptx
DIFFUSION TENSOR IMAGING_MFD .pptx
 
Interferometry 1
Interferometry 1Interferometry 1
Interferometry 1
 
IR Spectroscopy - Sudheerkumar Kamarapu, M. Pharmacy Lecture pdf
IR Spectroscopy - Sudheerkumar Kamarapu, M. Pharmacy Lecture pdfIR Spectroscopy - Sudheerkumar Kamarapu, M. Pharmacy Lecture pdf
IR Spectroscopy - Sudheerkumar Kamarapu, M. Pharmacy Lecture pdf
 
Usg physics
Usg physicsUsg physics
Usg physics
 
6. IR Spectroscopy 2022.pptx
6. IR Spectroscopy 2022.pptx6. IR Spectroscopy 2022.pptx
6. IR Spectroscopy 2022.pptx
 
LDV
LDVLDV
LDV
 
Infrared spectroscopy
Infrared spectroscopy Infrared spectroscopy
Infrared spectroscopy
 
Ec 2401 wireless communication unit 2
Ec 2401 wireless communication   unit 2Ec 2401 wireless communication   unit 2
Ec 2401 wireless communication unit 2
 
DIFFUSION & PERFUSION r MRI.ppt
DIFFUSION  &   PERFUSION  r MRI.pptDIFFUSION  &   PERFUSION  r MRI.ppt
DIFFUSION & PERFUSION r MRI.ppt
 
Underwater channel modelling
Underwater channel modellingUnderwater channel modelling
Underwater channel modelling
 
Underwater channel modelling
Underwater channel modellingUnderwater channel modelling
Underwater channel modelling
 
Underwater channel modelling
Underwater channel modellingUnderwater channel modelling
Underwater channel modelling
 
2. Introduction to Spectroscopy 2022.pptx
2. Introduction to Spectroscopy 2022.pptx2. Introduction to Spectroscopy 2022.pptx
2. Introduction to Spectroscopy 2022.pptx
 
6_2018_05_05!06_59_31_PM.ppt
6_2018_05_05!06_59_31_PM.ppt6_2018_05_05!06_59_31_PM.ppt
6_2018_05_05!06_59_31_PM.ppt
 
Propagation mechanisms
Propagation mechanismsPropagation mechanisms
Propagation mechanisms
 
Wave properties
Wave propertiesWave properties
Wave properties
 

Recently uploaded

Physiology of Special Chemical Sensation of Taste
Physiology of Special Chemical Sensation of TastePhysiology of Special Chemical Sensation of Taste
Physiology of Special Chemical Sensation of Taste
MedicoseAcademics
 
Factory Supply Best Quality Pmk Oil CAS 28578–16–7 PMK Powder in Stock
Factory Supply Best Quality Pmk Oil CAS 28578–16–7 PMK Powder in StockFactory Supply Best Quality Pmk Oil CAS 28578–16–7 PMK Powder in Stock
Factory Supply Best Quality Pmk Oil CAS 28578–16–7 PMK Powder in Stock
rebeccabio
 
Ophthalmology Clinical Tests for OSCE exam
Ophthalmology Clinical Tests for OSCE examOphthalmology Clinical Tests for OSCE exam
Ophthalmology Clinical Tests for OSCE exam
KafrELShiekh University
 
Pulmonary Thromboembolism - etilogy, types, medical- Surgical and nursing man...
Pulmonary Thromboembolism - etilogy, types, medical- Surgical and nursing man...Pulmonary Thromboembolism - etilogy, types, medical- Surgical and nursing man...
Pulmonary Thromboembolism - etilogy, types, medical- Surgical and nursing man...
VarunMahajani
 
Prix Galien International 2024 Forum Program
Prix Galien International 2024 Forum ProgramPrix Galien International 2024 Forum Program
Prix Galien International 2024 Forum Program
Levi Shapiro
 
Surat @ℂall @Girls ꧁❤8527049040❤꧂@ℂall @Girls Service Vip Top Model Safe
Surat @ℂall @Girls ꧁❤8527049040❤꧂@ℂall @Girls Service Vip Top Model SafeSurat @ℂall @Girls ꧁❤8527049040❤꧂@ℂall @Girls Service Vip Top Model Safe
Surat @ℂall @Girls ꧁❤8527049040❤꧂@ℂall @Girls Service Vip Top Model Safe
Savita Shen $i11
 
basicmodesofventilation2022-220313203758.pdf
basicmodesofventilation2022-220313203758.pdfbasicmodesofventilation2022-220313203758.pdf
basicmodesofventilation2022-220313203758.pdf
aljamhori teaching hospital
 
Alcohol_Dr. Jeenal Mistry MD Pharmacology.pdf
Alcohol_Dr. Jeenal Mistry MD Pharmacology.pdfAlcohol_Dr. Jeenal Mistry MD Pharmacology.pdf
Alcohol_Dr. Jeenal Mistry MD Pharmacology.pdf
Dr Jeenal Mistry
 
Flu Vaccine Alert in Bangalore Karnataka
Flu Vaccine Alert in Bangalore KarnatakaFlu Vaccine Alert in Bangalore Karnataka
Flu Vaccine Alert in Bangalore Karnataka
addon Scans
 
MANAGEMENT OF ATRIOVENTRICULAR CONDUCTION BLOCK.pdf
MANAGEMENT OF ATRIOVENTRICULAR CONDUCTION BLOCK.pdfMANAGEMENT OF ATRIOVENTRICULAR CONDUCTION BLOCK.pdf
MANAGEMENT OF ATRIOVENTRICULAR CONDUCTION BLOCK.pdf
Jim Jacob Roy
 
Are There Any Natural Remedies To Treat Syphilis.pdf
Are There Any Natural Remedies To Treat Syphilis.pdfAre There Any Natural Remedies To Treat Syphilis.pdf
Are There Any Natural Remedies To Treat Syphilis.pdf
Little Cross Family Clinic
 
Ozempic: Preoperative Management of Patients on GLP-1 Receptor Agonists
Ozempic: Preoperative Management of Patients on GLP-1 Receptor Agonists  Ozempic: Preoperative Management of Patients on GLP-1 Receptor Agonists
Ozempic: Preoperative Management of Patients on GLP-1 Receptor Agonists
Saeid Safari
 
Antiulcer drugs Advance Pharmacology .pptx
Antiulcer drugs Advance Pharmacology .pptxAntiulcer drugs Advance Pharmacology .pptx
Antiulcer drugs Advance Pharmacology .pptx
Rohit chaurpagar
 
Charaka Samhita Sutra sthana Chapter 15 Upakalpaniyaadhyaya
Charaka Samhita Sutra sthana Chapter 15 UpakalpaniyaadhyayaCharaka Samhita Sutra sthana Chapter 15 Upakalpaniyaadhyaya
Charaka Samhita Sutra sthana Chapter 15 Upakalpaniyaadhyaya
Dr KHALID B.M
 
heat stroke and heat exhaustion in children
heat stroke and heat exhaustion in childrenheat stroke and heat exhaustion in children
heat stroke and heat exhaustion in children
SumeraAhmad5
 
KDIGO 2024 guidelines for diabetologists
KDIGO 2024 guidelines for diabetologistsKDIGO 2024 guidelines for diabetologists
KDIGO 2024 guidelines for diabetologists
د.محمود نجيب
 
Cervical & Brachial Plexus By Dr. RIG.pptx
Cervical & Brachial Plexus By Dr. RIG.pptxCervical & Brachial Plexus By Dr. RIG.pptx
Cervical & Brachial Plexus By Dr. RIG.pptx
Dr. Rabia Inam Gandapore
 
Triangles of Neck and Clinical Correlation by Dr. RIG.pptx
Triangles of Neck and Clinical Correlation by Dr. RIG.pptxTriangles of Neck and Clinical Correlation by Dr. RIG.pptx
Triangles of Neck and Clinical Correlation by Dr. RIG.pptx
Dr. Rabia Inam Gandapore
 
ARTIFICIAL INTELLIGENCE IN HEALTHCARE.pdf
ARTIFICIAL INTELLIGENCE IN  HEALTHCARE.pdfARTIFICIAL INTELLIGENCE IN  HEALTHCARE.pdf
ARTIFICIAL INTELLIGENCE IN HEALTHCARE.pdf
Anujkumaranit
 
The Normal Electrocardiogram - Part I of II
The Normal Electrocardiogram - Part I of IIThe Normal Electrocardiogram - Part I of II
The Normal Electrocardiogram - Part I of II
MedicoseAcademics
 

Recently uploaded (20)

Physiology of Special Chemical Sensation of Taste
Physiology of Special Chemical Sensation of TastePhysiology of Special Chemical Sensation of Taste
Physiology of Special Chemical Sensation of Taste
 
Factory Supply Best Quality Pmk Oil CAS 28578–16–7 PMK Powder in Stock
Factory Supply Best Quality Pmk Oil CAS 28578–16–7 PMK Powder in StockFactory Supply Best Quality Pmk Oil CAS 28578–16–7 PMK Powder in Stock
Factory Supply Best Quality Pmk Oil CAS 28578–16–7 PMK Powder in Stock
 
Ophthalmology Clinical Tests for OSCE exam
Ophthalmology Clinical Tests for OSCE examOphthalmology Clinical Tests for OSCE exam
Ophthalmology Clinical Tests for OSCE exam
 
Pulmonary Thromboembolism - etilogy, types, medical- Surgical and nursing man...
Pulmonary Thromboembolism - etilogy, types, medical- Surgical and nursing man...Pulmonary Thromboembolism - etilogy, types, medical- Surgical and nursing man...
Pulmonary Thromboembolism - etilogy, types, medical- Surgical and nursing man...
 
Prix Galien International 2024 Forum Program
Prix Galien International 2024 Forum ProgramPrix Galien International 2024 Forum Program
Prix Galien International 2024 Forum Program
 
Surat @ℂall @Girls ꧁❤8527049040❤꧂@ℂall @Girls Service Vip Top Model Safe
Surat @ℂall @Girls ꧁❤8527049040❤꧂@ℂall @Girls Service Vip Top Model SafeSurat @ℂall @Girls ꧁❤8527049040❤꧂@ℂall @Girls Service Vip Top Model Safe
Surat @ℂall @Girls ꧁❤8527049040❤꧂@ℂall @Girls Service Vip Top Model Safe
 
basicmodesofventilation2022-220313203758.pdf
basicmodesofventilation2022-220313203758.pdfbasicmodesofventilation2022-220313203758.pdf
basicmodesofventilation2022-220313203758.pdf
 
Alcohol_Dr. Jeenal Mistry MD Pharmacology.pdf
Alcohol_Dr. Jeenal Mistry MD Pharmacology.pdfAlcohol_Dr. Jeenal Mistry MD Pharmacology.pdf
Alcohol_Dr. Jeenal Mistry MD Pharmacology.pdf
 
Flu Vaccine Alert in Bangalore Karnataka
Flu Vaccine Alert in Bangalore KarnatakaFlu Vaccine Alert in Bangalore Karnataka
Flu Vaccine Alert in Bangalore Karnataka
 
MANAGEMENT OF ATRIOVENTRICULAR CONDUCTION BLOCK.pdf
MANAGEMENT OF ATRIOVENTRICULAR CONDUCTION BLOCK.pdfMANAGEMENT OF ATRIOVENTRICULAR CONDUCTION BLOCK.pdf
MANAGEMENT OF ATRIOVENTRICULAR CONDUCTION BLOCK.pdf
 
Are There Any Natural Remedies To Treat Syphilis.pdf
Are There Any Natural Remedies To Treat Syphilis.pdfAre There Any Natural Remedies To Treat Syphilis.pdf
Are There Any Natural Remedies To Treat Syphilis.pdf
 
Ozempic: Preoperative Management of Patients on GLP-1 Receptor Agonists
Ozempic: Preoperative Management of Patients on GLP-1 Receptor Agonists  Ozempic: Preoperative Management of Patients on GLP-1 Receptor Agonists
Ozempic: Preoperative Management of Patients on GLP-1 Receptor Agonists
 
Antiulcer drugs Advance Pharmacology .pptx
Antiulcer drugs Advance Pharmacology .pptxAntiulcer drugs Advance Pharmacology .pptx
Antiulcer drugs Advance Pharmacology .pptx
 
Charaka Samhita Sutra sthana Chapter 15 Upakalpaniyaadhyaya
Charaka Samhita Sutra sthana Chapter 15 UpakalpaniyaadhyayaCharaka Samhita Sutra sthana Chapter 15 Upakalpaniyaadhyaya
Charaka Samhita Sutra sthana Chapter 15 Upakalpaniyaadhyaya
 
heat stroke and heat exhaustion in children
heat stroke and heat exhaustion in childrenheat stroke and heat exhaustion in children
heat stroke and heat exhaustion in children
 
KDIGO 2024 guidelines for diabetologists
KDIGO 2024 guidelines for diabetologistsKDIGO 2024 guidelines for diabetologists
KDIGO 2024 guidelines for diabetologists
 
Cervical & Brachial Plexus By Dr. RIG.pptx
Cervical & Brachial Plexus By Dr. RIG.pptxCervical & Brachial Plexus By Dr. RIG.pptx
Cervical & Brachial Plexus By Dr. RIG.pptx
 
Triangles of Neck and Clinical Correlation by Dr. RIG.pptx
Triangles of Neck and Clinical Correlation by Dr. RIG.pptxTriangles of Neck and Clinical Correlation by Dr. RIG.pptx
Triangles of Neck and Clinical Correlation by Dr. RIG.pptx
 
ARTIFICIAL INTELLIGENCE IN HEALTHCARE.pdf
ARTIFICIAL INTELLIGENCE IN  HEALTHCARE.pdfARTIFICIAL INTELLIGENCE IN  HEALTHCARE.pdf
ARTIFICIAL INTELLIGENCE IN HEALTHCARE.pdf
 
The Normal Electrocardiogram - Part I of II
The Normal Electrocardiogram - Part I of IIThe Normal Electrocardiogram - Part I of II
The Normal Electrocardiogram - Part I of II
 

Diffusion Weighted MRI (2011-09-29 이정원)

  • 1. Diffusion MRI 2011. 9. 29. KAIST 바이오및뇌공학과 이정원 1
  • 2. What is diffusion? • Fick’s Law (1855, Adolf Fick) J : diffusion flux (mol/m2s) D : diffusion coefficient or diffusivity (m2/s) Φ : Concentration in dimensions (mol/m3) x : the position (m) t : time (s) 2
  • 3. What is diffusion? • Brownian motion (Robert Brown, 1827) – the presumably random drifting of particles suspended in a fluid The characteristic bell-shaped curves of the diffusion of Brownian particles. 3
  • 4. What is diffusion? • Einstein recognized that Brownian motion was associated with diffusion – No macroscopic concentration gradient is needed. – Self-diffusion arising from local concentration fluctuations • Einstein derived the self-diffusion coefficient of the Brownian particle – Einstein expressed the energy change as the total work done by the particles contained within the volume – Diffusion coefficient • Einstein rewrote Fick’s laws for the diffusion – in terms of diffusion under probability gradients 𝐷 = 𝑘 𝐵 𝑇 6𝜋𝜂𝑅 : Sutherland-Einstein relation (1905) 𝑘 𝐵 ∶ 𝐵𝑜𝑙𝑡𝑧𝑚𝑎𝑛𝑛′ 𝑠 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡 𝜂 ∶ viscosity T ∶ absolute temperature R ∶ radius of the spherical particle 𝐾𝑛 𝜁 − 𝐷 𝛿𝑛 𝛿𝑥 = 0 𝐾 ∶ 𝑛𝑒𝑡 𝑓𝑜𝑟𝑐𝑒 𝑛 ∶ the number of Brownian particles per unit volume 𝜁 ∶ friction D ∶ diffusion coefficient X ∶ position 𝑃 𝑟 𝑟′ , 𝑡 : 𝑐𝑜𝑛𝑑𝑖𝑡𝑖𝑜𝑛𝑎𝑙 𝑝𝑟𝑜𝑏𝑎𝑏𝑙𝑖𝑡𝑦 𝑡ℎ𝑎𝑡 𝑎 𝑝𝑎𝑟𝑡𝑖𝑐𝑙𝑒 𝑠𝑡𝑎𝑟𝑡𝑖𝑛𝑔 𝑎𝑡 𝑟 𝑎𝑡 𝑡𝑖𝑚𝑒 𝑧𝑒𝑟𝑜 𝑤𝑖𝑙𝑙 𝑚𝑜𝑣𝑒 𝑡𝑜 𝑟′ 𝑎𝑓𝑡𝑒𝑟 𝑎 𝑡𝑖𝑚𝑒 𝑡 : Einstein equation for diffusion 4
  • 5. Why diffusion? • Tissue cellularity • Connectivity 5 DW-MRI DTI
  • 6. How to measure the diffusion in MRI • A review of MR imaging sequences Gradient Echo sequence Spin Echo sequence 6
  • 7. How to measure the diffusion in MRI 7 Allen W. Song, Brain Imaging and Analysis Center, Duke University, “Principles of MRI Physics and Engineering” Gradient Echo DW-MRI Spin Echo DW-MRI • Almost any MR imaging sequence can be designed to be sensitive to diffusion – By adding magnetic field gradients • To magnetically label spins carried by diffusing molecules • Only parallel component has an effect
  • 8. How to measure the diffusion in MRI Stationary water Mobile water Stationary water Mobile water 8
  • 9. How to measure the diffusion in MRI • The first gradient pulse – Alters the phase shift of each proton – By an amount dependent on the water molecule’s spatial location relative to the gradient • The second gradient pulse – if the water molecule does not move between the application of the first and second gradient pulses • Reverse this phase shift – If there is movement of the water molecule between application of the first and second gradient pulses • Complete rephasing cannot happen, causing signal loss from this spatial location • The amount of signal loss is directly proportional to the degree of water motion (the protons’ mean diffusional path length) • Two components measured – Magnitude: the extent to which protons are free to diffuse • Signal loss ∝ degree of water motion (the protons’ mean diffusional path length) – Direction: preferential diffusion direction • Signal loss is proportional to the motion component in the same direction as the diffusion gradient. No signal loss would occur if the motion was perpendicular to the gradient direction. 9
  • 10. How to measure the diffusion in MRI Gradient and spin 90 RF Dephasing Rephasing 10
  • 11. Imperfect refocusing =Signal loss! How to measure the diffusion in MRI If spin moves 90 RF Dephasing Rephasing G 11
  • 12. Equation of diffusion attenuation, and b-value • There is a particular problem – The combination of the imaging and the diffusion gradient pulses produce attenuation effects • So, b-value is suggested – To summarize all gradient effects (diffusion and imaging pulses) – The diffusion sensitivity of the sequence – Without additional gradients, SE imaging sequences has very low b-values (around 1 s/mm2) 𝐴 𝑇𝐸 : ln 𝑆 𝑆𝑜 = −𝛾2 𝐺2 𝛿2 ∆ − 𝛿 3 𝑫 = −𝑏𝑫 b-value SignalIntensity D 12
  • 13. Various sequences of diffusion-weighted MRI • Pulsed field gradient spin echo (PFGSE) • Double pulsed gradient spin echo – Two gradient pulse pairs on the same spin magnetization – To compensate flow • Stimulated echo • Gradient echo 𝐴 𝑇𝐸 = exp(−𝛾2 𝐺2 𝛿2 ∆ − 𝛿 3 𝐷) 𝐴 𝑇𝐸 = exp(−𝛾2 𝐺2 𝛿2 ∆ − 𝛿 3 + 𝜀3 30 − 𝛿𝜀3 6 𝐷) 13
  • 14. We can get diffusion-weighted MR images • Among various MRI images – T1-weighted MRI – T2-weighted MRI – FLAIR (Fluid attenuated inversion recovery) – Proton Density weighted MRI – Diffusion-weighted MRI – Diffusion Tensor Imaging – Susceptibility Weighted Imaging (SWI) – Dynamic Susceptibility Contrast (DSC) MRI – Magnetic Resonance Spectroscopy (MRS) – Functional MRI CT T1 weighted T2- weighted Diffusion weighted ADC map 14
  • 15. Diffusion-weighted image vs. Diffusion map • Diffusion-weighted image – Darkness: high diffusion – Brightness: low diffusion – Intensity is affected by many other parameters than diffusion • Diffusion map (ADC map) – To obtain pure maps of the diffusion coefficient – By acquiring two images with different b-values, b and b0 – Darkness: low, slow diffusion – Brightness: high, fast diffusion 𝐴 = [1 − exp − TR 𝑇1 ]exp − 𝑇𝐸 𝑇2 exp(−𝑏𝑫) 𝑫 𝑥,𝑦,𝑧 = −ln[ 𝐴 𝑥,𝑦,𝑧 𝑏 𝐴 𝑥,𝑦,𝑧 𝑏0 ]/(𝑏 − 𝑏0) Diffusion-weighted image ADC map 15
  • 16. Diffusion map • Two b-value acquisitions – Best precision: b-b0 = 1/D (in the brain b-b0 = 1000 to 1500 s/mm2) • More than two b-value acquisitions – Better accuracy – To get further information on tissue microstructure and dynamics 16b-value SignalIntensity D
  • 17. IVIM • IVIM (intravoxel incoherent motion) – Pseudo-diffusion process from movement of the blood in the microvasculature – A means to cover all molecular displacements to which “diffusion” MRI could be sensitive – Diffusion measurements with MRI may include perfusion effects and not just true diffusion • Perfusion effects at very low b-values (<200 s/mm2) – Only two b-values (0 and 1000 s/mm2) could include perfusion effect • Overestimation of the true diffusion coefficient D 17
  • 18. ADC (apparent diffusion coefficient) • ADC map – Describes microscopic water diffusibility in the presence of factors that restrict diffusion within tissues. – ADC is measured by combining two diffusion-weighted images • typically with (Sb) and without (So) diffusion weighting • or using two b-values – Multiple b-values are needed • To differentiate between perfusion and diffusion – The area of high diffusion is represented as a bright area; a high ADC value 18
  • 19. ADC (apparent diffusion coefficient) • To take into account diffusion and pseudo-diffusion processes • By replacing the microscopic diffusion coefficient D with a global parameter, ADC • In the brain, as larger b-values can generally be used and f is very small (2~4%) ADC ≡ −ln[ 𝐴(𝑏) 𝐴(𝑏0) ]/(𝑏 − 𝑏0) 𝐴𝐷𝐶 ≈ 𝐷 + 𝑓/𝑏 f : perfusion fraction Diffusion-weighted image ADC map 19
  • 20. Fast and slow diffusion pool • The biexponential model 𝐴 = 𝑓𝑠𝑙𝑜𝑤 exp −𝑏𝐷𝑠𝑙𝑜𝑤 + 𝑓𝑓𝑎𝑠𝑡exp(−𝑏𝐷𝑓𝑎𝑠𝑡) f: the volume fraction (fslow + ffast = 1) D: the diffusion coefficient 20
  • 21. Clinical applications of DW-MRI • Clinical applications – Tissue characterization (differentiating benign from malignant lesions) – Tumor staging – Predicting treatment outcomes (before and soon after starting therapy) – Monitoring treatment response after chemotherapy or radiation – Differentiating post-therapeutic changes from residual active tumor – Detecting recurrent cancer – Detecting lymph node involvement by cancer 21
  • 22. Biological processes involved in therapy induced changes in tumor ADC 22 식세포 활동
  • 23. Primary brain tumor in DW-MRI 23 Charles-Edwards, E.M. and deSouza, N.M. (2006). “Diffusion-weighted magnetic resonance imaging and its application to cancer.” Cancer imaging : the official publication of the International Cancer Imaging Society, 6, pp. 135-43. B-value = 0 B-value = 500 B-value = 1000 ADC map Edema Tumor
  • 24. Treatment response prediction • Functional diffusion map (fDM) as a biomarker 24
  • 25. Summary • Fick’s law of diffusion → Einstein equation • Why diffusion? – Tissue cellularity : DW-MRI – Connectivity : DTI • How to measure diffusion in MRI – By adding a pair of magnetic field gradients (diffusion gradient) – Diffusivity → signal attenuation • High signal : low diffusion • Low signal : high diffusion • The b-value – the diffusion sensitivity of the sequence (correlated with G, ∆, 𝛿) • ADC map: tissue cellularity – From (more than) two DW-MRI with different b-value → ADC map – High intensity : high diffusion – Low intensity : low diffusion • IVIM – Blood flow effect analysis • Biexponential model – Slow and fast diffusion pool – Intra-cellular and extra-cellular compartment • Clinical application – Tissue characterization – Tumor staging – prediction and monitoring of treatment response 25 𝐴 = 𝑓𝑠𝑙𝑜𝑤 exp −𝑏𝐷𝑠𝑙𝑜𝑤 + 𝑓𝑓 𝑎𝑠𝑡exp(−𝑏𝐷𝑓𝑎𝑠𝑡)