dr. renzo manara
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Dr. Renzo Manararmanara@unisa.it
Unraveling the brain:
advanced imaging and “old” techniques in
hematologic disorders
➢ What is “Magnetic Resonance” (MR)
➢ What is “conventional MR imaging and angiography”
➢ What are “advanced techniques”
➢ What are “advanced analyses”
➢ Possible applications for hematologic disorders
• Topics
➢ What is “Magnetic Resonance” (MR)
➢ What is “conventional MR imaging and angiography”
➢ What are “advanced techniques”
➢ What are “advanced analyses”
➢ Possible applications for hematologic disorders
• Topics
Magnetic Resonance is based on:
✓ a strong static magnetic field (1.5-11.2T),
✓ rapid magnetic gradients (small additional magnetic fields) activated in
specific sequences
✓ low-energy electromagnetic radiations
a strong static magnetic field (1.5-11.2T),
✓ iron and steel objects are attracted
Ferromagnetic objects are attracted and act as missile objects
The magnetic field is always active and the strength of the attraction
increases exponentially.
In 10 years in Padova I saw
1 monitor
1 polisher
2 oxygen cylinders
1 chair
2 IV poles
2 scissors
Several coins, keys and so on…
These objects might act as missile objects (rare cases of death, several cases
of severe patient injury)
rapid magnetic gradients (small additional magnetic fields)
✓ electric devices (e.g. pacemaker) do not work properly inside the
scanner room
The gradients might inactivate the pacemaker and induce overheating of the
metallic filament (burning lesions of the heart).
About 50% of patients die during the exam.
low-energy electromagnetic radiations
✓ the exam is non-invasive and can be repeated
BUT
✓ the exam lasts 30-60 minutes
✓ good compliance is required (non collaborative patients such as children
or those confused or affected by claustrofobia might require invasive
sedation)
➢ What is “Magnetic Resonance” (MR)
➢ What is “conventional MR imaging and angiography”
➢ What are “advanced techniques”
➢ What are “advanced analyses”
➢ Possible applications for hematologic disorders
• Topics
It includes all the sequences used in the clinical routine for investigating
brain parenchyma and intracranial vessels.
There are more than 50 sequences (each providing different information)
and each sequence lasts about 3-5 min.
Protocols include only some sequences according to the clinical problem.
Typical standard protocol
✓ T1-weighted
✓ FLAIR T2weighted
✓ Diffusion weighted imaging (DWI)
✓ T2 weighted
✓ T2 weighted gradient echo (T2*)
• conventional MR imaging and angiography
• conventional MR imaging and angiography
FSE T2-weighted MPRAGE T1-weighted
HASTE T2-weighted
• conventional MR imaging and angiography
FLAIR is especially used for detecting vascular like changes
DWI is especially used for detecting acute ischemic strokes
T2* is especially used for detecting microbleeds
• conventional MR imaging and angiography
FLAIR
DWI
• conventional MR imaging and angiography
MR-angiography MR-venography
(time of flight, ToF) (phase contrast, PC)
• conventional MR imaging
MR spectroscopy shows metabolite concentrations
in a chosen volume (e.g. NAA, choline, etc.)
Different sequences show different metabolites
(short/long TE, single voxel, 2D, 3D, etc)
The higher the magnetic field strength, the higher
the metabolite discrimination (i.e. 3T better than
1.5T)
MR spectroscopy
➢ What is “Magnetic Resonance” (MR)
➢ What is “conventional MR imaging and angiography”
➢ What are “advanced techniques”
➢ What are “advanced analyses”
➢ Possible applications for hematologic disorders
• Topics
They include sequences that usually require post-processing to show their
findings
Qualified personnel is needed (imaging engineers, highly qualified
technicians, dedicated physicians)
Imaging findings are usually choreographic in a clinical setting on single
subjects (rare cases diagnosed by these techniques), extremely interesting
and powerful in a research setting with group analysis
✓ diffusion tensor imaging (DTI)
✓ functional MRI (fMRI)
✓ metabolite imaging
✓ iron quantification/myelin maps
✓ T1rho maps, T2rho maps…
• advanced techniques
Isotropy and anisotropy
Characterization of diffusion
x
y
z
Measure diffusion along
various directions (> 6)Calculate shape of the
ellipsoid
l1
l2
l3
Characterization of diffusion
x
y
z
Measure diffusion along
various directions (> 6)Calculate shape of the
ellipsoid
l1
l2
l3
1. Measure
diffusion
along various
directions
(>6)
2. Calculate
shape
of the
ellipsoid
Diffusion
Magnitude
Diffusion
Direction
Eigenvector
Direction
field
Cat primary visual cortex – coronal view
• Pixel color reflects the
direction of the prevailing
eigenvectors.
•
• Pixel intensity depends on FA
value= TRASVERSAL
= ANTERO-POST.
• advanced techniques
• advanced techniques
• Reconstruction of 3D trajectory through the propagation of a line that follows local eigenvector orientation
Tractographic representation
• advanced techniques
Hemoglobin
Oxyhemoglobin
(Hb)
Diamagnetic (χ< 0)
Deoxyhemoglobin
(dHb)
Paramagnetic (χ> 0)
• advanced techniques
Task or Stimulus↓
change in neuronal activity↓
change in oxygen levels↓
change in magnetic properties of haemoglobin↓
endogenous contrast
fMRI
• advanced techniques
Brain activity
Oxygen consumptionn
Signal ↓:
hypointensity
deoxyHb
• advanced techniques
Brain activity
Oxygen consumptionn
Signal ↑: hyperintensity
In reality....
Hb↑ dHb ↓
Blood Flow ↑↑
T2* ↑
Magnetic susceptibility ↓
• advanced techniques
time0.5 - 2 sec 5 sec 10 sec
Signal Intensity
+1-5%
0
- <0.5%
stimulus
Hemodynamic response in time and space
BOLD Effect: Blood Oxygenation Level Dependent contrast
• advanced techniques
BOLD technique(Blood Oxygen Level dependent)
Short Stimulus
Long Stimulus
▪ initial dip (500 ms-1s)
▪ positive BOLD response (~6 s)
▪ post stimulus undershoot
P. Tofts, Quantitative MRI of
the Brain, Wiley
P. Tofts, Quantitative MRI
of the Brain, Wiley
• advanced techniques
EPI (Echo Planar Imaging)
- Very fast planar acquisition and good SNR
- Susceptibility artefacts
- Signal change due to the stimulus at 1.5T: 3-5%
• advanced techniques
Example time-courses
MRI signal from voxel that correlates well with task: Active
Task
TIME
Time-course of task versus rest periods
Rest
Task
Rest Rest
Signal from voxel that does NOT correlate with task: Inactive
• advanced techniques
fMRI samples huge 4D data-sets of brain images
• 100.000 points sampled in the brain
• signal changes due to noise and neural activity
• statistical methods discriminate between the twos
How does fMRI work
Scan 1°
Scan 2°
Signal changes due to
neural activity
a-priori reference
function
How does fMRI work
Statistical methods - Inferential processing
Language (repetition)
Colour represents statistical significance of how well the voxel’s activation correlates with the task.
The hi-res grayscale anatomical picture underneath the coloured blobs is a completely different type of image, from a different type of scan. Shows the anatomy at the spot where the significant voxel’s time-course was recorded.
Magnetic resonance imaging of glutamate
Kejia Cai1 Nature Medicine 2012
• advanced techniques
➢ Myelin maps
➢ R2* maps
➢ Thalassemia young patient
• advanced techniques
• advanced techniques
T1rho and T2rho are images based on novel contrast (rotating magnetic
vectors). Brain imaging changes in diseases is unexplored.
➢ What is “Magnetic Resonance” (MR)
➢ What is “conventional MR imaging and angiography”
➢ What are “advanced techniques”
➢ What are “advanced analyses”
➢ Possible applications for hematologic disorders
• Topics
MR-Morphometry
• Advanced analyses
They include post-processing based group analyses that allow parameter
quantification on conventional or advanced sequences.
They require normalization of the brain and allows a voxel-based
comparison between groups (e.g. patients and controls, treated and
untreated, etc.)
Qualified personnel is highly needed (imaging engineers, dedicated
physicians or physicists)
Imaging findings are extremely interesting and powerful but adapt only in a
research setting with group analysis
✓ Voxel based morphometry
✓ Cortical thickness
✓ Fractional anisotropy, mean, radial, axial diffusivity with DTI
✓ functional MRI (fMRI) task or event-related, resting state
✓ iron quantification/myelin maps
✓ T1rho maps, T2rho maps…
• Advanced analyses
• MRI post-processing quantitative techniques:
- detect parenchymal abnormalities even in patients with normal brain at conventional MRI
- allow for longitudinal evaluation of lesion burden
Sun et al. AJNR 2012
• Advanced analyses
➢ Quantifies gray and white matter density
➢Allows a voxel-wise comparison of the local concentration
of gray and white matter between two groups of subjects
Voxel-Based Morphometry (VBM)
• Advanced analyses
Voxel based Morphometry
(basis functions)
Time (months)
Hip
pocam
pal
volu
me
Navigation-related structural change
in the hippocampi of taxi drivers
VBM
E. A. Maguire, PNAS 2000
Freesurfer Subject 2 aligned with Subject 1
(Subject 1’s Surface)
Registration to a template (e.g. MNI/Talairach) doesn’t account for individual anatomy.
Vertex analysis
• Advanced analyses
Surfaces: White and Pial
• Advanced analyses
Cortical Thickness
white/gray surface
pial surface• Distance between white and pial surfaces
• One value per vertex
• Advanced analyses
PAT>CTRL CTRL>PAT
PAT
CTRL
➢ Contrast based on the directional rate of diffusion of water
molecules
➢Depicts brain structural integrity in terms of microscopic
white matter organization
Diffusion Tensor Imaging (DTI)
• Advanced analyses
➢ Mean Diffusivity (MD): magnitude of diffusion in a voxel
➢ Fractional Anisotropy (FA): extent to which diffusion is
directionally restricted
➢ Radial Diffusivity (RA): water diffusivity perpendicular to
axonal fiber
➢Axial Diffusivity (L1): water diffusivity parallel to axonal
fiber tracts
• Advanced analyses
Diffusion Tensor Imaging (DTI)
Feldman et al, 2010
• Advanced analyses
Diffusion Tensor Imaging (DTI)
fMRI
• Advanced analyses
Frequency
representation
(tonotopic maps)
in the human
auditory cortex
500 Hz
1000 Hz
3000 Hz
➢At rest, spontaneous coherent fluctuations of the blood
oxygen level-dependent signal are detected in brain areas
functionally connected
➢ It features (all) different typical neural networks (motor,
visual, acoustic…) simultaneously!
Raichle et al., 2001; van de Heuvel et al., 2008
• Advanced analyses
Resting State Functional MRI (fMRI)
➢ What is “Magnetic Resonance” (MR)
➢ What is “conventional MR imaging and angiography”
➢ What are “advanced techniques”
➢ What are “advanced analyses”
➢ Possible applications for hematologic disorders
• Topics
All MRI techniques and analyses might be applied in the field of
hematologic disorders for clinical and research purposes
• Possible applications
Ehineboh Itohan
PRES, LERRP
• Neuroimaging in SCD
M, 16 years
Metushi Sefer
• Neuroimaging in SCD
➢ Vertebral infarct
➢ Stroke and intracranial artery stenosis are major issues in SCD children
➢ The neuroimaging approach in the acute phases of a stroke does not differ than in non-SCD-related pediatric acute strokes (brain CT for excluding hemorrhage, brain MRI and intracranial artery MRA as soon as possible)
• Neuroimaging in SCD
M, 14 years
Territorial Strokes
Watershed Strokes
• 42/99 patients (42%) presented with vascular changeswith a global score >1
• weak correlation between vascular and parenchymalchanges in the supplied cerebral tissue
A1 A2 M1 M2 P1 P2 TICA
Dx 23/3 1 8 11/1 4/1 4 15/2
Sn 19/2 1 11 12/1 0 4 13/2
Our Sample(Padova and Modena)
• Do we need MRI and MRA?
• MRI is sensitive to silent cerebral infarcts that are present in about 20-37% of pediatric SCD patients
Miller et al. Pediatr 2001
Kwiatkowski et al. Haematol 2009
Pegelow et al. Blood 2002
Arkuszewski et al. Adv Med Sci 20146 yrs
• Silent cerebral infarcts have a (14-fold) higher risk of overt stroke
• Do we need MRI and MRA?
• MRA is sensitive to intracranial artery stenosis (detected in about 10% of children with normal TCD)
Arkuszewski et al. Adv Med Sci 2014
Ventura (Sung) Jasmeen
2010 2012 2014
• Are we looking at ischemic lesions?
QDEC (FreeSurfer)
Right Hemisphere
SCD children versus healthy controls
• Cortical thickness and age-classes
QDEC (FreeSurfer)
Left Hemisphere
SCD children versus healthy controls
• Cortical thickness and age-classes
Temporal evolution of cortical thickness
• Cortical thickness and age-classes
➢ Increased connectivity in SCD children vs healthy controls in the precuneus of the defaul mode network.
➢ The phenomenon is more evident in SCD children with initial cognitive impairment.
• Resting state fMRI DMN analysis
Vascular-like white matter lesions review
• Beta-thalassemia
High lesion burden
• Beta-thalassemia
• Beta-thalassemia
Studies without a control group
Patients and controls do not differ in terms of vascular like white
matter changes (46.7% vs 50.0%)
TDT and NTDT patients do not differ, as well
No association between lesion burden and splenectomy
No association with cognitive performances
• Beta-thalassemia
• Beta-thalassemia
• Precedenti studi sulla quantificazione del
ferro nell’encefalo di pazienti β-talassemici
hanno dato risultati disomogenei
• Beta-thalassemia
Iron overload is a major problem
The brain has been scarcely studied
• Beta-thalassemia
• Beta-thalassemiaE
• Beta-thalassemia
CONCLUSIONS
• Conventional Magnetic Resonance and advancedquantitative neuroimaging can help to unravel the issueof brain involvement in hematologic disorders
Aknowledgements
• Prof Perrotta Silvio, Dr.ssa Tartaglione Imma; Dr.ssa Caiazza Martina
• Dr.ssa Colombatti Raffaella, Dr.ssa Sainati Laura
• Dr. Ermani Mario, Dr.ssa Dalla Torre Alice,
• Prof. Esposito Fabrizio, Dr.ssa Canna Antonietta, Dr.ssa Ponticorvo Sara, Dr. Russo Gerardo Andrea
• Dr. Meneghetti Giorgio and Dr.ssa Rampazzo Patrizia
• Dr Palazzi Giovanni
Thanks for the attention
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