TCD for assessment of stroke risk in SCD

Report
CARDIAC MRI
Diagnostic Backgrounder
G-EXJ-1030713
May 2012
NOTE: These slides are for use in educational oral presentations only. If any published figures/tables from these slides are
to be used for another purpose (e.g. in printed materials), it is the individual’s responsibility to apply for the relevant permission.
Specific local use requires local approval
Outline
●
Introduction to iron overload
●
Assessing cardiac iron loading
●
●
–
echocardiography
–
cardiac MRI
Cardiac MRI in practice
–
preparation of the patient
–
acquisition of the image
–
analysis of the data
•
Excel spreadsheet
•
ThalassaemiaTools (CMRtools)
•
cmr42
•
FerriScan
•
MRmap
•
MATLAB
Summary
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MRI = magnetic resonance imaging.
Introduction to
iron overload
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Introduction to iron overload
● Iron overload is common in patients who require intermittent
or regular blood transfusions to treat anaemia and
associated conditions
– it may be exacerbated in some conditions by excess gastrointestinal
absorption of iron
● Iron overload can lead to considerable morbidity and mortality1
● Excess iron is deposited in major organs, resulting in
organ damage
– the organs that are at risk of damage due to iron overload include
the liver, heart, pancreas, thyroid, pituitary gland, and other
endocrine organs2,3
4
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1Ladis
V, et al. Ann NY Acad Sci. 2005;1054:445-50. 2Gabutti V, Piga A. Acta Haematol. 1996;95:26-36.
NF. N Engl J Med. 1999;341:99-109.
3Olivieri
Importance of analysing cardiac iron
●
●
In β-thalassaemia major, cardiac failure and arrhythmia are risk factors
for mortality1
–
signs of myocardial damage due to iron overload: arrhythmia, cardiomegaly,
heart failure, and pericarditis2
–
heart failure has been a major cause of death in β-thalassaemia patients in
the past (50–70%)1,3
In MDS, the results of studies are less comprehensible
–
the reported proportion of MDS patients with cardiac iron overload is
inconsistent; from high to only a small proportion of MDS patients4–7
–
cardiac iron overload occurs later than does liver iron overload4,7,8
–
however, cardiac iron overload can have serious clinical
consequences in MDS patients
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1Borgna-Pignatti
C, et al. Haematologica. 2004;89:1187-93. 2Gabutti V, Piga A. Acta Haematol.
1996;95:26-36. 3. Modell B, et al. Lancet. 2000;355:2051-2. 4Jensen PD, et al. Blood. 2003;101:4632-9.
5Chacko J, et al. Br J Haematol. 2007;138:587-93. 6Konen E, et al. Am J Hematol. 2007;82:1013-6.
7Di Tucci AA, et al. Haematologica. 2008;93:1385-8. 8Buja LM, Roberts WC. Am J Med. 1971;51:209-21.
Importance of analysing cardiac iron (cont.)
● In 2010, the overall mortality rate of β-thalassaemia major patients in
the UK was substantially lower than a decade ago
(1.65 vs 4.3 per 1,000 patient years)1,2
– due to improved monitoring and management of iron overload over
the last decade, 77% of patients have normal cardiac T2*1
– cardiac iron overload is no longer the leading cause of death in this
population1
70
Patients (%)
60
60
Baseline
Latest follow-up
50
40
30
p < 0.001
23
20
17 p < 0.001
10
7
0
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cT2* = cardiac T2*.
1Thomas
cT2* ≤ 20 ms
cT2* < 10 ms
AS, et al. Blood. 2010;116:[abstract 1011]. 2Modell B, et al. Lancet. 2000;355:2051-2.
Cardiac T2*: Overview of correlations with other
measurements
Transfusion
duration† ↑1
Ventricular
dysfunction ↑1-3
Arrhythmia and
heart failure ↑4
T2*↓
Need for cardiac
medication↑1-2
APFR↓
EPFR:APFR↑5
SF and
LIC1-3
Weak or no correlation
†For
thalassaemia, but not sickle cell.
APFR = atrial peak filling rate; EPFR = early peak filling rate; LIC = liver iron concentration;
SF = serum ferritin.
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1Wood
JC, et al. Blood. 2004;103:1934-6. 2Anderson LJ, et al. Eur Heart J. 2001;22:2171-9. 3Tanner
MA, et al. J Cardiovasc Magn Reson. 2006;8:543-7. 4Kirk P, et al. Circulation. 2009;120:1961-8.
5Westwood MA, et al. J Magn Reson Imaging. 2005;22:229-33.
Cardiac T2*: Relationship with LVEF
90
Normal T2* range
80
Normal
LVEF
range
LVEF (%)
70
60
Cardiac T2* value of
37 ms in a normal heart
50
40
30
20
10
0
0
10
20
30
40
50
60
70
80
90
100
Cardiac T2* (ms)
Myocardial T2* values < 20 ms are associated with a
progressive and significant decline in LVEF
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LVEF = left-ventricular ejection fraction.
Anderson LJ, et al. Eur Heart J. 2001;22:2171-9.
Cardiac T2* value of
4 ms in a significantly
iron-overloaded heart
Cardiac T2*: Relationship with cardiac failure
and arrhythmia
Arrhythmia
0.6
< 6 ms
0.5
0.4
6–8 ms
0.3
0.2
8–10 ms
0.1
> 10 ms
0
0
60
120
180
240
300
Follow-up time (days)
T2* < 10 ms: relative risk 159 (p < 0.001)
T2* < 6 ms: relative risk 268 (p < 0.001)
360
Proportion of patients
with arrhythmia
Proportion of patients
developing cardiac failure
Cardiac failure
0.30
0.25
< 10 ms
0.20
0.15
0.10
10–20 ms
0.05
> 20 ms
0
0
60
120
Kirk P, et al. Circulation. 2009;120:1961-8.
240
300
Follow-up time (days)
T2* < 20 ms: relative risk 4.6 (p < 0.001)
T2* < 6 ms: relative risk 8.65 (p < 0.001)
Low myocardial T2* predicts a high risk of developing
cardiac failure and arrhythmia
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180
360
Assessing
cardiac iron
overload
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Assessing cardiac iron loading: Agenda
● Echocardiography
● Cardiac MRI
– advantages and disadvantages of cardiac MRI
– MRI: a non-invasive diagnostic tool
– T2* is the standard method for analysing cardiac iron
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Echocardiography
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Assessing cardiac iron loading:
Echocardiography
Pros
Cons
• Readily available1
• Does not detect early damage2
• Relatively
inexpensive1
• Echocardiographic diastolic function
parameters correlate poorly with LVEF and T2*1
• Cannot directly or indirectly quantify cardiac
iron levels
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EF = ejection fraction.
1Leonardi B, et al. JACC Cardiovasc Imaging. 2008;1:572-8. 2Hoffbrand AV. Eur Heart J. 2001;22:2140-1.
Cardiac MRI
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MRI: A non-invasive diagnostic tool
● Indirectly measures levels of iron in
the heart
Protons
Magnetic field
● MRI measures longitudinal (T1) and
transverse (T2) relaxation times of
the protons
– iron deposition disrupts the
homogeneous magnetic field and
shortens T1 and T2 times in a
concentration-dependent manner
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RF/spin echo/gradient echo
Iron
Echo signal → T1, T2
Signal processing
RF = radio-frequency.
1Wood JC, Ghugre N. Hemoglobin. 2008;32:85-96. 2Wood JC, et al. Circulation. 2005;112:535-43.
3Wang ZJ, et al. Radiology. 2005;234:749-55. 4Ghugre NR, et al. Magn Reson Med. 2006;56:681-6.
MRI: A non-invasive diagnostic tool (cont.)
● If a spin-echo sequence is used,
the relaxation time is T2
Protons
Magnetic field
● If a gradient-echo sequence is
used, it is T2*
Most used in
clinical practice:
Gradient echo
Spin echo
Image acquired
at different TEs
Image acquired
at different TEs
Excel or
software
Excel or
software
T2* [ms}
T2* [ms}
R2* [Hz]=
1,000/T2*
R2* [Hz]=
1,000/T2*
● Cardiac MRI methods
– gradient-echo T2* MRI: most
used in clinical practice
– spin-echo T2 MRI: less useful
(motion artefacts common due to
characteristics of the heart)
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TE = echo time.
Adapted from Wood JC, Ghugre N. Hemoglobin. 2008;32:85-96.
Assessing cardiac iron loading:
Cardiac MRI
Advantages of MRI
Disadvantages of MRI
• Non- invasive
• Rapidly assesses iron content in the
septum of the heart
• Relative iron burden can be
reproducibly estimated
• Functional parameters can be
examined concurrently (e.g. LVEF)
• Iron status of liver and heart can be
assessed in parallel
• Allows longitudinal follow-up
• Good correlation with morbidity
and mortality outcomes
• Indirect measurement of
cardiac iron
• Requires MRI imager with
dedicated imaging method
• Relatively expensive and
varied availability
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FAQ: Cardiac MRI
What are sequences?
Sequences are a set of radio-frequency and gradient pulses (slight
tilts in the magnetization curves of the scanner) generated repeatedly
during the scan, which produce echoes with varied amplitudes and
shapes that will define the MR image
What is gradient echo?
A gradient-echo sequence is obtained after 2 gradient impulses are
applied to the body, resulting in a signal echo that is read by the coils.
In these sequences, the spins are not refocused and, therefore, are
subject to local inhomogeneities, with a more rapid decay curve. For
gradient-echo pulse sequences, the T2* relaxation times (which reflect
these inhomogeneities) on the signal are more significant
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1Image
from Ridgway JP. J Cardiovasc Magn Reson. 2010;12:71.
Gradient relaxometry (T2*, R2*) is the method
for analysing cardiac iron levels
T2* (gradient echo)
T2 (spin echo)
Pros
•
•
•
•
•
•
Greater sensitivity to iron deposition2
Shorter acquisition time1
Less affected by motion artefacts3
More readily available3
Easier to perform4
Good reproducibility5
•
Less affected by susceptibility
artefacts1, due to metal implants,
air–tissue interfaces, proximity to
cardiac veins
Cons
•
More sensitive to static magnetic field
inhomogeneity1
Noise, motion, and blood artefacts can
complicate analysis (particularly in
heavily iron-loaded hearts)7
•
•
•
Lack of sensitivity6
Motion artefacts6
Poor signal-to-background noise
ratios at longer TEs6
Longer acquisition time1
•
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1Guo
•
H, et al. J Magn Reson Imaging. 2009;30:394-400. 2Anderson LJ, et al. Eur Heart J.
2001;22:2171-9. 3Wood JC, Noetzli L. Ann N Y Acad Sci. 2010;1202:173-9.4Wood JC, Ghugre N.
Hemoglobin. 2008;32:85-96. 5Westwood M, et al. J Magn Reson Imaging. 2003;18:33-9.
6Hoffbrand AV. Eur Heart J. 2001;22:2140-1. 7He T, et al. Magn Reson Med. 2008;60:1082-9.
Gradient relaxometry (T2*, R2*) can
conveniently measure cardiac and liver iron
Liver MRI
[Fe] (mg/g dry wt)
14
12
10
8
6
4
R2 =
2
0.82540
0
0
100
200
300
400
HIC (mg Fe/g of dry weight liver)
Cardiac MRI
30
Hankins, et al.
25
20
Wood, et al.
15
10
Anderson, et al.
5
0
Cardiac R2* (Hz)
0
200
400 600 800
Liver R2* (Hz)
Cardiac and liver iron can be assessed together conveniently
by gradient echo during the a single MRI measurement.
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HIC = hepatic iron concentration
Carpenter JP, et al. J Cardiovasc Magn Reson. 2009;11 Suppl 1:P224.
Hankins et al Blood. 2009;113:4853-4855.
1000
Cardiac T2* MRI is usually measured in the
septum of the heart
Heart with normal iron levels
T2* = 22.8 ms or R2* = 43.9 Hz
Heart with severe iron overload
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T2* = 5.2 ms or R2* = 192 Hz
Images courtesy of Dr J. de Lara Fernandes.
What is R2*?
Conversion from T2* to R2* is a simple mathematical calculation:
R2* = 1,000/T2*
Level of cardiac iron overload
Normal
Mild, moderate
Severe
T2*, ms
R2*, Hz
 201
< 50
10–201
50–100
< 102
> 100
These values are only applicable to 1.5 T scanners1
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1Anderson
LJ, et al. Eur Heart J. 2001;22:2171-9. 2Kirk P, et al. Circulation. 2009;120:1961-8.
Why should the data be presented as R2* and
not T2*?
14
14
12
12
[Fe] (mg/g dry wt)
[Fe] (mg/g dry wt)
● Seven whole hearts from patients with transfusion-dependent
anaemias were assessed by histology and cardiac MRI
10
8
6
4
R2 = 0.949
2
10
8
6
4
R2 = 0.82540
2
0
0
0
10
20
30
40
50
60
70
0
Cardiac T2* (ms)
100
200
Cardiac R2* (Hz)
R2* has a linear relationship with tissue iron
concentration, which simplifies the interpretation of data
and allows comparison of changes over time
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Carpenter JP, et al. J Cardiovasc Magn Reson. 2009;11 Suppl 1:P224.
300
400
Why should the data be presented as R2* and
not T2*? (cont.)
The relationship between cardiac T2*/R2* and LVEF
Hockey stick effect?
Or a more gradual relationship?
100
90
80
80
LVEF (%)
LVEF (%)
70
60
50
40
60
40
30
20
20
10
0
0
0
10
20
30
40
50
60
70
80
Heart T2* (ms)
90
100
0
50
100
R2* (s–1)
R2* allows demonstration of cardiac risk in a more gradual way
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Anderson LJ, et al. Eur Heart J. 2001;22:2171-9.
150
200
250
Standard errors on a single measurement are approximately
constant with R2*, but are non-uniform with T2*
Transform to R2* 120
60
R2* first measurement (s–1)
T2* first measurement (ms)
Why should the data be presented as R2* and
not T2*? (cont.)
50
40
30
20
10
0
0
10
20
30
40
50
60
T2* second measurement (ms)
100
80
60
40
20
0
0
Westwood M, et al. J Magn Reson Imaging. 2003;18:33-9.
40
60
80
100 120
R2* second measurement (s–1)
R2* has a constant standard error that makes
assessment of the significance of changes easier
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20
Cardiac T2*
MRI in practice
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MRI scanners
●
●
●
Manufacturers
–
Siemens Healthcare (Erlangen, Germany; www.siemensmedical.com)
–
GE Healthcare (Milwaukee, WI, USA; www.gemedicalsystems.com)
–
Philips Healthcare (Best, the Netherlands; www.medical.philips.com)
Magnetic field
–
T2* varies with magnetic field strength1
–
need 1.5 T for cutoff levels of 20 ms (iron overload) and 10 ms
(severe iron overload)1,2
Cardiac package
–
needs to be acquired separately from the manufacturers. The cost is
about USD 40,000. However, in most centres, this is available since MRI
is frequently used in non-iron-related cardiovascular imaging
–
includes all necessary for acquisition of the image
–
sequences are included in Siemens and Philips Healthcare cardiac
packages, but for GE Healthcare they need to be acquired separately
(note: variations may exist between countries)
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1Anderson
LJ, et al. Eur Heart J. 2001;22:2171-9. 2Kirk P, et al. Circulation. 2009;120:1961-8.
Cardiac T2* MRI in practice: The process
1. Patient
preparation
2. Acquisition of
the MRI image
(5 min)
(approx. 5-20 min)
3. Analysis of
MRI data
(time depends
on experience*)
LIVER
TE
Please insert the values of TE and
ROI from an individual patient.
ROI
1.3
2.46
3.62
4.78
5.94
7.1
8.26
9.42
10.58
11.74
134
114
99
81
70
59
49
40
35
28
160
140
y = 166.48552e-0.14925x
R² = 0.99845
120
100
80
60
40
20
E
0.14925
0
T2*
2.1 ms
R2*
476.1905 Hz
0
2
4
6
LIC
12.88801 mg/g
LIC calculation according to: Hankins JS, et al. Blood. 2009;113:4853-5.
Normal
Normal
Normal
>11.4
<88
<2
Light
Light
Light
3.8 - 11.4
88-263
2-7
Moderate
Moderate
Moderate
8
1.8-3.8
263-555
7-15
10
12
Severe
Severe
Severe
14
<1.8
>555
>15
Please insert the value from the
graph, encircled green.
T2*, R2*
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*Time to manually calculate T2*/R2* values in an Excel spreadsheet depends on the experience
of the physician.
T2*
R2*
mg/g
Cardiac T2* MRI in practice: The process (cont.)
● Preparation of the patient
● Acquisition of the image
● Analysis of the data (post-processing)
•
Excel spreadsheet
•
ThalassaemiaTools, CMRtools
•
cmr42
•
FerriScan
•
MRmap
•
MATLAB
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Preparation
of the patient
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Preparation of the patient
● Standard precautions need to be taken
● There is no need for peripheral vein access since no contrast
agent is required
● Special care
– remove all infusion/medication pumps (e.g. with insulin,
pain-relieving drugs)
– stop continuous i.v. application of ICT during the measurement
– ECG signal should be positioned according to scanner specifications
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ECG = electrocardiography.
Cardiac T2* MRI in practice: The process (cont.)
● Preparation of the patient
● Acquisition of the image
● Analysis of the data (post-processing)
•
Excel spreadsheet
•
ThalassaemiaTools, CMRtools
•
cmr42
•
FerriScan
•
MRmap
•
MATLAB
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Acquisition
of the image
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Acquisition of the image: MRI pulse sequences
● Pulse sequences
– are a preselected set of defined radio-frequency and
gradient pulses
– are computer programs that control all hardware aspects of
the scan
– determine the order, spacing, and type of radio-frequency pulses
that produce magnetic resonance images according to changes in
the gradients of the magnetic field
● Several different pulse sequences exist1
– a gradient-echo sequence generates T2*
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1Wood
JC, Ghugre N. Hemoglobin. 2008;32:85-96.
The most common commercially available T2*
acquisition techniques
Group
Number of
echoes per
breath-hold
Heart
regions
Prepulse
RR
intervals
TR
Bright blood
(Anderson et al.)1
London
(Pennell)
1 (but multiple
breath-holds)
1 (septum)
No
1
Variable
Novel bright blood
(Westwood et al)2
London
(Pennell)
Multiple
1 (septum)
No
1
Fixed
Black blood
(He et al)3-4
London
(Pennell)
Multiple
1 (septum)
Yes
2
Fixed
Multi-slice
Pisa
(Pepe)
Multiple
Multiregion
No
1
Fixed
Sequence
(Pepe et al)5
The various techniques give clinically comparable results.2-3, 5
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1Anderson
LJ, et al. Eur Heart J. 2001;22:2171-9. 2Westwood M, et al. J Magn Reson Imaging.
2003;18:33-9. 3He T, et al. J Magn Reson Imaging. 2007;25:1205-9. 4He T, et al. Magn Reson Med.
2008;60:1082-9. 5Pepe A, et al. J Magn Reson Imaging. 2006;23:662-8.
Acquisition of the image: TEs
● The choice of minimum TE determines
the smallest
measurable T21
•
ideally, min TE  2 ms,
max TE 17‒20 ms
● Different T2* acquisition techniques
according to TE
•
•
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multiple breath-hold: acquire an
image for each TE in separate
breath-holds2
Mean R2* compared with true value in the case of
synthetic images for different minimum TEs,
but same echo duration (18 ms)4
Mean R2*: ramp, dualtone, &
uniform (Hz)
● Images are taken at a minimum
of 5 different TEs, normally 8‒121
Shortest TE = 2 ms
Shortest TE = 1 ms
Shortest TE = 4 ms
Shortest TE = 5.5 ms
True
500
450
400
350
300
250
200
150
100
50
0
0
100
200
True R2* (Hz)
single breath-hold multi-echo
acquisition: acquire images for
all TE during 1 breath-hold3
1Wood
300
JC, Noetzli L. Ann N Y Acad Sci. 2010;1202:173-9. 2Anderson LJ, et al. Eur Heart J.
2001;22:2171-9. 3Westwood M, et al. J Magn Reson Imaging. 2003;18:33-9. 4Ghugre NR, et al.
J Magn Reson Imaging. 2006;23:9-16.
400
500
How does the MRI data output looks like?
MRI data output
Frame
TE (ms)
Mean ST
0
1.9
89.5
1
3.6
83.6
2
5.3
76.8
3
7.0
70.6
4
8.7
64.5
5
10.4
59.2
6
12.2
54.9
7
13.9
50.2
8
15.6
45.8
9
17.3
42.4
Data visualization
During a single breath hold the pulse sequence run several
times at increasing echo time (TE), generating data points
corresponding to decreased signal intensity1
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1Wood
JC, Ghugre N. Hemoglobin. 2008;32:85-96.
FAQ: Acquisition technique
Which is recommended: single or multiple breath-hold technique?
Comparison of the 2 methods, single and multiple breath-hold,
showed no significant skewing between T2* values in all patients
with -thalassaemia major, regardless of their T2* value (see BlandAltman plots)1
However, in cardiac MRI the most recommended technique is single
breath-hold, because it allows quick acquisition of the information. This
is especially important to avoid movement artefacts (heart beating,
breathing) and assure the good quality of the MRI image
Patients with T2* < 20 ms1
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1Westwood
Patients with T2*  20 ms 1
M, et al. J Magn Reson Imaging. 2003;18:33-9.
Acquisition of the image
● Single breath-hold multi-echo acquisition
– take a short-axis slice of the ventricle (halfway between the base
and the apex): orange line
– image acquisition should occur immediately after the R wave
– do not alter any settings that could alter TE (e.g. FOV)
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Image courtesy of Dr J. de Lara Fernandes.
Cardiac T2* MRI in practice: The process (cont.)
● Preparation of the patient
● Acquisition of the image
● Analysis of the data (post-processing)
•
Excel spreadsheet
•
ThalassaemiaTools, CMRtools
•
cmr42
•
FerriScan
•
MRmap
•
MATLAB
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Analysis
of the data
(post-processing)
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How T2* is calculated from the MRI output?
Data visualization
Curve Fitting
T2*
Noise level
T2* calculation is fitting a curve on the data points and calculating
at what echo time no signal is left from iron (only noise)1
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1Wood
JC, Ghugre N. Hemoglobin. 2008;32:85-96.
Analysis of the data
● The data can be analysed manually or using
post-processing software
Manually
Post-processing software
•
•
•
•
•
•
Excel spreadsheet
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ThalassaemiaTools (CMRtools)
cmr42
FerriScan
MRmap
MATLAB
Analysis of the data (cont.)
Method
Pros
Cons
Excel spreadsheet
• Low cost
• Time-consuming
• Tedious
ThalassaemiaTools
(CMRtools)1
• Fast (1 min)2
• Easy to use
• FDA approved
• GBP 3,000 per year
cmr42(3)
• Easy to use
• FDA approved3
• Can generate T2*/R2* and T2/R2 maps
with same software
• Allows different forms of analysis
• Generates pixel-wise fitting with
colour maps
• 40,000 USD first year costs
• 12,000 USD per year after
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FDA = Food and Drug Administration.
1www.cmrtools.com/cmrweb/ThalassaemiaToolsIntroduction.htm. Accessed Dec 2010. 2Pennell DJ.
JACC Cardiovasc Imaging. 2008;1:579-81.3www.circlecvi.com. Accessed Dec 2010.
Analysis of the data (cont.)
Method
Pros
Cons
FerriScan1
• Centralized analysis of locally acquired data (206
active sites across 25 countries)
• Easy set-up on most MRI machines
• EU approved
• Validated on GE, Philips, and Siemens scanners
• USD 100 per scan
• Patients data are sent to
reference centre
MRmap2
• Uses IDL runtime, which is a commercial software
(less expensive than cmr42/CMRtools)
• Can quantify T1 and T2 map with the same
software
• Purely a research tool
• Not intended for diagnostic or
clinical use
MATLAB3
• Low cost
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1www.resonancehealth.com/resonance/ferriscan.
•
•
Available only locally
Physicists or engineers need to
write a MATLAB program for
display and T2* measurement
Accessed Dec 2010. 2www.cmr-berlin.org/forschung/
mrmapengl/index.html. Accessed Dec 2010. 3Wood JC, Noetzli L. Ann N Y Acad Sci. 2010;1202:173-9.
FAQ: Mistakes in analysing the data
What are the most common mistakes in analysing the data
that could lead to a wrong interpretation of the T2* value?
Interpreting the data from cardiac MRI is usually quite straightforward;
problems may arise when analysing data from patients with severe
cardiac iron overload. In this case, the signal from heavily iron-loaded
muscle will decay quickly and a single exponential decay curve does
not fit the data well.1
Models exist that can help to solve this issue (see next slide):
1. the offset model (Prof Wood and colleagues)
2. truncation of the data (Prof Pennell and colleagues)
Both models should give comparable results; the differences should
not be clinically relevant
Signal decay curve from a patient with
T2* ≈ 5 ms, showing that the data do
not fit well2
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1Wood
JC, Noetzli L. Ann N Y Acad Sci. 2010;1202:173-9. 2Ghugre NR, et al. J Magn Reson
Imaging. 2006;23:9-16.
FAQ: Mistakes in analysing the data (cont.)
What is truncation?
After the selection of the ROI, the signal decay can be fitted using different models.
In the truncation model, the late points in the curve that form a plateau are
subjectively discarded; the objective is to have a curve with an R 2 > 0.995. A new
single exponential curve is made by fitting the remaining signals.1
Generally, a truncation model should be used with the bright-blood technique to
obtain more reproducible and more accurate T2* measurements1
What is an offset model?
The offset model consists of a single exponential with a
constant offset. Using only the exponential model can
underestimate the real T2* values (at quick signal loss at short
TE, there is a plateau), while inclusion of the offset model into
the fitting equation can improve this.2
Generally, the offset model is recommended to be used with
the black-blood technique
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1He
T, et al. Magn Reson Med. 2008;60:1082-9. 2Ghugre NR, et al. J Magn Reson Imaging.
2006;23:9-16.
FAQ: How to start measuring cardiac
iron loading?
How to start measuring cardiac iron loading in a
hospital? What steps need to be taken?
To start assessing cardiac iron loading by MRI, these steps can be followed:
1. Check MRI machine requirements
• 1.5 T
• calibrated
2. Buy cardiac package from the manufacturer. It must include all that is
necessary for acquisition of the data (the sequences are included with
Siemens and Philips Healthcare cardiac packages, but for
GE Healthcare they need to be acquired separately)
3. Optional: buy software for analysing the data (if not, Excel spreadsheet can
be used)
4. Highly recommended: training of personnel for acquisition of cardiac MR
images (e.g. functional analyses)
5. Highly recommended: training of personnel on how to analyse the data
with the chosen software
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Implementation of liver and cardiac MRI
1.5T MRI Scanner
US$1.000.000
Yes
½ day training
Liver
Analysis
Experienced radiologist
No
1 day training
Post-processing analysis
Cardiac acquisition package
US$50.000
Yes
US$40.000 or US$4.000/y
or in-house or outsource
1-2 day training
Heart
Analysis
Routine cardiac MR exams
No
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4 day training
Slide presented at Global Iron Summit 2011 - With the permission of Juliano de Lara Fernandes
Summary
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Summary
●
Iron overload is common in patients who require intermittent or regular blood
transfusions to treat anaemia and associated conditions
●
Analysing cardiac iron levels is important
●
–
in β-thalassaemia major, cardiac failure and arrhythmia are risk factors for
mortality
–
in MDS, cardiac iron overload can have serious clinical consequences
–
due to improved monitoring and management of iron overload over the last
decade, 77% of patients have normal cardiac T2*1
MRI: the method to rapidly and effectively assess cardiac iron loading
–
T2* allows specific assessment of cardiac iron levels. The use of this convenient,
non-invasive procedure has had a significant impact on outcomes in patients with
cardiac iron overload1
–
R2* is a simple calculation from T2* and has a linear relationship
with cardiac iron concentration
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1Thomas
AS, et al. Blood. 2010;116:[abstract 1011]. 2Modell B, et al. J Cardiovasc Magn Reson.
2008;10:42-9.
GLOSSARY
OF TERMS
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GLOSSARY
● AML = acute myeloid leukemia
● APFR = Atrialp peak filling rate
● BA = basilar artery
● ß-TM = Beta Thalassemia Major
● ß-TI = Beta Thalassemia Intermedia
● BM = bone marrow
● BTM = bone marrow transplantation
● BW = bandwidth
● CFU = colony-forming unit
● CMML = chronic myelomonocytic leukemia
● CT2 = cardiac T2*.
● DAPI = 4',6-diamidino-2-phenylindole
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GLOSSARY
● DFS = = disease-free survival.
● DysE = dyserythropoiesis
● ECG = electrocardiography
● EDV = end-diastolic velocity
● EF = ejection fraction
● EPFR = early peak filling rate
● FatSat = fat saturation
● FAQ = frequently asked questions
● FDA = Food and Drug Administration
● FISH = fluorescence in situ hybridization.
● FOV = field of view
● GBP = Currency, pound sterling (£)
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GLOSSARY
● Hb = hemoglobin
● HbE = hemoglobin E
● HbF = fetal hemoglobin
● HbS = sickle cell hemoglobin.
● HbSS = sickle cell anemia.
● HIC = hepatic iron concentration
● HU = hydroxyurea
● ICA = internal carotid artery.
● ICT = iron chelation therapy
● IDL = interface description language
● IPSS = International Prognostic Scoring System
● iso = isochromosome
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GLOSSARY
● LIC = liver iron concentration
● LVEF = left-ventricular ejection fraction
● MCA = middle cerebral artery
● MDS = Myelodysplastic syndromes
● MDS-U = myelodysplastic syndrome, unclassified
● MRA = magnetic resonance angiography
● MRI = magnetic resonance imaging
● MV = mean velocity.
● N = neutropenia
● NEX = number of excitations
● NIH = National Institute of Health
● OS = overall survival
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GLOSSARY
● pB = peripheral blood
● PI = pulsatility index
● PSV = peak systolic Velocity
● RA =refractory anemia
● RAEB = refractory anemia with excess blasts
● RAEB -T = refractory anemia with excess blasts in transformation
● RARS = refractory anemia with ringed sideroblasts
● RBC = red blood cells
● RF = radio-frequency
● RCMD = refractory cytopenia with multilineage dysplasia
● RCMD-RS = refractory cytopenia with multilineage dysplasia with
ringed sideroblasts
● RCUD = refractory cytopenia with unilineage dysplasia
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GLOSSARY
● RN = refractory neutropenia
● ROI = region of interest
● RT = refractory thrombocytopenia
● SCD = sickle cell disease
● SD = standard deviation
● SI = signal intensity
● SIR = signal intensity ratio
● SF = serum ferritin
● SNP-a = single-nucleotide polymorphism
● SQUID = superconducting quantum interface device.
● STOP = = Stroke Prevention Trial in Sickle Cell Anemia
● STOP II = Optimizing Primary Stroke Prevention in Sickle Cell Anemia
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GLOSSARY
● T = thrombocytopenia
● TAMMV = time-averaged mean of the maximum velocity.
● TCCS = transcranial colour-coded sonography
● TCD = transcranial doppler ultrasonography
● TCDI = duplex (imaging TCD)
● TE = echo time
● TR = repetition time
● WHO = World Health Organization
● WPSS = WHO classification-based Prognostic Scoring System
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