cardiac MRI clinical applications,Principles

1. CARDIAC MRI
The New Frontier

2. Paul Lauterbur Raymond Damadian
Deceased 03/29/07

3. Peter Mansfield

5. Imaging in Heart Disease
• Chest X-ray
• Echocardiography
• Nuclear scintigraphy
• Catheterisation
Resolution
Information Radiation
• Cardiac MRI Invasiveness

6. The Comprehensive Cardiac MR (CMR)
Goal: <30 min acquisition, <10 min post-processing
• Cardiac and great vessel anatomy
• Cardiac volumes and mass
• Global and regional contractile function
• Regional myocardial tissue perfusion
• Regional myocardial tissue characteristics:
Viability, oedema, inflammation, fibrosis,
metabolism
• Coronary artery lumen, wall anatomy, blood flow

7. What CMR has to offer

8. Comprehensive CMR Study
• High resolution anatomy
• Global / regional function
• Regional perfusion
• Viability/Oedema/Fibrosis
• Coronary Angiography

9. Cmr physics

10. T1&T2 WEIGHTED IMAGES

11. What Are Electromagnetic
Waves?
 If electrons are moving in a wire, say a radio transmitting
antenna, they will set up changing electric fields.
 Changing electric fields set up magnetic fields. These
magnetic fields set up changing electric fields.
 Electric and magnetic fields oscillate and propagate
through space. They form an electromagnetic wave.
 visible light (and its color), ultraviolet light, infrared light,
radio waves, X-rays, or gamma ray

12. sequences
 Spin echo- Black Blood
refocussing RF pulse,
still image& excellent tissue contrast,longer time
 Gradient echo-Bright Blood
Refocussing gradients
Cine images,faster less tissue contrast
Perfusion,scar ,coronary imaging
Cine imaging-B`SSFP-Steady state freee precesssion,excellent
tissue contrast insensitive to blood accurate EF&Volumes
FLASH- FAST LOW ANGLE SHOT- abnormal perfused
remain dark,normal perfusion shows gadolinium increased
intensity

13. Coronal MRI shows aorta, av, lv
(can eval for stenosis and regurg)
Spin echo “black blood” Gradient echo “white blood”
anatomy function & flow

14. Cardiac Axial Alignment

15. Cardiac Function: True-FISP MRI
Horizontal long axis Vertical long axis
Jane Francis, MR technologist,
University of Oxford Centre for Clinical MR Research

16. Short axis Stack of short axes
Base +10mm +20mm +30mm +40mm
Apex
+50mm +60mm +70mm +80mm
+90mm
Simpson’s Rule

17. Pre-vs. post-surgery MRI
HLA cine
pre post Norm
EDV (ml) 1423 167 77-195
EF (%) 3 54 56-78
Selvanayagam J et al, Circulation 2003

39. Regional Tissue Contractility
Tissue Phase Mapping
3D Velocities: Radial, circumferential,
longitudinal
Petersen S et al, Radiology 2005

40. Delayed-enhancement short-axis
Bulls eye Plot
 Bull’s-eye plot
Tissue Phase Mapping

41. Wall thickening analysis of short-axis cine MR
images infarction left anterior descending artery.
 (a) Delayed-enhancement short-axis
Transmural hyperenhancement (arrows)
corresponds to scar tissue.
 (b) The endocardial and epicardial contours diagrammed on the
SSFP image.
Chords for measuring wall thickness are shown along the left
ventricular circumference.
 (c) Bull’s-eye plot shows the extent of wall thickening.
The smallest ring represents the apical region, and the largest
ring represents the basal region.

42. Dobutamine-Stress MR: 4-Chamber
rest 20 µg
30 µg 40 µg
Nagel E et al, Circulation 1999

43. Influence of image quality
100
90
80
70
60
50
40
sensitivity (DSE)
30
specificity (DSE)
20
sensitivity (DSMR)
10
specificity (DSMR)
0
good / very good moderate
E. Nagel, Z Kardiol 1999

44. Comprehensive CMR Study
• High resolution anatomy
• Global / regional function
• Regional perfusion -
GdDTPA
• Viability/Oedema/Fibrosis
• Coronary Angiography

45. “First pass” study: Time-intensity
curves
LV Blood pool
[Gd]
Norma
l
Ischemia/Infarct
<10s 10-20 min time
Perfusion Infarct

46. Myocardial Perfusion -
Quantification
Rest and stress
perfusion
(i.v. Adenosine 140 g/kg x
min)
• Qualitative (eyeballing)
• Semi-quantification (upslope)
→ perfusion reserve
• Absolute quantification (ml/min x g)
Wilke N et al. MRM
1993

47. Regional Myocardial
Perfusion
Nagel E el al. Circulation 2003
• Sensitivity 88%
• Specificity 90%
• Diagnostic accuracy 89%
Wolff SD et al, Circulation 2004
Giang TH et al, Eur Heart J 2004

48. MR IMPACT II
(Magnetic Resonance Imaging for Myocardial Perfusion Assessment
in Coronary artery disease Trial)
A phase III multicenter, multivendor trial
comparing perfusion cardiac magnetic resonance
versus
single photon emission computed tomography
for the detection of coronary artery disease.
J. Schwitter, 1 C. Wacker, 2 N. Wilke, 3
N. Al-Saadi, 4 N. Hoebel, 5 T. Simor 6
33 centres, 1.5 Tesla, 465 patients
• Patients with chest pain undergoing coronary angiography
• CAD defined as >50% diameter stenosis in at least one
vessel with at least 2mm diameter

49. CardioVascular
MR Center Zurich
MR-IMPACT II
33 Centers – Multivendor: Dose 0.075 mmol/kg Gd-DTPA-BMA
1 Perfusion-CMR
n=465
AUC: 0.75 0.02
0.75 SPECT all
* n=465
Sensitivity
AUC: 0.65 0.03
P=0.0004
0.5
gated-SPECT
n=277
AUC: 0.69 0.03
0.25 P=0.018
ungated-SPECT
n=188
AUC: 0.63 0.04
0 P=0.023
0 0.25 0.5 0.75 1 P=ns vs Gated
1-Specificity

50. CardioVascular
MR Center Zurich
MR-IMPACT II - MVD
33 Centers – Multivendor: Dose 0.075 mmol/kg Gd-DTPA-BMA
1 Perfusion-CMR
n=339
AUC: 0.80 0.03
0.75 SPECT all
n=339
Sensitivity
AUC: 0.72 0.03
P=0.003
0.5
gated-SPECT
n=188
AUC: 0.75 0.04
0.25 P=0.040
ungated-SPECT
n=140
AUC: 0.69 0.05
0 P=0.049
0 0.25 0.5 0.75 1 P=ns vs Gated
1-Specificity 1-3 VD SPECT

51. Superior to SPECT for the
detection of sub-endocardial
infarction
Wagner et al Lancet 361:378

52. CardioVascular
MR Center Zurich
MR-IMPACT II
It is the largest multicenter MR/SPECT trial performed
so far using 99mTc-tracers and ECG-gating (33 centers,
465 patients)
It shows:
 Perfusion-CMR (at 0.075 mmol/kg Gd-DTPA- BMA) is superior to SPECT for
the detection of coronary artery disease
 Perfusion-CMR is a short and safe test, is sensitive and specific, and can be
recommended as an alternative for SPECT imaging in experienced centers

53. Comprehensive CMR Study
• High resolution anatomy
• Global / regional function
• Regional perfusion
• Viability/Oedema/Fibrosis
• Coronary Angiography

54. Delayed Enhancement MRI
• 10 – 20 min post Gd DTPA
• Inversion recovery
FLASH or True-FISP
• “Bright is dead”
• Normal, stunned, hibernating
myocardium is dark
Kim R et al, Circulation 1999

55. Delayed Enhancement
MRI
In vivo infarct imaging
Kim R et al, NEJM 2001

56. Example: Acute Antero-Septal
Infarction
LV Function: cine Myocardial Viability:
MRI DE-MRI
Superior to SPECT for the
detection of sub-endocardial
infarction
Wagner et al Lancet 361:378

57. Relationship between transmural extent of HE before
bypass surgery and likelihood of increased contractility
after surgery
All Dysfunctional Segments
100
Improved contractility (%)
80
60
Selvanayagam J et al
40
Circulation 2004
20
0
Transmural Extent of Hyperenhancement (%)

58. Delayed Enhancement
Phenomenon
Not specific for ischemic injury
Acute Myocarditis HCM: Fibrosis DCM: Fibrosis
M. Friedrich et al S. Petersen et al McCrohon et al Circulation 2003

59. Comprehensive CMR Study
• High resolution anatomy
• Global / regional function
• Regional perfusion
• Viability/Oedema/Fibrosis
• Coronary Angiography

60. CT Coronary Angiography
Achenbach S,
Erlangen
University
Spatial resolution Temporal resolution
0.4 x 0.4 x 0.4 mm 120 ms

61. MR Coronary Angiography
Sakuma H,
Matsusaka
Central Hospital,
Mie, Japan
Spatial resolution Temporal resolution
0.6 x 0.6 x 0.6 mm minutes (navigator)

62. MR Coronary Angiography:
Fundamental challenges
• Small structures (1-4mm diameter)
• Need 3 D resolution
• Move rapidly with cardiac cycle
and respiration (RCA by ~ 10cm)
Spatial resolution Temporal resolution
Cardiac cath 0.3 x 0.3 mm 8 ms (shutter speed)

63. Myocardial Viability
The Clinical Problem:
Akinetic myocardium,
supplied by stenosed coronary artery
Viable Non-viable
= Stunning, Hibernation = Scar
Revascularisation No Revascularisation
(PTCA, CABG)

64. contrindications
 Pacemakers &ICDS  Cochlear implants
 Intravascular  Aneurysmal clips
coils,stents,filters(after  Foleys catheter(temp..
6-8wks) Sensors)
 Prosthesis
 Occluder devices
 Ecg electrodes

65. Thank u

66. Clinical history
 A 75 year old
hypertensive female
with angina pectoris
presented with
unstable angina and
CHF.
 Labs
 The resting ECG
showed anterolateral
T-wave abnormalities

67. cardiac catheterization showed
 90% mid LAD
stenosis with
dyskinetic anterior
and apical walls.
 70% stenosis in a
large OM branch of
the left circumflex

68. . The LVEF was estimated to be 30-35%.
 The patient underwent
an IV Dipyridamole
TL-201 stress test with
limited exercise
 She developed
dyspnea, hypotension,
and 1.5 mm horizontal
ST depression in cc5

69. The patient went on to have a 2 vessel
CABG operation

70. What clinical clues suggest that this patient has
substantial dysfunctional-viable myocardium?
 Chronic stable angina, unstable angina prior to
presentation, the absence of a previous or present MI and
the absence of Q waves on the electrocardiogram are clues
for the presence of myocardial viability

71. Detail the scintigraphic findings.
 severe defect involving the anterior, apical and apical inferior wall
with partial reversibility on delayed imaging after re-injection
Moderately severe defect involving the lateral wall with nearly
complete reversibility on delayed imaging after re-injection.
 There is transient cavity dilatation.
Conclusion: moderate degree of reversible ischemia involving a
moderately large part of the LAD territory probably superimposed on
a prior anteroapical infarction.
 severe reversible ischemia involving a moderately large part of the
left circumflex vascular territory.

72. Do you predict an improvement in regional and/or
global left ventricular function with successful
revascularization of the LAD?
 Nevertheless, the major redistribution
between stress and delayed imaging in this
territory does predict that the corresponding
dysfunctional myocardium will recover
with LAD revascularization.

73. What is the rationale for myocardial viability testing in
patients with coronary disease and severely reduced left
ventricular systolic function?
 Identify those patients in whom revascularization
is likely to improve functional class, augment
regional and global LVEF and increase survival.
 Connversely, the presence of predominant
myocardial scarring predicts increased operative
mortality and the absence of these salutary effects.