Cardiac MRI provides concise summaries of medical documents in 3 sentences or less: Cardiac MRI has a history dating back to the 1970s when the first MRI machine was developed and techniques for generating images were discovered, leading to the Nobel Prize. MRI uses magnetic fields and radio waves to generate detailed images of the heart and blood vessels without using ionizing radiation. Cardiac MRI is now used clinically to assess cardiac structure and function, detect ischemia and scar tissue, and evaluate various cardiomyopathies.

1. Cardiac MRI

2. History of MRI
• Magnetic resonance imaging (MRI), nuclear magnetic resonance
imaging (NMRI), or magnetic resonance tomography (MRT)
• Raymond Damadian, an Armenian-American physician, scientist
- worlds first MRI machine 1972
• Paul Lauterbur - technique to generate images from MRI
• Peter Mansfield - mathematical technique to generate images
from MRI
• Nobel Prize in Physiology or Medicine for their "discoveries
concerning magnetic resonance imaging"

3. Paul Lauterbur Raymond Damadian Peter Mansfield

4. • MR System Components
• Main magnet coils
• Static magnetic field B0
• 3 gradient coils
• integral RF transmitter coil

6. • Application of RF pulse tilts net magnetisation vector - flip angle
• two independent relaxation processes return the net magnetization vector to
its thermal equilibrium
• Longitudinal relaxation results from the transfer of energy from the excited
protons to surrounding molecules in the local environment.
• T1 - time to recover 63% of original energy
• Transverse or spin-spin relaxation, describes the decay of the
magnetization vector in the transverse plane
• T2 - time to lose 63% of transverse momentum
• T1 and T2 properties of tissue

9. • Advantages of CMR over other cardiac imaging modalities
• Lack of ionizing radiation
• Free choice of imaging planes
• Capability for tissue characterisation
• Qualitative and quantitative evaluation of the motion of
both the blood and the myocardium
• Assessment of regional perfusion

10. MRI Safety
• Powerful magnetic field
• 1.5 T approx 30,000 times earth’s magnetic field
• Objects near entry - pulled into machine
• objects within machine - experience torque
• Rapid change in field with distance from magnet

11. • Heating effects
• RF magnetic fields can cause heating if
concentrated in small areas - ECG leads,
thermistor leads, may damage device or cause
burns
• Claustrophobia
• 4% of patients

12. Cardiac gating
• Essential component of cardiac MRI to overcome
blurring of images caused by myocardial contraction
and flow effects from pulsatile blood
• Data collected over same point in ECG over
successive heart beats
• Good lead placement, prominent R wave
• Avoid loop formation

13. • Prospective gating
• Data acquisition over at start of cardiac cycle over several cycles
• Better temporal resolution
• Retrospective gating
• Continuous data acquisition and then post processing for images at certain time points
• Whole cardiac cycle can be imaged
• Less sensitive to arrhythmias
• Useful for cine images
• Better for regional and global wall motion assessment
• Temporal blurring

15. Respiratory Gating
• Maximum motion craniocaudal
• Some degree of anteroposterior and transverse motion
• Approx 1 cm movement craniocaudally
• Breath holding - Acquisition times 10 sec
• Varies within cycles
• Adequate respiratory reserve
• Imaging with breath holding at end tidal position

16. • Diaphragmatic tracking - by respiratory navigator
• Respiratory monitoring using bellows

17. Pulse Sequence Structure
• An individual pulse sequence is a combination of radiofrequency
pulses, magnetic gradient field switches, and timed data
acquisitions, all applied in a precise order, that results in either
accentuation or suppression of specific biological
• Imaging engine
• provides the spatial relationship of objects i.e. the image
• Modifier
• Optional components that add specific information or speed
the image

20. Examination sequence
• Scouting
• Function/Volumes
• Perfusion at stress/rest
• Viability and Infarction
• Additional
• Morphology
• Flow/Velocity
• T2 Weighted Edema imaging

21. • Scouting
• First procedure
• To establish long and short axis of heart with
respect to scanner coordinates
• Single shot
• Steady state free precession (SSFP), Half Fourier
single-shot TSE (HASTE)

23. Function and volumes
• CineMRI using Gradient Recall Echo(GRE) or SSFP
• Captures movie of beating heart
• 20-25 frames per cycle, 35-45 ms per frame
• Single shot/segmented
• Core examination
• Short-axis stack from mitral valve plane to apex
• Two, Three and Four Chamber long axis views
• Slices - 5-6mm

27. Perfusion at Stress and Rest
• Fasting growing use
• Movie of the transit of contrast media (typically
gadolinium-based) with the blood during its initial
pass through the left ventricular (LV) myocardium
(first-pass contrast enhancement).
• 4 to 5 short-axis views are obtained every heartbeat
• Total of 40 to 60 heartbeats consisting of the entire
first-pass

28. • Patient then partially pulled out
• Adenosine 140 mcg/kg/min
• Patient returned after 2 minutes
• Gadolinium contrast administered (0.075-0.10 mmol/kg) 4ml/s
• After contrast clears from LV myocardium adenosine stopped (total 3 - 3.5 mins)
• 15 minutes for contrast to wash out from blood pool
• Rest perfusion scan
• Additional gadolinium contrast (0.075-0.10 mmol/kg) 4ml/s
• Same imaging
• Delayed enhancement imaging
• After 5 minutes
• Total duration ~ 45 minutes

30. Viability and Infarction
• Delayed enhancement MRI (DE-MRI), Late
Gadolinium enhancement CMR, delayed
hyperenhancement imaging
• Images with high contrast between abnormal
myocardial tissue, which generally accumulates
excess gadolinium (after intravenous
administration), and normal tissue, in which
gadolinium concentration is low.

31. • Gadolinium cannot penetrate intact sarcolemmal membrane
• Injured myocytes take up gadolinium and increased tissue
concentration
• Chronic infarction, interstitial space is increased
• High tissue concentrations of gadolinium leads to shortened
T1 relaxation times
• Infarct - bright/hyperenhanced
• Viable - black/nulled

33. • Morphology scan
• Usually cardiac and proximal vascular structures are imaged in the core
examination
• If additional information required
• congenital heart disease, cardiac masses, aortic root dilation
• Bread loaf - parallel slices, axial, sagittal or coronal
• Single shot using
• SSFP - blood bright (bright blood technique)
• TSE - flowing blood dark (black blood technique)

34. Flow/velocity
• Velocity encoded cine imaging (VENC-MRI), phase
contrast velocity mapping
• Signal from moving blood or tissue will undergo a phase
shift relative to stationary tissue if a magnetic field
gradient is applied in the direction of motion
• Cine loop across cardiac cycle - pixel intensity
proportional to blood velocity
• Grayscale - White maximum in one direction, black
maximum in the other direction

35. • Segmented GRE during breath hold
• versus doppler echocardiography
• flow through an orifice is directly measured on an
enface image of the orifice with through-plane
velocity encoding

39. T2 weighted edema imaging
• Necrotic myocardium - tissue water content
increases markedly
• longer intrinsic T2 for infarcted myocardium (60-65
ms) compared with that of normal (45-50 ms)
• Uses
• Chronic lesions from those of recent onset
• Possible role in identifying myocardium at risk

40. Contrast agents
• Only gadolinium based contrast agents(GBCA) are used
at present
• Following iv injection
• 15 to 30 seconds for a first pass through the cardiac
chambers and blood vessels (first-pass phase)
• 10 to 15 minutes transient plateau of GBCA
concentration (equilibrium between contrast washing
in to the extracellular space and washing out to the
blood pool)

41. • Myocardial perfusion CMR and most types of
magnetic resonance angiography (MRA) are
performed during the first-pass phase,
• Late gadolinium enhancement (LGE) images are
obtained during the equilibrium phase
• Mild allergic reactions 0.01% to 0.07%
• Serious adverse effects rare

42. Nephrogenic Systemic
Fibrosis
• Fibrosing disorder seen only in renal failure patients
• Thickening and hardening of the skin overlying the
extremities and trunk
• Marked expansion and fibrosis of the dermis in
association with CD34-positive fibrocytes
• Excess exposure to free Gd3+ in patients with
kidney disease leads to tissue damage

43. • Skin
• symmetrical, bilateral fibrotic indurated papules, plaques,
or subcutaneous nodules
• ankles, lower legs, feet, and hands
• Systemic
• Muscle induration
• Lung fibrosis, diaphragm, myocardium, pericardium,
pleura and dura mater

44. • Chronic unremittant course
• Review - 28% no improvement, 20% modest, 28%
death
• Prevention - avoid Gadolinium

45. Assessment of Coronary
Artery Disease

46. Imaging of myocardial
infarction
• Late Gadolinium enhancement
• Currently the most precise and accurate noninvasive
method to quantify infarct size and morphology
• correlates with serum CK, time to treatment and ST
resolution
• In both acute and chronic infarcts sensitivity 99%
and specificity of 94%

47. • First 5 mins of LGE detects microvascular
obstruction (no reflow) as dense hypoenhanced
area within the core of a bright region of infarction
• Myocardial hemorrhage marker of reperfusion injury
• High sensitivity in detecting infarcted tissue - upto
few grams

49. • Significance of LGE
• Marker of unrecognised MI - independent and strong
predictor of cardiac death
• Diabetics without clinical/ECG evidence of MI, LGE
consistent with MI has 3.6 fold elevated hazard of
death

51. • Cheong and colleagues has
reported that LGE scar
transmurality index is a strong
independent predictor of death
or cardiac transplantation at a
median follow-up of 4.4 years;
this provides complementary
prognostic information to the
left ventricular (LV) ejection
fraction

52. • Tissue inhomogeneity in LGE tissues may identify
arrhythmogenic substrates
• Schmidt and colleagues have developed methods for
quantifying the heterogeneous peri-infarct zone
• Roes and coworkers have found that peri-infarct zone is
the strongest predictor of spontaneous ventricular
arrhythmias that required appropriate ICD therapy
• Future studies needed to establish standard to quantify
peri-infarct zone

53. Assessment of myocardial
viability
• Myocardial viability defined as preservation of
cellular function without any irreversible cellular
damage
• Augmentation of regional function in response to low
dose dobutamine (5-10 mcg/kg/min)
• Contractile reserve defined as increase in systolic
thickening by 2 mm (sensitivity 89%, specificity
94%) in predicting segmental viability

54. • Transmural extent of LGE scar predicts a
progressive stepwise decrease in the likelihood of
function recovery accurately, despite successful
coronary revascularization. (Kim and associates)
• Especially with resting akinesia/dyskinesia
• 88% of segments with less than 25% transmural
extent of LGE improved contractile function,
whereas only 4% of segments with more than
50% transmural extent of LGE

55. • LGE
• easy to perform and interpret
• 50% cutoff sensitive in predicting contractile segmental
recovery
• Low dose dobutamine
• physiologic assessment of the midmyocardial and sub-
epicardial contractile reserve, particularly in segments
with subendocardial infarction involving less than 50% of
the transmural extent.

56. • Wellnhofer and coworkers assessed 29 patients before
and 3 months after coronary revascularization with both
low-dose dobutamine cine imaging and LGE imaging,
and reported better prediction of segmental contractile
recovery by dobutamine cine imaging
• low-dose dobutamine cine CMR can be complementary
in assessing myocardial viability early after acute MI
when tissue edema is prominent or when there is a
need to assess the benefit of bypass surgery in
patients at high preoperative risk

57. • Detection and differentiation of ACS from non coronary
causes
• qualitative assessment of T2-weighted imaging and
LGE yielded a 96% specificity in differentiating acute
from chronic MI.
• Patients with acute chest pain presenting with ECG and
enzyme negative, adding T2-weighted imaging and LV
wall thickness to cine and LGE imaging increases the
specificity from 84% to 96% without any loss of
sensitivity

58. Detecting and Quantifying
Myocardial Ischemia
• Qualitative assessment of vasodilator stress CMR
myocardial perfusion is rapid and accurate in
detecting CAD
• Combined multicomponent CMR provides higher
accuracy than a single component alone
• MRA, LGE, and cine CMR reached an excellent
sensitivity of 96% while maintaining a high specificity
of 83% in detecting coronary stenosis(Plein et all)

59. • CMR stress perfusion versus radionuclide perfusion
imaging
• Not limited by attenuation artefacts
• No need for ionizing radiation
• Three- to fourfold higher spatial resolution than SPECT.
• Stress CMR - 30-45 mins, SPECT - 2 hours
• Can characterise dynamic blood flow, not limited by plateau
effect as in nuclear tracers

60. • MR-IMPACT
• CMR perfusion better than SPECT
• Especially patients with multi vessel stenoses
• Perfusion can be assessed by quantitative methods like signal
intensity versus time curves derived from LV myocardial
segments
• Absolute blood flow in ml/gm/min
• Quantitative methods minimised reader bias, also maps of
perfusion reserve can be used in testing novel therapies

63. Dobutamine Stress CMR
• Sensitivity 83-86%
• Specificity 83-86%
• Superior to dobutamine stress echocardiography
when echo windows poor
• Real time cine CMR imaging eliminates requirement
for breath holding or ECG gating during dobutamine
stress

64. • Strong prognostic value
• Ingkanisorn et all
• Adenosine stress CMR - sensitivity 100% and
specificity 93% for clinical events at 1 year
• Jahnke et al
• CMR with dobutamine stress cine and adenosine
perfusion normal - 99.2% negative 3 year event
rate for cardiac death/acute MI

67. Imaging of atherosclerotic plaques
• Carotid artery and Descending aorta
• Most comprehensive non invasive method to assess plaque
structure and activity
• Carotid bifurcation is relatively immobile, large, and superficial to the
skin surface, and it shows the full spectrum of atherosclerotic lesion
types.
• Contrast weighted sequences
• carotid plaque fibrous cap, hemorrhage, calcifications, and loose
matrix.
• Contrast enhanced dynamic MRI - plaque neovascularisation

68. • USPIO (Ultrasmall super-paramagnetic particles of iron oxide)
• target macrophage activity at high affinity based on histologic
and electron microscopic analyses of atherosclerotic plaques.
• 24 to 36 hours after USPIO injection carotid macrophage plaque
activity can be measured
• MRI of aortic plaques
• Difficult due to increased signal-noise ratio in achieving
submillimeter spatial resolution and blood flow artifacts.
• Intravascular MR coils recent advancement

69. • Coronary artery
• Plaque imaging difficult
• cardiac and respiratory motion and small vessel size
• Targeted contrast - fibrin-binding contrast agent EP-
2104R (EPIX Pharmaceuticals) - coronary thrombus
• Intravascular coils
• High field CMR

70. Cardiomyopathies

71. Hypertrophic
Cardiomyopathy
• CMR cine imaging of LV structure, function and tissue characterisation helpful
• Pathological and physiological LVH
• end-diastolic wall thickness–to–cavity volume ratio less than 0.15 mm/mL/m2
and lack of LGE of the ventricular myocardium can provide accurate
differentiation between physiologic and pathologic LVH
• Helpful in patients with poor echocardiographic windows
• Echo underestimates hypertrophy in basal anterolateral wall by 20%
• Extreme hypertrophy (>30 mm) by 10%
• Apical hypertrophy in apical HCM not detected by echo
• Where discrepancy between ECG and echocardiography

72. • Can assess septal thickness after surgical
myomectomy/Alcohol septal ablation
• especially severe septal hypertrophy and symptomatic
dynamic LV outflow obstruction
• markedly elevated LV mass index (men > 91 g/m2;
women > 69 g/ m2) sensitive (100%), maximal wall
thickness of more than 30 mm specific (91%) for
cardiac deaths
• RVH or myocardial edema by T2W imaging

74. Arrhythmogenic Right
Ventricular Cardiomyopathy
• Predisposition to ventricular arrhythmias that
precede overt morphologic abnormalities, histologic
substrate and by diverse phenotypic manifestation
• Quantitative and volumetric assessment of cardiac
function
• Characterization of myocardial fibrofatty tissue
• CMR had a sensitivity of 96% and a specificity of
78% in detecting ARVC

77. Myocarditis
• Myocardial edema by T2-weighted imaging, regional
hyperemia and capillary leak by early gadolinium
enhancement ratio (EGEr), and myocardial necrosis or
fibrosis by LGE imaging.
• In cases with high index of clinical suspicion but negative
CMR tissue findings, a repeat study in a few weeks may be
necessary for diagnosis because inflammation may be focal
and difficult to detect in the first few days of disease.
• Early evidence has indicated that a persistence of LGE 4
weeks after symptom onset is predictive of adverse
functional and clinical outcomes

79. Cardiac Sarcoidosis
• Detects disease through successive histological stages
• Tissue edema, non- caseating granulomatous infiltration, and patchy
myocardial fibrosis
• DE-MRI 2 fold increase in detection as compared to Japanese
Ministry of Health Criteria
• LGE positive patients 9 fold increase in death
• Can guide endomyocardial biopsy
• Can monitor disease progression accurately
• Limited to monitoring tool for progression

81. Cardiac amyloidosis
• DE-MRI shows diffuse LV hyper enhancement
• Subendocardium preferentially involved not limited
to arterial territory
• Difficult to detect mild amylodosis

83. Iron overload
cardiomyopathies
• Hemolytic anemias/iron overload pathologies
• T2 mapping to exclude cardiac siderosis
• T2 CMR enables amount of myocardial iron to be
estimated
• T2 value < 20 ms highly suggestive of cardiac siderosis
• T2 < 10 ms prone for heart failure
• Used to assess response to chelation therapy

84. Pericardial Disease
• Constrictive Pericarditis
• > 4 mm abnormal
• <2 mm normal
• TSE morphology and SSFP
• Realtime CineMRI
• increased ventricular interdependence, a
hemodynamic hallmark of pericardial constriction.

86. • Pericardial effusion
• Loculated and circumferential effusions
• Simple transudative effusions typically appear bright and
homogenous on T2-weighted images and dark on T1-weighted
images. On SSFP cineMRI, which exhibits T2/T1 weighing, simple
effusions appear bright with the same or even higher image
intensity than epicardial fat.
• Complex effusions may appear heterogeneous and darker on T2
and SSFP imaging. Additionally, unlike simple effusions, complex
effusions may demonstrate increased image intensity on T1-
weighted imaging after administration of gadolinium contrast
media

87. Hemodynamics
• VENC-MRI
• ASD
• en face imaging of ASD
• rim of tissue separating the ASD from the base of the aorta
(retroaortic rim), tricuspid valve, vena cavae, and coronary sinus
can be viewed from a single image plane
• Qp/Qs measurement
• additional information multiple ASDs, extent of rim tissue,
presence of sinus venosus defects with anomalous pulmonary
vein

89. • Aortic stenosis
• Planimetry by cineMRI correlates well with other
modalities
• Peak velocity also correlates with Doppler
echocardiography
• Correct plane along peak velocity

90. Cardiac masses
• Protocol sequence to assess morphology, motion, perfusion, and delayed
enhancement, in addition to inherent differences in T1 and T2 and abnormal
physiology
• benign masses - atrial myxoma, rhabdomyoma, fibroma, and endocardial
fibroelastoma
• Atrial myxoma
• left atrium (75%), right atrium (20%), or ventricles or mixed chambers
(5%)
• inhomogeneous brightness in the center on cine SSFP imaging because
of its gelatinous content
• may have a pedunculated attachment to the fossa ovalis.

91. • Metastatic malignancy 20 times more common than primary
malignancy
• direct invasion (lung and breast), lymphatic spread
(lymphomas and melanomas), and hematogenous spread
(renal cell carcinoma)
• Primary
• children/young adults
• angiosarcoma,fibrosarcoma, rhabdomyosarcoma, and
liposarcoma.

92. • LV thrombus
• LGE imaging can detect thrombus with a higher sensitivity than
echocardiography by depicting high contrast between the dark
thrombus and its adjacent structures and by imaging in three
dimensions.
• Mural thrombus does not enhance on first-pass perfusion and
often has a characteristic etched appearance (black border
surrounding a bright center) on LGE imaging, thus providing higher
diagnostic specificity than anatomic information alone
• Microvascular obstruction from MI can be confused with mural
thrombus, but it is usually confined within the infarcted
myocardium characterized by LGE.