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How We Do CMR Perfusion
Robert Manka, Rolf Gebker, Eike Nagel
German Heart Institute Berlin
and
www.cmr-academy.com
Created October 2007 for SCMR
This presentation posted for members of scmr as an educational guide – it represents the views and
practices of the author, and not necessarily those of SCMR.
Perfusion
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The occurrence of myocardial perfusion deficits
is a very sensitive indicator of ischemia in the
presence of significant coronary artery stenoses.
Most perfusion defects occur during stress, such
as pharmacological vasodilation.
Adenosine is a safe and well tolerated
pharmacological stress agent.
In-plane resolution of 2-3 mm allows separate
visualization of the endo- and epicardial layers
of the left ventricle.
How we do Perfusion
Pharmacological Agent
Stressor agent:
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1.
Adenosine: i.v. 140 mcg/kg/min
(preferable
concentration 5mg/ml)
- A potent vasodilator of most vascular beds, except for hepatic and
renal arterioles. It exerts its pharmacological effect through the
activation of purine A1 and A2 cell-surface adenosine receptors
- Half-life 4-10 seconds
Antidote:
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1.
2.
Adenosine infusion should be discontinued
Aminophylline i.v (250mg slowly injected under ECG monitoring)
Patient instruction:
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1.
2.
No caffeine (tea, coffee, chocolate)
No aminophyline or nitrates for 24 hours
How we do Perfusion
Adenosine- Side-Effects
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Mild-to-moderate reduction in systolic, diastolic and mean
arterial blood pressure (< 10 mmHg) with a reflex increase in
heart rate.
Some patients complain about chest pain, which is rather
nonspecific and does not reliably indicate the presence of CAD.
Direct depressant effect on the SA and AV nodes transient first-,
second- and third-degree AV block and sinus bradycardia have
been reported in 2.8%, 4.1% and 0.8% of patients.
Increases in minute ventilation, reduction in arterial PCO2 and
respiratory alkalosis.
Approximately 14% of patients complain of dyspnea.
How we do Perfusion
Contraindications/Termination
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Contraindication for Adenosine
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Myocardial infarction <3 Days
Unstable angina pectoris
Asthma or severe obstruktive
pulmonary disease
AV-block >IIa
Claustrophobia
Non compatible biometallic
implants (pacemaker/AICD)
Caution
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Stenotic valvular disease
Autonomic dysfunction
Cerebrovascular insufficiency
How we do Perfusion
Termination criteria
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Persistent or symptomatik AVblock
Significant drop in systolic
pressure (>20 mmHg)
Persistent or symptomatic
hypotension
Severe respiratory difficulty
Scanner environment
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The pts lies in the supine position
1.5 or 3 Tesla (T) whole body scanner
Gradient strength 30 mT/m,
slew rate 150 mT/m/ms
5 element cardiac synergy coil
Multichannel ECG (Vector-ECG)
How we do Perfusion
Contrast Agents and Injection
Scheme
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Bolus with a dosage of 0.05 mmol/kg bw of an
extracellular Gd-based CA (dose may be lower with
Gd-DTPA-BMA)
Injection speed of 4 ml/s is used at the German Heart
Institute Berlin
The bolus is followed by a 20 ml saline flush using the
same injection rate to facilitate a compact bolus passage
We recommend the use of an automatic infusion
system
Two 18 gauge venflons for separate administration of
the stress agent and CA
How we do Perfusion
Imaging Procedure
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Cine wall motion imaging of the heart at rest, perfusion imaging
under vasodilator stress, and finally delayed enhancement
imaging
Examination time may vary between 40-75 minutes
Breathhold should be performed during expiration to ensure
reproducible slice geometry
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First is a about 6 to 10 seconds during baseline acquisition of myocardial
signal intensity.
Then the patient is asked to inhale and exhale once more and to hold his
breath as long as possible. Right before starting this breathhold command
the contrast bolus is administered.
The patient should stop breathing at least for 15 to 20 seconds resulting
in a fixed slice geometry during the first-pass of the contrast agent
How we do Perfusion
Survey
Perfusion
Flowchart
(1) Transversal
(2) Single-angulated view
(3) Double-angulated view
Resting wall motion
(4) Short axis (apical, mid, basal slice)
(5) 4 chamber/3 chamber
(6) 2 chamber
Adenosine infusion (140 µg/kg/min)
over 4 minutes
Inject gadolinium
0.05 mmol/kg
Stress Perfusion
(8) Start imaging (60 dynamics) after
4 minutes of adenosine infusion
Stop adenosine infusion
wait 10 min
(9)
Rest Perfusion
Repeat (8) without adenosine
infusion
wait 10 min
(10)
Delayed Enhancement
Determine optimal inversion time
How we do Perfusion
Inject gadolinium
0.05 mmol/kg
Inject gadolinium
0.1 mmol/kg
RR, rhythm & respiratory monitoring
Carefully exclude any wraparound
If necessary enlarge field of view
Perfusion test scan
(7) Slice geometry identical to (4)
acquisition of 5 dynamic images
Scanning procedure
start scan
contrast injection
1st
breathhold
1 breathing
cycle
2nd breathhold
free breathing
scanning interval
Baseline 5 dyn,
start contrast
injection
RV contrast
uptake: 2nd breath
hold command
LV contrast uptake
How we do Perfusion
First pass
myocardial
contrast uptake
Second pass
myocardial
contrast uptake
Pulse Sequences
1.
2.
3.
T1-weighted
In-plane resolution of 2-3 mm to separately
visualize the endo- and epicardial layers.
We use a balanced SSFP-technique which
shows a higher peak enhancement and
superior image quality compared with other
sequences (T1-GrE, GrE-EPI).
How we do Perfusion
Monitoring requirements
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Heart rate & rhythm: continuously
Blood pressure: every minute
Pulse oximetry: not required when the vectorECG used
Symptoms: continuously
Defibrillator
All medications for emergency treatment
How we do Perfusion
Analysis of MR Perfusion Studies
cover 16 out of 17 myocardial segments
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Visual Analysis
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For routine clinical use, we do a qualitative analysis
by visual comparison of the contrast enhancement
in different myocardial regions (see next slide)
Quantitative
Absolute Tissue Perfusion (Unit:
(requires mathematical modeling)
 Semiquantification
(stress induced change of upslope)
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How we do Perfusion
ml/g/min)
Visual assessment of regional
myocardial perfusion
Evaluate the equatorial slice first, then check whether the suspected perfusion defect
can be followed in corresponding segments of the apical or basal slice
Abnormalities:
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Signal intensity Pattern and Location
Dark regions arising from the subendocardium with usually irregular intramyocardial
border or with completely transmural extent.
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Dynamic myocardial filling pattern
Initially, slow or missing enhancement persistent over a few dynamics with
consecutive signal intensity increase starting from the defects epicardial border.
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Comparison Stress vs. Rest
If a regional defect is found in the stress scan, but not in the rest scan, inducible
ischemia is confirmed. Regional persistence of the perfusion deficit shows
myocardial scar.
How we do Perfusion
Report
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Data is reported for 16/17 segments (segment 1 – 16). The
apical segment (17) is not visualized with 3 short axis views.
Perfusion defects are reported with their transmurality
(transmural defect vs. subendocardial defect).
Perfusion images are compared to cine and late enhancement
images
How we do Perfusion
Stress-Perfusion
Baseline
RV contrast
uptake
Early mycardial
contrast uptake
How we do Perfusion
Late myocardial
contrast uptake
Baseline
RV contrast
uptake
StressPerfusion
RestPerfusion
Viability and
coronary
angiography
How we do Perfusion
LV contrast
uptake
Myocardial
contrast uptake