Download Bez nadpisu - Univerzita Karlova v Praze

NUCLEAR CARDIAC
IMAGING
K.Michalová
Klinika nukleární medicíny a endokrinologie UK 2. LF a FN Motol
Nuclear medicine methods in Cardiology
are available for the evaluation of
1. Myocardial Perfusion
2. Ventricular Function
3. Cardiac Metabolism and Myocardial Viability
4. Myocardial Innervation
5. Infarct Imaging
Kupka K .a kol: Nukleární medicína, 2007
MYOCARDIAL PERFUSION SCINTIGRAPHY
This test is designed to evaluate regional
myocardial perfusion under rest and stress
condition
in order to define regional myocardial
perfusion reserve.
MYOCARDIAL PERFUSION SCINTIGRAPHY
It involves the injecton of a radiolabelled
substance which is extracted by the myocardium
and accumulates in proportion to myocardial
blood flow.
Such radipharmaceuticals are injected under
stress as well as resting conditions, and images
are obtained to define the regional distribution
of radioactivity within the myocardium.
MYOCARDIAL PERFUSION SCINTIGRAPHY
The main indication is
the detection and localization
of myocardial ischaemia or scar.
MYOCARDIAL PERFUSION SCINTIGRAPHY
Myocardial ischaemia is defined as a
perfusion defect present during stress
but not resting conditions.
Scar tissue is associated with a relative
perfusion defect at rest as well as
under stress.
MYOCARDIAL PERFUSION SCINTIGRAPHY
RADIOPHARMACEUTICALS
201Thallium
99mTc-Labeled
Myocardial Perfusion Agents
99mTc-SESTAMIBI
(MIBI,
2-methoxy-isobutyl-isonitril,
Cardiolite, CardioSPECT…)
99mTc-Tetrofosmin (Myoview)
99mTc-Teboroxim
MYOCARDIAL PERFUSION SCINTIGRAPHY
201Thallium
- is an analog of potassium
- it is actively transported
into cardiac muscle
via the sodium-potassium ATPase pump
MYOCARDIAL PERFUSION SCINTIGRAPHY
201Thallium
- is a cyclotron-produced radiopharmaceutical
- emits x-rays of energy 69- to 83 keV
- physical half-life is 74 h
MYOCARDIAL PERFUSION SCINTIGRAPHY
99mTc-SESTAMIBI
x
201THALLIUM
ADVANTAGES :
- increased myocardial count density
- lower radiation doses
- no wash out of myocardium
MYOCARDIAL PERFUSION SCINTIGRAPHY
Tc-99m-Labeled Myocardial Perfusion Agents
99mTc-SESTAMIBI
= is a lipophilic cationic Tc-99m complex
- it enteres pasivelly into the cells
- and binds at the intracells membranes,
especially of mitochondrials
- it does not wash out of the myocardium in 3-4 hours
MYOCARDIAL PERFUSION SCINTIGRAPHY
99mTc-SESTAMIBI
99mTc
- gamma rays of energy 140 keV
- half life T1/2 = 6 hours
Two-Day Patient Protocol
Dose
Position
Exercise
Rest
700 MBq
700 MBq
Supine or prone
Supine or prone
Delay Time (Intervals)
Injection - Imaging
15 min
60-90 min
Exercise Stress
* is performed by cardiologist
* graded stress is usually performed
with bicycle ergometr
* it is necessary to reach the gender and
age predicted 85% maximal heart rate
* suboptimal stress level reduce sensitivity
of this procedure for detection of CAD
* the radiopharmaceutical is injected 1-2 minut
before end of exercise
Pharmacologic Stress
Patients who are unable to exercise
for non cardiac reasons - e.g.arthritis, amputation,
neurologic diseases
or cardiac reasons - with LBBB
may be stress farmacologically
Pharmacologic Stress
* vasodilators : adenosine
dipyridamole
* inotropic : dobutamine
Pharmacologic Stress using dipyridamole
* mechanism of action different from exercise
* directly tests flow reserve
* dipyridamol causes vasodilatation
* normal vessel vasodilate, increasing flow five times
* stenotic vessels are already maximally vasodilatated,
cannot increase flow
* results in heterogenity on scan
* does not depend on induction of ischemia
* Heart rate increases 13 beats per minute (20%)
* Blood pressure decreases 6 mm Hg (2 ti 8%)
* Contraindication: Asthma bronchiale
Pharmacologic Stress produced by dobutamine
* similar to exercise
* indirectly tests flow reserve
* increases myocardial oxygen consumption
1) chronotropic effects
2) ionotropic effects
Acquisition SPECT study
Dual head gamma camera moves around the patient
viewing the object in 180 degrees in 64 steps for 25 seconds
45 deg.
RAO
135 deg.
LPO
GATED SPECT study
• ECG is acquired at the time of the SPECT
acquisition
• for simultaneous assessment of perfusion and
function of the left ventricle in one examination
evaluation of regional wall motion
ejection fraction
systolic thickening of the walls
GATED SPECT study
We obtain myocardial perfusion images within
one representative cardiac cycle :
from end-diastole through end-systole to end-diastole
of next cardiac cycle
Kamínek M. et al. : Atlas of Nuclear Cardiology, 2003
Initial Display
of selected studyReconstruction
With ellipse we select
region of the heart
in anterior view
in left lateral view.
The selected data sets
are processed.
We must alignment
axes of heart
for creation of the
vertical
long and short axis
tomograms
Summed imageadded multiple projection images
slices in the short axis
slices in the long axis vertical
slices in the long axis horisontal
99m TcMIBI
MYOCARDIAL ISCHEMIA
Can be identified by comparing
the results of exercise-injected studies and rest
images .
As narrowing of coronary vessel approaches 70%
lesion is hemodynamically significant during
exercise.
99m-TcMIBI
Polar maps
Short axis slices
are sequentially
diplayed from
base to apex.
Conical myocardium
is transformed into
a disk.
MYOCARDIAL PERFUSION IMAGING
INTERPRETATION CRITERIA
1. NORMAL FINDINGS
2. REVERSIBILE DEFECT - lesion is seen at stress
and improves on the rest - is usually due to ischemia
3. NONREVERSIBILE DEFECT - lesion at rest is
usually associated with myocardial scar or with
severe ischemia.
NORMAL FINDING
57 yo MALE
REVERSIBILE DEFECT
NONREVERSIBILE DEFECT
MYOCARDIAL PERFUSION IMAGING
Clinical Indications
Diagnosis of coronary artery disease
- presence
- location (coronary territory)
-extent (number of vascular territories
involved)
Determine prognosis
Society of Nuclear Medicine Procedure Guideline for Myocardial Perfusion Imaging
MYOCARDIAL PERFUSION IMAGING
Clinical Indications
Determination of the significance
of anatomic lesions detected by angiography
MYOCARDIAL PERFUSION IMAGING
Clinical Indications
Monitoring treatment effect
after coronary revascularization
MYOCARDIAL PERFUSION IMAGING
Determine prognosis
risk stratification
*Patients with normal perfusion imaging after adequate
stress have a very low cardiac event rate independently
of the presence or absence of angiographic CAD (yearly
rate of myocardial infarction or death of less than 1%).
*A benign prognosis is asociated with a small fixed defect
and a normal global left ventricle function.
57 yo MALE
MYOCARDIAL PERFUSION IMAGING
Determine prognosis
risk stratification
* The risk of cardiac event can be suspected in all patients
with the reversible perfusion defect.
* A higher risk can be expected in patients
with a large perfusion defect,
when more territories are affected,
if the anterior wall is affected
or if signs of postress dysfunction appear (transient
ischemic dilation, deterioration of postress EF, increased
uptake 201Tl in the lungs).
MYOCARDIAL VIABILITY
detection of myocardial viability has clinical importance for
- patients with chronic ischaemic left
ventricular dysfunction
and low left ventricle ejection fraction
it is necessary to know, if defect of myocardial perfusion is
- ischemia vs. scar
- predict improvement in function
following revascularization
REQUIREMENTS FOR CELLULAR VIABILITY
-adequate myocardial blood flow
-sarcolemmal metabolic integrity
-preserved metabolic activity
MYOCARDIAL VIABILITY
The gold standard method
evaluation of myocardial glucose utilisation with
fluorine-18 fluorodeoxyglucose (FDG)
and positron emission tomography (PET)
MYOCARDIAL VIABILITY
Principle
Under fasting conditions the normal
myocardium primarily utilises free fatty acids.
In ischaemic myocardium glucose becomes
an important energy substrate, FDG uptake will
be enhanced.
VIABLE MYOCARDIUM
is characteristic in
NONREVERSIBILE PERFUSION DEFECT
( 99m-Tc MIBI)
vs.
PRESERVED MYOCARDIAL METABOLISM
(18-FDG)
= mismatch
99mTc
MIBI
18FDG
non viable
viable
match
mismatch
- we can expect improvement in function
following revascularization
99m-TcMIBI
SCAR
is characteristic in
NONREVERSIBILE PERFUSION DEFECT
( 99m-Tc MIBI)
vs.
NO PRESERVED MYOCARDIAL METABOLISM
(18-FDG )
= match
99mTc
MIBI
18FDG
nonviable
viable
match
mismatch
- we can´t expect improvement in function
following revascularization