cardiac scanning in nuclear medicine lecture in master on clinical oncology in Alexandria university

2. NUCLEAR CARDIAC
SCANNING
BY /DR.MAHRAN MOHAMMED

3. 2. Ventricular Function
1. Myocardial Perfusion
3. Cardiac Metabolism and Myocardial Viability
4. Myocardial Innervation
Nuclear medicine methods in Cardiology are available
for the evaluation of :
5. Infarct Imaging

4. 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.

5. 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.

6. MYOCARDIAL PERFUSION SCINTIGRAPHY
The main indication is
the detection and localization
of myocardial ischaemia or scar.

7. MYOCARDIAL PERFUSION IMAGING
Clinical Indications
•Diagnosis of coronary artery disease
- presence
- location (coronary territory)
-extent (number of vascular territories
involved)
•Determine prognosis
•Determination of the significancof anatomic lesions
detected by angiography.
•Monitoring treatment effect after coronary
revascularization.

8. 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.

9. 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).

10. 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.

11. MYOCARDIAL PERFUSION SCINTIGRAPHY
RADIOPHARMACEUTICALS
99mTc-Labeled Myocardial Perfusion Agents
•99mTc-SESTAMIBI (MIBI,
2-methoxy-isobutyl-isonitril,
Cardiolite, CardioSPECT…)
• 99mTc-Tetrofosmin (Myoview)
• 99mTc-Teboroxim (cardioTec)
201Thallium

12. MYOCARDIAL PERFUSION SCINTIGRAPHY
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
Tc-99m-Labeled Myocardial Perfusion Agents
99mTc - gamma rays of energy 140 keV
- half life T1/2 = 6 hours

13. MYOCARDIAL PERFUSION SCINTIGRAPHY
201Thallium
- is an analog of potassium
- it is actively transported into cardiac muscle
via the sodium-potassium ATPase pump
- physical half-life is 73 h
- is a cyclotron-produced radiopharmaceutical
- emits x-rays of energy 69- to 83 keV
- also emits gamma rays 167 kev 10%

14. Imaging protocol
• Single day protocol
the patient receive a lower dose of radiopharmaceuticals
for the initial study (8-10 mCi ) and several fold higher
dose (25-30 mCi )for the second study , which
commences approximately 1.5 hour later to allow time
for background activity ,biological clearance and decay.
• Tow day protocol
The patient receive maximum dose (25-30mCi)for both
studies on separate days.
Most commonly used on obese patients .

15. 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

17. 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 pharmacologically .

18. Pharmacologic Stress
* vasodilators : adenosine
dipyridamole
* inotropic : dobutamine

19. 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: bronchial Asthma .

20. Pharmacologic Stress produced by dobutamine
* similar to exercise
* indirectly tests flow reserve
* increases myocardial oxygen consumption
1) chronotropic effects
2) ionotropic effects

21. 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

23. Initial Display
of selected study-
Reconstruction
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 image-
added multiple projec-
tion images

24. 99m Tc-
MIBI
slices in the short axis
slices in the long axis vertical
slices in the long axis horisontal

26. 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.

27. 99m-Tc-
MIBI

28. Polar maps
Short axis slices
are sequentially
diplayed from
base to apex.
Conical myocardium
is transformed into
a disk.

31. 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.

32. NORMAL FINDING
57 yo MALE

33. REVERSIBILE DEFECT

34. NONREVERSIBILE DEFECT

35. 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

36. 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

37. 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

38. REQUIREMENTS FOR CELLULAR VIABILITY
-adequate myocardial blood flow
-sarcolemmal metabolic integrity
-preserved metabolic activity

39. MYOCARDIAL VIABILITY
The gold standard method
evaluation of myocardial glucose utilisation with
fluorine-18 fluorodeoxyglucose (FDG)
and positron emission tomography (PET)

40. 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.

41. VIABLE MYOCARDIUM
is characteristic in
NONREVERSIBILE PERFUSION DEFECT
( 99m-Tc MIBI)
vs.
PRESERVED MYOCARDIAL METABOLISM
(18-FDG)
= mismatch

42. 99mTc MIBI
18FDG
non viable
match
viable
mismatch
- we can expect improvement in function
following revascularization

43. SCAR
is characteristic in
NONREVERSIBILE PERFUSION DEFECT
( 99m-Tc MIBI)
vs.
NO PRESERVED MYOCARDIAL METABOLISM
(18-FDG )
= match

44. 99mTc MIBI
18FDG
nonviable
match
viable
mismatch
- we can t expect improvement in function
following revascularization