This document discusses myocardial perfusion scintigraphy, which uses radiopharmaceuticals and gamma camera imaging to evaluate regional myocardial blood flow and detect any perfusion abnormalities. It describes the key aspects of the technique, including the mechanisms of radiotracer uptake, imaging modalities like SPECT, stress testing protocols, and factors that can influence image interpretation like soft tissue attenuation. Common radiotracers like Thallium-201, Technetium-99m sestamibi, and tetrofosmin are also covered in terms of their properties and localization within heart tissue.

2. Dr. Mustafa Sayed
Prof . Of Nuclear Medicine
Asyut University , Egypt.

3.  Myocardial perfusion scintigraphy descrip sequential
physiological events:
-First, the materials(radiopharmacuticals) must be
delivered to the myocardium.
-Second, a viable metabolically active myocardial cell
must be present to extract this material.
-Finally, a significant amount of the material must
remain within the cell to allow for imaging.
 The scintigraphic images are a map of regional
myocardial perfusion.
 If a patient has reduced regional perfusion as a result
of hemodynamically significant (CAD) or a loss of
cell viability as a result of myocardial infarction, a
perfusion defect or cold region is seen on the images.
 All diagnostic patterns in the many diverse
applications follow from these observations

4.  The radiopharmaceutical is a combination of
radioactive material used alone or mixed with
inert kits. These materials have selective
affinity to target cell components.
 These radiopharmaceuticals emit gamma rays
which are collected by special instrumentations
called gamma camera which has different
types.
 These types include multi view planar imaging
which was followed by single-photon emission
tomography (SPECT), gated SPECT,
SPECT/CT, then positron emission
tomography (PET),and PET/CT.

5.  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.

 First used for myocardial scintigraphy in the mid-
1970s, it was the only perfusion agent available
until the 1990s, when Tc-99m–labeled radiotracers
were introduced. Tl-201 is less commonly used today
because of its poorer image quality.
 At some imaging clinics it is used for the rest
study in dual-isotope studies or for viability
studies

6.  Mechanism of Localization and Pharmacokinetics:
After intravenous injection, Tl-201 blood clearance is
rapid. It is transported across the myocardial cell
membrane via the Na+/K+ ATPase pump. More
than 85% is extracted by the myocardial cell on
first pass through the coronary capillary
circulation . Peak myocardial uptake occurs by 10
minutes. Approximately 3% of the administered
dose localizes in the myocardium.
Extraction is proportional to relative regional
perfusion over a range of flow rates. At high flow
rates, extraction efficiency decreases; at low rates,
it increases.
It can only be extracted by viable myocardium, but
not in regions of infarction or scar.

7. Tc-99m is the radiotracer which emits gamma rays
and can be labelled with different materials.
= Technetium-99m MIBI: approved by the (FDA)
for clinical use in 1990. Generic Tc-99m sestamibi
became available late (chemical name: hexakis 2-
೦Methoxy Iso Butyl Isonitrile).
Mechanism of Localization and Uptake: Because it is lipid
soluble, Tc-99m mibi diffuses from the blood into
the myocardial cell. It is retained intracellular in
the mitochondria because of its negative
transmembrane potential. First-pass extraction
fraction is 60% . Extraction is proportional to
coronary blood flow.

8. = Technetium-99m Tetrofosmin:Tc-99m
tetrofosmin (Myoview) was approved by the
FDA in 1996. An advantage over Tc-99m mibi
is its more rapid liver clearance.
 Mechanism of Localization and Uptake: Similar to
mibi, Tc-99m tetrofosmin is a lipophilic cation
that localizes inside mitochondria in the
myocardial cell and remains fixed at that site.
First-pass extraction is slightly less than that of
mibi (50% vs. 60%). Extraction is proportional
to blood flow, but underestimated at high flow
rates. It is widely used nowadays.

9.  Single Photon Emission Computed
Tomography:
SPECT is the standard method for myocardial
perfusion scintigraphy. The cross-sectional
images have high contrast resolution and are
displayed three-dimension along the short and
long axis of the heart providing good
delineation of the various regional myocardial
perfusion beds supplied by their individual
coronary arteries.

10. The diagram shows a photon reaching the NaI crystal through the collimator and
undergoing photoelectric absorption. The photomultiplier tubes (PMTs) are
optically coupled to the NaI crystal. The electrical outputs from the respective
PMTs are further processed through positioning circuitry to calculate (x, y)
coordinates and through addition circuitry to calculate the deposited energy of the
pulse. The energy signal passes through the pulse height analyzer. If the event is
accepted, it is recorded spatially in the location determined by the (x,y) positioning
pulses to form the image.

12. Cardiac SPECT software: reconstructs cross-sectional
cardiac images along the short and
long axes of the heart , that is, transaxial (short
axis), coronal (horizontal long axis), and
sagittal (vertical long axis) .
The SPECT cross-sectional images descrip the
regional perfusion of the myocardium as it
relates to the coronary artery supplying blood
to that region and permits visual estimation of
the degree and extent of the perfusion
abnormality

14.  Cardiac stress testing with ECG monitoring has
long been used to diagnose ischemic coronary
artery diseases.
 Cardiac stress can be physical by graded
treadmill or pharmacological with specific
drugs.
 The SPECT imaging provides valuable
information on the extent and severity of
coronary artery disease which is useful for risk
assessment, prognosis, and patient
management.

15.  The patients must be fasting for 4 to 6 hours before the
test to prevent stress-induced gastric distress and
minimize splanchnic blood distribution.
 Cardiac medications may be held depending on the
indication for the stress test—that is, whether for
diagnosis or to determine the effectiveness of therapy
and type of stress.
Beta blockers may prevent achievement of maximum
heart rate.
Nitrates and calcium channel blockers may mask or
prevent cardiac ischemia,so limiting the test’s
diagnostic value.
Assessment of drug therapy effectiveness requires the
patient to remain on medication.
Thyophylline and caffeine also held before
pharmacological test.

16. Withdrawal Drugs interval
48 hours
24 hours (also with pharma.)
24 hours (also with pharma.)
24 hours
24 hours
In EXERCIS
beta blockers
Calcium channel blockers
Nitrates
In PHARMACOLOGICAL
Thyophylline derivatives
Caffeine

17.  In addition to a standard 12-lead baseline ECG, an intravenous line is
kept open. The patient is continuously monitored during the study.
 Graded treadmill exercise is performed according to a standardized
Bruce protocol.
 When the patient has achieved maximal exercise or peak patient
tolerance the radio-pharmaceutical is injected.
 The adequacy of exercise is judged by the degree of cardiac work.
Patients achieving more than 85% of the age-predicted maximum
heart rate (220 − age = maximum predicted heart rate) are considered
to have achieved adequate exercise, stress metabolic equivalents
(METS) also can be used to judge the adequacy of exercise. Failure to
achieve adequate exercise is the most common reason for a false negative
stress test result.
 Exercise is continued for another 1 minute after injection of
radiotracer to ensure adequate uptake.
 Early discontinuation of exercise may result in tracer distribution
reflecting perfusion at sub maximal exercise levels.

18. 1- Coronary Vasodilating Drugs: Dipyridamole,
Adenosine, and Regadenoson.
 Dipyridamole (Persantine) and adenosine
(Adenoscan) are coronary vasodilating drugs that have
long been used for stress myocardial perfusion
imaging. Regadenoson (Lexiscan) was approved by the
FDA in 2009 but dipyridamole is the widely used .
 The vasodilators increase coronary blood flow in
normal vessels 3 to 5 times. Because coronary arteries
with significant stenoses cannot increase blood flow to
the same degree as normal vessels, vasodilator stress
results in vascular regions of relative hypoperfusion on
myocardial perfusion scintigraphy similar to that seen
with exercise-induced ischemia.

19.  Dipyridamole injection protocol:
- Dose 0.56 mg / Kg diluted in 50 ml normal saline
and given as infusion for 4 minutes.
- The radiopharmaceutical should be injected after
2-4 minutes after completion of infusion.
- It is contraindicated in bronchial asthma and
preferred in LBBB cases.
- Heart rate, blood pressure and ECG should be
measured and recorded at baseline and every 2
minutes during the infusion until stress-induced
haemodynamic changes are improving and the
patient regains baseline status.

20.  2- Inotropic Drugs: Dobutamine is a synthetic
catecholamine that acts on alpha- and beta-adrenergic
receptors producing inotropic and chronotropic effects
that increase cardiac work.
 In normal coronary arteries, increased blood flow is the
result. In the face of significant stenosis, regional flow
does not increase, producing scintigraphic patterns
similar to that seen with ischemia .
 Dobutamine injection protocol: Initial infusion rate is 5
μg/kg/min over 3 minutes, then increased to 10
μg/kg/min for another 3 minutes and further
increased by that amount every 10 minutes until a
maximum of 40 μg/kg/min is achieved.
The radiopharmaceutical is injected after the maximal
tolerable dose reaching the target heart rate and the
dobutamine infusion is continue for 1 minute.

21. Stress Rest
Radiopharmaceutical 25 m Ci 25 m Ci
dose
Supine or prone
45-60 min.
Supine or prone
20 – 30 min with
exercise
45-60 min with drugs
Patient position
Injection - Imaging
Time

26. After initial assessment of the presence or absence
of perfusion defects, a complete evaluation of
the stress study includes assessment of the
location, size, severity, and likely vascular
distribution of the visualized abnormalities.
A true perfusion defect should be seen on more
than one cross-sectional slice and in other
cross-section planes. Certainty increases with
lesion size and the degree or severity of photon
deficiency.

28. 1
0
4
2
4
4
1
2
2
3
4
4
100%
70
50
30
10
0
4 normal 100 - 70%
3 mild 70 - 50%
2 moderate 50 - 30%
1 severe 30 - 10%
0 absent 10 - 0%

31. Perfusion defects in more than one coronary
artery distribution area indicate multiple vessel
disease. Prognosis worsens with increasing
number and size of perfusion defects .
Not all significant coronary artery stenoses are
always seen on stress perfusion scans.
N.B. Stress-induced ischemia of the most severe
stenotic lesion limits further exercise, and thus
other stenoses may not be seen and multiple
vessel disease may be underestimated.

33. The normal cardiac response is to dilate mildly
during stress and return to normal size
promptly with cessation of exercise.
Post stress significant ventricular dilation is
abnormal and suggests multi vessel disease.
One explanation for this finding is myocardial
stunning during stress ,another is widespread
subendocardial ischemia.

35. The effects of soft tissue attenuation can be seen
on most cardiac images and are worse with
large patients. Males typically have decreased
activity in the inferior wall .
This is called diaphragmatic attenuation, meaning
attenuation by subdiaphragmatic organs
interpositioned between the heart and gamma
camera.
The amount of attenuation effect is dependent
on patient size, shape, and internal anatomy.

37. Women often have relatively decreased activity in
the anterior wall, apex, or anterior lateral
portion of the heart, secondary to breast
attenuation, depending on the size and
position of the breasts.
Women also may have sub diaphragmatic
attenuation, but breast attenuation is dominant
and most commonly noted.
The cinematic rotating raw data should be
reviewed for the presence of attenuation and
motion. If the breasts are in different positions
for the two studies, this could be
misinterpreted as ischemia

40. Exercise-induced reversible hypo perfusion of the septum
can be seen in patients with left bundle branch block
(LBBB) in the absence of coronary disease.
Typically, the apex and anterior wall are not involved, as
would be expected with left anterior descending (LAD)
coronary artery disease.
The stress-induced decreased septal blood flow is thought to
be caused by asynchronous relaxation of the septum,
which is out of phase with diastolic filling of the
remainder of the ventricle when coronary perfusion is
maximal.
This scan abnormality is less seen with pharmacological
stress, and thus the latter is indicated in patients with
LBBB or ventricular pacemakers.

42.  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 and systolic
thickening of the left ventricular walls .
 Left ventricular end-diastolic volume, end-systolic
volume, stroke volume and ejection fraction may
be calculated automatically, although the values
obtained should be checked against initial
qualitative assessment

46.  Decreased sensitivity and specificity in single vessel
CAD ( 60 – 76% )
 Diffuse disease in all three vessels (Balanced
ischemia)
 Diffuse disease without segmental stenosis
(Vulnerable for plaque rupture and coronary events)
 Early disease identification
 Artifacts – Non uniform attenuation
 Relative low efficiency of Gamma camera
 Longer acquisition protocols

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