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Case of the Month
Jenny Delfin MD and
Ola Akinboboye MD MPH MBA FACC.
Case Presentation

The patient is a 51 year old male with a history of
hypertension, DM (II), and hyperlipidemia who
presented to our institution with the chief
complaint of non-exertional chest pain.

A 2 day stress-rest Tc-99m-sestamibi perfusion
study was performed because of his size.

Exercise stress testing was performed on a
treadmill using the Bruce protocol.
Case Presentation

Approximately 40 mCi of Tc-99m sestamibi
was injected at rest and during stress.

Gated perfusion imaging was performed
with attenuation correction using vantage
software.
Case Presentation
The patient was able to perform 7 minutes of
Bruce protocol. Exercise was interrupted
because of breathlessness, generalized and
leg fatigue. The patient had no chest
discomfort during exercise and recovery.
Case Presentation

The maximum heart rate and blood pressure
during exercise were 171 bpm (101% of the
predicted maximum heart rate for age) and
194/70 mmHg respectively.

The maximum workload attained was 9
METS. Cardiac exam was normal before
and after exercise.
Case Presentation

The resting electrocardiogram revealed ST-T
abnormalities. There was no electrocardiographic
evidence of ischemia during exercise.

The SPECT myocardial perfusion scan raw data
showed good image quality with a normal sized left
ventricle.

Gated analysis did not reveal any significant wall
motion abnormality.
Perfusion Scans

There was no significant perfusion abnormality on
the uncorrected perfusion scans (fig 1).
 The corrected scans showed a medium-size
reversible basal-anterior perfusion abnormality
with moderate reduction in counts (fig 2).
 However, the quality control indices (fig 3) for the
stress and rest studies showed critically low counts
and the presence of truncation that was deemed to
be non-critical.
Fig 1
Fig 2
Case Presentation

Because the patient has multiple risk factors
including diabetes and an equivocal
perfusion study, the referring physician
elected to perform coronary angiography,
which did not reveal any evidence of
luminal coronary artery disease.
Teaching Point

The role of single photon emission computed
tomography (SPECT) myocardial perfusion
imaging in diagnosing and risk stratifying patients
with known or suspected coronary artery disease
(CAD) has been well established over the years.
The sensitivity and specificity of SPECT MPI in
detecting angiographically significant CAD are
88% (range 73-98%) and 77% (range 53-96%),
respectively.[1]
Teaching Point

One of the major limitations of SPECT MPI is
attenuation artifact. More recently, commercialized
SPECT attenuation correction systems have been
used to overcome this major limitation [2]
.
 External collimated radionuclide sources or x-ray
CT with hybrid systems are utilized in SPECT
attenuation correction systems to measure the nonhomogeneous attenuation distribution. The
attenuation map produced using these
commercialized attenuation correction systems is
essential for accurate attenuation correction.
Teaching Point

Quality control indices used for SPECT
attenuation correction include count statistics,
presence or absence of truncation, and presence or
absence of banding. High quality attenuation
maps should have high count density, minimal or
no truncation, and minimal or no banding. Only
studies with high quality attenuation maps should
be used in assessing for attenuation artifact. [3]
.
 Manufacturers of SPECT attenuation correction
programs recommend that quality control indices
be checked for every patient.
Teaching Point

Despite this recommendation, many physicians who
interpret attenuation corrected images often forego
this very important step, thus leading to incorrect
interpretation of these images.

The presence of truncation, though non-critical and
low count statistics on the transmission scan
probably caused the false-positive perfusion
abnormality on the attenuation corrected scans.
Teaching point

It is incumbent upon the physician reading
attenuation corrected perfusion scans to
confirm that quality control indices are of
high quality prior to interpretation of the
images.
References

[1] Lee TH, Boucher CA. Noninvasive tests in
patients with stable coronary artery disease.
NEJM 2001; 344: 1840-45.
 [2] Bateman TM, Cullom SJ. Attenuation
correction single-photon emission computed
tomography myocardial perfusion imaging.
Semin Nucl med 2005; 35:37-51.
 3)Attenuation correction of myocardial perfusion
SPECT scintigraphy: A joint position statement by
the American society of nuclear cardiology and
the society of nuclear medicine. June 2003.