CAD – leading cause of death
Cardiac SPECT – steady growth in last two decades & played an important role in clinical mangement
Radionuclide ventriculography (MUGA)
First pass studies
PET/CT
2. Radionuclide studies in
cardiology
CAD – leading cause of death
Cardiac SPECT – steady growth in last two
decades & played an important role in clinical
mangement
Radionuclide ventriculography (MUGA)
First pass studies
PET/CT
3. Detection of Ischemia
Noninvasive Testing: Critical Concepts
• Differences between testing options
• Diagnostic accuracy and pretest likelihood
of disease
• Posttest risk assessment
9. Indications for Stress Testing
Objective confirmation of ischaemia
Assessing extent of ischaemia
Documenting exercise capacity
Functional assessment of known CAD
Determining risk and prognosis
Determining need for angiography
High risk cut points
Assessing response to treatment
10. Contraindications for stress
testing
Acute myocardial infarction (within two days)
Unstable angina pectoris
Uncontrolled arrhythmias causing symptoms of
hemodynamic compromise
Symptomatic severe aortic stenosis
Uncontrolled symptomatic heart failure
Active endocarditis or acute myocarditis or
pericarditis
Acute aortic dissection
Acute pulmonary or systemic embolism
Acute noncardiac disorders that may affect exercise
performance or may be aggravated by exercise
12. Sensitivity and Specificity of Non-
invasive Tests for the Diagnosis of
CAD*
Diagnostic
Test
Sensitivity
% (range)
Specificity
% (range)
# Studies # Patients
TMT 68 77 132 24,027
Planar MPI 79
(70-94)
73
(43-97)
6 510
SPECT 88
(73-98)
77
(53-96)
8 628
Stress echo 76
(40-100)
88
(80-95)
10 1174
* NEJM Vol. 344, No. 24 June 14, 2001
13. Exercise stress testing
Treadmill or bicycle
ergometer
Protocols vary -
symptom limited
Bruce most popular
8 stages
Incline and speed
increment every 3
minutes
Target 85-100%
maximum age
predicted HR
Achieve at least 6 METS
for diagnostic accuracy
14. ECG Patterns Indicative of Myocardial Ischaemia
ECG Patterns Not Indicative of Myocardial Ischaemia
15. Indications for Myocardial
Perfusion Imaging (Exercise or
Pharmacologic Stress) Suspected false +ve
or-ve TMT
Resting ST changes
LBBB,RBBB,LVH,
digitalis,pre-excitation
or pacemaker
Women with +ve TMT
and low or
intermediate
probability CAD
Inability to exercise
Prognosis of known CAD
Detecting post PTCA or
CABG ischaemia
Assessing myocardial
viability
Risk evaluation in non-
cardiac surgery patients
Assessment functional
significance of
documented coronary
stenosis
39. Limitations of cardiac SPECT
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
40. Characteristics of SPECT vs. PET.
SPECT PET
Availability Wide Limited
Atten. correction Less accurate
Accurate
Spatial resolution 12-15 mm 5-7 mm
Protocol 2 days <1 hour
Radiation >10 mSv <10 mSv
Images Qualitative Quantitative
Hybrid with CT Yes Yes
41. Rationale for PET/CT MPS
To decrease invasive coronary
angiography unless necessary i.e if
therapeutic
Highly sensitive and specific
Absolute Quantification of myocardial
blood flow
Assesment of coronary flow reserve
Blood flow,myocardial cell integrity,Wall
motion and LVEF
Calcium score & Luminal narrowing
42. Imaging Protocol
Patient preparation and stress testing
- Dypiridamole & adenosine
Imaging 82 Rb varies with PET scanner crystal
Reconstruction of images
Perfusion: filtered back
projection
Gated wall motion : iterative
2 D Vs 3 D & 4 D PET
LVEF
PET Vs planar gated blood pool ( r = 0.81)
PET Vs MIBI SPECT ( r = 0.91)
43. Current status of Cardiac PET
Extensive infrastructure
Improved PET scanners with LSO
crystal
Availability of PET-CT
Rubidium –82 PET perfusion tracer
-Generator produced
- Reimbursible since 1995 in USA
- Already clinically useful in tertiary
care and community hospitals
44. Present Status
CMS Reimbursment Fee Schedule Changes State a
20% Increase in Cardiac PET and a 36% Decrease in
SPECT
Clinical Indications :
Low risk CAD
Intermediate risk CAD
LBBB
Women
Obese
Diabetes
Research : Endothelial function and Plaque bilology
45. Cardiac PET Perfusion Tracers
Agent Physical
half life
Extraction Production
13N NH3 10 min 80 % Cyclotron
82 Rb 75 sec 50-60% Generator
15 O H2O 2 min Diffusible Cyclotron
46. Rb – 82 Production
Cation like Tl-201 and Potassium analogue
Uptake reflects function of blood flow and
myocardial cell integrity
Generator produced from Sr-82
Replaced every 4 weeks
Decays by positron emission with short half
life (75 sec)
Eluted with 25-50 ml normal saline by
controlled elution pump and connected with
IV tubing to patient
Fully replenished every 10 min and 90% of
max. activity can be available after 5 min.
47. Imaging Protocol for Rb 82 PET
imaging With a LSO PET-CT Scanner
Procedure Time
Positioning (Scout) 1 min
CT transmission scan 1 min
Rest gated imaging 8 min
Rest perfusion imaging 8 min
Pharmacological stress 7 min
CT transmission scan 1 min
Stress imaging 8 min
Total duration 34 min
48.
49.
50.
51.
52.
53. Diagnostic Accuracy of PET MPI for CAD
Author Year Agent No.of
Patient
Sensitivit
y
Specificit
y
Gould et
al
1986 NH3,Rb
82
50 95 100
Demer 1989 Rb 82 193 94 95
Go et al 1990 Rb 82 202 93 78
Schelbert 1982 NH 3 45 97 100
Yonekura 1987 NH 3 49 93 100
Williams 1989 Rb 82 146 98 93
Stewart 1991 Rb 82 81 84 88
Tamaki 1988 NH 3 25 95 95
Average 791 93 92
54. Comparison of PET and SPECT MPI for
detection of CAD in same patient
Author
et al
Year Tracer Accurac
y (% )
Sensitivi
ty
Specifici
ty
Go
n=132
1990 Rb 82
Tl-201
92
78
95
79
82
76
Stewart
n = 81
1991 Rb 82
Tl 201
85
78
87
87
82
52
Tamaki
n=51
1988 NH 3
Tl 201
98
98
98
96
100
100
Total
n=264
PET
SPECT
91
81
93
85
82
67
57. Clinical applications of PET/CT MPS
Diagnosis of coronary artery disease
Assesment of blood flow : Prognosis
(Yosinaga K et al JACC 2006 :48;Sept.1029-30)
Noninvasive coronary angiography (CTA)
High false positivity- 25 %
Poor assesment of lumen – 18-24%
Early detection of CAD in asymptomatic
patients
Identifying plaques by molecular markers
Assesment of heart failure
59. Radiation dose from PET/CT
Study Effective radiation dose (mSv)
PET
F-18 FDG (370 MBq) 7.0
N-13 NH3 rest/stress (2×550 MBq) 2.2
Rb-82 rest/stress (2×740 MBq) 3.6
H2O-15 rest/stress (2×740 MBq) 1.4
Transmission Ge-68 rod sources 0.08–0.13
MSCT
Calcium scoring 0.7–6.2
CT angiography 3.7–13.0
CT based PET attenuation correction 0.23–5.66
60. Utility of PET/CT in CAD
Excellent noninvasive imaging procedure
Extent & severity of perfusion abnormality
Extent of tissue viability
Risk stratify each patient prior to clinical
decision making
Attractive translational research tool in
combination with molecular probes i.e
Cell therapy or Gene therapy
The ischemic cascade is a series of temporal events that occurs after the experimental occlusion of a coronary artery, or clinically, the production of myocardial ischemia.
By definition, flow disparities are the first physiological changes noted. Abnormalities in ventricular function, first diastolic, then systolic, are noted shortly after the onset of ischemia. This is followed by the development of electrocardiographic (ECG) changes and usually by the onset of angina pectoris.
Noninvasive testing using exercise ECG relies on late findings within the ischemic cascade. Stress echocardiography depends on the production of ischemia-induced wall motion abnormalities. Flow disparities on stress perfusion imaging are noted early in the ischemic cascade.
The numbers 1 to 5 correspond to those on the next slide.
[Adapted from Sigwart U, et al. In: Silent Myocardial Ischemia. W Rutishauser, H Roskamm, eds. Springer-Verlag, Berlin, 1984:29-36.]
The gated portion of the SPECT study allows both the visual and quantitative assessment of left ventricular function. These measures include left ventricular ejection fraction and end-diastolic and end-systolic volumes. In addition, this modality achieves excellent visualization of both the endocardial and epicardial surfaces, allowing for the evaluation of left ventricular wall motion and wall thickening.
In this scan, the top row represents 3 short axis images (apical, mid, and basal short-axis slices) and the bottom row represents the mid horizontal and vertical long-axis slices.