Download Single-photon emission computed tomography/computed

Cardiac Hybrid Imaging:
SPECT/CT or PET/CT?
Heikki Ukkonen, MD,PhD
Department of Medicine
Turku University Hospital
Finland
No conflicts of interest regarding this presentation
Hybrid imaging PET- CT
Hybrid imaging SPECT-CT
64-slice CT Scanner (5-sec acquisition of the heart)
Ultrafast SPECT (2-min acquisition of the heart)
Cardiac PET vs. SPECT
Advantages of PET
– Faster
• short-lived tracers allow faster rest and stress
studies  higher patient throughput
– Low radiation dose (O-15-water, NH3 1 mSv and 82Rb
1.85 mSv (<1 mSv with 3D )
– Less image artefacts
• Routine attenuation correction, no rotating camera
heads higher specificity
Cardiac PET vs. SPECT
Advantages of PET
– Higher accuracy
• Higher spatial resolution and heart-to-background ratio 
• More accurate detection of disease
– Quantitative technique
• Higher temporal resolution  dynamic imaging  absolute
quantification
• Extraction and kinetics of PET agents
– Versatile method (molecular imaging, plaques, viability with
higher sensitivity, monitoring of disease)
– PET/64MDCT is a standard issue
Tracer uptake characteristics
18F-Flurpiridaz
Knuuti J Nucl Cardiol 2009
Cardiac PET vs SPECT
• Limitations of PET
– Costs and reimbursement
– Availability
– Limited prognostic data of perfusion studies
– Less data in obese, diabetic, women….
– Tools for quantititative analysis
– Tracer availability
PET/CT vs. SPECT/CT
Advances in SPECT and SPECT/CT
– Hardware
•
•
•
•
•
SPECT/64MDCT now available
Dedicated cardiac imaging systems
Improved collimation (multiple pin-hole priciple, ultra-high sens. Detectors)
Optimized scanner geometry higher photon sensitivity
Solid-state photon detectors (Cadmium Zinc Telluride [CZT], Cesium iodode
[CSi]More accurate detection of disease
 short (< 5min) stress-only protocols possible
– Software
• New reconstruction algorithms
New instrumentation and lower dose
*
*(CTA 2.2±0.7 mSv)
Slomka J 2012
Hybrid imaging: SPECT/CT
Pazhenkottil et al EHJ 2011
Hybrid imaging: PET/CT
LAD
D1
LAD
Turku PET Centre, Finland
Impact of image fusion (SPECT/CTA) on
revascularization rate
Pazhenkottil et al EHJ 2011
Added value of
myocardial blood flow reserve
Fiechter J Nucl Med 2012
Absolute MBF by H2O15-PET and stress
perfusion defect by Tc-99m tetrofosmin
Group A =
stenosis (+)
stress PD (+)
Group B =
stenosis (+)
stress PD (-)
Group C =
stenosis (-)
stress PD (-)
Yoshinaga et al JNC 2003
Hybrid PET/CTA vs. ICA + FFR
MDCT
PET
MDCT-PET hybrid
Sensitivity (%)
Specificity (%)
PPV (%) NPV (%) Accuracy (%)
75
95
76
94
91
Figure
3: Vessel
Analysis
against
ICA +FFR
94
93
77
98
93
95
99
96
99
98
Vessel analysis in patients with intermediate likelihood of CAD, N=107
100
90
80
percentage
70
60
MDCT
50
PET
40
MDCT-PET hybrid
30
20
10
0
PPV (%)
NPV (%)
Accuracy (%)
MDCT
76
94
91
PET
77
98
93
MDCT-PET hybrid
96
99
98
Kajander et al Circulation 2010
Absolute quantification in 106
patients with suspected CAD
Per vessel analysis
100
90
80
70
60
50
40
30
20
10
0
%
%
%
%
%
%
%
%
%
%
%
absolute
relative
PPV
NPV
acc
106 patients with 30-70% pretest likelihood of CAD
Quantitative hybrid PET/CT imaging vs. invasive angiography with FFR
Kajander et al Circ Cardiovasc Imaging 2011
Quantitation vs relative analysis of perfusion
A Saraste and J Knuuti JNC 2012
Absolute quantification in patients
with multi-vessel disease
Per vessel analysis
100
90
80
70
60
50
40
30
20
10
0
%
%
%
%
%
%
%
%
%
%
%
absolute
relative
PPV
NPV
acc
Quantitative hybrid PET/CT imaging vs. invasive angiography with FFR
Kajander et al Circ Cardiovasc Imaging 2011
Ziadi MC, et al J Nucl Cardiol 2012.
Challenges in perfusion imaging of CAD –
and suggested solutions
Challenge
– LM disease
– Balanced 3 VD
– Multivessel disease
– Anatomical location
– Non-ischemic CAD
– Microvascular disease
Solution
Hybrid imaging
Quantitation/hybrid imaging
Quantitation/hybrid imaging
Hybrid imaging
Hybrid imaging
Quantitation/hybrid imaging
Quantification of myocardial perfusion
What could be the clinical value?
• Balanced 3 vessel • Useful - not a clinical
problem with SPECT/MDCT?
disease
• Useful but how often
quantification brings new
• Culprit lesion
information?
• Not currently in clinical use
• Early changes in
coronary
dysfunction
Diagnostic accuracy of hybrid imaging
Gaemperli, Bengel and Kaufmann EHJ 2011
Conclusions
• SPECT/CTA and PET/CTA (with relative perfusion)
appear to be comparable in finding/excluding
obstructive CAD
• Due to advances in instrumentation, SPECT/CTA
(stress only) can be performed with relatively low
radiation dose (< 5 mSvi)
• Quantification of MBF with PET offers a great
potential for more comprehensive assessment of
CAD (prognosis, multivessel disease)
• Further studies are needed to assess whether the
potential of MBF quantification can be translated
into better patient outcome or not