Presentation given at Arab Health congress on Jan. 29th 2013, with information about (dual source) Cardiac CT of the coronary arteries with technical & practical information and some clinical use cases
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State-of-the-art Cardiac CT of the coronary arteries
1. Cardiac CT
E. R. Ranschaert
Radiologist
Arab Health Congress, Jan 28-31, 2013
2. Introduction
Technical aspects
Scanning procedure
Indications for c-CTA
Clinical cases
64 slice
dual source CT
Copyright E. R. Ranschaert
3. Coronary CTA
Main purpose: morphology
Detection and analysis of
coronary artery disease
Depict anatomy of coronary
vasculature
Possible to obtain functional
information in same scan
contractility of myocardium
valve morphology and function
“viability” of myocardium
(perfusion-CT)
Copyright E. R. Ranschaert
5. Multislice CT - MDCT
Evolution of Cardiac CT is
strongly linked to technical
improvements in CT-
scanners
Preferably 64-slice scanner
or more
Our current machine:
dual source CT 2x64 slice
(Somatom Definition Flash)
Other vendors: 256-slice or
higher
Copyright E. R. Ranschaert
6. Volume coverage – helical scan
Time to cover heart decreases with larger detector arrays,
shorter tube rotation times and faster table movement
4 x 1 mm slice 16 x 1mm slices 64 x 0.5 mm slices
4 mm 16 mm 32 mm
~48 sec ~12 sec ~6 sec
Copyright E. R. Ranschaert 0.5 s rotation, 0.33 pitch
Courtesy of Sue Edyvean, ImPACT – www.impactscan.org
7. “Old” generation scanners
16-slice 64-slice
Images used with permission of James Carr, MD
Copyright E. R. Ranschaert
8. Newer generation scanners
Complete coverage High pitch
Toshiba Acquilion Siemens Definition Flash
Seq 256-slice, spiral 64-slice 2x 64 slice
single rotation fast pitch, no gaps
Copyright E. R. Ranschaert Courtesy of Sue Edyvean, ImPACT – www.impactscan.org
9. Multi-sector scanning
Min. 2 sectors needed per image
Graphics used with permission of Sue Edyvean, ImPACT – www.impactscan.org
Copyright E. R. Ranschaert
10. Multi-sector scanning
GE Philips Siemens Siemens Toshiba
1 tube 2 tubes
# sectors 1,2,4 up to 5 1 or 2 1 or 2 up to 5
Graphics used with permission of Sue Edyvean, ImPACT – www.impactscan.org
Copyright E. R. Ranschaert
11. Dual source CT
(0,285 s rotation for entire heart)
Graphics used with permission of Sue Edyvean, ImPACT – www.impactscan.org Copyright E. R. Ranschaert
14. Patient Preparation
General CT-preparation:
Renal function, hydration, stop Metformin if
GFR<60, premedication for iodine allergy
Specific cardiac-CT preparation:
Information sheet specifically for cardiac CT
Beta-blockers: P.O. (in advance)
Other premedication if needed
Copyright E. R. Ranschaert
15. Day of scanning
3-4 h in advance: no meal, no coffee, no tea
2h in advance 25-100 mg metoprolol
P.O. (selective β1 receptor blocker)
Fine tuning HR with IV injection, 5-20 mg extra
Selection of scan protocol depending on bpm
variability
For Flash: ≤65 bpm and regular HR needed
Copyright E. R. Ranschaert
16. ECG monitoring on scan
ECG monitoring is used to “freeze” cardiac motion
Images made during phase of least cardiac motion
Phase is given as % of R-R interval
Courtesy of Sue Edyvean, ImPACT – www.impactscan.org
Copyright E. R. Ranschaert
17. Scanning
Breath hold on ¾ of full inspiration (prevents
Valsalva manoeuvre)
Breathing instructions are practiced with
patient before scanning
Nitroglycerine spray immediately before
scanning 1 puff
Contrast (high iodine concentration) is injected
at 5-6 ml/sec
Copyright E. R. Ranschaert
18. Stable HR needed
Motion needs to be repeatable – regular heart rate
reduce potential for mis-registration
applies for both axial and helical
iiiii
iiiii
iiiii
ECG
Copyright E. R. Ranschaert
20. Calcium scoring
First calcium score is
determined
low dose non-enhanced
triggered scan
Semi-automated
calculation of score
Decision to make c-CTA
based upon score and
age
Score 0 >60j: no cCTA
>600: no cCTA
Copyright E. R. Ranschaert
21. Selection CTA scan protocol
3 acquisition modes with ECG synchronisation
1. Retrospective gating
2. Prospective triggering = sequential/axial =
“adaptive sequence” (Siemens)
3. FLASH = prospective triggering spiral scan with
very high pitch
Copyright E. R. Ranschaert
22. 1. Retrospective gating
Spiral scan technique
Small overlapping pitch ≅ 0,2
Heart scanned in all phases
Breath hold = 7-12 sec
Retrospective selection of
best phase for
reconstruction/reviewing
Functional information
10-12 mSv
Courtesy of Sue Edyvean, ImPACT – www.impactscan.org
Copyright E. R. Ranschaert
23. Cardiac CT – ECG phases
Optimal phase for reconstruction for CTA
diastole @ ~ 70 %
Optimal reconstruction phase
R R
70% R-R
Eg. 50 60 70 80
Courtesy of Sue Edyvean, ImPACT –R. Ranschaert
Copyright E. www.impactscan.org
24. 2. Prospective triggering
ACS: Adaptive Cardio Sequence
Sequential technique
ECG-signal is used to trigger scanning
(R-wave)
“Padding” opens scan pulse
(30-80% RR)
With “padding” more phases are
available for review (steps of 1 – 20%)
Dose reduction up to 87% compared
with retrospective scanning (2,5 - 3 mSv)
Usable in patients with slightly irregular
heart beat
Courtesy of Siemens: Thomas Flohr, Cardiac CT Acquisition modes
Copyright E. R. Ranschaert
25. Triggering
R wave recognised - scan triggered
Radiation on
(and attenuation
data acquired)
Courtesy of Sue Edyvean, ImPACT – www.impactscan.org
Copyright E. R. Ranschaert
26. Management of extrasystoles
Selection Low / Medium / High protocol depends on
HR (60-85 bpm)
ACS makes analysis of ECG, ectopic heart beats are
detected
Start of scan is prospectively based upon last 3 cycles
Scan is omitted & delayed when extrasystole is
detected before scan
Scan is repeated when extrasystole occurs during or
shortly after scan
Flex padding uses extended acquisition window: gives
more flexibility to find optimal reconstruction phase
Copyright E. R. Ranschaert
27. Copyright E. R. Ranschaert
Padding
„padding‟ for
CTA
Radiation on
(and attenuation
data acquired)
480° rotation
28. Copyright E. R. Ranschaert
Padding
„padding‟ for
CTA
Radiation on
(and attenuation
data acquired) 70
Required data
for image
recon.
29. Copyright E. R. Ranschaert
Padding
Axial scanning with „padding‟
More flexibility with reconstructed phase position
„padding‟ for
CTA
Radiation on
(and attenuation
data acquired). 60
Required data
for image
recon.
30. Copyright E. R. Ranschaert
Padding
Axial scanning with „padding‟
More flexibility with reconstructed phase position
„padding‟ for
CTA
Radiation on
(and attenuation
data acquired).
Required data
for image
recon.
31. 3. Flash – single beat, high pitch
• 2 Sectors of data acquired simultaneously in ¼ rotation = 75 ms
• Whole heart in 3¼ rotations = 0,28 sec
• No misregistration, no stair-step artefacts: 1 shot!
Copyright E. R. Ranschaert Courtesy Siemens
32. Which protocol to use?
RETROSPECTIVE:
Only with patients that are not suited for prospective
scanning due to arythmia, high HR or both
If functional imaging is needed (LVA)
PROSPECTIVE:
Stable and low HR
Slight arythmia
With ACS: 65-85 bpm
Low – medium – high protocol
Also LVA possible with adaptive sequence (padding)
Use Flash whenever possible!
SCCT guidelines on radiation dose and dose-optimization strategies in cardiovascular CT,
Halliburton SS et al., J Cardiovasc Computed Tomogr (2011)5, 198-224
Copyright E. R. Ranschaert
34. Indications for c-CTA
Calcium scoring
Risk stratification
Decisive before CTA examination
Coronary CTA
Anatomy of coronary vessels (CAG difficult)
CAD (low to intermediate risk)
Stent viability
Anatomy and patency of grafts after CABG
Functional analysis
Copyright E. R. Ranschaert
35. Calcium scoring
“Gatekeeper” for further cardiac
examination if pre-test probability is low and
EST is not possible
Added value in risk stratification (re-
stratification of medium risk)
With men and female >60y
score = 0 is very reassuring (high NPV)
Copyright E. R. Ranschaert
36. Assessment of stenoses
Visual assessment
Significant
(obstructing) is > 50%
Non-significant or non-
obstructive < 50%
Resolution vs. CAG:
20% margin is taken Non-obstructing stenosis
Significant stenosis
into account
Copyright E. R. Ranschaert
37. Limitations of cCTA
Irregular HR
obesity
stents < 3 mm
Calcium and stents:
“blooming” artefacts lower
specificity of cCTA
Copyright E. R. Ranschaert
38. Copyright E. R. Ranschaert
Blooming Artefact
Blooming artefact – calcium/stent obscures vessel
Improvement with better spatial resolution
Improved spatial
resolution
and display
(recon alg., fov)
49
Courtesy of Sue Edyvean, ImPACT – www.impactscan.org
39. Copyright E. R. Ranschaert
Diagnostic accuracy of cCTA
CAG is gold standard
cCTA
Ideally patients with
stable HR +
stable AP complaints Sens 96-99%
or atypical chest pain
Very useful to exclude
Spec 88-91%
significant CAD: high
NPV NPV >90%
Low to intermediate risk patiënts
40. Anatomy
Left main stem
RCA
AM
PDA Cx
Diag branch
LAD
Copyright E. R. Ranschaert
48. Case 3
M, 33y
SEH left thoracic pain
irradiation to left arm
CAG: no significant
stenoses demonstrated,
“catheter spasm”
In history probably limited
myocardial infarction
cCTA performed 3m later
Copyright E. R. Ranschaert
49. yright E. R. Ranschaert
Non-stenosing non-calcified plaque in prox. circumflex artery
50. Case 4
M, 43j
Chest pain, arm pain while
painting during 30 min
Normal EST,
ECG normal
cCTA
Copyright E. R. Ranschaert
51. Case 4
Chronically
occluded RCA
ectatic coronary
system
Copyright E. R. Ranschaert
52. RCA
Reinjection via left system
Copyright E. R. Ranschaert
54. Case 5
Woman, 1967
Atypical precordial
pain PA
Ao
Cycling test negative
Low risk
PA
RCA
Ao
Copyright E. R. Ranschaert
55. Anomalous RCA
Anomalous RCA arising
from left sinus of valsalva
AA PA Most common pathway for
ectopic RCA
RCA
Associated with sudden
cardiac death in 30% of pts
Dilatation of Ao during
RCA
PA excercise comprises RCA,
may lead to AMI
inter-arterial course of RCA
Ao
Copyright E. R. Ranschaert
57. Anatomic variant
Left CA main branch: origin
posterior on AA
from non-coronary sinus of
Valsalva
Retro-aortic course
Usually no clinical
relevance
LA
D
Cx
Copyright E. R. Ranschaert
69. Findings case 4
LIMA – LAD anastomosis Distal LAD
Stenosis
Copyright E. R. Ranschaert
70. Case 5
History Calcium scoring
Female, 1963
Referred by GP for atypical
chest pain, dyspnea with
effort
Bicycle ergometry: not
conclusive
ECG mild abnormalities
Copyright E. R. Ranschaert
71. Case 6
cCTA Flash mode
MIP
Copyright E. R. Ranschaert
73. Case 6 – stent evaluation
Pre-stenting Post-stenting
Copyright E. R. Ranschaert
74. Case 6: stent evaluation
Stent LAD Diagonal branch
Copyright E. R. Ranschaert
75. Case 7
Female, 51 y
Dyspnoea with effort,
fatigue, no chest pain
FA: father sudden death at
55y, probably AMI
ECG normal
Copyright E. R. Ranschaert
76. Case 7
RCA
Non-calcified stenosis 70%
Copyright E. R. Ranschaert
77. The End
Thank you!
http://nl.linkedin.com/in/eranschaert/
e.ranschaert@jbz.nl